The Effect Of Gas-liquid Interface Curvature On Drag Reduction In Superhydrophobic Microchannels

In recent years,inspired by hydrophobic property of lotus leaves,rice leaves and taro leaves in nature,people have paid more and more attention to the characteristics of superhydrophobic surfaces,which have good application prospects in reducing the flow resistance and self-cleaning materials.There are rough microstructures in superhydrophobic surfaces,and due to the effect of surface tension,the flowing liquid cannot fully penetrat the cavities in between the microridges and a gas-liquid interface thus forms between two adjacent microridges with air being trapped in the cavities,which greatly reduces the solid-liquid contact area on the surface and thus decreases the viscous resistance of the flowing liquid.The researches on the flow drag reduction in superhydrophobic microchannels show that the gas-liquid interface curvature has significant influence on the slip length and drag reduction effect.Therefore,this paper has emphatically studied the effect of the gas-liquid interface on drag reduction in superhydrophobic microchannels.The main contents of this paper are as follows:(1)For the flow drag reduction characteristics in superhydrophobic microchannels with transverse cavities,the VOF model is employed to simulate the two-dimensional single slip flow in microchannels with given parabolic gas-liquid interfaces.The flow kinematics characteristics in superhydrophobic microchannels are analyzed in the laminar regime,and the effects of the inlet velocity,the cavity fraction,the microchannel height,the parabolic height,the cavity depth and the cavity shape on drag reduction are examined.(2)In order to further investigate the effect of gas-liquid interface curvature on flow drag reduction in superhydrophobic microchannels comprehensively,the angle between the tangent line of the gas-liquid interface and the horizontal line on the surface of the microridge is defined as protrusion angle ?,and the two-dimensional bilateral slip flow in superhydrophobic microchannels is simulated for ?=-90?~90?.The effects of the protrusion angle,the shear-free fraction,the microchannel height and Reynolds number on drag reduction are investigated.