A prediction of drag reduction by entrapped gases in hydrophobic transverse grooves  

作　　者：WANG Bao WANG JiaDao CHEN DaRong 

机构地区：[1]State Key Laboratory of Tribology, Tsinghua University

出　　处：《Science China(Technological Sciences)》2013年第12期2973-2978,共6页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51075228 and 51021064)

摘　　要：The drag reduction effect of super-hydrophobic surface induced by the entrapped gas is unstable due to the gradual disappearance of the trapped gas.In this paper,a hydrophobic transverse grooved surface was designed to sustain gas in valleys.A detail numerical simulation was presented to investigate the flow field near the proposed surface.When water flowed over this surface,the entrapped gas was blocked by the ridges and the solid-liquid interface was replaced by the liquid-gas interface due to the entrapped gas,furthermore the micro-vortex formed in the groove.Because there was an effective slippage between water and solid induced by the entrapped gas,the velocity gradient of boundary layer decreased,which contributed to a remarkable drag reduction effect.Additionally,considering the extra undesired pressure drag reduction which negatively impacted the drag reduction effect of this method,the total drag coefficient including the viscous drag coefficient and the pressure coefficient was analyzed.An effective drag reduction rate of about 15%was achieved and the effect of this method was confirmed by experiments conducted in a high-speed water tunnel when grooves were optimized.

关 键 词：hydrophobic transverse groove GAS SKIN-FRICTION drag reduction computational fluid dynamics（CFD） 

分 类 号：TB30[一般工业技术—材料科学与工程]