Wind Tunnel Study of Buildings

1. WIND TUNNEL STUDIES FOR
ORIGAMI INSPIRED BUILDINGS
Guide – Prof. P. Pavan Kumar
Presented by
Rachana. S, 8th Semester
B.Arch, UVCE
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2. INDEX
TITLE Page no.
Origin 3
Theory of Operation of Wind Tunnels 4
How it Works 6
Why do Wind Tunnel Testing? 7
When should Wind Tunnel Testing be done? 8
Areas of Application 9
Common Techniques of Wind Tunnel Testing 10
Experimental Studies 16
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3. ORIGIN
• English military engineer and mathematician Benjamin
Robins invented a whirling arm apparatus to determine drag and
did some of the first experiments in aviation theory.
• Sir George Cayley also used a whirling arm to measure the drag and
lift of various airfoils.
• Francis Herbert Wenham, a Council Member of the Aeronautical
Society of Great Britain, addressed these issues by inventing,
designing and operating the first enclosed wind tunnel in 1871.
• Danish inventor Poul la Cour applied wind tunnels in his process of
developing and refining the technology of wind turbines in the early
1890s.
• The Wright brothers' use of a simple wind tunnel in 1901 to study
the effects of airflow over various shapes while developing
their Wright Flyer.
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4. THEORY OF OPERATION
• Wind tunnels were first proposed as a means of studying vehicles,
primarily airplanes, in free flight.
• The wind tunnel was envisioned as a means of reversing the usual
paradigm: instead of the air's standing still and the aircraft moving
at speed through it, the same effect would be obtained if the
aircraft stood still and the air moved at speed past it.
• In that way a stationary observer could study the aircraft in action,
and could measure the aerodynamic forces being imposed on the
aircraft.
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5. THEORY OF OPERATION
• Wind tunnel study came into its own, the effects of wind on man
made structures or objects needed to be studied when buildings
became tall enough to present large surfaces to the wind, and the
resulting forces had to be resisted by the building's internal
structure.
• Determining such forces was required before building codes could
specify the required strength of such buildings and such
tests continue to be used for large or unusual buildings.
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6. HOW IT WORKS
• Air is blown or sucked through a duct equipped with a viewing port
and instrumentation where models or geometrical shapes are
mounted for study.
• Typically the air is moved through the tunnel using a series of fans.
• For very large wind tunnels several meters in diameter, a single
large fan is not practical, and so instead an array of multiple fans
are used in parallel to provide sufficient airflow.
• Due to the sheer volume and speed of air movement required, the
fans may be powered by stationary turbofan engines rather than
electric motors.
• observation is usually done through transparent portholes into the
tunnel.
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7. WHY DO WIND TUNNEL TESTING?
• Today’s architects and engineers challenge the traditional
boundaries of their craft, using high-tech materials and innovative
structural design techniques to create buildings and structures as
true art expressions.
• In addition, new structures are being designed for complex
situations and surroundings (i.e., near terrain or other structures).
Yet, wind loads provided in most codes and standards haven’t kept
up.
• They are based on a range of building shapes that were common
over 40 years ago and many codes recognize that wind tunnel tests
will lead to more reliable loading estimates that result in savings,
peace of mind and maximum creative freedom.
• Progressive designers and engineers understand that significant
savings in cost of structure and cladding can be obtained by
completing a wind tunnel test in the early stage of the design.
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8. WHEN SHOULD WIND TUNNEL
TESTING BE DONE?
• Early Design Stage
In the early planning stages, careful attention to the effects of wind,
snow, ventilation, vibration and related microclimate environmental
issues on buildings and structural are proven to save time, save money
and reduce risk.
• Tall Buildings / Unique Designs
Wind tunnel testing is advisable on buildings higher than 22 stories (10
stories in hurricane areas) or where the building or structure is an
unusual shape or construction methodology. Unusual terrain or
surrounding structures in the area also make wind tunnel testing an
important step to optimize cost efficiencies, generate accurate results
to enhance the safety of a project, minimize assumptions and allow for
maximum design freedom.
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9. AREAS OF APPLICATION
• The primary reasons for carrying out such studies are to improve
the reliability of structure and during the period of construction.
Wind tunnel model studies frequently lead to cost savings.
• Other candidates for wind tunnel tests are building and structures
that have an unusual sensitivity to the action of wind or that fall
outside existing experience. Examples are tall, slender and flexible
buildings, observation towers, masts and chimneys, immediate and
long span bridges, pedestrian bridges, transmission line systems
and various special structures, such as large span flexible roofs,
cooling towers, large cranes etc.
• The presence of unusual terrain and surroundings, and close
proximity to major buildings or prominent topographic features are
also areas of concern.
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10. COMMON TECHNIQUES FOR WIND
TUNNEL TESTS.
Type of Test Typical Informtion provided
Local pressures
Tests of local pressures using scaled static
models instrumented with pressure taps.
• Mean and fluctuating local exterior
pressures on curtain wall, cladding and roof
components.
• Estimates of wind induced interior
pressures, including fluctuations in the
presence of significant opening.
• Estimates of differential pressures on
components of exterior envelope.
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11. COMMON TECHNIQUES FOR WIND
TUNNEL TESTS.
Type of Test Typical Informtion provided
Area and overall wind loads
Tests of wind loads on specific tributary
areas, using pressure models and spatial
or time averaging of simultaneously
acting local pressure.
• Mean and fluctuating wind loads on
particular tributary areas dur to external or
internal pressures, or both.
• Measures of the dynamic structural loads
and actions as a result of spatially averaged
wind loads on particular tributary areas.
• Overall loads on buildings, long span
bridges and other structures, including
generalised wind forces associated with
particular modes of vibration.
• Simultaneously measured pressures on
exterior surfaces of a building can be used
to determine the generalized wind forces
for various modes of vibration.
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12. COMMON TECHNIQUES FOR WIND
TUNNEL TESTS.
Type of Test Typical Informtion provided
High frequency force balance
Direct measurements of overall wind
loads on scaled static models, including
high frequency base balance tests for tall
buildings.
• Aerodynamic coefficients, which can be
used with analytical methods to estimate
the peak response assuming linear or
nonlinear structural action.
• Wind force spectra from which the resonant
dynamic response can be obtained.
• High frequency base balance tests are
commonly used to evaluate loads associated
with the fundamental sway and torsional
modes of tall buildings.
• Estimates of the wind induced responses,
including building drift and accelerations,
are made analytically after the forces are
determined.
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13. COMMON TECHNIQUES FOR WIND
TUNNEL TESTS.
Type of Test Typical Informtion provided
Section Model Tests
Section model tests using dynamically
mounted models. Usually for bridges, but
also for other structures.
• Overall mean and dynamic wind induced
forces and response.
• Aerodynamic derivatives as required in
analytical models.
Terrain and Topographic Studies
Small scale topographic model tests using
flow visualization, hot wire anemometry
or both.
• Character of flow over complex terrain,
including the assessment of terrain
roughness.,
• Correlations of flows at different locations
and heights as required in te calibration of
anemometer stations.
• Assessments of the wind energy potential of
particular sites.
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14. COMMON TECHNIQUES FOR WIND
TUNNEL TESTS.
Type of Test Typical Informtion provided
Aerolelastic Studies
Aeroelastic tests using dynamically
scaled models of buildings, bridges
and structures.
• Aeroelastic model tests provide information on
the wind induced responses of buildings and
structures due to all wind induced forces,
including those which are experienced by objects
that move relative to the wind flow.
• Direct measures of the overall mean and
dynamic loads and responses of buildings and
structures, including displacements, rotations
and accelerations.
• Influence of pressurization on behaviour of air
supported structures.
• Effectiveness of active and passive systems to
control dynamic motion.
• Interaction of wind loads and direct indications
of maximum combined force effects.
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15. COMMON TECHNIQUES FOR WIND
TUNNEL TESTS.
Type of Test Typical Informtion provided
Pedestrian Winds
Evaluations of pedestrian level winds using
scaled static models of buildings or
structures.
• Character of flow around buildings and
structures.
• Measures of local wind speeds and
directions required for environmental
assessments.
• Selection evaluations and fine tuning of
remedial measures.
• Evaluation of helipad operations.
Air Quality
Tests to evaluate the dispersion of pollutants
and determine the resulting air quality
around buildings and in urban areas.
• Plume trajectories to indicate possible
impingement and/or reingestion into
fresh air intakes.
• Concentrations of exhausted pollutants,
expressed as a ratio of their ratio of
their source concentration.
• Wind-induced ventilation rates in open
areas. 15

16. EXPERIMENTAL STUDY
WIND TUNNEL TESTS CONDUCTED
FOR ORIGAMI INSPIRED STRUCTURE
(UNIQUE BUILDING)
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17. WIND TUNNEL EXPERIMENT
• Materials required –
Procedure –
All the above materials are assembled as shown in plate 1.
A singular light entry such that the smoke pattern is seen.
Two openings are created to insert the straws and the
exhaust side of the hair dryer. One large window is
created to observe the wind flow pattern and behavior.
The observations were recorded in a camera.
Hair Dryer
Bunch of
Incense sticks
Bunch of
straws
Origami folded sheet
A box as a Wind Tunnel
PLATE 1 17

18. EXPERIMENTAL STUDY 1
OBSERVATION – The pattern of the wind flow over the study model is mostly over than
around. As seen in a sphere, the wind patterns are mostly and over, in this model due to
the sudden ridges the wind is seen to be traversing through them.
CONCLUSION – Due to the 3 dimensional flow of the wind, there is abundant wind only on
three sides. Whereas there are prominent negative spaces left due to the curvature of the
structure.
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19. EXPERIMENTAL STUDY 2
OBSERVATION – The pattern of the wind flow over the study model is mostly around the
model.. As seen in a sphere, the wind patterns are mostly around than over. Similarly, in
this model due to the sudden ridges the wind is seen to be traversing around but
through them.
CONCLUSION – The wind flow is 2 dimensional in this study model owing to the tallness
and the close similarity to a sphere. The wind travels from 2 directions and meets on
one side creating high wind pressures on that side.
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20. EXPERIMENTAL STUDY 3
OBSERVATION – This study model is a compressed form of Study model 1. The behavior
of wind is around and over. As seen, it is much easier for the winds to get accumulated on
one side creating a lot of negative zones on the model.
CONCLUSION – The wind flow is 3 dimensional, but mostly over than around the model.
Conclusively, a high pressure zone is quickly created on the opposite side.
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21. EXPERIMENTAL STUDY 4
OBSERVATION – As the piece of origami folding is very flexible, here the study model
created has been spread out and stretched in such a way that the wind flow is diverted
to flow in all the ridges of the structure.
CONCLUSION – The wind flow is multi dimensional. It is a combination of a spherical
and square shapes, that helps it to avoid developing pressure zones around the
building. Also, the wind is spread uniformly throughout the surface of the structure,
keeping it stable.
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22. EXPERIMENTAL STUDY 5
OBSERVATION – The study model, here, is placed vertically representing a tower to study
the behavior of winds on a vertically rising structure. Winds traverse over the tower and
pass over it.
CONCLUSION – The wind flow is basically seen to cover the front surface rather than go
around it. The wind forces that go around create a high pressure at the base of the
structure.
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23. EXPERIMENTAL STUDY 6
OBSERVATION – This study model is a modification of model number 5. The origami
sheet is slightly twisted and placed to imitate the wind movement. The wind moves
across rather than over the structure.
CONCLUSION – The wind flow doesn’t go around the structure and settle at it’s base.
The wind traverses the ridges on the structure and passes through it making the
structure more aerodynamic than the previous study model (5).
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24. CONCLUSION
From all the experimental studies conducted, study model 4 has the most desired results
for an origami inspired structure to remain stable. This structure is flexed such that the
winds do not cause any lift and affect the structure.
Similarly, study model 6 is favorable for a tower. The twist in the structure deviates the
wind to pass across and not hit the structure and make it sway.
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Study model – 6 Study model - 4

25. THANK YOU
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