A Westervelt equation for acoustic wave propagation through weakly stratified, arbitrary Mach number atmospheres

Abstract: Nonlinear distortion of infrasonic waves through atmospheres up to thermospheric altitudes govern large-range ground-level observations of explosive noise sources, causing large differences between the near and far field. Propagation modelling in this scenario to include realistic nonlinear effects has thus far been limited to high-fidelity, numerically intensive Direct Numerical Simulations of the Navier-Stokes equations, or nonlinear parabolic equations with restrictions on the mean flow Mach number. For the accurate modelling of nonlinear waveform synthesis through realistic atmospheric winds up to thermospheric altitudes, this work presents nonlinear wave equation analysis which results in in a Westervelt equation for weakly stratified, arbitrary Mach number atmospheres. This is intended to be used as a benchmark for model development and numerical analyses such that alternative low-fidelity numerical calculations to Direct Numerical Simulations can be sought.