Numerical acoustic wave propagation in the atmosphere

Abstract

A method is presented which simulates the acoustic wave-field in the atmosphere using a Chebyshev pseudo spectral approach. The aero-acoustic equation of motion is solved in spherical coordinates. The computational time is significantly reduced by applying a rotationally symmetric approximation. Since the complete wave-field is calculated for the two-dimensional model the solution provides pictures of the pressure propagation from the source to the receiver. These images make it possible to study two effects in detail: How the sound and wind profiles affect the synthetic barograms for a fixed source, and in which way the source in space and time is reflected in the synthetic recordings for a stationary elastic model. Examples for both applications are shown where measured data are compared with synthetics. The recording at the German IMS station I26DE of the September 21, 2001, chemical explosion in Toulouse is considered as a benchmark for synthetic barograms calculated for two-dimensional profiles based on NRL-G2S and MSISE/HWM. In the second example the estimation of the source functions of super-sonic moving bodies is demonstrated. The synthetic waveforms are compared with the signals of two bolides recorded at the French IMS station I24FR at Tahiti from the December 1, 2003.