期刊
ACTA MECHANICA SINICA
卷 35, 期 3, 页码 457-471出版社
SPRINGER HEIDELBERG
DOI: 10.1007/s10409-018-0828-2
关键词
Turbulent drag reduction; Riblets; Coherent structures
资金
- National Basic Research Program of China (973 program) [2014CB744802, 2014CB744804]
- National Natural Science Foundation of China [11772194, 91441205]
- Center for High Performance Computing, Shanghai Jiao Tong University
Direct numerical simulations (DNS) of turbulent flow over a drag-reducing and a drag-increasing riblet configuration are performed. Three-dimensional two-point statistics are presented for the first time to quantify the interaction of the riblet surfaces with the coherent, energy-bearing eddy structures in the near-wall region. Results provide statistical evidence that the averaged organization of the streamwise vortices in the drag-reducing case is lifted above the riblet tip, while in the drag-increasing case the streamwise vortices are embedded further into the riblet cove. In the spanwise direction, the cores of the streamwise vortices over the riblet surfaces are shown to be closer to each other than those for flow over the smooth wall, and wider riblet spacing leads to more reduction on their spanwise distances. In the cases with riblets the streamwise vortices have longer streamwise lengths, but their inclination angles do not change much.
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