剪切气流驱动下微沟槽表面液滴受力分析

Force Analysis of Liquid Droplets on Micro-Grooved Surfaces with Air Flow

通过对剪切气流驱动下液滴在平行微沟槽表面的受力及变形的理论分析,提出了沟槽表面液滴在剪切气流下脱落的力学模型.在卡特皮勒力计算中,分别改进了积分式中固液接触角、接触半径项,采用一个更符合实际物理现象的分段函数表征了积分式中的接触角项;而对于接触半径项,利用椭圆接触线方程导出.在拖拽力的计算中,引入了无滑移边界条件下的剪应力公式简化了已有的拖拽力表达式.利用小型风洞,对所建立的力学模型进行了验证.测量结果表明,液滴脱落所需要的风速随着沟槽尺寸的增大而增大,沟槽方向垂直切向流放置情况下液滴所需要的脱落风速明显大于平行方向放置情况.实验观测结果与理论受力模型具有较好的一致性,表明所建立的力学模型合理有效.

The dynamics of a liquid droplet driven by an air flow and displaced on the micro-grooved surface was investigated, and a force balance model in terms of dynamic contact angle was obtained. Two terms of θ（a） and r （a） were improved in the calculation of capillary force. The term θ（a） was expressed by a piece wise function while term r （a） was deduced by the equation of elliptical contact line. The drag force was simplified by importing the no-slip boundary condition. Then the model was tested in a wind tunnel experi mentally. The test results turned out to be consistent with the experimental results, which proved that the force balance model was rational and effective.