Coherent near-wall structures and drag reduction by spanwise forcing

We examine interaction mechanisms between the drag-reducing streamwise-traveling waves of spanwise wall velocity applied at a turbulent channel flow, and near-wall coherent structures. In particular, we focus our analysis on drag-reduction-induced modifications quasi-streamwise vortices that populate region flows through conditional averaging procedure. observe that, while share most with oscillations, some important differences related to finite phase speed wave different properties generalized Stokes layer exist.