The structural modes driven by low wave-number components of smooth elastic wall pressure provide a relatively weak coupling between the flow and the wall motion. We examine the problem in which the elastic thin plate is subject to pressure fluctuations under turbulent boundary layer. Measurements are presented of the frequency spectra of the near-field pressure and radiated sound contributed by the various wave modes of the thin elastic plate. Their dependence on elastic properties of thin plate is addressed, e.g. mass density of thin plate or tensions applied to the plate. Dispersion equation for wave motions of elastic plate was used to investigate the effect of bending waves of relatively low wave numbers on radiated sound. The low-wave number motion of elastic plate was observed to have much less influence on the low-frequency energy of wall pressure fluctuations than that of radiated sound. High amplitude events of the wall pressure were observed to contribute to the weak coupling with high-frequency energy of radiated sound for the case of low tension applied to the plate. The sound source localization was applied to the measurement of radiated sound by using an acoustic mirror system.
展开▼
