The Design, Fabrication, and Evaluation of a Low-Speed, Low-Turbulence, Anechoic Wind Tunnel

In order to provide a means for testing noise reduction techniques in propellers and fans, a low-speed, low-turbulence, anechoic wind tunnel was designed, fabricated and evaluated at Embry-Riddle Aeronautical University. This open circuit wind tunnel was designed using several other existing wind tunnels as a guide and incorporated an open jet test section. The tunnel, which was built almost entirely out of wood and fiberglass, is powered by a 15 hp centrifugal fan. Tufts of yarn, a pitot-static tube, and a hot film anemoter were used to determine the flow characteristics in the test section of this wind tunnel. From the hot film anemometer, values of velocity, standard deviation and turbulence intensity were determined for three different velocity settings; approximately 114 ft/s, 145 ft/s, and 215 ft/s respectively. For the 215 ft/s and 114 ft/s tests, the turbulence intensity ranged from 0.42% to 0.87% within a seven inch diameter about the centerline. This seven inch diameter was mapped out to simulate a seven inch diameter propeller. For the 145 ft/s test, the turbulence intensity became more erratic, and ranged between 0.67% and 1.5%. The velocity across the test section for all three tests varied by less than 2.0%, with 90% of the points varying by less than 1.0%