Influence of uniform momentum zones on frictional drag within the turbulent boundary layer  

作　　者：Kangjun Wang Nan Jiang 王康俊;姜楠(Department of Mechanics,School of Mechanical Engineering,Tianjin University,Tianjin 300350,China;Tianjin Key Laboratory of Modern Engineering Mechanics,Tianjin 300072,China)

机构地区：[1]Department of Mechanics,School of Mechanical Engineering,Tianjin University,Tianjin 300350,China [2]Tianjin Key Laboratory of Modern Engineering Mechanics,Tianjin 300072,China

出　　处：《Chinese Physics B》2021年第3期356-363,共8页中国物理B（英文版）

基　　金：Project supported by the National Natural Science Foundation of China(Grant Nos.11732010,11972251,11872272,11902218,and 11802195);the National Key R&D Program of China(Grant No.2018YFC0705300).

摘　　要：Based on a set of experimental databases of turbulent boundary layers obtained from particle image velocimetry in the streamwise-wall-normal plane at friction-velocity-based Reynolds number Reτ=612,the influence of uniform momentum zones(UMZs)on the skin-friction drag is investigated.The skin-friction drag is measured by the single-pixel ensemble correlation method.The results show that the velocity fields with the number of UMZs larger than the mean value have a relatively low skin-friction drag,while the velocity fields with the number of UMZs less than the mean value have a relatively high skin-friction drag.By analyzing the statistical characteristics of UMZs,the dynamic correlation between the UMZs and skin-friction drag is explored.The velocity fields with a low number of UMZs present a sweep event.These sweep motions intensify the small-scale Reynolds shear stress in the near-wall region by modulation effects.The enhancement of small-scale Reynolds shear stress is the direct reason for the high skin-friction drag.Increasing the proportion of velocity fields with high UMZs amount may be a direction to reduce the skin-friction drag within the TBL.

关 键 词：turbulent boundary layers uniform momentum zones skin-friction drag 

分 类 号：O357.5[理学—流体力学]