Simulation of acoustic scattering from a trailing edge

Three model problems were examined to assess the difficulties involved in u sing a hybrid scheme coupling flow computation with the Ffowcs Williams and Hawkings equation to predict the noise generated by vortices passing over a sharp edge. The results indicate that the Ffowcs Williams and Hawkings eq uation correctly propagates the acoustic signals when provided with accurat e flow information on the integration surface. The most difficult of the mo del problems investigated flow over a two-dimensional, thin NACA airfoil wi th a bluff-body vortex generator positioned at 98% chord. Vortices rolled u p downstream of the bluff body. The shed vortices possessed similarities to large coherent eddies in boundary layers in that they interacted and occas ionally paired as they convected past the sharp trailing edge of the airfoi l. The calculations showed acoustic waves emanating from the airfoil traili ng edge. Acoustic directivity and Mach number scaling were obtained. (C) 20 00 Academic Press.