波纹通道内过渡领域流动特性的数值研究

Numerical Study on Gas Flow in the Transition Regime in a Wavy Microchannel

本文基于离散速度方向模型,数值研究了过渡领域内气体在正弦波纹通道中的流动特性。首先,对模型的控制方程进行了坐标转换,提出了分子在曲边边界上的反射处理方法,将原模型计算范围拓展到了不规则区域。基于此,采用结构化网格和二阶迎风格式对正弦波纹通道内处于过渡领域的气体流动进行了数值研究。结果表明,与连续介质领域和滑移领域不同,过渡领域内通道截面最大速度在Kn=1附近出现极小值;随着Kn数的增加,壁面滑移速度随之增加,而摩擦常数随之降低;此外,通道的渐扩过程滑移速度以及摩擦常数均降低,渐缩过程与此相反。

The characteristics of gas flow in the transition regime in a wavy microchannel were investigated numerically based on the Discrete Velocity Direction model in the paper. A plane coordinate transformation was applied to the governing equations, and a method to describe the reflection of discrete molecules on curved wall boundary was proposed. By this method, the Discrete Velocity Direction model has been extended to the irregular regions. Next, the gas flows in a wavy microchannel was numerically calculated using the second order upwind scheme based on structured grids. The results show that there is a minimum of velocity along the centerline at around Kn=1,which is very different from the phenomenon in the continuum and slip regimes. With the increase of Kn, the slip velocity increases and the constant coefficient of friction decreases. In addition, both the slip velocity and the constant coefficient decreases in the expended section, on the contrary, they increase in the contraction section.