Effects Of Micro-channel Surface Wettability On Interfacial Drag

Boundary slip can reduce the drag between the fluid and the wall, and make a great significance to the liquid flow in the micro-fluidic system In this paper, the effects of micro-channel surface wettability on interfacial drag are studied by Preparing different wettability surfaces, assembling micro-channels and computational fluid dynamics simulating, the findings have an important reference value to the micro-fluidic device design and preparation.Using the micro performance intercross valuation technique experiments the Slip velocity of four micro-channels with different surfaces wettability made by silicon wafer, studying the effect of surface wettability on micro-channel interfacial drag in unilateral and bilateral slip micro-channels. The results show that:boundary slip not occurs on hydrophilic surface but the hydrophobic surface, and the stronger the boundary surface hydrophobicity the greater the slip velocity; When the width and flow of micro-channel is constant, micro-channel flow rate at the center reduce and the fluid velocity contour become gentle with the surface hydrophobicity strengthen; The slip velocity and slip length of a same surface is not identical, and the values in unilateral slip micro-channels is much larger than in bilateral slip micro-channels.Using slip and no-slip alternating wall model to simulate the micro-channel flow distributions with different micro-structures in laminar conditions, the results show that: the drag reduction of superhydrophobic surface increases with the slightly projections diameter addition, reduces with the slightly projections area ratio and the micro-channel width addition, and less affected with the Reynolds number.A solid-gas complex wall model is built to make a compare with the slip and no-slip alternating wall model, and study the effect of superhydrophobic surface micro-structure depth and shape on micro-channel interfacial drag. The results show that:In the same micro-channel dimensions and fluid environment conditions, the pressure drop values of the three models are close, but the slip velocity of slip and no-slip alternating wall model is much larger, micro-structural shapes can affect the Superhydrophobic surface drag reduction, and the sequence of effect increase in the order of triangular, trapezoidal, rectangular, dovetail. Superhydrophobic drag reduction increase with the micro-structure depth increasing, and when it exceeds a certain value after not increased.