Abstract
Different from conventional streamwise-aligned riblets, converging and diverging (C–D) riblets are arranged obliquely along the main-flow direction, intending to induce a large-scale secondary flow that modulates or controls the existing large-scale vortical structures in wall turbulence. In this study, we perform direct numerical simulations of turbulent flow over the C–D riblets at a low Reynolds number and investigate the impacts of the C–D riblets on aerodynamic forces, turbulence statistics, and coherent structures. The results show that the C–D riblets can reduce the skin-friction drag, but at the expense of a significantly increased pressure drag in the diverging region, which leads to an increase in the total drag. We present detailed mean and statistical flow-fields to assess the flow characteristics in the presence of the C–D riblets, including modifications on the distributions of velocities, pressure, Reynolds stresses, and turbulence kinetic energy. Moreover, the re-arrangement of turbulence structures over the C–D riblets is examined in terms of instantaneous flow-fields and two-point correlations. The findings provide more insight into the physics of flow over C–D riblets and may contribute to the further development of this flow control strategy.
Funder
National Natural Science Foundation of China
Subject
Condensed Matter Physics,Fluid Flow and Transfer Processes,Mechanics of Materials,Computational Mechanics,Mechanical Engineering
Cited by
1 articles.
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