Overcoming Optical and Seeding Challenges for PIV in the Penn State Compressed Air Wind Tunnel

This presentation outlines the development and implementation of a custom Particle Image Velocimetry (PIV) system tailored for the Penn State Compressed Air Wind Tunnel (CAWT). The CAWT is a closed-loop facility that operates with compressed air as the working fluid and features a 1 meter diameter test section capable of withstanding pressures up to 34.5 bar. This enables high Reynolds number testing on larger models than typically possible in compressed-air tunnels, expanding the scope of experimental capabilities beyond prior works. To date, rotor wake characterization measurements in the CAWT have been limited to a two-dimensional pointwise grid. The goal of the present work is to enhance the capabilities of the tunnel through the integration of PIV. Key challenges in this effort include the tunnel's restricted optical access, in-situ calibration, and the complexity of flow seeding at high pressures, of which the solutions will be the main discussion of this paper.