AIAA 99-0231 Simulation of Acoustic Scattering from a Trailing Edge

Three model problems were examined to assess the diiculties involved in using a hybrid scheme coupling ow computation with the the Ffowcs Williams and Hawkings equation to predict noise generated by v ortices passing over a sharp edge. The results indicate that the Ffowcs Williams and Hawkings equation correctly propagates the acoustic signals when provided with accurate ow information on the integration surface. The most diicult of the model problems investigated inviscid ow o ve r a t wo-dimensional thin NACA airfoil with a bluu-body vortex generator positioned at 98 percent c hord. Vortices rolled up downstream of the bluu body. The shed vortices possessed similarities to large coherent eddies in boundary layers. They interacted and occasionally paired as they convected past the sharp trailing edge of the airfoil. The calculations showed acoustic waves emanating from the airfoil trailing edge. Acoustic directivity and Mach n umber scaling are shown.