Hanford Amanda D, Long Lyle N
Applied Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16804, USA.
J Acoust Soc Am. 2009 Feb;125(2):640-50. doi: 10.1121/1.3050279.
With the recent success of the Huygens lander on Titan, a moon of Saturn, there has been renewed interest in further exploring the acoustic environments of the other planets in the solar system. The direct simulation Monte Carlo (DSMC) method is used here for modeling sound propagation in the atmospheres of Earth, Mars, and Titan at a variety of altitudes above the surface. DSMC is a particle method that describes gas dynamics through direct physical modeling of particle motions and collisions. The validity of DSMC for the entire range of Knudsen numbers (Kn), where Kn is defined as the mean free path divided by the wavelength, allows for the exploration of sound propagation in planetary environments for all values of Kn. DSMC results at a variety of altitudes on Earth, Mars, and Titan including the details of nonlinearity, absorption, dispersion, and molecular relaxation in gas mixtures are given for a wide range of Kn showing agreement with various continuum theories at low Kn and deviation from continuum theory at high Kn. Despite large computation time and memory requirements, DSMC is the method best suited to study high altitude effects or where continuum theory is not valid.
随着惠更斯号着陆器最近在土星的卫星土卫六上取得成功，人们对进一步探索太阳系中其他行星的声学环境重新产生了兴趣。本文采用直接模拟蒙特卡罗（DSMC）方法，对地球、火星和土卫六表面上方不同高度处大气中的声音传播进行建模。DSMC是一种粒子方法，通过对粒子运动和碰撞进行直接物理建模来描述气体动力学。DSMC在整个克努森数（Kn）范围内的有效性（其中Kn定义为平均自由程除以波长），使得能够探索所有Kn值下行星环境中的声音传播。给出了地球、火星和土卫六不同高度处的DSMC结果，包括气体混合物中非线性、吸收、色散和分子弛豫的细节，这些结果在很宽的Kn范围内显示出与各种连续介质理论在低Kn时一致，而在高Kn时偏离连续介质理论。尽管计算时间长且内存需求大，但DSMC是最适合研究高空效应或连续介质理论无效情况的方法。
