Investigation of nonreflective boundary conditions for computational aeroacoustics

Direct aeroacoustic computations require nonreflective boundary conditions that allow disturbances to leave the domain freely without anomalous reflections. In the present paper we analyze a series of nonreflective boundary conditions already published in the literature and propose an improved outflow nonreflective boundary condition with reflection characteristic that is reduced greatly. For the solution of the linearized Euler equations, a sixth-order compact finite-difference algorithm is used together with a sixth-order explicit digital filter that suppresses the high-frequency spurious oscillations in the solution. A number of representative test cases are presented. The new outflow boundary condition is recommended for the simulation of sound produced by turbulence.