Wind Tunnel Components

• Wind tunnels measure how atmospheric winds affect moving objects. Kim Steele/Photodisc/Getty Images

  To understand wind tunnel components and their function, we must recognize the function of wind engineering. According to NASA, researchers use wind tunnels to understand how atmospheric forces affect moving objects. These tunnels have various designs --- such as open-circuit, closed-circuit, low-speed, trans-sonic, supersonic and pressure wind tunnels --- but they all comprise five major components.

Settling Chamber

• The primary function of the settling chamber is to straighten the air flow as it enters the wind tunnel and passes to the next section. A honeycomb-shaped structure and mesh wire screens remove turbulence, because air currents become smoother as they pass through these components. The speed of the air currents also becomes more consistent, because the settling chamber reduces fluctuations in velocity.

Contraction Cone

• The contraction cone reduces a large quantity of air into a smaller quantity, which increases the air's velocity. In addition, the contraction cone prevents variations in velocity, making the final wind speed more consistent.

Test Section

• The test section houses the test object, along with sensors that measure its response to wind forces. One force measured in the test section is lift, which causes objects to rise. Another is drag, which is a measure of an object's resistance to air as it moves through the atmosphere. Based on these results, researchers can determine how the test object will react to atmospheric forces in the real world. The test section can take many different shapes, and may have special features like slotted or flexible walls.

Diffuser

• The diffuser slows the high velocity of air in the wind tunnel before it exits the system and recirculates. As the air enters the diffuser, it slows down in response to the shape of the diffuser. This part of the wind tunnel also reduces the power required, which lowers the cost of operating the tunnel.

Drive Section

• The drive section is responsible for pulling air through the entire tunnel. Normally, large exhaust fans draw air through the tunnel before recirculating it. Large-scale wind tunnels are capable of producing winds faster than the speed of sound by using "pressurized gases and/or vacuum cylinders."