난류경계층에서 컴플라이언트 코팅과 점탄성 벽면의 방사소음에 관한 실험적 연구

초록

We examine the problem in which porous / viscoelastic compliant-coated plates are subject to pressure fluctuations under transitional or turbulent boundary layer. Measurements are presented of the frequency spectra of the near-field pressure and radiated sound by compliant surface. A porous plate consisting of 5mm thick, open-cell foam with fabric covering and a viscoelastic-coated plate of 1mm thickness over an acoustic board of 4mm thickness were placed over a rigid surface in an anechoic wind tunnel. The wall pressure autospectra and streamwise wavenumber- freauency spectra were nondimensionalized and compared to see attenuation effects of compliant coatings. Streamwise velocity and wall pressure measurements were shown to highly attenuate the convective wall pressure energy when the convective wave-number (kch) was 3.0 or more. The sound source localization on the rigid/ compliant walls is applied to the measurement of radiated sound by using an acoustic mirror system.