Direct numerical simulations of turbulent flow over the converging and diverging riblets

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 existing vortical structures in wall turbulence. In this study, we perform direct numerical simulations of turbulent over C–D at low Reynolds number investigate impacts on aerodynamic forces, turbulence statistics, coherent structures. The results show can reduce skin-friction drag, but expense significantly increased pressure drag region, which leads an increase total drag. We present detailed mean statistical flow-fields assess characteristics presence including modifications distributions velocities, pressure, stresses, kinetic energy. Moreover, re-arrangement is examined terms instantaneous two-point correlations. findings provide more insight into physics may contribute further development control strategy.