Maximizing Natural Ventilation By Design In Low Rise Residential [PDF]

MAXIMIZING NATURAL VENTILATION BY DESIGN IN LOW RISE RESIDENTIAL BUILDINGS USING WIND CATCHERS IN THE HOT ARID CLIMATE OF UAE

by Rashed Khalifa Al-Shaali

A Thesis Presented to the FACULTY OF THE SCHOOL OF ARCHITECTURE UNIVERSITY OF SOUTHERN CALIFORNIA In Partial Fulfillment of the Requirements of the Degree MASTER OF BUILDING SCIENCE

August 2002

Copyright 2002

Rashed Khalifa Al-Shaali

UNIVERSITY OF SOUTHERN CALIFORNIA The Graduate School University Park LOS ANGELES, CALIFORNIA 90089-1695

This thesis, written by …………………………………………………..

Under the direction of h…………….. Thesis Committee, and approved by all its members, Has been presented to and accepted by The Graduate School, in particular fulfillment of requirements for the degree of ………………………………………………. ………………………………………………. Dean of Graduate Studies Date …………………….. THESIS COMMITTEE ……………………………………………….. Chairperson ……………………………………………….. ………………………………………………..

Acknowledgements First of all, I would like to thank Allah (God) for granting me patience that carried me through all the difficult times. Second, I would like to thank my father and mother, the most wonderful friends I have ever had and loved, for all the sacrifices, caring and guidance and for giving me such a wonderful sister and brothers. The list of people whom I want to thank is very long. However, I would like to value the following people for their indispensable help: Professor Pierre Koenig, my chief advisor, for his ultimate and important support, direction, encouragement and patience. Professor Marc Schiler, for his guidance, support and forbearance through out all the study period and for opening the doors of opportunities when I thought that all of them are closed. Professor Ralph L. Knowles, for his assistance, kindness and for always reminding me of the spiritual side of Architecture. Professor Murray Milne, for providing me with all the necessary computer documents and his immediate and positive responses to my questions. I would also like to especially thank my friend Ahmad Al Awar for his incessant help, as well as Nasser Al-Shaali, Khalid Al Hammadi, Zainab A. AlRustamani and Dr. D. E. Ordway for their assist and kindness. Last but not least, I would like to thank my wife Amal for her support and love that carried me smoothly through a lot of difficult time and for giving me the best gifts I have ever had, our children Khalifa and Reem.

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Table of Contents Acknowledgements_________________________________________________________i List of Figures____________________________________________________________vi Abstract_________________________________________________________________xi 1

UAE _______________________________________________________________ 1 1.1

Physical features _________________________________________________ 1

1.2

Climatic conditions _______________________________________________ 2

1.3

Housing ________________________________________________________ 2

1.4

Social needs and demands__________________________________________ 3

1.5 Environmental and cultural issues ___________________________________ 3 1.5.1 Vernacular architecture styles_____________________________________ 4 1.5.2 Environmental sense and consideration _____________________________ 4 1.6

Wind and wind catchers ___________________________________________ 5

REFERENCES: _________________________________________________________ 6 2

Climatic Data and Analysis ____________________________________________ 7 2.1 Writing TMY2 Data Format ________________________________________ 7 2.1.1 What is TMY2 Data ____________________________________________ 7 2.1.2 TMY2 Data Format ____________________________________________ 7 2.1.3 Calculating the Missing Data _____________________________________ 8 2.1.3.1 Direct Beam Solar Radiation __________________________________ 8 2.1.3.2 Total Horizontal (diffused) Solar Radiation_______________________ 9 2.1.3.3 Dew point outdoor air temperature_____________________________ 10 2.2 SCRAM _______________________________________________________ 10 2.2.1 What is SCRAM Data _________________________________________ 10 2.2.2 SCRAM Data Format __________________________________________ 11 2.3 Climatic Data Charts ____________________________________________ 2.3.1 City of Abu Dhabi ____________________________________________ 2.3.1.1 Temperature Range ________________________________________ 2.3.1.2 Temperature + Relative Humidity _____________________________ 2.3.1.3 Wind Velocity Range _______________________________________ 2.3.1.4 Bioclimatic Timetable ______________________________________ 2.3.1.5 Psychrometric Chart________________________________________ 2.3.2 City of Al-Ain________________________________________________ 2.3.2.1 Temperature Range ________________________________________ 2.3.2.2 Temperature + Relative Humidity _____________________________ 2.3.2.3 Wind Velocity Range _______________________________________ 2.3.2.4 Bioclimatic Timetable ______________________________________ 2.3.2.5 Psychrometric Chart________________________________________

13 13 13 14 15 16 17 18 18 19 20 21 22

2.4 Wind Roses ____________________________________________________ 23 2.4.1 City of Abu Dhabi ____________________________________________ 23 2.4.2 City of Al-Ain________________________________________________ 25

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REFERENCES: ________________________________________________________ 27 3

Wind and Ventilation ________________________________________________ 28 3.1 Wind Characteristics_____________________________________________ 3.1.1 Wind near the Ground _________________________________________ 3.1.2 Wind in an Urban Environment __________________________________ 3.1.3 Wind Flow __________________________________________________

28 28 30 30

3.2 Natural Ventilation for Thermal Comfort _____________________________ 3.2.1 Removal of Excess Heat________________________________________ 3.2.2 Cooling Effect over the Human Body _____________________________ 3.2.3 Cooling the Structure __________________________________________

31 32 32 33

REFERENCES: ________________________________________________________ 35 4

Historical Precedents ________________________________________________ 36 4.1 Hot and Arid Zones ______________________________________________ 4.1.1 The Malqaf __________________________________________________ 4.1.2 The Badgir (Barjeel)___________________________________________ 4.1.3 Wind Scoops_________________________________________________

36 38 43 49

4.2 Design Examples of Wind Catchers _________________________________ 51 4.2.1 Qatar University in Doha _______________________________________ 51 4.2.2 Concept drawings _____________________________________________ 54 REFERENCES: ________________________________________________________ 57 5

Setting the Variables_________________________________________________ 60 5.1

Hypothesis_____________________________________________________ 60

5.2 When to use Natural Ventilation ____________________________________ 60 5.2.1 City of Abu Dhabi ____________________________________________ 61 5.2.2 City of Al-Ain________________________________________________ 78 5.3 Model Drawings and Testing Environment____________________________ 96 5.3.1 Helium Bubble Generator_______________________________________ 96 5.3.2 Drawings ___________________________________________________ 96 6

Wind Catcher with Different Sizes and Outlets__________________________ 103 6.1 1/3 Wind Catcher ______________________________________________ 6.1.1 Case 0 _____________________________________________________ 6.1.1.1 Speed 1 _________________________________________________ 6.1.1.2 Speed 2 _________________________________________________ 6.1.1.3 Speed 3 _________________________________________________ 6.1.2 Case 1 _____________________________________________________ 6.1.2.1 Speed 1 _________________________________________________ 6.1.2.2 Speed 2 _________________________________________________ 6.1.2.3 Speed 3 _________________________________________________ 6.1.3 Case 2 _____________________________________________________ 6.1.3.1 Speed 1 _________________________________________________ 6.1.3.2 Speed 2 _________________________________________________ 6.1.3.3 Speed 3 _________________________________________________ 6.1.4 Case 3 _____________________________________________________ 6.1.4.1 Speed 1 _________________________________________________ 6.1.4.2 Speed 2 _________________________________________________

104 104 105 106 106 109 109 110 111 114 114 115 116 119 119 120

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6.1.4.3

Speed 3 _________________________________________________ 121

6.2 1/2 Wind Catcher ______________________________________________ 6.2.1 Case 0 _____________________________________________________ 6.2.1.1 Speed 1 _________________________________________________ 6.2.1.2 Speed 2 _________________________________________________ 6.2.1.3 Speed 3 _________________________________________________ 6.2.2 Case 1 _____________________________________________________ 6.2.2.1 Speed 1 _________________________________________________ 6.2.2.2 Speed 2 _________________________________________________ 6.2.2.3 Speed 3 _________________________________________________ 6.2.3 Case 2 _____________________________________________________ 6.2.3.1 Speed 1 _________________________________________________ 6.2.3.2 Speed 2 _________________________________________________ 6.2.3.3 Speed 3 _________________________________________________ 6.2.4 Case 3 _____________________________________________________ 6.2.4.1 Speed 1 _________________________________________________ 6.2.4.2 Speed 2 _________________________________________________ 6.2.4.3 Speed 3 _________________________________________________

125 126 126 127 127 130 130 131 134 136 136 137 137 140 141 141 142

6.3 Full Length Wind Catcher________________________________________ 6.3.1 Case 0 _____________________________________________________ 6.3.1.1 Speed 1 _________________________________________________ 6.3.1.2 Speed 2 _________________________________________________ 6.3.1.3 Speed 3 _________________________________________________ 6.3.2 Case 1 _____________________________________________________ 6.3.2.1 Speed 1 _________________________________________________ 6.3.2.2 Speed 2 _________________________________________________ 6.3.2.3 Speed 3 _________________________________________________ 6.3.3 Case 2 _____________________________________________________ 6.3.3.1 Speed 1 _________________________________________________ 6.3.3.2 Speed 2 _________________________________________________ 6.3.3.3 Speed 3 _________________________________________________ 6.3.4 Case 3 _____________________________________________________ 6.3.4.1 Speed 1 _________________________________________________ 6.3.4.2 Speed 2 _________________________________________________ 6.3.4.3 Speed 3 _________________________________________________

145 146 146 147 147 150 150 151 151 153 154 154 156 158 159 159 160

6.4 Additional Tests________________________________________________ 163 6.4.1 Wind catcher with Smaller Opening______________________________ 163 6.4.2 Wind Catcher in the Middle of the Windward Façade ________________ 166 6.5

Suggestion ____________________________________________________ 167

7

Future Work ______________________________________________________ 170

8

Bibliography ______________________________________________________ 171

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List of Figures Figure 1-1 United Arab Emirates Map .............................................................................................. 1 Figure 2-1 Scram Data Format........................................................................................................ 11 Figure 2-2 Abu Dhabi 1997 Temperature Range ............................................................................. 13 Figure 2-3 Abu Dhabi 1997 Temperature + Relative Humidity........................................................ 14 Figure 2-4 Abu Dhabi 1997 Wind Velocity Range .......................................................................... 15 Figure 2-5 Abu Dhabi 1997 Bioclimatic Timetable ......................................................................... 16 Figure 2-6 Abu Dhabi 1997 Psychrometric Chart............................................................................ 17 Figure 2-7 Al-Ain 1997 Temperature Range ................................................................................... 18 Figure 2-8 Al-Ain 1997 Temperature + Humidity ........................................................................... 19 Figure 2-9 Al-Ain 1997 Wind Velocity Range ................................................................................ 20 Figure 2-10 Al-Ain 1997 Bioclimatic Timetable ............................................................................. 21 Figure 2-11 Al-Ain 1997 Psychrometric Chart ................................................................................ 22 Figure 2-12 Abu Dhabi 1997 Wind Rose ........................................................................................ 23 Figure 2-13 Abu Dhabi 1991, 92, 93, 94, 95, 97, 98 and 99 Wind Rose ........................................... 24 Figure 2-14 Al-Ain 1997 Wind Rose .............................................................................................. 25 Figure 2-15 Al-Ain 1995, 96, 97, 98 and 99 Wind Rose .................................................................. 26 Figure 3-1 Typical Record of the Wind Velocity near the Ground .................................................. 28 Figure 3-2 Wind Patterns (a) Constricted by Topography. (b) Above and Below Tall Buildings. (c) Around large Buildings. ........................................................................................................ 29 Figure 3-3 Effect of Terrain on Wind Velocity Profiles ................................................................... 30 Figure 3-4 Wind Pressure around Building ..................................................................................... 31 Figure 3-5 Wind Pressure Drives Cross Ventilation......................................................................... 31 Figure 3-6 Heat Generated and lost (approximate) by a person at rest (rh fixed at 45%)................... 33 Figure 3-7 Isocomfort Curve........................................................................................................... 34 Figure 3-8 Isocomfort Curve Parametrized as a Function of the air velocity..................................... 34 Figure 4-1 Wind Tower in the Middle East ..................................................................................... 36 Figure 4-2 Catching Efficiency for Different Wind Catcher Designs................................................ 37 Figure 4-3 Roof plan of the Fu'ad Riyad house in Cairo, showing the malqaf with sectional details.. 38 Figure 4-4 Section of the Fu'ad Riyad house showing the malqaf..................................................... 39 Figure 4-5 Section of a modern villa designed for Saudi Arabia showing the use of malqaf.............. 39 Figure 4-6 Section through the hall of Muhib Ad-Din Ash-Shaf'i Al-Muwaqqi showing the malqaf and central location of the hall............................................................................................... 40 Figure 4-7 Arrows indicate the direction of airflow; arrow length corresponds to airspeed. The measurements where made on 2 April 1973 by scholars from the Architectural Association School of Architecture in London. All wind and airspeeds are given in meters per second. ..... 40 Figure 4-8 Malqaf with wetted baffles and a wind-escape. Design by Hassan Fathy ........................ 41 Figure 4-9 Details of the malqaf with wetted baffles........................................................................ 42 Figure 4-10 Barjeel details.............................................................................................................. 43 Figure 4-11 Mohamed Sharif house, first floor................................................................................ 44 Figure 4-12 Wooden doors and opening.......................................................................................... 45 Figure 4-13 Interior view of the Wooden doors and openings.......................................................... 45 Figure 4-14 Shaikh Saeed house (North Elevation) ......................................................................... 46 Figure 4-15 Shaikh Saeed house (East Elevation)............................................................................ 46 Figure 4-16 Shaikh Saeed house (Courtyard view) .......................................................................... 46 Figure 4-17 Traditional Square Barjeel ........................................................................................... 47 Figure 4-18 Unusual cylindrical Barjeel.......................................................................................... 47 Figure 4-19 The Barjeel Closed to Block Undesirable Wind............................................................ 48 Figure 4-20 A fort in the City of Ajman uses the Barjeel for Natural Ventilation ............................. 48 Figure 4-21 Wind scoop, Hyderabad, Sind, Pakistan ....................................................................... 49 Figure 4-22 Wind Scoops facing the prevailing wind ...................................................................... 49 Figure 4-23 Scoops in Pakistan at different levels ........................................................................... 50

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Figure 4-24 A picture from the roof ................................................................................................ 51 Figure 4-25 Section/Elevation of Humanities Faculty Modules ....................................................... 51 Figure 4-26 An External Picture of the Wind Catchers .................................................................... 52 Figure 4-27 A picture from the courtyard........................................................................................ 52 Figure 4-28 Qatar University (Phase 1), Kamal El-Kafrawi ............................................................. 53 Figure 4-29 Ariel View of Qatar University .................................................................................... 53 Figure 4-30 From above: Wind tower; monodirectional wind tower and scoop; multidirectional wind tower and scoop; combined wind tower and scoop ................................................................. 54 Figure 4-31 Day and Night reverse wind directions......................................................................... 55 Figure 4-32 Concept Drawings for rotating wind scoops ................................................................. 56 Figure 5-1 Hours to Block Natural Ventilation in Abu Dhabi .......................................................... 61 Figure 5-2 January Wind Rose........................................................................................................ 62 Figure 5-3 February Wind Rose...................................................................................................... 63 Figure 5-4 March Wind Rose.......................................................................................................... 64 Figure 5-5 April Wind Rose ........................................................................................................... 65 Figure 5-6 May Wind Rose............................................................................................................. 66 Figure 5-7 June from Midnight to 7am Wind Rose.......................................................................... 67 Figure 5-8 June from 15pm until Midnight Wind Rose.................................................................... 68 Figure 5-9 July from Midnight to 7am Wind Rose .......................................................................... 69 Figure 5-10 July from 3pm to Midnight Wind Rose ........................................................................ 70 Figure 5-11 August from Midnight to 7am Wind Rose .................................................................... 71 Figure 5-12 August from 2pm to Midnight Wind Rose.................................................................... 72 Figure 5-13 September from Midnight to 7am Wind Rose............................................................... 73 Figure 5-14 September from 2pm to Midnight Wind Rose .............................................................. 74 Figure 5-15 October Wind Rose ..................................................................................................... 75 Figure 5-16 November Wind Rose.................................................................................................. 76 Figure 5-17 December Wind Rose .................................................................................................. 77 Figure 5-18 Hours to Block Natural Ventilation in Al-Ain .............................................................. 78 Figure 5-19 January Wind Rose...................................................................................................... 79 Figure 5-20 February Wind Rose .................................................................................................... 80 Figure 5-21 March Wind Rose........................................................................................................ 81 Figure 5-22 April Wind Rose.......................................................................................................... 82 Figure 5-23 May from Midnight to 8am Wind Rose ........................................................................ 83 Figure 5-24 May from 3pm to Midnight Wind Rose........................................................................ 84 Figure 5-25 June from Midnight to 7am Wind Rose ........................................................................ 85 Figure 5-26 June from 5pm to Midnight Wind Rose........................................................................ 86 Figure 5-27 July from Midnight to 7pm Wind Rose ........................................................................ 87 Figure 5-28 July from 5pm to Midnight Wind Rose ........................................................................ 88 Figure 5-29 August from Midnight to 7am Wind Rose .................................................................... 89 Figure 5-30 August from 5pm to Midnight Wind Rose.................................................................... 90 Figure 5-31 September from Midnight to 7am Wind Rose............................................................... 91 Figure 5-32 September from 4pm to Midnight Wind Rose .............................................................. 92 Figure 5-33 October Wind Rose ..................................................................................................... 93 Figure 5-34 November Wind Rose.................................................................................................. 94 Figure 5-35 December Wind Rose .................................................................................................. 95 Figure 5-36 Helium Bubble Generator ............................................................................................ 96 Figure 5-37 Side and Top View of the Model.................................................................................. 97 Figure 5-38 1/3 Wind Catcher, Top View, Section and Front View ................................................. 98 Figure 5-39 2/3 Wind Catcher, Top View, Section and Front View ................................................. 99 Figure 5-40 Full Length Wind Catcher, Top View, Section and Front View .................................. 100 Figure 5-41 Leeward Elevation with different Apertures ............................................................... 101 Figure 5-42 General Setup of the Experiments .............................................................................. 102 Figure 6-1 Model Position in respect to the Wind Catcher ............................................................. 103 Figure 6-2 1/3 Wind Catcher Front Axonometric View ................................................................. 104

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Figure 6-3 Case 0 Back Axonometric View .................................................................................. 104 Figure 6-4 Six Frames Combined ................................................................................................. 105 Figure 6-5 Four Frames Combined ............................................................................................... 105 Figure 6-6 Five Frames Combined................................................................................................ 106 Figure 6-7 Two Frames Combined................................................................................................ 106 Figure 6-8 Five Frames Combined................................................................................................ 107 Figure 6-9 Case 0 3D Drawing ..................................................................................................... 107 Figure 6-10 Case 0 Side View ...................................................................................................... 108 Figure 6-11 Speed Vs Location..................................................................................................... 108 Figure 6-12 Case 1 Back Axonometric View ................................................................................ 109 Figure 6-19 Six Frames Combined................................................................................................ 109 Figure 6-27 Seven Frames Combined ........................................................................................... 110 Figure 6-33 Five Frames Combined.............................................................................................. 110 Figure 6-40 Six Frames Combined................................................................................................ 111 Figure 6-46 Five Frames Combined.............................................................................................. 111 Figure 6-47 Case 1 3D Drawing ................................................................................................... 112 Figure 6-48 Case 1 Side View ...................................................................................................... 112 Figure 6-49 Speed Vs Location..................................................................................................... 113 Figure 6-50 Case 2 Axonometric Back View ................................................................................ 114 Figure 6-58 Eight Frames Combined ............................................................................................ 114 Figure 6-63 Five Frames Combined.............................................................................................. 115 Figure 6-73 Nine Frames Combined ............................................................................................. 115 Figure 6-81 Five Frames Combined.............................................................................................. 116 Figure 6-88 Five Frames Combined.............................................................................................. 116 Figure 6-89 Case 2 3D Drawing ................................................................................................... 117 Figure 6-90 Case 2 Side View ...................................................................................................... 117 Figure 6-91 Speed Vs Location..................................................................................................... 118 Figure 6-92 Case 3 Axonometric Back View ................................................................................ 119 Figure 6-98 Five Frames Combined.............................................................................................. 119 Figure 6-101 Two Frames Combined............................................................................................ 120 Figure 6-108 Five Frames Combined............................................................................................ 120 Figure 6-114 Six Frames Combined.............................................................................................. 121 Figure 6-115 Case 3 3D Drawing.................................................................................................. 121 Figure 6-116 Case 3 Side View..................................................................................................... 122 Figure 6-117 Speed Vs Location................................................................................................... 122 Figure 6-118 Speed Vs Cases ....................................................................................................... 123 Figure 6-119 Speed Vs Cases ....................................................................................................... 124 Figure 6-120 Speed Vs Cases ....................................................................................................... 124 Figure 6-1211/2 Wind Catcher Front Axonometric View .............................................................. 125 Figure 6-122 Case 0 Back Axonometric View............................................................................... 126 Figure 6-128 Five Frames Combined............................................................................................ 126 Figure 6-134 Six Frames Combined.............................................................................................. 127 Figure 6-139 Four Frames Combined............................................................................................ 127 Figure 6-140 Case 0 3D Drawing.................................................................................................. 128 Figure 6-141 Case 0 Side View..................................................................................................... 128 Figure 6-142 Speed Vs Location................................................................................................... 129 Figure 6-143 Case 1 Axonometric Back View............................................................................... 130 Figure 6-150 Seven Frames Combined ......................................................................................... 130 Figure 6-159 Eight Frames Combined........................................................................................... 131 Figure 6-164 Bubble Speed 0.95 m/s ............................................................................................ 131 Figure 6-165 The Bubble Exiting from the Bottom Opening and other Bubbles following the same Path .................................................................................................................................... 132 Figure 6-166 Some Bubbles Exit using the Bottom Opening and some Bubbles head Upwards...... 132 Figure 6-167 Bubbles headed Upward creating a Vortex ............................................................... 133

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Figure 6-168 Nine Frames Combined ........................................................................................... 133 Figure 6-173 Four Frames Combined............................................................................................ 134 Figure 6-174 Case 1 3D Drawing.................................................................................................. 134 Figure 6-175 Case 1 Side View..................................................................................................... 135 Figure 6-176 Speed Vs Location................................................................................................... 135 Figure 6-177 Case 2 Axonometric Back View............................................................................... 136 Figure 6-184 Six Frames Combined.............................................................................................. 136 Figure 6-191 Six Frames Combined.............................................................................................. 137 Figure 6-197 Five Frames Combined............................................................................................ 137 Figure 6-206 Eight Frames Combined........................................................................................... 138 Figure 6-207 Case 2 3D Drawing.................................................................................................. 138 Figure 6-208 Case 2 Side View..................................................................................................... 139 Figure 6-209 Speed Vs Location................................................................................................... 139 Figure 6-210 Case 3 Axonometric Back View............................................................................... 140 Figure 6-216 Six Frames Combined.............................................................................................. 141 Figure 6-222 Five Frames Combined............................................................................................ 141 Figure 6-228 Six Frames Combined.............................................................................................. 142 Figure 6-229 Case 3 3D Drawing.................................................................................................. 142 Figure 6-230 Case 3 Side View..................................................................................................... 143 Figure 6-231 Speed Vs Location................................................................................................... 143 Figure 6-232 Speed Vs Cases ....................................................................................................... 144 Figure 6-233 Speed Vs Cases ....................................................................................................... 144 Figure 6-234 Speed Vs Cases ....................................................................................................... 145 Figure 6-235Full Length Wind Catcher Front Axonometric View ................................................. 145 Figure 6-236 Case 0 Axonometric Back View............................................................................... 146 Figure 6-241 Five Frames Combined............................................................................................ 146 Figure 6-246 Five Frame Combined ............................................................................................. 147 Figure 6-250 Three Frame Combined ........................................................................................... 147 Figure 6-251 Case 0 3D Drawing.................................................................................................. 148 Figure 6-252 Case 0 Side View..................................................................................................... 148 Figure 6-253 Speed Vs Location................................................................................................... 149 Figure 6-254 Case 1 Axonometric Back View............................................................................... 150 Figure 6-260 Five Frame Combined ............................................................................................. 150 Figure 6-266 Five Frame Combined ............................................................................................. 151 Figure 6-271 Six Frame Combined ............................................................................................... 151 Figure 6-272 Case 1 3D Drawing.................................................................................................. 152 Figure 6-273 Case 1 Side View..................................................................................................... 152 Figure 6-274 Speed Vs Location................................................................................................... 153 Figure 6-275 Case 2 Axonometric Back View............................................................................... 153 Figure 6-281 Five Frame Combined ............................................................................................. 154 Figure 6-287 Other Bubbles taking a Different Path ...................................................................... 154 Figure 6-288 Bubbles Exiting the Model....................................................................................... 155 Figure 6-289 Seven Frame Combined........................................................................................... 155 Figure 6-294 Bubbles Grouping together to Exit ........................................................................... 156 Figure 6-295 Six Frame Combined ............................................................................................... 156 Figure 6-296 Case 2 3D Drawing.................................................................................................. 157 Figure 6-297 Case 2 Side View..................................................................................................... 157 Figure 6-298 Speed Vs Location................................................................................................... 158 Figure 6-299 Case 3 Axonometric Back View............................................................................... 158 Figure 6-306 Six Frame Combined ............................................................................................... 159 Figure 6-311 Five Frame Combined ............................................................................................. 159 Figure 6-315 Three Frame Combined ........................................................................................... 160 Figure 6-316 Case 3 3D Drawing.................................................................................................. 160 Figure 6-317 Case 3 Side View..................................................................................................... 161

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Figure 6-318 Speed Vs Location................................................................................................... 161 Figure 6-319 Speed Vs Cases ....................................................................................................... 162 Figure 6-320 Speed Vs Cases ....................................................................................................... 162 Figure 6-321 Speed Vs Cases ....................................................................................................... 163 Figure 6-322 1/3 Wind Catcher with Smaller Intake Opening........................................................ 164 Figure 6-323 Eighteen Frames Combined with Fan Speed No.1 .................................................... 164 Figure 6-324 Six Frames Combined with Fan Speed No.2............................................................. 165 Figure 6-325 Six Frames Combined with Fan Speed No.3............................................................. 165 Figure 6-326 1/3 Wind Catcher in the Middle of the Windward Façade......................................... 166 Figure 6-327 Front View .............................................................................................................. 166 Figure 6-328 3D Drawing............................................................................................................. 167 Figure 7-1 Curved Wind Catcher .................................................................................................. 170 Figure 7-2 Openings on the Opposite Wall.................................................................................... 170

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Abstract This research studies natural ventilation in a residential building using different wind catcher sizes and exhausts to maintain a comfortable environment that would reduce energy consumption in a hot arid zone. All the simulated airflow tests were performed on a 1:48 scale model of a building 14’ wide, 28’ long and 10’ high. A wind catcher with three different sizes was built and tested. All three sizes had the same section but varying lengths, which represented 1/3, 1/2 and all of the windward façade. The leeward façade was used as an exhaust in two general configurations: the first configuration used the entire façade as an outlet (10' X 14'), while the second used an opening of 4' X 14' placed at varying locations. A Helium Bubble Generator was used to investigate the air speed and pattern inside the model. The device produces neutrally buoyant bubbles filled with helium. The bubbles follow the air flow streamlines. The tests were recorded using a Digital camcorder. All the wind catcher sizes showed an acceptable air speed inside the model. The major distinction was in the plan exposure area, where it becomes narrower as smaller wind catcher is used. On the other hand, this type of wind catcher can not provide sufficient air flow for cooling the ceiling. In addition, if the same exhaust was used with different fan speeds the air pattern will remain the same.

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1 UAE 1.1 Physical features Established on 2nd of December, 1971, the United Arab Emirates is a federation of seven emirates: Abu Dhabi, Dubai, Sharjah, Ajman, Umm al-Qaiwain, Ras al-Khaimah and Fujairah. Comprising an area of 83,600 square kilometers, the country lies between latitudes 22°–26.5°N and longitudes 51°–56.5°E. It is bordered to the north by the Arabian Gulf, to the east by the Gulf of Oman and Sultanate of Oman, to the south by the Sultanate of Oman and Saudi Arabia, and to the west by Qatar and Saudi Arabia. The UAE has 700 kilometers of coastline, including 100 kilometers on the Gulf of Oman. Along the Arabian Gulf coast are offshore islands, coral reefs and salt marshes, whilst stretches of gravel plain and barren desert characterize the inland region.1

Figure 1-1 United Arab Emirates Map2

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1.2 Climatic conditions The UAE lies in the arid tropical zone extending across Asia and North Africa. Climatic conditions in the area are strongly influenced by the Indian Ocean. This explains why high temperatures in summer are always accompanied by high humidity along the coast. There are noticeable variations in climate between the coastal regions, the deserts of the interior and mountainous areas. Prevailing winds, which are influenced by the monsoons, vary between south or southeast, to west or north to northwest, depending upon the season and location. Average rainfall is low at less than 6.5 centimeters annually, more than half of which falls in December and January. 1

1.3 Housing In 1985 Government spending on housing stood at 20.1% of total government expenditure. By 1993 this had climbed to almost 30%. There has been a noticeable improvement in overall housing standards within the UAE. The Abu Dhabi Department of Social Services and Commercial Buildings had 504 buildings and villas under construction in Abu Dhabi and Al Ain in mid 1995 and was studying 417 new projects. The Department has constructed 40,000 housing units since its inception in 1976. The Department's investments rose from Dh 79 million in 1976 to Dh 11 billion in 1993. All the Municipal authorities in the UAE have provided important housing schemes and government funding has been substantial. In addition a number of

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schemes funded by personal contributions have been undertaken. Among these is the scheme for construction of 2,000 houses for UAE nationals, financed by the President Sheikh Zayed bin Sultan Al Nahyan.3

1.4 Social needs and demands One of the major UAE Government projects is the Housing Ministry's building of neighborhoods for citizens. The Ministry established the project in fulfillment of a personal order from the president of the UAE. Natural ventilation and day-lighting is neglected in the design of these houses because of two main reasons: •

The Energy (mainly electricity) is very cheap at 8.97 fils/kwh (0.02 US$) because of government support for the prices of Gas.4

•

There is modest (almost none) awareness of environmental issues.

Nearly all the new neighborhoods and houses ignored the cumulative knowledge that shaped the form and style of old houses. Old houses had a lot of respect for Natural Forces, mainly Sun and Wind, which underpinned two major traditional elements, the courtyards and cooling towers.

1.5 Environmental and cultural issues UAE is a unique case when it comes to the mix of ethnic groups living on its soil. According to CIA publications (1982), Citizens form only 19% of the population, Iranian and other Arabs 23%, South Asian 50%, other expatriates 8%. These percentages have been more or less sustained up to this year.5

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The unbalanced structure of the population, along with relaxed environmental laws, caused setbacks in two major and notably related topics:

1.5.1 Vernacular architecture styles This style is drawing its last breath, mostly for aesthetic reasons, but more importantly because of no understanding of natural forces that was the key factor to building in that style. The deterioration of Vernacular styles is due mainly to the implementation of designs from other cultures that are not suitable for climatic conditions in the UAE, which gives rise to the second topic.

1.5.2 Environmental sense and consideration More than half of the population is transient, living in the UAE for a short period of time, which makes them less interested in environmental and power savings issues. This and slack laws make it the perfect combination to produce the following for a country with only 3 million inhabitants (Based on International Energy Agency (IEA) and (EIA) International Energy Annual 1999): •

Total Energy Consumption (1999E): 1.9 Quadrillion Btu* (0.5% of world total energy consumption)

•

Energy-Related Carbon Emissions (1999E): 32.2 million Metric tons of carbon (0.5% of world total carbon emissions)

•

Per Capita Energy Consumption (1999E): 652.7 million Btu (vs. U.S. value of 355.8 million Btu)

4

•

Per Capita Carbon Emissions (1999E): 11.2 metric tons of carbon (vs. U.S. value of 5.5 metric tons of carbon)

•

Renewable Energy Consumption (1998E): 0.71 Trillion Btu* (0% increase from 1997)6

1.6 Wind and wind catchers Through recent history, generally two groups of people lived in two very different divisions in UAE. These two dominions searched for possible survival methods; one colonized in the desert area and became cattle breeders (Bedouin), forcing them to move from an oasis to another looking for plants and water for them and their animals. The other group became fishermen and the sea became their major source of life, either by going into long fishing trips or traveling to other countries for trading purposes. Understanding the wind was a major survival tool for Bedouin as it was for fishermen. The Bedouin predicted the rare seasons of rain that was very much dictated by wind movement. They were also warned by the warm winds that dried their bodies of valuable and scarce water. The direction and time of wind was a matter of life and death for the fishermen and their starving families also. This very careful trial-and- error process gave a jump-start in building wind towers and orienting them in the right direction.

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REFERENCES:

1 United Arab Emirate. The official site for the Ministry of Information and Culture in the UAE. The Country. 29 Jan. 2002 . 2 The University of Texas library Online. United Arab Emirates Map. 15 Jan. 2002 3 The Emirates Center For Strategic Studies and Research. Housing. 5 Jan. 2002 . 4 United Arab Emirate. The official site for the Ministry of Information and Culture in the UAE. CMS Energy Signs Taweelah A2 Deal 3 Jun. 2002 . 5 Central Intelligence Agency. United Arab Emirates. 20 Dec. 2001 . 6 Energy Information Administiration. United Arab Emirates. 22 Dec. 2001 .

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2 Climatic Data and Analysis 2.1 Writing TMY2 Data Format 2.1.1 What is TMY2 Data The TMY2s (Typical Meteorological Year) are data sets of hourly values of solar radiation and meteorological elements for a 1-year period. Their intended use is for computer simulations of solar energy conversion systems and building systems to facilitate performance comparisons of different system types, configurations, and locations in the United States and its territories. Because they represent typical rather than extreme conditions, they are not suited for designing systems to meet the worstcase conditions occurring at a location. Yet, it can be a good tool for architects to understand the weather they are trying to design for.1

2.1.2 TMY2 Data Format CLIMATE CONSULTANT is a computer program. It only reads weather data if it is in the following format: MMDDHHBBBBBHHHHHTTTTKKKKWWWWCCZZZ MM

Month 01 to 12

DD

Day 01 to 31

HH

Hour 01 to 24

BBBBB

Direct Beam Solar Radiation in kilojoules per square meter

HHHHH Total Horizontal Solar Radiation in kJ/sq m TTTT

Dry-bulb outdoor air temperature in degrees C times 10

7

KKKK

Dew point outdoor air temperature in degrees C times 10

WWWW Wind speed in meters per second times 10 CC

Sky cover in tenths (00 to 10)

ZZZ

Wind direction in degrees from north

Every line represents an hour, which will result in an 8760 lines of data that represent the TMY2 year.

2.1.3 Calculating the Missing Data The weather data I obtained from the United Arab Emirates was missing some major components such as: •

Direct Beam Solar Radiation

•

Total Horizontal Solar Radiation

•

Dew point outdoor air temperature

2.1.3.1 Direct Beam Solar Radiation Direct radiation is rays that we get directly from the sun and is capable of casting shadow.2 The sun's radiation for a day is represented by a sine curve. The area under the curve is the sum of the direct beam radiation of the day which is the radiation data format I got from the UAE. In order to change it to an hourly data I did the following calculation: A = M t1 ∫

t2

(sin π t / ∆ t) dt3

Where, A is Area under the curve M is the Maximum amplitude

8

t1 ،t2 is time of start and end of radiation. t is the time in hours with t = 0 representing midnight. ∆ t is the overall time of sun-shine (t2-t1). From this equation and knowing the area under the curve (the sum of the direct beam radiation of the day) we can obtain M (Maximum amplitude) M = A / t1 ∫ t2 (sin π t / ∆ t) dt =A*π/N*2 Where, N is the number of sun exposure hours, which of course differ each day of the year. Therefore, I considered the 21st as a typical day for the month. After obtaining the Maximum amplitude we can get the amplitude at any given hour using the following equation: Y = M sin (π t / ∆ t) Y is the amplitude at any given hour. t is the time in hours with t = 0 representing midnight. ∆ t is the overall time of the sun-shine (t2-t1). 2.1.3.2 Total Horizontal (diffused) Solar Radiation As solar radiation passes through the earth's atmosphere, part of the radiation is intercepted by dust particles and dry air while other parts may be absorbed by the ozone on the upper levels and by water vapor in the surface near the ground. The result would be a scattered radiation in all directions4, which is most noticed in a cloudy day, where the clouds block all the direct beams of the sun and there is no obvious or well-defined shadow.

9

We can obtain the total horizontal radiation from direct radiation using the following equation: Global horizontal Gh = Direct normal x Cos (zenith angle) + scattered radiation Also Gh= Direct normal x Sin (horizontal angle) + scattered radiation 2.1.3.3 Dew point outdoor air temperature Dewpoint calculated from Dry Bulb Temperature and Relative Humidity B = (ln (RH / 100) + ((17.27 * T) / (237.3 + T))) / 17.27 D = (237.3 * B) / (1 – B) Where: T = Air Temperature (Dry Bulb) in Centigrade (C) degrees RH = Relative Humidity in percent(%) B = intermediate value (no units) D = Dewpoint in Centigrade (C) degrees5

2.2 SCRAM 2.2.1 What is SCRAM Data The SCRAM (MET144) format is essentially a reduced version of the traditional CD-144 format. CD-144 refers to the "Card Deck 144 format". The SCRAM (MET 144) format consists of fewer weather variables. The file is composed of one record per hour, with all weather elements reported in a 28-column card image.6

10

2.2.2 SCRAM Data Format 1-5

Surface Station Number

6-7

Year

8-9

Month

10-11

Day

12-13

Hour

14-16

Ceiling Height (Hundreds of Feet)

17-18

Wind Direction (Tens of Degrees)

19-21

Wind Speed (Knots)

22-24

Dry Bulb Temperature (Degrees Fahrenheit)

25-26

Total Cloud Cover

27-28

Opaque Cloud Cover Figure 2-1 Scram Data Format

5

Surface Station Number - The WBAN number identifying the NWS surface observation station for which hourly meteorological data are input to the met processing program .

Year, Month and Day of Record - Identifies the year, month and day during which the meteorological data were observed. Only the last two digits of the year are reported .

11

Hour - Identifies the hour of the meteorological data observation. Hour is based on the 24-hour clock and is recorded as 00 through 23. Times are Local Standard Time (LST) and are adjusted in PCRAMMET to the 01 - 24 clock in which hour 24 is the same as hour 00 of the next day .

Ceiling Height - The height of the cloud base above local terrain and is coded in hundreds of feet .

Wind Direction - The direction from which the wind is blowing, based on the 36 point compass, e.g. 09=East=18 ،South, 27=West, 36=North, 00=Calm .

Wind Speed - The wind speed measured in knots (00=Calm) .

Dry Bulb Temperature - The ambient temperature measured in whole degrees Fahrenheit .

Cloud Cover - There are two cloud cover parameters, opaque cloud cover and total cloud cover in the SCRAM meteorological data files.5

12

2.3 Climatic Data Charts 2.3.1 City of Abu Dhabi 2.3.1.1 Temperature Range The temperature range for Abu Dhabi can be plotted using Climate Consultant. (See Figures 2-2 through 2-10) In summary, the year can be classified into three main groups: •

Group 1: The hottest months, May, June, July, August and September where the temperature mean value exceeded the comfort zone range.

•

Group 2: The Moderate months from November through March that showed moderate temperatures plotted around the human comfort zone.

•

Group 3: April and October, which were the transmission months to and from the hot 5 months mentioned in group 1.

Figure 2-2 Abu Dhabi 1997 Temperature Range

13

2.3.1.2 Temperature + Relative Humidity A typical day for Abu Dhabi with dry-bulb temperature and relative humidity level can be plotted using Climate Consultant. (See figures 2-11 through 2-19) The same three temperature groups (discussed in section 2.3.1.1) can be noticed here also with a high humidity level all through the year with a RH difference that can reach 40% sometimes between day and night.

Figure 2-3 Abu Dhabi 1997 Temperature + Relative Humidity

14

2.3.1.3 Wind Velocity Range The wind velocity range for Abu Dhabi can be plotted using Climate Consultant. (See Figures 2-20 through 2-28) The wind low and high average velocities for all the years showed a very similar pattern that ranged from 2.5 to 15 mph. In addition, there was an irregular pattern of the record high speeds which is most probably caused by occasional storms.

Figure 2-4 Abu Dhabi 1997 Wind Velocity Range

15

2.3.1.4 Bioclimatic Timetable The bioclimatic timetable for Abu Dhabi can be plotted using Climate Consultant. (See Figures 2-29 through 2-37) According to the following charts, there are three categories of months: •

1st Category from October 15 through March 15: The day and night is in the comfortable temperature range.

•

2nd Category from March 15 through June 15 and from September 15 through November 15: The nigh only is in the comfortable temperature range.

•

3rd Category from June 15 through September 15: The overheated period lasts 24 hour.

Figure 2-5 Abu Dhabi 1997 Bioclimatic Timetable

16

2.3.1.5 Psychrometric Chart The Psychrometric chart for Abu Dhabi can be plotted using Climate Consultant. (See Figures 2-38 through 2-46) There is almost a 20'F difference in dry-bulb temperature between day and night. In summer, the change in absolute humidity values was greater than the other seasons while in winter only a change in relative humidity appeared with a constant absolute humidity value. The charts suggest that the effective strategy would be ventilation (zone 6) coupled with high mass and night ventilation (zone 7&8), all under sun shading (zone 5). Furthermore, there are some months (like July and August) that are too hot and humid for such strategies to work successfully

Figure 2-6 Abu Dhabi 1997 Psychrometric Chart

17

2.3.2 City of Al-Ain 2.3.2.1 Temperature Range The temperature range for Al-Ain can be plotted using Climate Consultant. (See Figures 2-47 through 2-52) In summary, the year can be classified into three main groups: •

Group 1: The hottest months, May, June, July, August and September where the temperature mean value exceeded the comfort zone range.

•

Group 2: The Moderate months from November through March that showed moderate temperatures plotted around the human comfort zone.

•

Group 3: April and October, which were the transmission months to and from the hot 5 months mentioned in group 1.

Figure 2-7 Al-Ain 1997 Temperature Range

18

2.3.2.2 Temperature + Relative Humidity A typical day for Al-Ain with dry-bulb temperature and relative humidity level can be plotted using Climate Consultant. (See figures 2-52 through 2-56) The same three temperature groups (discussed in section 2.3.2.1) can be noticed here also with a high humidity level (sometimes 80%) from November through May. On the contrary, the relative humidity percentages drop to 20% in April through October during the night and about 45% during the day.

Figure 2-8 Al-Ain 1997 Temperature + Humidity

19

2.3.2.3 Wind Velocity Range The wind velocity range for Al-Ain can be plotted using Climate Consultant. (See Figures 2-57 through 2-61) The wind low and high average velocities for all the years showed a very similar pattern that ranged from 2.5 to 18 mph. In addition, there was an irregular pattern of the record high speeds which is most probably caused by storms that is more frequently appearing in the city of Al-Ain.

Figure 2-9 Al-Ain 1997 Wind Velocity Range

20

2.3.2.4 Bioclimatic Timetable The bioclimatic timetable for Al-Ain can be plotted using Climate Consultant. (See Figures 2-62 through 2-66) According to the following charts, there are three categories of months: •

1st Category from October 15 through March 15: The day and night is in the comfortable temperature range.

•

2nd Category from March 15 through June 15 and from September 15 through November 15: The nigh only is in the comfortable temperature range.

•

3rd Category from June 15 through September 15: The overheated period lasts 24 hour.

Figure 2-10 Al-Ain 1997 Bioclimatic Timetable

21

2.3.2.5 Psychrometric Chart The Psychrometric chart for Al-Ain can be plotted using Climate Consultant. (See Figures 2-67 through 2-71) There is almost a 25'F difference in dry-bulb temperature between day and night. In summer, the relative humidity values decreases although the absolute humidity value increases. The charts suggest that the effective strategy would be ventilation (zone 6) coupled with high mass and night ventilation (zone 7&8), all under sun shading (zone 5). Moreover, there are some days that are too hot and dry for such strategies to work successfully.

Figure 2-11 Al-Ain 1997 Psychrometric Chart

22

2.4 Wind Roses 2.4.1 City of Abu Dhabi The wind rose can be plotted using WR Plot. (See Figures 2-72 through 2-80) The prevailing wind for Abu Dhabi is northwest. However, there are some years that had two prevailing wind direction, northeast, south and southeast. WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

W ind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.88 m/s

2.11%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jan 1 - Dec 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 2-12 Abu Dhabi 1997 Wind Rose

23

WIND ROSE PLOT

Station # 11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.16 m/s

2.17%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1991 1992 1993 1994 1995 1999 1998 1997 Jan 1 - Dec 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WR PLOT View 3.5 by Lakes Environmental Software - www .lak es -environmental.com

Figure 2-13 Abu Dhabi 1991, 92, 93, 94, 95, 97, 98 and 99 Wind Rose

24

2.4.2 City of Al-Ain The wind rose can be plotted using WR Plot. (See Figures 2-80 through 2-86) The prevailing wind for Al-Ain is northwest. However, there are some years that had two prevailing wind direction, northeast, south and southeast.

WIND ROSE PLOT

Station # 22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.02 m/s

1.22%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jan 1 - Dec 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRP LOT View 3.5 by Lakes Environmental Software - www .lakes -environmental.com

Figure 2-14 Al-Ain 1997 Wind Rose

25

WIND ROSE PLOT

Station # 22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.11 m/s

4.10%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1995 1996 1997 1998 1999 Jan 1 - Dec 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

W RPLOT View 3.5 by Lakes Environm ental Software - www .lakes -environm ental.com

Figure 2-15 Al-Ain 1995, 96, 97, 98 and 99 Wind Rose

26

REFERENCES:

1 The Renewable Resource Data Center . TMY2 User's Manual. 5 Mar. 2002 2 Kreider, Jan F, and Kreith, Frank. Solar Heating and Cooling: Engineering, Practical Design, and Economics. Washington, D.C.: Hemisphere, 1975, pp 5. 3 Larson, Roland E., and Hostetler, Robert P. Calculus with analytical geometry. Toronto: Heath and Company, 1986, pp 278. 4 Threlkeld, James L., Thermal Environmental Engineering, New Jersey: Englewood Cliffs, 1970, pp 294. 5The University of Arizona. Dewpoint Formulas. 2 Jan. 2002 6 The Meteorological Resource Center. Met Data Guide. 4 Jan. 2002.

27

3 Wind and Ventilation 3.1 Wind Characteristics Wind is a key design factor for Architects. It can increase the occupant satisfaction level in a space and make them thermally comfortable. Therefore, understanding the nature of wind is crucial if the building is to be environmentally useful.

3.1.1 Wind near the Ground Wind is a very irregular phenomenon. In the lower layer of the atmosphere, various obstacles and objects as well as landforms and vegetation cause turbulence. Turbulence slow the speed of wind in general where obstacles change wind patterns inducing increasing velocity in some areas, while protects other areas.1

Figure 3-1 Typical Record of the Wind Velocity near the Ground 1

28

Figure 3-2 Wind Patterns (a) Constricted by Topography. (b) Above and Below Tall Buildings. (c) Around large Buildings.2

29

3.1.2 Wind in an Urban Environment The friction caused by numerous obstacles that increase the roughness of the ground affects the wind velocity. In an urban environment, a reduction of 20% to 30% in the average wind speed and an increase of 50% to 100% in the turbulence intensity are noticed when moving from the countryside in addition to the more frequent weak winds.3

Figure 3-3 Effect of Terrain on Wind Velocity Profiles4

3.1.3 Wind Flow Wind is a direct result of low and high pressure. The sun radiation heats the equatorial zone which raises the air causing low pressure that invites wind from other areas with higher pressure. Similarly, flow in a building is mainly introduced by the different pressures in and around the building. Wind flow is produced when an inlet is positioned in an area of positive pressures and outlets are placed in areas of negative pressures. The pressure differences between the inlet and outlets induce the air to move through a building.5

30

Figure 3-4 Wind Pressure around Building 6

Figure 3-5 Wind Pressure Drives Cross Ventilation5

3.2 Natural Ventilation for Thermal Comfort Natural ventilation is the movement of air into and out of a space through openings intentionally provided for this purpose or it is simply the use of outside cool breezes when possible. The main purpose of natural ventilation is to provide fresh air and a cooling effect either by replacing the hot interior air or by the motion itself.7

31

3.2.1 Removal of Excess Heat Heat is mainly gained in a space by solar radiation and conduction through the building envelope; it is also generated in the space by different means such as people, lights, mechanical and electrical systems. As the air temperature increases the air rises to the top of the space and increases the temperature of the ceiling, which radiates heat into the space. The removal of this excess heat can decrease the overall cooling load of the space and move the temperature more towards the comfort zone.

3.2.2 Cooling Effect over the Human Body When the body core temperature increases the hypothalamus calls for changes in our blood distribution system. Because blood carries heat, the blood flow toward the skin increases which will result in an increase of the sweat glands and eventually evaporation. When the air molecules pass by the skin it absorbs heat and will decrease the temperature of the body. Once air and surface temperature approach the human body temperature (37 'C or 98.6 'F) evaporation becomes more important and most effective.8

32

Figure 3-6 Heat Generated and lost (approximate) by a person at rest (rh fixed at 45%)8

3.2.3 Cooling the Structure The air movement over the different surfaces of the interior decreases the heat gain through convection and long-wave radiation. The faster the air velocity over the surface, the cooler it becomes. This happens mainly in a strategy termed nocturnal ventilation or night time flushing, when the day time ventilation is not possible due to the high day time temperatures of the region. Nocturnal ventilation is used with high mass building envelope. The high mass envelope basically stores the heat during the day-time and delays the heat transfer to the interiors. When the night falls and the wall becomes ready to transfer heat into the space, wind is driven into the space in order to carry the heat outside the building. This process decreases the surface temperature of the interior and makes the space ready for the next day.

33

Figure 3-7 Isocomfort Curve9

Figure 3-8 Isocomfort Curve Parametrized as a Function of the air velocity. 9

Figures 3-7 and 3-8 show Isocomfort graphs with some of the possible combinations achieved with a ventilation strategy. All the points appearing on the Isocomfort curve has the same comfort conditions9. Furthermore, the wind becomes less effective as the temperature reaches 33'C, which means that faster wind velocity is needed with higher temperatures.

34

REFERENCES:

1 Allard, Francis. Natural Ventilation in Buildings: A design handbook. London: James & James, 1998, pp 11. 2 Bradshaw, Vaughn. Building Control Systems. New York: John Wiley & Sons. 1993, pp 71. 3 Allard, Francis. Natural Ventilation in Buildings: A design handbook. London: James & James, 1998, pp 22. 4 Brown, G. Z., and Dekay, Mark. Sun, Wind and light: Architectural Design Strategies. New York: John Wiley & Sons. 2001, pp17 5 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 17 6 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6 pp 16 7 Bradshaw, Vaughn. Building Control Systems. New York: John Wiley & Sons. 1993, pp 246 8 Stein, Benjamin, and Reynolds, John S. Mechanical and Electrical Equipment for Building. New York: John Wiley & Sons, 2000, pp 39 9 Allard, Francis. Natural Ventilation in Buildings: A design handbook. London: James & James, 1998, pp 45

35

4 Historical Precedents 4.1 Hot and Arid Zones Before the industrial revolution, residents of hot arid zones were encouraged to figure out natural ways to cool their houses and keep them as comfortable as possible during hot days. In the Middle East, different approaches had been attempted by dwellers according to different cultural and climate conditions (besides material availability).

Figure 4-1 Wind Tower in the Middle East1

36

Figure 4-2 Catching Efficiency for Different Wind Catcher Designs2

37

4.1.1 The Malqaf This wind catcher device is widely used in Egypt. It is mainly a scoop rising above the building to collect stronger and cooler prevailing wind. Wind is predominantly driven into large spaces below the Malqaf and then forced out through openings in the top of a central hall. In addition to the cooling effect over the body as a result of wind flow, it also removes excess heat that is generated from occupants. The disadvantages of the Malqaf are that it can only catch the wind from one direction and it would only have an effect over limited rooms when forced through the top of the central hall.

Figure 4-3 Roof plan of the Fu'ad Riyad house in Cairo, showing the malqaf with sectional details3

38

Figure 4-4 Section of the Fu'ad Riyad house showing the malqaf4.

Figure 4-5 Section of a modern villa designed for Saudi Arabia showing the use of malqaf5

39

Figure 4-6 Section through the hall of Muhib Ad-Din Ash-Shaf'i Al-Muwaqqi showing the malqaf and central location of the hall6

Figure 4-7 Arrows indicate the direction of airflow; arrow length corresponds to airspeed. The measurements where made on 2 April 1973 by scholars from the Architectural Association School of Architecture in London. All wind and airspeeds are given in meters per second.7

40

In dryer conditions, Architect Hassan Fathy suggested wetted baffles which can help reduce the air temperature by evaporation. Air is mainly directed over a fountain or a basin of still water, to increase air humidity. He also mentioned that baffles can reduce air flow which can be overcome by increasing the size of the Malqaf and suspending the wetted matting in its interior.8

Figure 4-8 Malqaf with wetted baffles and a wind-escape. Design by Hassan Fathy 9

41

Figure 4-9 Details of the malqaf with wetted baffles10

42

4.1.2 The Badgir (Barjeel) This type of wind catcher was developed in Iran around 900 AD11. It is principally a shaft that rises 3 meters above the building with two partitions placed diagonally with openings on all four sides.

Figure 4-10 Barjeel details12

The Badgir (Barjeel) would work both as an intake and exhaust at the same time. Wind is sucked out by the negative pressure that is created in the leeward side of the tower. When there is no air movement in the region, stack effect would remove hot air that is generated inside the space below the Barjeel. The Barjeel is 43

mostly positioned in the corner of the building and directly over the place where people either gather or sleep. The room or space that is ventilated by the Barjeel is always being situated near the courtyard of the house and uses it as a major exhaust. The air that is channeled through the barjeel is transferred to other rooms through wooden doors or openings on the top of the room. These wooden doors will be closed if the wind reached uncomfortable velocities. (Figure 4-11 and 4-12)

Figure 4-11 Mohamed Sharif house, first floor13

44

Figure 4-12 Wooden doors and opening14

Figure 4-13 Interior view of the Wooden doors and openings15

45

Figure 4-14 Shaikh Saeed house (North Elevation)16

Figure 4-15 Shaikh Saeed house (East Elevation)

Figure 4-16 Shaikh Saeed house (Courtyard view)

46

Figure 4-17 Traditional Square Barjeel

Figure 4-18 Unusual cylindrical Barjeel

47

Figure 4-19 The Barjeel Closed to Block Undesirable Wind17

Figure 4-20 A fort in the City of Ajman uses the Barjeel for Natural Ventilation18

48

4.1.3 Wind Scoops In high density cities multi-storey buildings are likely to appear which decreases the wind velocity near the ground. Windows wouldn't be efficient to provide the necessary air flow for cooling the inhabitants. The only way around this problem is to reach for the higher wind velocities by rising above the city skyline. That is exactly what happened in Hyderabad in Pakistan, where the wind scoops peak over the roofs of the buildings direct air into spaces below multi-storey houses. Subsequently, the windows act as an exhaust and guide the wind to the exterior.

Figure 4-21 Wind scoop, Hyderabad, Sind, Pakistan19

Figure 4-22 Wind Scoops facing the prevailing wind20

49

Figure 4-23 Scoops in Pakistan at different levels21

50

4.2 Design Examples of Wind Catchers 4.2.1 Qatar University in Doha The university was built in the Arabian Gulf area, for this reason the design came in favor of natural ventilation. The wind catcher that rose above the octagonal shaped building was the dominating view from every side of the university. Besides the astonishing view from the courtyards that surrounds these beautiful traditional elements, the Barjeels give the impression of being guards protecting the adjacent spaces from harsh environment.

Figure 4-24 A picture from the roof22

Figure 4-25 Section/Elevation of Humanities Faculty Modules23

51

Figure 4-26 An External Picture of the Wind Catchers24

Figure 4-27 A picture from the courtyard25

52

Figure 4-28 Qatar University (Phase 1), Kamal El-Kafrawi26

Figure 4-29 Ariel View of Qatar University27

53

4.2.2 Concept drawings The effectiveness of the wind tower and wind catcher depends first and foremost on how much the device can make use of pressure differences created in and around the building. Furthermore, the microclimate of the region has to be examined with awareness of other factors that can influence the direction in which the wind blows from. For example, sites near the sea are subject to reverse wind direction from day to night as a result of differences in thermal inertia between land and water. Similarly, sites located in mountain areas would have the same changing direction of prevailing wind.

Figure 4-30 From above: Wind tower; monodirectional wind tower and scoop; multidirectional wind tower and scoop; combined wind tower and scoop28

54

Figure 4-31 Day and Night reverse wind directions29

55

Therefore, designers suggested a new breed of wind scoops that can face the wind and maximize ventilation without any need of a mechanical system, yet, the new scoop needs a lot of structural balance low friction bearings and a good centre of gravity in order to rotate easily with weak low velocity wind.30

Figure 4-32 Concept Drawings for rotating wind scoops31

56

REFERENCES:

1 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp25 2 Brown, G. Z., and Dekay, Mark. Sun, Wind and light: Architectural Design Strategies. New York: John Wiley & Sons. 2001, pp 189 3 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 131 4 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 130 5 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 128 6 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 116 7 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 117 8 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp59 9 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 124 10 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 125 11 Allard, Francis. Natural Ventilation in Buildings: A design handbook. London: James & James, 1998, pp237

57

12 UAE. Dubai Municipality: the Historical Building Section. Elements of Traditional Architecture in Dubai. Dubai: Dubai Municipality, 2000, pp C-(1). 13 UAE. Dubai Municipality: the Historical Building Section. Elements of Traditional Architecture in Dubai. Dubai: Dubai Municipality, 2000, pp A-(8-1). 14 Forman, Werner, Phoenix Rising: The United Arab Emirates Past, present and future. London: The Harvill. 1996, pp 183. 15 Prakash Subbarao, Sheikh Saeed Al Maktoum House. 12 Dec. 2001 16 UAE. Dubai Municipality: the Historical Building Section. Elements of Traditional Architecture in Dubai. Dubai: Dubai Municipality, 2000, pp B-(1-1). 17 Forman, Werner, Phoenix Rising: The United Arab Emirates Past, Present and Future. London: The Harvill. 1996, pp 13. 18 Vine, Peter. UAE in Focus: A photographic history of the United Arab Emirates. London: Trident. 1998, pp 134. 19 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 26 20 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 27 21 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986, pp 114 22 Roger Williams University. Qatar University. 2 May. 2002 23 Brown, G. Z., and Dekay, Mark. Sun, Wind and light: Architectural Design Strategies. New York: John Wiley & Sons. 2001, pp 188. 24 Roger Williams University. Qatar University. 2 May. 2002 25 Roger Williams University. Qatar University. 2 May. 2002

58

26 Brown, G. Z., and Dekay, Mark. Sun, Wind and light: Architectural Design Strategies. New York: John Wiley & Sons. 2001, pp 188 27 Roger Williams University. Qatar University. 2 May. 2002 28 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 30 29 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 14 30 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 34 31 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6, pp 35

59

5 Setting the Variables 5.1 Hypothesis Wind catchers can be adapted to provide comfort without overly constraining either development or design possibilities for new housing in hot-arid climates.

5.2 When to use Natural Ventilation As discussed in section 3.2.2, when the air temperature approaches human body temperature (37 'C or 98.6 'F), all the cooling effect is credited to evaporation. Furthermore, heat loss via convection and radiation decreases to a minimum and eventually becomes nil. In addition, if the temperature rises above 37 'C and the evaporation rate decreases, the human body will start gaining heat via convection from warmer air moving around the body. When air moves over a wet skin, it will without doubt give a cooling sensation even if the temperature was amazingly high. On the other hand, there was no scientific way to prove it. Accordingly, the human body temperature was used as a reference point for ventilation and the assumption that natural ventilation would be effective only when temperatures are lower than 37 'C was made for this thesis. Above that temperature, the human body could gain heat from wind. Year 1997 was chosen as a typical year for both cities to find the optimum orientation for the wind catcher; an orientation that will collect wind at the right times (below 37'C) in order to have a positive effect over the comfort zone.

60

5.2.1 City of Abu Dhabi

Figure 5-1 Hours to Block Natural Ventilation in Abu Dhabi

Hours to block wind would be as follows: June from 7:00 to 15:00 July from 7:00 to 15:00 August from 7:00 to 14:00 September from 7:00 to 14:00

61

The prevailing wind for Abu Dhabi is northwest which is also the case in the afternoon period; however, the wind had almost a reverse direction from midnight through the early morning hours where the wind blows from the south, southeast and southwest. WIND ROSE PLOT

Station # 11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.64 m/s

1.48%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jan 1 - Jan 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-2 January Wind Rose

62

WIND ROSE PLOT

Station #11111 - ,

NORTH

30%

24%

18%

12%

6%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.12 m/s

1.04%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Feb 1 - Feb 29 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-3 February Wind Rose

63

WIND ROSE PLOT

Station #11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.24 m/s

1.21%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Mar 1 - Mar 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-4 March Wind Rose

64

WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.00 m/s

1.53%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Apr 1 - Apr 30 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-5 April Wind Rose

65

WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.77 m/s

0.67%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 May 1 - May 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-6 May Wind Rose

66

WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.52 m/s

2.50%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jun 1 - Jun 30 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-7 June from Midnight to 7am Wind Rose

67

WIND ROSE PLOT

Station #11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.61 m/s

1.85%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jun 1 - Jun 30 3 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-8 June from 15pm until Midnight Wind Rose

68

WIND ROSE PLOT

Station #11111 - ,

NORTH

25%

20%

15%

10%

5%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.61 m/s

2.02%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jul 1 - Jul 31 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-9 July from Midnight to 7am Wind Rose

69

WIND ROSE PLOT

Station #11111 - ,

NORTH

25%

20%

15%

10%

5%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.65 m/s

2.87%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jul 1 - Jul 31 3 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-10 July from 3pm to Midnight Wind Rose

70

WIND ROSE PLOT

Station #11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.34 m/s

3.63%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Aug 1 - Aug 31 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-11 August from Midnight to 7am Wind Rose

71

WIND ROSE PLOT

Station #11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.83 m/s

2.26%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Aug 1 - Aug 31 2 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-12 August from 2pm to Midnight Wind Rose

72

WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.39 m/s

5.83%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Sep 1 - Sep 30 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-13 September from Midnight to 7am Wind Rose

73

WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.60 m/s

8.33%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Sep 1 - Sep 30 2 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-14 September from 2pm to Midnight Wind Rose

74

WIND ROSE PLOT

Station #11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.78 m/s

4.57%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Oct 1 - Oct 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-15 October Wind Rose

75

WIND ROSE PLOT

Station #11111 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.64 m/s

1.94%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Nov 1 - Nov 30 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-16 November Wind Rose

76

WIND ROSE PLOT

Station #11111 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.63 m/s

2.02%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Dec 1 - Dec 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-17 December Wind Rose

77

5.2.2 City of Al-Ain

Figure 5-18 Hours to Block Natural Ventilation in Al-Ain

Hours to block wind would be as follows: May from 8:00 to 15:00 June from 7:00 to 17:00 July from 7:00 to 17:00 August from 7:00 to 17:00 September from 7:00 to 14:00

78

The prevailing wind for Al-Ain is northwest which is also the case in the afternoon period; however, the wind had almost a reverse direction from midnight through the early morning hours where the wind blows from the south, southeast and southwest and occasionally east.

WIND ROSE PLOT

Station # 22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.82 m/s

0.81%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jan 1 - Jan 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRP LOT View 3.5 by Lakes Environmental Software - www .lakes -environmental.com

Figure 5-19 January Wind Rose

79

WIND ROSE PLOT

Station #22222 - ,

NORTH

25%

20%

15%

10%

5%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.14 m/s

0.15%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Feb 1 - Feb 29 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-20 February Wind Rose

80

WIND ROSE PLOT

Station #22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.30 m/s

1.61%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Mar 1 - Mar 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-21 March Wind Rose

81

WIND ROSE PLOT

Station #22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.19 m/s

0.56%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Apr 1 - Apr 30 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-22 April Wind Rose

82

WIND ROSE PLOT

Station #22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.91 m/s

1.43%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 May 1 - May 31 Midnight - 8 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes -environmental.com

Figure 5-23 May from Midnight to 8am Wind Rose

83

WIND ROSE PLOT

Station #22222 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.62 m/s

2.15%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 May 1 - May 31 3 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-24 May from 3pm to Midnight Wind Rose

84

WIND ROSE PLOT

Station #22222 - ,

NORTH

25%

20%

15%

10%

5%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.14 m/s

3.33%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jun 1 - Jun 30 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-25 June from Midnight to 7am Wind Rose

85

WIND ROSE PLOT

Station #22222 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.65 m/s

1.90%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jun 1 - Jun 30 5 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-26 June from 5pm to Midnight Wind Rose

86

WIND ROSE PLOT

Station #22222 - ,

NORTH

30%

24%

18%

12%

6%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.71 m/s

2.02%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jul 1 - Jul 31 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-27 July from Midnight to 7pm Wind Rose

87

WIND ROSE PLOT

Station #22222 - ,

NORTH

25%

20%

15%

10%

5%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.43 m/s

3.69%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Jul 1 - Jul 31 5 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-28 July from 5pm to Midnight Wind Rose

88

WIND ROSE PLOT

Station #22222 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.59 m/s

1.61%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Aug 1 - Aug 31 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-29 August from Midnight to 7am Wind Rose

89

WIND ROSE PLOT

Station #22222 - ,

NORTH

25%

20%

15%

10%

5%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.67 m/s

4.15%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Aug 1 - Aug 31 5 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-30 August from 5pm to Midnight Wind Rose

90

WIND ROSE PLOT

Station #22222 - ,

NORTH

30%

24%

18%

12%

6%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.07 m/s

1.67%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Sep 1 - Sep 30 Midnight - 7 AM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-31 September from Midnight to 7am Wind Rose

91

WIND ROSE PLOT

Station #22222 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.64 m/s

1.25%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Sep 1 - Sep 30 4 PM - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-32 September from 4pm to Midnight Wind Rose

92

WIND ROSE PLOT

Station #22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

2.04 m/s

0.40%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Oct 1 - Oct 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-33 October Wind Rose

93

WIND ROSE PLOT

Station #22222 - ,

NORTH

15%

12%

9%

6%

3%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.88 m/s

1.53%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Nov 1 - Nov 30 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-34 November Wind Rose

94

WIND ROSE PLOT

Station #22222 - ,

NORTH

20%

16%

12%

8%

4%

WEST

EAST

SOUTH

Wind Speed (m/s)

>

.

DISPLAY

UNIT

Wind Speed

m/s

- .

AVG. WIND SPEED

CALM WINDS

- .

1.68 m/s

2.02%

.

- .

ORIENTATION

PLOT YEAR-DATE-TIME

.

- .

Direction (blowing from)

1997 Dec 1 - Dec 31 Midnight - 11 PM

.

-

. .

.

COMMENTS

WRPLOT View 3.5 by Lakes Environmental Software - www.lakes-environmental.com

Figure 5-35 December Wind Rose

95

5.3 Model Drawings and Testing Environment 5.3.1 Helium Bubble Generator The Helium Bubble Generator is a device that produces neutrally buoyant bubbles filled with helium. The bubbles follow the air flow streamlines and rarely collide with objects. Additionally, the bubbles will follow laminar and turbulent airflows.

Figure 5-36 Helium Bubble Generator

5.3.2 Drawings All the simulated airflow tests were preformed on a 1:48 scale model of a building 14’ wide, 28’ long and 10’ high.

96

Side View

Top View

Figure 5-37 Side and Top View of the Model

A wind catcher with three different sizes was built and tested. All three sizes had the same section but varying lengths, which represented 1/3, 1/2 and all of the windward façade.

97

a

a

Top View

Section a-a

Front View

Figure 5-38 1/3 Wind Catcher, Top View, Section and Front View

98

a

a

Top View

Section a-a

Front View

Figure 5-39 2/3 Wind Catcher, Top View, Section and Front View

99

a

a

Top View

Section a-a

Front View

Figure 5-40 Full Length Wind Catcher, Top View, Section and Front View

100

The leeward façade was used as an exhaust in two general configurations: the first configuration used the entire façade as an outlet (10' X 14'), while the second used an opening of 4' X 14' placed at varying locations.

Full Opening (CASE 0)

2' X 2' X 14' (CASE 1)

Top Opening 4' X 14' (CASE 2)

Bottom Opening 4' X 14' (CASE 3)

Figure 5-41 Leeward Elevation with different Apertures

101

Side View Fan Bubble Output

Model

Light Projector

Table

Top View Wall

Fan

Bubble Output

Model

Light Projector

Figure 5-42 General Setup of the Experiments

102

6 Wind Catcher with Different Sizes and Outlets All the tests were performed with the wind blowing perpendicular to the wind catcher's façade.

Top View Wind

Leeward

Windward

Side View

Wind

Figure 6-1 Model Position in respect to the Wind Catcher

The tests were recorded using a digital camcorder with a 30 frame per second rate. The duration of each frame is 0.033 second. In short, every 1 inch in the picture represents 60 inch per second or 0.76 meters per seconds. The fan had three speeds, as follows: •

Fan Speed 1 = 5 ft/s = 1.5 m/s = 3.4 mph

•

Fan Speed 2 = 7.5 ft/s = 2.3 m/s = 5.1 mph

•

Fan Speed 3 = 10 ft/s = 3.1 m/s = 6.8 mph

103

6.1 1/3 Wind Catcher

Figure 6-2 1/3 Wind Catcher Front Axonometric View

6.1.1 Case 0

Figure 6-3 Case 0 Back Axonometric View

104

6.1.1.1 Speed 1 Bubble 1

Figure 6-4 Six Frames Combined

Bubble 2

Figure 6-5 Four Frames Combined

105

6.1.1.2 Speed 2

Figure 6-6 Five Frames Combined

6.1.1.3 Speed 3 Bubble 1

Figure 6-7 Two Frames Combined

106

Bubble 2

Figure 6-8 Five Frames Combined

Figure 6-9 Case 0 3D Drawing

107

Figure 6-10 Case 0 Side View Case 0 2.5

2

Speed m/s

1.5

1

0.5

0 speed 1 B1

speed 1 B2

speed 2

speed 3 B1

speed 3 B2

Figure 6-11 Speed Vs Location

The general flow of the wind takes an almost direct path to the exit. However, there is some variation appearing at the top of the model where a region of positive pressure is forcing the wind into a loop. The air that is pushed to the wall opposite to the one adjacent to the wind catcher is taking a coil-like shape and ends up joining either the general flow towards the exhaust or enter the loop on the top of the model.

108

6.1.2 Case 1

Figure 6-12 Case 1 Back Axonometric View

6.1.2.1 Speed 1 Bubble 1

Figure 6-13 Six Frames Combined

109

Bubble 2

Figure 6-14 Seven Frames Combined

6.1.2.2 Speed 2

Figure 6-15 Five Frames Combined

110

6.1.2.3 Speed 3 Bubble 1

Figure 6-16 Six Frames Combined

Bubble 2

Figure 6-17 Five Frames Combined

111

Figure 6-18 Case 1 3D Drawing

Figure 6-19 Case 1 Side View

112

Case 1 2.5

2

Speed m/s

1.5

1

0.5

0 speed 1 B1

speed 1 B2

speed 2

speed 3 B1

speed 3 B2

Figure 6-20 Speed Vs Location

In this case, most of the bubbles are using the bottom opening to exit but with some difficulty appearing in the form of turbulence. Less turbulence was observed as the airflow velocity was increased. Furthermore, an increase in velocity forced some of the airflow to sweep upwards against the back wall, using the top opening to exit. As for the speed of wind inside the model, the highest speed would be under the wind catcher which is in the first third. Nevertheless, the wind decelerates and reaccelerates throughout the model until it reaches the exhaust, where a speed higher than the one in the middle zone is noticed most of the time. For example, fan speed 2 in this case showed the highest speed for the exhaust.

113

6.1.3 Case 2

Figure 6-21 Case 2 Axonometric Back View

6.1.3.1 Speed 1 Bubble 1

Figure 6-22 Eight Frames Combined

114

Bubble 2

Figure 6-23 Five Frames Combined

6.1.3.2 Speed 2

Figure 6-24 Nine Frames Combined

115

6.1.3.3 Speed 3 Bubble 1

Figure 6-25 Five Frames Combined

Bubble 2

Figure 6-26 Five Frames Combined

116

Figure 6-27 Case 2 3D Drawing

Figure 6-28 Case 2 Side View

117

Case 2 2.5

2

Speed m/s

1.5

1

0.5

0 speed 1 B1

speed 1 B2

speed 2

speed 3 B1

speed 3 B2

Figure 6-29 Speed Vs Location

This is the best self adjusting solution observed in this prototype. Compared to other exhaust types tested, this configuration maintained the narrowest range with various airflow velocities near the exit. At slower speeds, the air takes a smoother path to the exit and as the speed increases, the air is slowed due to the sharper path angles. Using fan speed 1, the wind takes a smooth path that becomes smoother with fan speed 2. However, when using speed 3 the wind tends to go downward and starts to have sharper air flow patterns.

118

6.1.4 Case 3

Figure 6-30 Case 3 Axonometric Back View

6.1.4.1 Speed 1

Figure 6-31 Five Frames Combined

119

6.1.4.2 Speed 2 Bubble 1

Figure 6-32 Two Frames Combined

Bubble 2

Figure 6-33 Five Frames Combined

120

6.1.4.3 Speed 3

Figure 6-34 Six Frames Combined

Figure 6-35 Case 3 3D Drawing

121

Figure 6-36 Case 3 Side View Case 3 2.5

2

Speed m /s

1.5

1

0.5

0 1

2 speed 1

3 speed 2 B1

4 speed 2 B2

5 speed 3

Figure 6-37 Speed Vs Location

122

The velocity of the airflow is high compared with the other cases because the opening is in the natural airflow direction of the wind, hence that the opening is smaller than Case 0 which forces the wind to accelerate. Nevertheless, a bigger positive zone is created to the upper right corner of the creating a large number of vortexes. Theses vortices are acting against the smooth flow of wind as they become more affective with higher speeds. Moreover, this type of opening will be obstructed by furniture since the wind is taking a path closer to the ground but would be a very good alternative if body cooling was needed the most.

Speed 1 2.5

/s

1.5

Speed m

2

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-38 Speed Vs Cases

123

Speed 2 2.5

Speed m /s

2

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-39 Speed Vs Cases Speed 3 2.5

2

Speed m/s

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-40 Speed Vs Cases

124

In case 1, the big air velocity differences occurred because air going through the bottom opening is much faster than the wind exiting through the top opening, while in case 2 the difference was because of the faster speed of wind in the first part of the model and the slowed down flow near the exhaust. Case 3 did not have a noticeably higher air velocity inside the model with higher fan speeds, which confirms the assumption that higher wind creates more turbulence inside the model which results in a slower air flow.

6.2 1/2 Wind Catcher

Figure 6-411/2 Wind Catcher Front Axonometric View

125

6.2.1 Case 0

Figure 6-42 Case 0 Back Axonometric View

6.2.1.1 Speed 1

Figure 6-43 Five Frames Combined

126

6.2.1.2 Speed 2

Figure 6-44 Six Frames Combined

6.2.1.3 Speed 3

Figure 6-45 Four Frames Combined

127

Figure 6-46 Case 0 3D Drawing

Figure 6-47 Case 0 Side View

128

Case 0 1.8

1.6

1.4

Speed m/s

1.2

1

0.8

0.6

0.4

0.2

0 speed 1

speed 2

speed 3

Figure 6-48 Speed Vs Location

The larger wind catcher is allowing a greater volume of air into the model. As a result, airflow is observed to follow a more linear path both in plan and section, forcing the wind to rise to the upper part of the opening. In fan speed 1 and 2, the air accelerates as it exits, while in fan speed 3 it is noticed that some kind of positive pressure is building up near the exhaust that results in a slower airflow.

129

6.2.2 Case 1

Figure 6-49 Case 1 Axonometric Back View

6.2.2.1 Speed 1

Figure 6-50 Seven Frames Combined

130

6.2.2.2 Speed 2 Bubble 1

Figure 6-51 Eight Frames Combined

Bubble 2

Figure 6-52 Bubble Speed 0.95 m/s

131

Figure 6-53 The Bubble Exiting from the Bottom Opening and other Bubbles following the same Path

Figure 6-54 Some Bubbles Exit using the Bottom Opening and some Bubbles head Upwards

132

Figure 6-55 Bubbles headed Upward creating a Vortex

Figure 6-56 Nine Frames Combined

133

6.2.2.3 Speed 3

Figure 6-57 Four Frames Combined

Figure 6-58 Case 1 3D Drawing

134

Figure 6-59 Case 1 Side View Case 1 2 .5

Speed/s m

2

1 .5

1

0 .5

0 sp e e d 1

sp e e d 2 B 1

sp e e d 2 B2

sp e e d 3

Figure 6-60 Speed Vs Location

The air pattern near the exhaust did not change at all compared with the smaller wind catcher. Nonetheless, the airflow velocity increased especially through the bottom opening and the coverage area expanded both in plan and section.

135

6.2.3 Case 2

Figure 6-61 Case 2 Axonometric Back View

6.2.3.1 Speed 1

Figure 6-62 Six Frames Combined

136

6.2.3.2 Speed 2

Figure 6-63 Six Frames Combined

6.2.3.3 Speed 3 Bubble 1

Figure 6-64 Five Frames Combined

137

Bubble 2

Figure 6-65 Eight Frames Combined

Figure 6-66 Case 2 3D Drawing

138

Figure 6-67 Case 2 Side View

Case 2 2.5

2

Speed /s m

1.5

1

0.5

0 speed 1

speed 2

speed 3 B1

speed 3 B2

Figure 6-68 Speed Vs Location

139

This exhaust shows again that it is a better option, even with a larger wind catcher -although the air did not behave the same way as with the smaller wind catcher, particularly under the wind catcher. The wind is driven further to the exhaust as the speed increases unlike the smaller wind catcher where the wind is driven downward. Yet it is still a better alternative because the air flow covers the majority of the first bottom meter which is very effective for cooling the human body.

6.2.4 Case 3

Figure 6-69 Case 3 Axonometric Back View

140

6.2.4.1 Speed 1

Figure 6-70 Six Frames Combined

6.2.4.2 Speed 2

Figure 6-71 Five Frames Combined

141

6.2.4.3 Speed 3

Figure 6-72 Six Frames Combined

Figure 6-73 Case 3 3D Drawing

142

Figure 6-74 Case 3 Side View

Case 3 1.4

1.2

Speed m /s

1

0.8

0.6

0.4

0.2

0 spe ed 1

spe ed 2

spe ed 3

Figure 6-75 Speed Vs Location

143

An increase of the airflow velocity is observed again in this case in addition to a larger positive pressure zone in the top of the model. More turbulence is appearing with increased velocities as well as vortices in the back upper corner of the model. Speed 1 2.5

Speed m/s

2

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-76 Speed Vs Cases Speed 2 2.5

Speed m/s

2

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-77 Speed Vs Cases

144

Speed 3 2.5

Speed m/s

2

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-78 Speed Vs Cases

Very similar to 1/3 wind catcher (section 6.4.1.3), Case 1 and 2 showed again a wide range in wind velocities. Case 3 with higher wind creates more turbulence inside the model which result in a slower air flow.

6.3 Full Length Wind Catcher

Figure 6-79Full Length Wind Catcher Front Axonometric View

145

6.3.1 Case 0

Figure 6-80 Case 0 Axonometric Back View

6.3.1.1 Speed 1

Figure 6-81 Five Frames Combined

146

6.3.1.2 Speed 2

Figure 6-82 Five Frame Combined

6.3.1.3 Speed 3

Figure 6-83 Three Frame Combined

147

Figure 6-84 Case 0 3D Drawing

Figure 6-85 Case 0 Side View

148

Case 0 3

2.5

Speed/s m

2

1.5

1

0.5

0 speed 1

speed 2

speed 3

Figure 6-86 Speed Vs Location

Due to the large opening in this configuration, a massive amount of air is blown inside the model. However, the positive pressure in the top of the model decreases in size as the airflow velocity increases. The vortex that is created under the wind catcher (bottom left corner) becomes larger and more obvious in comparison with smaller wind catchers.

149

6.3.2 Case 1

Figure 6-87 Case 1 Axonometric Back View

6.3.2.1 Speed 1

Figure 6-88 Five Frame Combined

150

6.3.2.2 Speed 2

Figure 6-89 Five Frame Combined

6.3.2.3 Speed 3

Figure 6-90 Six Frame Combined

151

Figure 6-91 Case 1 3D Drawing

Figure 6-92 Case 1 Side View

152

Case 1 1.6

1.4

1.2

Speed /m s

1

0.8

0.6

0.4

0.2

0 s peed 1

s peed 2

s peed 3

Figure 6-93 Speed Vs Location

The pattern in this case appears to be identical to that observed using smaller wind catchers with this exhaust. However, this prototype covered all the floor area from wall to wall which did not happen with smaller prototypes.

6.3.3 Case 2

Figure 6-94 Case 2 Axonometric Back View

153

6.3.3.1 Speed 1

Figure 6-95 Five Frame Combined

6.3.3.2 Speed 2

Figure 6-96 Other Bubbles taking a Different Path

154

Figure 6-97 Bubbles Exiting the Model

Figure 6-98 Seven Frame Combined

155

6.3.3.3 Speed 3

Figure 6-99 Bubbles Grouping together to Exit

Figure 6-100 Six Frame Combined

156

Figure 6-101 Case 2 3D Drawing

Figure 6-102 Case 2 Side View

157

Case 2 1.8

1.6

1.4

Speed /m s

1.2

1

0.8

0.6

0.4

0.2

0 speed 1

speed 2

speed 3

Figure 6-103 Speed Vs Location

This case proves again that the pattern near the exit will not be affected by the size of the wind catcher even though the speed slightly increased.

6.3.4 Case 3

Figure 6-104 Case 3 Axonometric Back View

158

6.3.4.1 Speed 1

Figure 6-105 Six Frame Combined

6.3.4.2 Speed 2

Figure 6-106 Five Frame Combined

159

6.3.4.3 Speed 3

Figure 6-107 Three Frame Combined

Figure 6-108 Case 3 3D Drawing

160

Figure 6-109 Case 3 Side View

Case 3 2.5

2

Speed m/s

1.5

1

0.5

0 speed 1

speed 2

speed 3

Figure 6-110 Speed Vs Location

161

Speed 1 1.8 1.6 1.4

Speed m/s

1.2 1 0.8 0.6 0.4 0.2 0 Case 0

Case 1

Case 2

Case 3

Figure 6-111 Speed Vs Cases Speed 2 2.5

Speed m/s

2

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-112 Speed Vs Cases

162

Speed 3 3

2.5

Speed m/s

2

1.5

1

0.5

0 Case 0

Case 1

Case 2

Case 3

Figure 6-113 Speed Vs Cases

The velocities recorded in the model with fan speed 1 were in a close range. This means that with slower wind speed the exhaust does not have a lot of influence over the air velocity inside the model. In fan speed 2 and 3 a greater differences in velocities is noticed with a lot of similarity between case 1 and 2 with different fan speeds.

6.4 6.4.1

Additional Tests Wind catcher with Smaller Opening This experiment was performed using a smaller intake opening to test if it is

possible to reduce the speed of the wind when it is undesirable.

163

a

a

Top View

Section a-a

Front View

Figure 6-114 1/3 Wind Catcher with Smaller Intake Opening

Figure 6-115 Eighteen Frames Combined with Fan Speed No.1

164

Figure 6-116 Six Frames Combined with Fan Speed No.2

Figure 6-117 Six Frames Combined with Fan Speed No.3

As noticed in the previous images, the wind will take a straight path until it collides with the bottom surface of the model, then move parallel to the floor surface to the exhaust. In addition, the bubbles are trying to travel up the wind catcher tower which creates a positive pressure at the bottom end of the tower.

165

6.4.2 Wind Catcher in the Middle of the Windward Façade This experiment was performed using the 1/3 wind catcher with the bigger opening but place between the corners of the windward façade.

Figure 6-118 1/3 Wind Catcher in the Middle of the Windward Façade

Figure 6-119 Front View

166

Figure 6-120 3D Drawing

The wind clearly took the middle zone straight to the exit, while the side sectors were subject to slower airflow with more turbulence.

6.5 Suggestion •

As mentioned in section 4.2.2, the microclimate of the region has to be examined before starting the design process.

•

The longer the house in the direction of the prevailing wind, the more efficient the air flow becomes inside the building.

•

This type of wind catcher will be most efficient when the wind is perpendicular to the intake opening.

167

•

The wind catcher should face northwest to catch the prevailing wind for Abu Dhabi especially in the afternoon periods.

•

The prevailing wind for Al Ain is northwest and south to southeast. The wind catcher should face northwest because the wind is blowing repeatedly from northwest in the afternoon period were ventilation is most needed.

•

The small size wind catcher is efficient enough if the designer does not need the whole floor area to be covered.

•

Areas like Abu Dhabi need a higher air change rate due to higher humidity levels during summer. In other words, the full length wind catcher is recommended.

•

The upper opening (case 2) is –in my opinion- the best exhaust, which can also be adapted to be used as an intake when wind is blowing from the other direction. This is mostly the case from midnight until the early morning hours.

•

If the smaller wind catcher is to be used in a building, it is recommended to be on the west side of the house to reduce the heat generated from the afternoon sun over the west façade. The air moves faster and spread wider over the wall adjacent to the wind catcher which would decrease the temperature of the west wall surface and the Mean Radiant Temperature.

168

•

This type of wind catcher would not be very effective for cooling the ceiling, so the house would be much better off with a second floor or a high ceiling with exhaust. Yet, the air that circulates in the upper part of the room will be sufficient enough to remove excess heat.

169

7 Future Work For future studies, the same model may be used with the same 1/3 wind catcher but with a curved bottom rather than the 45 degree angle. This would help to find out if it is possible for the wind to have more efficient flow over the ceiling. In addition, the effect of openings on the wall opposite to the one adjacent to the wind catcher can be studied to eliminate the turbulence that builds up. Also it would be very useful to see how the 4 sided Barjeel (mentioned in section 4.1.2) would perform with various exhausts.

Figure 7-1 Curved Wind Catcher

Figure 7-2 Openings on the Opposite Wall

170

8 Bibliography Allard, Francis. Natural Ventilation in Buildings: A design handbook. London: James & James, 1998 Bradshaw, Vaughn. Building Control Systems. New York: John Wiley & Sons. 1993 Brown, G. Z., and Dekay, Mark. Sun, Wind and light: Architectural Design Strategies. New York: John Wiley & Sons. 2001 Fathy, Hassan. Natural Energy and Vernacular Architecture: Principles and Examples with Reference to Hot Arid Climates. Chicago: University of Chicago. 1986 Forman, Werner, Phoenix Rising: The United Arab Emirates Past, present and future. London: The Harvill. 1996 Kreider, Jan F, and Kreith, Frank. Solar Heating and Cooling: Engineering, Practical Design, and Economics. Washington, D.C.: Hemisphere, 1975 Lakes Environmental. WRPLOT View software. 3 Jan. 2002 Larson, Roland E., and Hostetler, Robert P. Calculus with analytical geometry. Toronto: Heath and Company, 1986 Milne, Murray. Climate Consultant, University of California, Los Angeles, 1991. The Renewable Resource Data Center . TMY2 User's Manual. 5 Mar. 2002 Stein, Benjamin, and Reynolds, John S. Mechanical and Electrical Equipment for Building. New York: John Wiley & Sons, 2000 Threlkeld, James L., Thermal Environmental Engineering, New Jersey: Englewood Cliffs, 1970 UAE. Dubai Municipality: the Historical Building Section. Elements of Traditional Architecture in Dubai. Dubai: Dubai Municipality, 2000 Vine, Peter. UAE in Focus: A photographic history of the United Arab Emirates. London: Trident. 1998 "Wind Towers: Detail in Building". Battle McCarthy Consulting Engineers. 1999: 6

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