气?面相互作用对均匀加热微梁系统中稀薄气体流动特性影响的数值研究

在微型设备和宏观尺度的真空环境中，非均匀温度场会引起稀薄气体流动，且浸没在气体中的结构会受到辐射力。文章采用直接模拟蒙特卡罗（DSMC）方法结合Cercignani-Lampis（CL）气?面相互作用模型，研究法向能量调节系数（NEAC）和切向动量调节系数（TMAC）对一对冷热微梁周围稀薄气体流动特性的影响。研究结果表明，流场结构、传热特性、压力分布和辐射力特性对表面调节系数的变化高度敏感——在单独改变冷梁表面调节系数的情况下，辐射力随着NEAC的降低呈近似线性增加，随着TMAC的降低呈非线性减小；在同步改变冷梁和热梁表面调节系数的情况下，辐射力随着TMAC的降低呈非线性增加，随着NEAC的降低呈先减小后增大的趋势。研究结果可作为设计、制造MEMS器件时的选材参考，以获得尽可能大的辐射力。

Numerical investigation of gas-surface interaction effects on rarefied gas flow characteristics in the system of uniformly heated microbeams

In micro devices or under a vacuum circumstance of a macroscale, the flows of rarefied gas are induced by the non-uniform temperature fields, with a force named the radiometric force on the immersed structures. In this paper, the direct simulation Monte Carlo (DSMC) method is applied in combination with the Cercignani-Lampis (CL) gas-surface interaction model, to investigate the effects of the normal energy accommodation coefficient (NEAC) and the tangential momentum accommodation coefficient (TMAC) on the characteristics of the rarefied gas flows around a pair of cold-hot microbeams. It is shown that the flow patterns, the thermal transfer performance, the pressure distributions, and the radiometric force characteristics are very sensitive to the variations of the accommodation coefficients. By only varying the accommodation coefficient of the cold microbeam, the radiometric force increases approximately linearly with the decrease of the NEAC, and decreases nonlinearly with the decrease of the TMAC. By concurrently varying the accommodation coefficients of both microbeams, the radiometric force increases nonlinearly with the decrease of the TMAC, while it reduces first and then increases as the NEAC decreases. The results can be used in the design and manufacturing of MEMS devices to obtain as large radiometric force as possible.