A Synthesis Approach for Reproducing the Response of Aircraft Panels to Turbulent Boundary Layer Excitations

Abstract

Random wall-pressure fluctuations due to a Turbulent-Boundary Layer (TBL) are a feature of the air flow over an aircraft fuselage under cruise conditions, creating undesirable effects such as cabin noise annoyance. In order to test potential solutions for the reduction of TBL-induced noise, a cost-efficient alternative to in-flight measurements or wind-tunnel testing involves simulating the response of aircraft structures to TBL excitation in the laboratory. The authors have already shown that the TBL simulation using a near-field array of loudspeakers is limited to the very low frequency range due to the rapid decay of the spanwise correlation length as frequency increases. The present study addresses the problem of directly simulating the vibroacoustic response of an aircraft skin panel using a near-field array of suitably driven loudspeakers. It is compared with the use of an array of shakers and piezoelectric actuators. It is shown how the wavenumber filtering capabilities of the panel reduces the number of sources required, thus dramatically enlarging the frequency range over which the TBL vibro-acoustic response is reproduced with accuracy. Direct reconstruction of the TBL-induced panel response is found to be feasible over the hydrodynamic coincidence frequency range using a limited number of actuators driven by optimal signals. It is shown that piezoelectric actuators, which have more practical implementation than shakers, provide a more effective reproduction of the TBL response than near-field loudspeakers.