Abstract:

Based on the model of volume of fluid, two-dimensional fluid laminar flow in superhydrophobic microchannels was numerically simulated with given parabolic gas-liquid interfaces. The effects of several flow and structural parameters on fRe, the normalized slip length and pressure drop were investigated. The results show that superhydrophobic microchannels with rectangular microcavities exhibited significant drag reduction in a way that fRe increased slightly with increase of Reynolds number whereas normalized pressure drop decreased slightly with increase of inlet velocity. When the area ratio of microcavities was increased or the microchannel diameter was decreased, fRe was reduced but normalized pressure drop was enhanced. In case of small microchannel diameter, the area ratio of microcavities significantly affected fRe. With increase of the parabolic height, the ratio of normalized pressure drop and the normalized slip length decreased linearly, however fRe increased linearly. The impact of microcavities on the normalized slip length and the ratio of normalized pressure drop was minimal provided that the microcavity depth was greater than 40% of its width. The dovetail microcavities exhibited the greatest effect on drag reduction, followed by the rectangular, trapezoidal, triangular microcavities in the order of high to low.

Key words: superhydrophobic surfaces, microchannels, numerical simulation, gas-liquid interface, laminar flow, microscale, two-phase flow

摘要：

针对超疏水表面微通道中的流动减阻特性，基于抛物线形气-液界面假设，采用VOF模型模拟了微通道中的二维层流流动，分析了流动和结构参数对减阻效果的影响。结果表明，含矩形微坑的超疏水表面微通道具有显著减阻作用，fRe随Reynolds数增大而略有提高，量纲1压降比随入口速度增大而略有下降。当增大微坑面积比或减小微通道高度时，fRe减小，量纲1压降比增大；且微通道高度越小，微坑面积比对fRe的影响越显著。随抛物线形高度增加，压降比和滑移长度均线性减小，而fRe则线性增加。当微坑深度大于其宽度的40%时，压降比和滑移长度趋于定值。微坑形状对减阻效果的影响依次是燕尾形、矩形、梯形和三角形。

关键词: 超疏水表面, 微通道, 数值模拟, 气-液界面, 层流, 微尺度, 两相流