Fan array wind tunnels: characterization, performance, and visualization

Fan array wind tunnels, FAWT, offer a versatile, configurable alternative to traditional wind tunnel design and testing. Utilizing an array of DC-powered off-the-shelf cooling fans (in place of one singular drive section) allows for greater flow control, overall decreased mixing lengths, and comparably large useable test section areas when compared with its effective footprint. The fan array itself is fully and individually software addressable, which translates to the capability of generating a variety of traditional and non-traditional spatially- and temporally- varying flows. Characterization of the 2.88m x 2.88m open-loop FAWT housed in the Center for Autonomous Systems and Technologies (CAST) at Caltech is accomplished through standard hot-wire anemometry as well as a multi-hole pitot probe system that provides real-time, visual feedback of time-averaged flow quantities. Standard 2D and volumetric flow reconstructions are presented to accurately quantify velocity variation, flow angularity, and turbulence intensity through the extent of the entire FAWT with in-plane spatial resolutions of less than 1mm. Steady uniform and shear flows will be highlighted.