On reduction of turbulent wall friction through spanwise wall oscillations

A model for turbulent skin friction, proposed by Orlandi & Jimenez, involvi ng consideration of quasi-streamwise vortices in the cross-stream plane, is used to study the effect on the skin friction of oscillating the surface b eneath the boundary layer in the spanwise direction. Using an exact solutio n of the Navier-Stokes equations, it is shown that the interaction between evolving, axially stretched, streamwise vortices and a modified Stokes laye r on the oscillating surface beneath, leads to reduction in the skin fricti on, the Reynolds stress and the rate of production of kinetic energy, consi stent with predictions based on experiments and direct numerical simulation s.