Abstract

The Resolution of Components of Wall Pressure Spectra for Experimental Study of Wall-Near Pressure Fluctuations Beneath Turbulent Boundary Layer

E.Kudashev (Space Research Institute, Moscow, Russia)

e-mail: eco@iki.rssi.ru

Near-wall pressure fluctuations in turbulent flows are of considerable interest in physics of flow noise. We shall concentrate on a number of specific questions related to the resolution of components of wall pressure spectra. Our emphasis shall be on outstanding problems of experimental methods for the acoustics of the turbulent flows and will be motivated by the desire to improve the resolution of surface pressure fluctuations. A study on pressure fluctuations transducer.s resolution has been performed on the basis upon experimental measurements. The problem of vibration noise compensation in hydrodynamic acoustics is important for the study of near-wall pressure fluctuations since a miniature piezoelectric sensor not only reacts to turbulent pressure but also generates a signal which is proportional to the applied force. In a turbulent flow, the sensor is placed in the zone of intense vibration induced by near-wall pressure fluctuations. In such conditions, pi! ezoelectric sensor transduces not only pressure but acceleration as well. There is thus a necessity to distinguish between turbulent and vibration signals registered by the sensor. Piezoelectric pressure transducer generates the signal also on vibration influence. Algorithm of assign of turbulent surface pressure in conditions of flow-induced-vibration is suggested. An active method of vibration control has been developed. We represent also the active method of acoustic noise compensation on the basis of an effect of spatial filter.

Section : 7