The New Penn State University Compressed Air Tunnel for Investigating High Reynolds Number Unsteady Aerodynamics

Achieving large Reynolds numbers is a continual challenge for the experimentalist, who is often limited by space and resources to relatively small wind tunnel facilities of moderate power. Periodicity in the flow, due to unsteady motion or rotation, creates further complications by producing a nondimensional frequency which must also be matched, typically at the expense of the Reynolds number. However, by using compressed air as the working fluid, a dynamically similar flow is possible in a small facility with modest drive power, enabling high Reynolds numbers without high cost. This is the approach taken by the new Penn State University Compressed Air Tunnel (PSU-CAT) where static pressures in the facility can be increased to 34 bar (500 psi). This results in kinematic viscosities which are 34 times lower than atmospheric air and Reynolds numbers of 29 million/meter in the 1 meter diameter test section, enabling the PSU-CAT to act as a much larger wind tunnel . The design and fabrication of the facility will be discussed as well as measurement capabilities including stereoscopic particle image velocimetry (sPIV) and hot wire anemometry (HWA) on the wakes of static and rotating models.