Computational Simulation of 3-D Riblets for Skin Friction Drag Reduction

摘要

This paper describes large eddy simulations on conventional riblets and riblets with variable streamwise ridge height variation or '3-D' riblets. Conventional riblets are V-shaped grooves or vertical blades with height and spacing between the peaks of 20 to 100 microns for aircraft applications; the ideal height and spacing depends on the local shear stress and Reynolds number. The goal of 3-D riblet designs is to modify the flow topology in a manner similar to conventional riblets but with reduced wetted area, thereby achieving a greater drag reduction. Simulations are performed for a low Reynolds number turbulent channel flow with periodic boundary conditions in the spanwise and streamwise directions. The simulations examine the parametric space of 3-D riblet configurations including the length of the riblet section, smooth section and transition sections between riblet and smooth surfaces. A preliminary evaluation of riblet cross sections has also been performed. The pressure drag and viscous drag have been determined for each configuration. In addition, velocity profiles and Reynolds stress profiles are compared for the riblet surface and smooth surface boundary layers.