UPWIND SCHEME FOR ACOUSTIC DISTURBANCES GENERATED BY LOW-SPEED FLOWS

Computation of acoustic disturbances generated by unsteady, low-speed flows, such as flows including vortices and shear layers, can be obtai ned by a recently proposed two-step method. This method requires a hyd rodynamic field solution and obtains the acoustic field from the pertu rbed, inviscid, compressible how equations, A numerical method for the solution of the equations governing the acoustic field is presented. The primitive variable form of the governing equations is used for the numerical solution. Time integration is performed with a fourth-order , Runge-Kutta method, Discretization of the primitive variables space derivatives is obtained with a high-order, upwind-biased numerical sch eme. Upwinding of these convective fluxes is performed according to th e eigenvalue sign of the coefficient matrices. Nonreflecting boundary conditions are applied to properly convect outgoing waves away from th e computational domain. Solutions are obtained for the acoustic field generated by a pair of corotating point vortices. Computed results are compared with the existing analytic solution for the sound field.