微通道内气体流动的Onsager交叉耦合效应
Onsager's Cross Coupling Effects in Gas Flows Confined to Micro-channels
摘要：
在稀薄气体中，质量和热量的输运过程相互干扰，导致机械热效应和热渗透效应，这是理论研究和实际应用的重要内容。我们采用统一的气体动力学方案来研究微通道内气体流动的交叉耦合效应。我们的数值模拟覆盖渠道的平面表面和棘轮表面的渠道，与Onsager的相互关系验证这两种情况下。对于平面通道，在很宽的努森数范围内进行了模拟，数值结果与文献结果吻合良好。对于棘轮表面的通道，对滑移和过渡状态进行模拟，并且我们的数值结果不仅证实了理论预测[Phys.Rev.Lett. 107，164502（2011）]，但也表明交叉耦合效应的非对角动力学系数在过渡区的克努森数处最大化。最后，对基于棘轮面通道的努森泵的几何形状进行了初步的优化研究。
英文摘要：
In rarefied gases, mass and heat transport processes interfere with each other, leading to the mechano-caloric effect and thermo-osmotic effect, which are of interest to both theoretical study and practical applications. We employ the unified gas-kinetic scheme to investigate these cross coupling effects in gas flows in micro-channels. Our numerical simulations cover channels of planar surfaces and also channels of ratchet surfaces, with Onsager's reciprocal relation verified for both cases. For channels of planar surfaces, simulations are performed in a wide range of Knudsen number and our numerical results show good agreement with the literature results. For channels of ratchet surfaces, simulations are performed for both the slip and transition regimes and our numerical results not only confirm the theoretical prediction [Phys. Rev. Lett. 107, 164502 (2011)] for Knudsen number in the slip regime but also show that the off-diagonal kinetic coefficients for cross coupling effects are maximized at a Knudsen number in the transition regime. Finally, a preliminary optimization study is carried out for the geometry of Knudsen pump based on channels of ratchet surfaces.
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