Acta Physica Sinica, Volume. 68, Issue 7, 074702-1(2019)
Drag reduction by riblets has drawn the attention of many researchers because of its low production cost and easy maintenance. But due to the fact that the rather low drag reduction riblets can offered, an easy modification to the structure of riblets to improve the performance would be more than necessary. In this work, an investigation of the influences on coherent structure of straight riblets and sinusoidal riblets (s-riblets) in a turbulent boundary layer (TBL) at various Reynolds numbers is carried out experimentally by using the time-resolved particle image velocimetry (TR-PIV). It is found that the skin friction of the turbulent boundary layer is reduced close to the wall, and the logarithmic velocity profile shifts upwards over riblets and s-riblets. The turbulence intensity and Reynolds shear stress are also reduced in the near wall region compared with the scenario of the smooth case, and a better performance on drag reduction is obtained over s-riblets. Coherent structures including hairpin vortex and low speed streaks are extracted over test plates by using the correlation coefficient and
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Shan Li, Nan Jiang, Shao-Qiong Yang.
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Received: Oct. 19, 2018
Accepted: --
Published Online: Oct. 29, 2019
The Author Email: Yang Shao-Qiong (shaoqiongy@tju.edu.cn)