多孔質材料の特性が多孔質材料を備えた角柱から発生する流体騒音に与える影響

抄録

A passive noise control technique for the flow-induced noise using a porous material was studied experimentally. The purpose of this study was to decrease the aerodynamic sound using porous material that permeated only sound and clarify that reduction mechanism. In the experiment, flow-induced noises emitted from three types of rectangular cylinders was measured in a low-noise wind tunnel. One cylinder was made of four aluminum plates and others were made of two or three aluminum plates. Measurement results show that the frequency of the distinct tonal noise was different among three cylinders, that frequency was higher for using porous material. It was also found that the sound pressure level of the noise was also different and that of the cylinder using two porous material plates was 25 dB smaller at maximum. Velocity field of the wake of cylinders were examined by the PIV measurement and that showed that time and space scale of separated vortices around cylinder were smaller for using two porous material plates. It is assumed that the change of aerodynamic sound was caused by that change in velocity field. However, changes in the sound pressure level and frequency of the generated sound were small due to the little changes of the velocity field in the wake of the cylinder when only one porous material plate was used.