Comparative analysis of drag reduction characteristics of two-type riblets based on numerical simulation

Abstract

Turbulent drag reduction has always been a hot issue in fluid mechanics. Among various turbulent drag reduction methods, riblets has attracted wide attention due to its simple structure and convenient application. In order to investigate the effect of the riblets shape on the drag reduction, the effect of the triangular and trapezoidal riblets on the turbulent boundary layer flow field and drag reduction characteristics has been studied numerically by adopting the CFD method and based on the large eddy simulation (LES). The numerical simulation of turbulent channel flow was conducted by RANS, DES and LES methods respectively, and their results were compared with the results of direct numerical simulation (DNS) to verify the accuracy and feasibility of the large eddy simulation method. According to the experimental results in references, the flow field parameters such as integral statistics, first-order statistics and second-order statistics of the triangular and trapezoidal riblets on the turbulent boundary layer flow fields were compared and analyzed. The drag reduction characteristics of two-type riblets were investigated by studying the variation in physical parameters such as drag reduction rate, time-averaged velocity, root mean square velocity fluctuation, shear stress, turbulent kinetic energy generation and contour of spanwise velocity fluctuation, and it was concluded that the trapezoidal riblets have better drag reduction effect than the triangular riblets under the same dimensionless condition.

Keywords

• turbulent drag reduction
• large eddy simulation method
• turbulent boundary layer flow
• riblets