Wind tunnels are just ducting with fans at one or both ends. With four primary sections: the settling chamber, air monitoring station, test section, and drive section. The settling chamber does precisely what its name implies: It helps to settle and straighten the air, often using panels with honeycomb-shaped holes or even a mesh screen. 

Air Monitoring station is a calibrated device used to calculate ACFM or SCFM over a specific range. It has a Pitot Traverse Station or flow traverse station that combines honeycomb air straightener-equalizer with proven multi-point, self-averaging Pitot technology.  Applications could require another air monitor located downstream of the test section. The test section is where Engineers place their scaled models, where sensors record data, electrical characteristics, and make visual observations.  The drive section houses the fan that creates high-speed airflow. A fan can be upstream and or downstream, depending on the application.