The direct simulation of acoustics on Earth, Mars, and Titan

摘要

With the recent success of the Huygens lander on Titan, a moon of Saturn, there has been renewedinterest in further exploring the acoustic environments of the other planets in the solar system. Thedirect simulation Monte Carlo (DSMC) method is used here for modeling sound propagation in theatmospheres of Earth, Mars, and Titan at a variety of altitudes above the surface. DSMC is a particlemethod that describes gas dynamics through direct physical modeling of particle motions andcollisions. The validity of DSMC for the entire range of Knudsen numbers (Kn), where Kn isdefined as the mean free path divided by the wavelength, allows for the exploration of soundpropagation in planetary environments for all values of Kn. DSMC results at a variety of altitudeson Earth, Mars, and Titan including the details of nonlinearity, absorption, dispersion, and molecularrelaxation in gas mixtures are given for a wide range of Kn showing agreement with variouscontinuum theories at low Kn and deviation from continuum theory at high Kn. Despite largecomputation time and memory requirements, DSMC is the method best suited to study high altitudeeffects or where continuum theory is not valid.