Asymptotic Behavior in the Numerical Propagation of FiniteAmplitude Jet Noise

One issue of interest pertaining to the development of a numerical model applicable to the nonlinear propagation of jet noise is the behavior of spectral predictions at large distances. In this study, a recorded noise waveform from a military jet aircraft is numerically propagated via a hybrid time-frequency domain solution to the generalized Burgers equation that incorporates spherical spreading and atmospheric absorption and dispersion. Numerical results show that the spatial rate of change of the difference between the nonlinearlyand linearlypredicted power spectra appears to approach constant nonzero behavior at high frequencies. This asymptotic relationship is analogous to that predicted by analytical theory for initiallysinusoidal plane and spherical waves.