论文标题
使用分子模拟来计算分子气的传输系数
Using Molecular Simulation to Compute Transport Coefficients of Molecular Gases
论文作者
论文摘要
现有的气体动力学理论是基于一种分析方法，该方法对除最简单的分子以外的所有人都变得棘手。在这里，我们提出了一个简单的数值方案，以计算无限稀释极限的分子气体的转运特性。我们提出的方法是近似的方法，但是我们对扩散率$ d $，粘度$η$和热导率的结果$λ$的硬球，Lennard-Jones颗粒和粗糙的硬球的结果很好地与标准（最低订单）Chapman-Enskog结果一致。我们还为氮的Lennard-Jones-Dimer模型提供了结果，为此没有分析结果。对于多原子分子（我们考虑N-辛烷），我们的方法仍然很简单，并为扩散性和粘度提供了良好的预测。计算多原子分子的导热率需要对其量化的内部模式进行近似处理。我们表明，将$λ$与$ d $和$η$相关的众所周知的近似值可产生良好的结果。我们注意到，我们的方法应产生$ d $，$η$和$λ$的确切值的下限。有趣的是，粗糙的硬球的最复杂（高阶）Chapman-Enskog结果似乎违反了这一约束。
The existing kinetic theory of gases is based on an analytical approach that becomes intractable for all but the simplest molecules. Here we propose a simple numerical scheme to compute the transport properties of molecular gases in the limit of infinite dilution. The approach that we propose is approximate, but our results for the diffusivity $D$, the viscosity $η$ and the thermal conductivity $λ$ of hard spheres, Lennard-Jones particles and rough hard spheres, agree well with the standard (lowest order) Chapman-Enskog results. We also present results for a Lennard-Jones-dimer model for nitrogen, for which no analytical results are available. In the case of poly-atomic molecules (we consider n-octane), our method remains simple and gives good predictions for the diffusivity and the viscosity. Computing the thermal conductivity of poly-atomic molecules requires an approximate treatment of their quantized internal modes. We show that a well-known approximation that relates $λ$ to $D$ and $η$, yields good results. We note that our approach should yield a lower limit to the exact value of $D$, $η$ and $λ$. Interestingly, the most sophisticated (higher-order) Chapman-Enskog results for rough hard spheres seem to violate this bound.
