Waves of spanwise velocity traveling along the walls of a plane turbulent channel flow are studied by Direct Numerical Simulations. We consider waves of spanwise velocity which are oscillating in time and modulated in space along the streamwise direction. Waves which slowly travel forward produce a large reduction of drag. Faster waves, with a phase speed corresponding to the convection velocity of the turbulent fluctuations at the wall, lock with the convecting near-wall turbulent structures and yield drag increase. Backward-traveling waves, on the other hand, invariably produce a drag-reducing effect. To explain the physical mechanisms involved, the generalized Stokes layer induced by the traveling waves is studied in the laminar regime.
The Response of Wall Turbulence to Streamwise-Traveling Waves of Spanwise Wall Velocity
QUADRIO, MAURIZIO
2010-01-01
Abstract
Waves of spanwise velocity traveling along the walls of a plane turbulent channel flow are studied by Direct Numerical Simulations. We consider waves of spanwise velocity which are oscillating in time and modulated in space along the streamwise direction. Waves which slowly travel forward produce a large reduction of drag. Faster waves, with a phase speed corresponding to the convection velocity of the turbulent fluctuations at the wall, lock with the convecting near-wall turbulent structures and yield drag increase. Backward-traveling waves, on the other hand, invariably produce a drag-reducing effect. To explain the physical mechanisms involved, the generalized Stokes layer induced by the traveling waves is studied in the laminar regime.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.