Outline of Wind Tunnel Testing

What is Wind Tunnel Testing?

Wind tunnel testing has a wide-range of purposes and fields for the application. Based on our comprehensive experience particularly in the field of architecture, the wind tunnel testing used in the area is outlined below.
Large scale buildings, such as taller skyscrapers are being erected by “people” one after another in our living environment. While they have made our lives convenient and comfortable, these large-scale constructions have some adverse impacts on the surrounding environment and vice versa.
Among the various environmental factors, “Wind” certainly has higher priority of significance these days. Although people can build large-scale buildings, the natural wind flow cannot be extinguished. We need to carefully design buildings so that they are in harmony with the wind.
Wind tunnel testing is one of the frequently used methods to evaluate the “harmonization between wind and buildings”.

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A wind tunnel system consists of a tubular air passage and a fan/blower. The air flow generated by either fan or blower emulates natural wind after it passes through several filters. This wind reaches the test section where an experimental model of buildings and the surrounding city area and terrain is located. The phenomenon caused by the wind is recorded by the sensors embedded in the model. Measured data are analyzed, evaluated and used to mitigate the adverse impact on the environment.

 

What Wind Tunnel Tests Can Assess

Wind Environment

Skyscrapers have a negative impact on the environment by generating gusty winds, known as “building winds”. Building winds affect serious issues in recent years. They scatter dust, lift roofing tiles of neighboring houses, produce noise and disturb cyclists and pedestrians. The wind tunnel tests validate the possible impact of building winds generated by new skyscrapers, and also examine the effectiveness of the building designs and surrounding vegetation to reduce the impact of the winds. The tests are repeated over and over again using various conditions.

Wind Resistant Design

Wind loads on buildings depend on their size, height and locations. The data acquired in the wind tunnel tests can provide insight into the necessary structure of buildings and required strength for external walls.

Amenity and Livability

Wind may cause skyscrapers to vibrate. To ensure the amenity and livability of the buildings, various shaped models are used in wind tunnel testing to examine wind-induced vibration and frequency of the occurrence.

Wind Tunnel System

Wind tunnel systems vary in structures and installed fans/blowers etc., and basic features are briefly summarized below:

1.Wind Tunnel Configuration

 

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The figure shows a basic configuration of the Eiffel Type wind tunnel. This form remains the same regardless of the size of wind tunnels. (Traverse and turntable are optional.)

2.Difference in the Air Path

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Eiffel Type Wind Tunnel

This is an open-circuit wind tunnel. The air circulates inside the room in which the tunnel is located. It is a space-saving and cost effective wind tunnel.

Goettingen Type Wind Tunnel

This is a closed-circuit wind tunnel. It produces a superior flow quality in the test section which provides an ideal environment for measurements.

Example of the Eiffel Type Wind Tunnel

Kyoto University Multifunctional Wind Tunnel Experimental Equipment

This is a multifunctional wind tunnel with various experimental devices and a simulator for structural response. Acrylic resin panels are used for the entire surface of the test section providing the excellent visibility and appearance.

風洞装置-京都大学多機能風洞システム

Example of the Goettingen Type Wind Tunnel

National Institute of Occupational Safety and Health, Japan Construction Environmental Simulator

This simulates the impact of the wind on facilities and workers at construction sites. It features the second test section for large specimens such as full scale scaffolds.

産業安全研究所_施工環境シミュレータ

3.Selection of Blower

Fans/blowers are generally classified as axial flow fan and centrifugal (sirocco) blower.

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Axial Flow Fan

It has a large air supply (high wind speed) and can apply to both Eiffel and Goettingen type. Some models can adjust the angle of the rotor blades for versatile applications.

Centrifugal Blower

Due to the structural limitations, it is not suitable for the Goettingen type wind tunnels. However, it is a space-saving and more cost effective compared to axial flow fans. It is commonly used for the small Eiffel-type wind tunnels and wind tunnels with relatively small air supply (low wind speed).

4.Air Flow Accuracy

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The air flow accuracy, which is a function of “wind speed distribution” and “intensity level of turbulence”, is important as well as the maximum wind speed to determine the performance of the wind tunnel. Various kinds of equipment, e.g. diffuser, settling chamber, contraction etc., are also placed in a tube to maintain the air flow accuracy.

Diffuser

The diffuser expands the airflow generated by the fan/blower to the size of the settling chamber in conjunction with reducing the speed. For a steep angle diffuser, mesh screens are used to further adjust the flow separation.

Settling Chamber

In a settling chamber, the wind speed distribution and turbulence are controlled by a series of mesh screens. Honeycombs reduce swirling airflow and straighten the flow in the axial direction.

Contraction

A straightened airflow is accelerated to the desired velocity. As the cross section narrows, the upstream wind speed distribution becomes more uniform and the turbulence reduces.

5.Supplemental Equipment for Wind Tunnel Tests

Aside from models and various sensors required for the wind tunnel tests, several auxiliary devices are utilized when necessary.

4-axis Traverse System

4-axis Traverse System

This device precisely maneuvers measuring sensors to arbitrary positions by remote control. The device is generally controlled by a programmable logic controller (PLC) or PC and run with measuring software installed. The operation can be programmed. For smaller wind tunnels, a hand-powered device (without motors) is also available.

 

2-axis Traverse System

2-axis Traverse System

This device precisely maneuvers measuring sensors to arbitrary positions by remote or manual control. The device can be remotely operated by either PLC or PC similarly to the 4-axix traverse.

 

Turntable

Turntable

This device precisely turns a disk-shaped architectural model by remote control. The device is generally controlled by a programmable logic controller (PLC) or PC and run with measuring software installed. The operation can be programmed.

 

Spring Suspension System

Spring Suspension System

This is a spring suspension system to support bridge and airfoil flutter models from the internal side walls of the test section during vibration tests. It can turn precisely (in tilt direction) with models being suspended. The device is generally controlled by a programmable logic controller (PLC) or PC and run with measuring software installed. The operation can be programmed.

 

Vibration Balance System

Vibration Balance System

This spring suspension system located on the floor supports architectural or simple shaped models during vibration tests. It can be manually turned or synchronized with the turntable. A concrete block of large mass may also be used to absorb the vibration from the wind tunnel.

6.What We Can Do for You.

We have explained the outline of wind tunnels and supplemental equipment. Designing high performance wind tunnels requires extensive experience in addition to engineering considerations.
WINDEC proposes a well-thought-out wind tunnel designs to meet the requirements of our customers.
We will take one more step to add value to your wind tunnel experiment to seek superb results based on our comprehensive experience beyond those numerical data and equations.