Quiet Down the Air-flow Self Noise in Acoustic Wind Tunnel

Abstract

In the acoustic wind tunnel for experiments of aerodynamic sounds, it is required to make the background noise of the measurement section even quieter. The unsteady structure of shear flow of the jet from the nozzle attached with fine tiny vortex generating adapters was studied by numerical flow analysis by the lattice Boltzmann method and the experiment confirmed the stability of the airflow and the quiet ability. It was found that the collector throat can be downsized as compared with the conventional one, and the measurement chamber background noise can be quieter than the conventional one by about 3 dB. In addition, it was confirmed by imaging by numerical flow analysis that the fine tiny vortex generation adapter induces a longitudinal vortex flow effective for quieting.