中国物理B ›› 2021, Vol. 30 ›› Issue (3): 34703-.doi: 10.1088/1674-1056/abc7a6

• ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS • 上一篇    下一篇

  

  • 收稿日期:2020-08-17 修回日期:2020-10-05 接受日期:2020-11-05 出版日期:2021-02-22 发布日期:2021-02-22

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

Kangjun Wang(王康俊)1 and Nan Jiang(姜楠)1,2,†   

  1. 1 Department of Mechanics, School of Mechanical Engineering, Tianjin University, Tianjin 300350, China; 2 Tianjin Key Laboratory of Modern Engineering Mechanics, Tianjin 300072, China
  • Received:2020-08-17 Revised:2020-10-05 Accepted:2020-11-05 Online:2021-02-22 Published:2021-02-22
  • Contact: †Corresponding author. E-mail: nanj@tju.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant Nos. 11732010, 11972251, 11872272, 11902218, and 11802195) and the National Key R&D Program of China (Grant No. 2018YFC0705300).

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Abstract: 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.

Key words: turbulent boundary layers, uniform momentum zones, skin-friction drag

中图分类号:  (Drag reduction)

  • 47.85.lb
47.85.ld (Boundary layer control) 47.27.nb (Boundary layer turbulence ?) 47.27.De (Coherent structures)