A general model for riblets simulation in turbulent flows

The shark-skin-inspired riblets could effectively reduce the turbulence wall-skin friction compared with the smooth surface. Nevertheless, computations of the flow field over riblets in the practical configurations (e.g., airplanes and wind turbines) remain unfeasible for its huge computational cost. In this study, a general strategy for modelling the effects of riblets in turbulent flows is proposed. Riblets are modelled by adopting a slip-boundary condition on the smooth wall. A quantitative relationship between the riblet geometric parameters and the slip length is theoretically built for the first time. This modelling method could greatly reduce grid numbers in the validating procedure by using Large-Eddy Simulation, and the modelling results indicate that the flow fields in logarithmic and wake regions over riblets could be accurately reproduced. Additionally, considering the slip-boundary model is not capable of reproducing the near-wall flow, a simplified calculating method is developed.