Flow Simulation of Various Riblet Shapes and a Uniform Model for Boundary Layer

Various riblet shapes are simulated through the computational fluid dynamics method for the elucidation of riblet effects on turbulent boundary layers and skin friction reduction. For the different shapes, seven typical riblet models are investigated by using renormalization group k-epsilon turbulence models. Simulation results are consistent with the existing theoretical data regarding flat plate and experimental results obtained from the riblet shapes. The riblet velocity profiles cannot satisfy the existing von Kármán’s constants in the logarithmic law boundary layer. The slope and intercept of the logarithmic law are strongly affected by geometric parameters and riblet shapes, and the effect of geometric parameters can be modeled. Meanwhile, the effects of riblet shapes can be modeled with a shape factor composed of a nondimensional cavity ratio and nondimensional top flatness. Therefore, a uniform model of the boundary layer can be obtained to illustrate the effects of various riblet shapes.