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中国物理学会期刊

多参数入射条件下分子碰撞对适应系数的影响

CSTR: 32037.14.aps.75.20251261

Effects of molecular collisions on accommodation coefficients under multi-parameter incident conditions

CSTR: 32037.14.aps.75.20251261
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  • 有效的气体-表面相互作用参数对准确预测气体在稀薄环境中的流动特性至关重要. 然而微观分子碰撞模型中不同分子动力学模拟方法得到的适应系数差异很大. 为了准确描述非平衡环境中分子碰撞与动量、能量适应的关系, 本文采用分子动力学模拟研究了氩与铂表面的相互作用. 通过单个散射(SS)和连续散射(CS)方法系统地讨论了气-气碰撞对适应系数的影响. 比较了两种方法在不同表面形态、表面温度、入射气体分子速度等影响因素下的气体-表面相互作用特性. 得到了适应系数与表面温度、入射速度等参数之间的依赖关系. 通过分析两种模拟方法的差异, 揭示了多参数入射条件下适应系数变化的物理机制, 为建立更精准的气体-表面相互作用模型提供了重要基础和依据.

     

    In rarefied gas flows, accommodation coeffcients (ACs) serve as core parameters for gas-surface interactions and play a crucial role in the accuracy of mesoscopic model simulations. However, there exist significant discrepancies in the ACs obtained by different molecular dynamics simulation methods. To accurately characterize the momentum and energy accommodation properties of rarefied gases with solid surfaces under non-equilibrium conditions, this study systematically investigates the gas-surface interactions between argon molecules and platinum surfaces using molecular dynamics (MD) methods. By using single scattering (SS) and continuous scattering (CS) methods, the effects of gas-gas collisions on tangential momentum accommodation coeffcient (TMAC), normal momentum accommodation coeffcient (NMAC), and energy accommodation coeffcients (EAC) are compared and analyzed, as well as the operating rules of parameters such as surface morphology, surface temperature, incident velocity, and mean free path (MFP). The results demonstrate that gas density exerts a dual effect on momentum and energy accommodation: at smaller MFP, the high gas density within the interaction region impedes the accommodation of subsequent incident molecules with the surface, resulting in lower ACs; at moderate MFP, gas-gas collisions promote the accommodation by increasing the frequency of gas-surface collisions, thereby enhancing ACs. Within the MFP range of 2.0–60.0 nm, the deviation in ACs between the CS and SS methods ranges from –14.88% to 5.21%, validating the dual role of gas density. Furthermore, at larger MFP, the TMAC and NMAC obtained via the CS method exhibit different trends with the increase of MFP across surfaces of varying morphologies. In contrast to gas density, increases in both surface temperature and incident velocity shorten the interaction time, resulting in reduced ACs. Notably, the effect of temperature varies across surfaces with different morphologies: elevated temperatures on smooth surfaces enhance the thermal fluctuations of surface atoms, thereby increasing NMAC, while elevated temperatures on rough surfaces make the rough structures smoother, thereby suppressing accommodation. Under high-speed incident conditions, gas-gas collisions enhance NMAC on smooth surfaces, inhibit both TMAC and NMAC on rough surfaces, and suppress EAC across all surfaces. In addition, the ACs obtained via both the CS and SS methods decrease with the increase of incident velocity on surfaces of different morphologies.

     

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