Efficient Domain Decomposition Technique for Solution of High Amplitude Acoustic Wave Scattering in Nonuniform Flows

摘要

In this paper acoustic scattering of high amplitude waves in nonuniform flows is considered. Three numerical solutions are compared: (i) linearized unsteady flows, (ii) nonlinear unsteady flows and (iii) a domain decomposition technique that combines a partially linearized and nonlinear flow domain. For all three solutions, higher order finite difference DRP scheme is applied to all spatial derivatives and LDDRK scheme is applied for the temporal integration. PML is applied at the edges of the computational domain to ensure that no reflections contaminate the solution. To include complex bodies and geometries the overset grid is used. Numerical results suggest that linear flow simulations are acceptable for very low amplitude acoustic pulses as expected from analytic theory and perturbation analysis. Tests were conducted to investigate the importance of mean flow gradients in a converging-diverging channel and in the vicinity of a stagnation point. The results show that accounting for nonlinear effects is not significant for low amplitude acoustic pulses in accelerating flows; however, it must be .accounted for in the vicinity of stagnation points. The results show that accounting for nonlinear flow effects by using a domain decomposition technique can eliminate the need of computing the entire domain using as nonlinear solver and that both the computational and time requirements can be reduced by about 40%. The results show that the nonlinear domain around the scattering body does not need to be very thick, just a few cell widths in the normal direction to the body.