A low-noise, low-turbulence subsonic acoustic wind tunnel is designed for investigation of flow noise process. The design was carried out to meet both the high standard of aerodynamic and acoustic performances. Good flow qualities at the tunnel test section is required to achieve the aerodynamic performance such as low-turbulence level, uniformity of velocity profile and high maximum velocity. To achieve above requirements, the following analyses are studied; pressure loss at the duct system, possibility of separation at the contraction and turbulence reduction capability of the screens, honeycomb and contraction. The acoustic performance was emphasised on the quiet background noise level at the test section. For the quiet background noise level, two resonator mufflers, one splitter muffler and λ/4 resonator muffler are designed and applied to the tunnel circuit.
The designed tunnel performance is expected to have a square test section of 0.35m×0.35m with maximum mean velocity of approximately 62.8m/s. At the test section, the low turbulence reduction factor is obtained by 6 screens and contraction area ratio of 21:1. The large noise attenuation of 70dB below 1000Hz and 65dB above 1000Hz is obtained by using 3 type mufflers and two 90 degrees bended ducts.