多孔質材料を用いた空力騒音の低減とそのメカニズムの解明

抄録

A passive noise control technique for the flow-induced noise using a porous media was studied experimentally. The purpose of this study was to decrease the aerodynamic sound using porous media that permeated only sound and clarify that reduction mechanism. In experiment, flow-induced noises emitted from two types of rectangular cylinders was measured in a low-noise wind tunnel. One cylinder was made of four aluminum plates and the other was two aluminum and porous media plates each. Measurement results show that the frequency of the distinct tonal noise was different between two cylinders, that frequency was higher for using porous media. It was also found that the sound pressure level of the noise was also different and that of the cylinder using porous media plate was 25 dB smaller at maximum. Velocity field around cylinders were examined by the PIV measurement and that showed that time and space scale of separation vortex street around cylinder were smaller for using porous media. It is assumed that the change of aerodynamic sound was caused by that change in velocity field.