非球形颗粒布朗运动的涨落-格子Boltzmann数值研究

Brownian Motion of Non-spherical Particles:Fluctuating-Lattice Boltzmann Investigation

  • 摘要: 采用涨落-格子Boltzmann方法对非球形颗粒(二维)的布朗运动进行直接数值模拟.数值结果包括椭圆形、矩形颗粒的速度均方值及速度自相关函数等.研究发现,对于非球形颗粒,其方向性并没有影响能量均分原理的适用性,每个自由度的能量由其速度或角速度的均方值确定,而且计算的颗粒平动温度和转动温度一致.此外,颗粒的速度自相关函数在相对长的时间内以~ct-1的规律衰减,其系数c与颗粒的形状无关.

     

    Abstract: A fluctuating-lattice Boltzmann method is used for direct numerical simulations of Brownian motion of non-spherical particles. Numerical results include mean-square velocities and velocity autocorrelation functions of elliptical and rectangular particles. It showns that equi-partition theorem applies to non-spherical particles as well and energy of each degree of freedom depends on corresponding mean-square velocity or rotational velocity. Furthermore, translational temperature of Brownian particle is identical to its rotational temperature. Finally, velocity autocorrelation function of Brownian particle decays at relative long times as~ct-1, where coefficlent c is independent of particle shape.

     

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