Design and performance of an ultra-compact, low-speed, low turbulence level, wind tunnel for aerodynamic and animal flight experiments

We present a novel closed-circuit ultra-compact wind tunnel with an 8:1 contraction ratio and high flow quality. Its overall footprint area is less than half that of a conventional tunnel with the same test section size and same contraction ratio, enabling significantly smaller material and construction costs. The tunnel's key features which enable the small footprint include a two-dimensional main diffuser, a minimum-length contraction, and expanding turning vanes with a 1.167:1 ratio in corner two and an aggressive 1.875:1 ratio in corner four. Separation in the latter is prevented using a screen and honeycomb integrated into each vane passage-the first time this has been used in a wind tunnel. The tunnel exhibits excellent flow quality with less than +/- 1% mean flow variation in the test section core and a freestream turbulence level of 0.03% at 12 m/s over a 4 Hz-20kHz bandwidth.

Automated summary

We introduce a new wind tunnel design that is ultra-compact and provides high flow quality. This tunnel has a smaller footprint compared to conventional tunnels with the same test section size and contraction ratio, resulting in lower material and construction costs. Several key features of this tunnel contribute to its small footprint, such as a two-dimensional main diffuser, a minimum-length contraction, and specially designed turning vanes. The tunnel demonstrates excellent flow quality with minimal mean flow variation and low freestream turbulence.