Generalized characteristic boundary conditions for computational aeroacoustics, part 2

Abstract

A previous paper introduced generalized characteristic boundary conditions for computational aeroacoustics (CAA), especially in the focus of far-field nonreflecting conditions. Strict wall boundary conditions are now developed on the basis of the generalized characteristics. True multidimensionality of the characteristic relations is guaranteed by maintaining entire terms of governing equations, which had been approximated virtually by local one-dimensional inviscid relations during the past two decades. Treating the transverse and viscous terms as source terms in the characteristic relations leads to an exact and simple formalism of wall boundary conditions. The formalism does not include any kind of extrapolation or assumption. The proposed inviscid and viscous wall boundary conditions are applied to typical CAA problems for verifying numerical accuracy in actual implementations. The computations are performed on nonorthogonal grids to exhibit the effect of multidimensionality on the solutions in acoustic fields. It is shown that the present results are in good agreement with analytic estimations and experimental data. This demonstrates the feasibility of the proposed wall boundary conditions for further practical CAA applications.