Direct computations of unsteady flows about thin airfoils

The intent of this paper is to investigate the effectiveness of direct nume rical computation in capturing acoustic fields. It has been the trend to us e high-order schemes whenever there is interest in resolving the acoustic f ield, even though there has never been a complete study of the accuracy of low-order schemes. We revisit a long-standing benchmark problem in aeroacou stics to show the validity of such low-older schemes. The problem we consid er is that of a flat-plate airfoil in a non-uniform flow. We show that when the linearized Euler equations are used to model problems in aeroacoustics , a simple second-order numerical scheme is powerful enough to provide accu rate aeroacoustic results. We validate this computational approach by compa ring both the RMS and instantaneous pressure on the airfoil and in the far held to semianalytic and asymptotic results.