This information is provided courtesy of NASA's Observatorium. A wind tunnel is really a fairly simple device.
Most designs feature each of the five components described below.
The purpose of the settling chamber is to straighten the airflow. The test section is where the test article and sensors are placed. Diffuser - The diffuser slows the speed of airflow in the wind tunnel. Drive Section - The drive section provides the force that causes the air to move through the wind tunnel. The design influences whether or not the air is recirculated in the tunnel.