Assessment and Comparison of Fan Array Wind Tunnel Facilities

A fan array wind tunnel (FAWT) is a relatively new testing equipment that bridges the gap in size between traditional, enclosed wind tunnels and outdoor field tests. These ``meso''-scale facilities produce open test sections and can be dynamically programmed to produce arbitrary wind profiles and inhomogeneous turbulent flow fields that can simulate the atmospheric flows. Unlike field testing, wind profiles produced by the convergence of an array of fan jets are repeatable. While FAWTs have an open test section, they are often placed inside a large laboratory facility, which affects the flow, circulation, and flow rates through the fans, test section, and the surrounding space. Due to the length scales of laboratories, we employ Reynolds Averaged Navier-Stokes (RANS) simulations with actuator-based parameterization for individual fan outputs to investigate three facilities and their configurations of the FAWT: California Institute of Technology, the University of Memphis, and Mississippi State University. While all facilities have high-bay ceilings and retractable, large garage doors, large recirculation zones develop in corners, and the test section jet responds to the facility geometry and layout. Large exterior openings need to be especially considered, as they can act simultaneously as inlets and outlets. The RANS modeling identifies circulation paths and mean flow field patterns; however, the turbulence modeling is shown to be overly diffusive in the inhomogeneous, high-shear regions produced by large arrays of fans when compared with experimental measurements. The resultant flow fields reveal that facility configuration and FAWT placement significantly affect test section development and the ability for robust testing.