疏水微槽道内层流减阻的实验研究

研究了光滑和带有横向凹槽结构的疏水微槽道内层流的流动特性和表面滑移效应。在硅片上加工了矩形截面微槽道，利用十八烷基三氯硅烷（octadecyltrichlomsilane OTS）在槽道内壁形成疏水薄膜。实验结果表明在光滑疏水微槽道内的水流压降比无滑移条件下的理论值减少8％。对于侧壁带有凹槽结构的疏水微槽道，流动阻力可以降低10％～30％。笔者采用micro—PIV测量得到的壁面表观滑移速度约为槽道中心速度的8％，滑移长度约为2μm。实验结果与滑移壁面条件下三维槽道内层流的解析解吻合，同时得到了带有凹槽结构的疏水微槽道内的流速分布。

Experimental study on laminar drag reduction in hydrophobic microchannels

In this work, the apparent slip effects of laminar water flow in smooth hydrophobic microchannel and patterned hydrophobic microchannels have been investigated. These microchannels are fabricated from silicon wafer using photolithography and are coated with hydrophobic OTS （octadecyhrichlorosilane）. Pressure drop reductions of approximately 8 % are found in the smooth microchannel coated with hydrophobic OTS. Using micro-PIV, we measured an apparent slip velocity at the wall of approximately 8 % of the centerline velocity, yielding a slip length of approximately 2 μm. These results are in agreement with the analytical solution derived for three-dimensional flow in microchannel with a slip boundary condition at the hydrophobic walls. The pressure drop reductions ranging from 10% to 30% are found in the patterned microchannels. The pressure drop reduction is shown to increase with increasing microridge spacing and decreasing microehannel width. The airwater interface can be directly observed in some scenarios, and the velocity fields of the flow near the air-water interface are measured using micro-PIV.