表面张力对疏水微结构表面减阻的影响

Drag reduction on micro-structured hydrophobic surfaces due to surface tension effect

通过构造具有棋盘状微结构的疏水表面,考虑表面张力的影响,利用定常与非定常结合的数值模拟方法,研究了疏水表面在湍流状态下的减阻特性以及微结构内气体封存的效果,其中Re=3000—30000.在低雷诺数下,疏水表面微结构内气体封存状态良好,减阻率最高约为30%;随着雷诺数的增大,压差阻力增大,减阻率有下降趋势.当来流速度过大时,水会大量进入微结构,疏水表面的减阻率变化剧烈,且已经不再减阻.结果表明,表面张力削弱了壁面切应力的影响,使得低雷诺数下微结构内气体能够有效封存,进而减小壁面阻力.

This article studies drag reduction rule and gas restoration and retention of hydrophobic surfaces numerically when taking into consideration the surface tension efiect, the microstructure here is chessboard-like and the Reynolds number varies from 3,000 to 30,000. Results show that gas restoration and retention keep well, and a maximum drag reduction rate of approximately 30% has been gained at small Reynolds number（Re 15000）. When Re is too large, water will swarm into microstructures, and keeping a good gas-liquid interface becomes dificult. Meanwhile, drag reduction rate remains variable and hydrophobic surfaces do not reduce drag. Through mechanical analysis we find that the infiuence of shear stress is weakened due to surface tension efiect, thus the gas in microstructures can be efiectively stored at lowfiow speed and drag is reduced.