| 气体-表面相互作用中动量和能量分量间转化机制的分子动力学研究 |
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| 引用本文： | 于航,张冉,杨帆,李桦.气体-表面相互作用中动量和能量分量间转化机制的分子动力学研究[J].物理学报,2021(2):363-372. |
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| 作者姓名： | 于航 张冉 杨帆 李桦 |
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| 作者单位： | 国防科技大学空天科学学院;西北核技术研究所 |
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| 基金项目： | 国家自然科学基金(批准号:11472004)资助课题. |
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| 摘 要： | 气体分子与壁面之间的相互作用是影响稀薄气体流动状态的主要因素,但是由于其物理上的复杂性和微观性,这一过程的机理并没有得到充分揭示.本文利用分子束法对Ar分子在金属Pt表面的碰撞过程进行了分子动力学模拟,并探究了入射速度、角度和壁面粗糙度对动量、能量转化机制的影响.结果表明,当气体分子以5o的极角入射时,分子的法向速度分量占主导因素,在与壁面发生碰撞之后,分子的切向和法向动量都会损失,法向动能会向切向转移,并且当分子速度不低于2.0时,切向和法向动能的比值会稳定在一个很小的区间,而粗糙度对动量和能量转化的影响不明显.与小角度入射时不同,当气体分子以75o的极角与金属表面碰撞时,粗糙度的影响就不能再被忽略了.大极角入射的气体分子在光滑壁面散射之后,其运动规律基本符合Maxwell所假设的镜面反射,动量和能量分量的变化都不明显.而粗糙度的引入则会促进气体分子切向动量和能量向法向转移,并且会使分子总能量的损失更加显著.
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| 关 键 词： | 气体-表面相互作用 分子动力学 动量和能量转化 |
Molecular dynamics study on the conversion mechanism between momentum and energy components in gas-surface interaction |
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| Yu Hang,Zhang Ran,Yang Fan,Li Hua.Molecular dynamics study on the conversion mechanism between momentum and energy components in gas-surface interaction[J].Acta Physica Sinica,2021(2):363-372. |
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| Authors: | Yu Hang Zhang Ran Yang Fan Li Hua |
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| Affiliation: | (College of Aerospace Science and Engineering,National University of Defense Technology,Changsha 410073,China;State Key Laboratory of Laser Interaction with Matter,Northwest Institute of Nuclear Technology,Xi’an 710024,China) |
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| Abstract: | With the rapid development of micro-nano technology and aerospace technology,researches related to rarefied gas flows have received more and more attention.For micro-/nanoscale systems and spacecraft in a rarefied environment,the reduction in the frequency of intermolecular collisions in the flow field makes the interaction between gas molecules and the solid surface develop into a major factor affecting the flow state.However,the mechanism of gas-surface interaction in rarefied flow has not been fully revealed due to its microscopic nature and physical complexity,and the existing simulation methods cannot accurately reflect the effect of this process on the flow state.In this paper,molecular beam method is adopted to simulate the scattering process of argon molecules on platinum surface,and the impacts of incident velocity,angle and wall roughness on the momentum and energy conversion mechanism are explored.By simulating the molecular scattering process under the two incident angles of 5o and 75o,the following conclusions are obtained.When colliding with the wall at an angle close to vertical,both components of the momentum of the gas molecules are lost.The normal energy transfers to the tangential direction,and when the molecular velocity is not less than 2.0,the transfer rate is not significantly affected by the incident energy of the molecule and the surface roughness.The total energy loss of gas molecules after scattering becomes significant with the increase of incident velocity,and it is not sensitive to changes of surface roughness.When the gas molecules are incident at 75o,the roughness of the surface has a significant impact on the conversion mechanism of molecular momentum and energy.After colliding with a smooth wall,the momentum and energy values of the gas molecules remain basically unchanged,only the direction of the momentum is reversed.The motion state of molecules is close to the mirror reflection,and the conversion between momentum and energy components is not obvious.The introduction of roughness enhances the degree of accommodation between gas molecules and metal surface,and promotes the transfer of molecular tangential momentum and kinetic energy to the normal direction.When incident at a large polar angle,as opposed to the small-angle cases,the total energy loss of molecules is not sensitive to changes of incident velocity,it goes up significantly with the surface roughness increasing.The research in this article not only explores the gas-surface interaction mechanism,but also provides a useful reference for the high-fidelity simulation of rare gas flow and the development of appropriate gas-surface interaction models. |
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| Keywords: | gas-surface interaction molecular dynamics momentum and energy conversion |
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