Molecular-dynamics study on characteristics of energy and tangential momentum accommodation coefficients.
Molecular-dynamics study on characteristics of energy and tangential momentum accommodation coefficients.
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DOI：
10.1103/physreve.96.013116
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发表时间：
2017-07
期刊：
影响因子：
--
通讯作者：
H. Yamaguchi;Y. Matsuda;T. Niimi
中科院分区：
文献类型：
--
作者：
H. Yamaguchi;Y. Matsuda;T. Niimi
通过分子动力学方法研究气体-表面相互作用，以定性研究调节系数的特征。对大量气体分子碰撞和从表面散射的轨迹进行统计分析，以计算能量（热）调节系数（EAC）和切向动量调节系数（TMAC）。考虑到调节系数的实验测量，对入射速度进行随机采样以代表整体条件。稀有气体的调节系数与实验值显示出定性的一致性。为了详细研究这些调节系数的特征，通过一一改变气体分子质量、气体-表面相互作用强度和气体分子尺寸来参数化地研究气体-表面相互作用。 EAC随着各参数的增加而增加，而TMAC随着相互作用强度的增加而增加，但随着分子质量和分子尺寸的增加而减少。因此，实验测量的稀有气体 TMAC 中的矛盾结果可能是由于表面粗糙度和/或吸附分子导致的分子质量、相互作用强度和分子尺寸等有效参数之间平衡的测量中采用的表面条件之间的差异造成的。还研究了同时存在气体和表面温差以及整体流动的热流体动力学场的调节系数。
Gas-surface interaction is studied by the molecular dynamics method to investigate qualitatively characteristics of accommodation coefficients. A large number of trajectories of gas molecules colliding to and scattering from a surface are statistically analyzed to calculate the energy (thermal) accommodation coefficient (EAC) and the tangential momentum accommodation coefficient (TMAC). Considering experimental measurements of the accommodation coefficients, the incident velocities are stochastically sampled to represent a bulk condition. The accommodation coefficients for noble gases show qualitative coincidence with experimental values. To investigate characteristics of these accommodation coefficients in detail, the gas-surface interaction is parametrically studied by varying the molecular mass of gas, the gas-surface interaction strength, and the molecular size of gas, one by one. EAC increases with increasing every parameter, while TMAC increases with increasing the interaction strength, but decreases with increasing the molecular mass and the molecular size. Thus, contradictory results in experimentally measured TMAC for noble gases could result from the difference between the surface conditions employed in the measurements in the balance among the effective parameters of molecular mass, interaction strength, and molecular size, due to surface roughness and/or adsorbed molecules. The accommodation coefficients for a thermo-fluid dynamics field with a temperature difference between gas and surface and a bulk flow at the same time are also investigated.