Drag reduction of compressible wall turbulence with active dimples  

作　　者：SUN ZhenSheng REN YuXin LARRICQ Cedric 

机构地区：[1]Department of Engineering Mechanics.Tsinghua University,Beijing 100084 ,China [2]Xi'an Research Institute of High-tech,Xi'an 710025,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2011年第2期329-337,共9页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Natural Science Foundation of China (Grant Nos.10932005 and 50910222)

摘　　要：Direct numerical simulations are carried out to assess the potential drag reduction of compressible turbulent flow between isothermal walls.For the sake of achieving drag reduction,the flow is actively controlled by deformable dimples lying on the bottom wall of the channel.The first stage of the procedure consists in assessing the optimum geometry of the dimples.In this regard,the lower wall is allowed to freely deform itself according to the loop of control.This method is called the smart wall approach in this paper.By an analysis of the typical shape of the wall deformation thus obtained,it is found that dimples should be thinner than or comparable to the width of streaky structures in the spanwise direction and elongated in the streamwise direction.With active dimples as the wall-deformation actuators,a 15% drag reduction is obtained for the flow at Mam = 0.35 while the drag reduction rate is about 12% for the flow at Mam = 1.5.The fundamental mechanism of the drag reduction is then discussed in this paper.The drag reduction is believed to result from two aspects:the reduction of the mean streamwise velocity gradient near the deformable wall and the suppression of the turbulent fluctuations.Direct numerical simulations are carried out to assess the potential drag reduction of compressible turbulent flow between isothermal walls.For the sake of achieving drag reduction,the flow is actively controlled by deformable dimples lying on the bottom wall of the channel.The first stage of the procedure consists in assessing the optimum geometry of the dimples.In this regard,the lower wall is allowed to freely deform itself according to the loop of control.This method is called the smart wall approach in this paper.By an analysis of the typical shape of the wall deformation thus obtained,it is found that dimples should be thinner than or comparable to the width of streaky structures in the spanwise direction and elongated in the streamwise direction.With active dimples as the wall-deformation actuators,a 15% drag reduction is obtained for the flow at Mam = 0.35 while the drag reduction rate is about 12% for the flow at Mam = 1.5.The fundamental mechanism of the drag reduction is then discussed in this paper.The drag reduction is believed to result from two aspects：the reduction of the mean streamwise velocity gradient near the deformable wall and the suppression of the turbulent fluctuations.

关 键 词：compressible wall turbulence direct numerical simulation active dimples drag reduction 

分 类 号：O357.5[理学—流体力学] TE869[理学—力学]