Mechanism of tangential Knudsen force at different Knudsen numbers
Mechanism of tangential Knudsen force at different Knudsen numbers
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DOI：
10.1063/5.0096324
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发表时间：
2022-07-01
影响因子：
4.6
通讯作者：
Yonemura, Shigeru
中科院分区：
文献类型：
--
作者：
Otic, Clint John Cortes;Yonemura, Shigeru
在具有非均匀温度场的稀薄气体中，出现的一种现象是切向努森力。各种研究都对切向努森力进行了研究，但仅限于特定情况。在这项研究中，我们研究了热诱导切向努森力的机制，在完全扩散条件下，并为一系列的努森数的理论分析。具体来说，我们制定了一个理论表达式来描述切向努森应力考虑两种动量通量转移的表面上的利益。一种是由直接来自另一个表面的分子而不经历分子间碰撞带来的，另一种是由来自体区域的分子在经历分子间碰撞后带来的。作为参考，我们使用了一个通道，其中下表面是热棘轮结构，上表面是平坦的冷物体。通过理论分析得到的物体上的切向Knudsen力与我们以前的工作，我们进行了数值实验的结果进行了比较，通过直接模拟蒙特卡罗方法。通过比较，发现切向努森力是由三种机制引起的。首先是来自不同温度的另一表面的撞击分子的贡献。其次是热驱动流动的粘性效应的贡献，而第三是热应力的贡献，这是显着的小努森数。(C)2022年作者。
In a rarefied gas with a non-uniform temperature field, one phenomenon that arises is the tangential Knudsen force. Various research studies have investigated the tangential Knudsen force but have been limited to specific cases. In this study, we investigated the mechanism of the thermally induced tangential Knudsen force, using theoretical analysis under fully diffusive conditions and for a range of Knudsen numbers. Specifically, we formulated a theoretical expression to describe the tangential Knudsen stress by considering the two kinds of momentum fluxes transferred on a surface of interest. One is brought by molecules directly coming from the other surface without experiencing intermolecular collisions, and the other is brought by molecules coming from the bulk region after experiencing intermolecular collisions there. As a reference, we used a channel where the lower surface is a hot ratchet structure and the upper surface is a flat cold object. The tangential Knudsen force on the object obtained by the theoretical analysis was compared with the results from our previous work where we performed numerical experiments by the direct simulation Monte Carlo method. Based on the comparison, it is found that the tangential Knudsen force is caused by three mechanisms. First is the contribution of impinging molecules coming from the other surface with different temperature. Second is the contribution of viscous effect of thermally driven flows, while the third is the contribution of thermal stress, which is noticeable in small Knudsen numbers. (C) 2022 Author (s).