On the Development of a Time Domain Method for Caa “The Successes and Failures”

Abstract

A summary of the successes and failures encountered in developing a time domain steady state numerical method for aeroacoustics in two space dimensions is presented. The equations and boundary conditions governing nonlinear acoustic disturbances propagating through a viscous compressible internal steady flow field are presented. These equations and boundary conditions are evolved to a steady state on a supercomputer using an unsplit MacCormack method. The capabilities of the method are demonstrated by presenting solutions to several linear and nonlinear problems for which the expected trends were known. Results calculated from the method are shown to be superior to those obtained using direct numerical simulation. Also included is the development of a new strategy for evolving acoustic systems to a steady state. This strategy is shown to be very effective in eliminating transient acoustic waves. Failure to obtain the expected steady state solution was observed to occur only in cases where the boundary conditions were inadequate.