Streamwise oscillation of spanwise velocity at the wall of a channel for turbulent drag reduction

Abstract

Steady forcing at the wall of a channel flow is studied via DNS to assess its ability of yielding reductions of turbulent friction drag. The wall forcing consists of a stationary distribution of spanwise velocity that alternates in the streamwise direction. The idea behind the forcing builds upon the existing technique of the spanwise wall oscillation, and exploits the convective nature of the flow to achieve an unsteady interaction with turbulence. The analysis takes advantage of the equivalent laminar flow, that is solved analytically to show that the energetic cost of the forcing is unaffected by turbulence. In a turbulent flow, the alternate forcing is found to behave similarly to the oscillating wall; in particular an optimal wavelength is found that yields a maximal reduction of turbulent drag. The energetic performance is significantly improved, with more than 50% of maximum friction saving at large intensities of the forcing, and a net energetic saving of 23% for smaller intensities. Such a steady, wall-based forcing may pave the way to passively interacting with the turbulent flow to achieve drag reduction through a suitable distribution of roughness, designed to excite a selected streamwise wavelength.

Cited by in corpus (17)

• A review of turbulent skin-friction drag reduction by near-wall transverse forcing
• Experimental assessment of drag reduction by traveling waves in a turbulent pipe flow
• The laminar generalized Stokes layer and turbulent drag reduction
• Drag Reduction by Herringbone Riblet Texture in Direct Numerical Simulations of Turbulent Channel Flow
• Turbulent skin-friction reduction by wavy surfaces
• Turbulent drag reduction through oscillating discs
• Turbulent drag reduction by spanwise wall forcing. Part 1: Large-eddy simulations
• Prediction of turbulence control for arbitrary periodic spanwise wall movement
• Spinning out of control: wall turbulence over rotating discs
• A fundamental limit on energy savings in controlled channel flow, and how to beat it
• Turbulence suppression by streamwise-varying wall rotation in pipe flow
• Reduction of turbulent skin-friction drag by passively rotating discs
• Experimental assessment of square wave spatial spanwise forcing of a turbulent boundary layer
• Turbulent skin-friction drag reduction via spanwise forcing at high Reynolds number
• Response of a turbulent boundary layer to steady, square-wave-type transverse wall-forcing
• Linear stability of Poiseuille flow over a steady spanwise Stokes layer
• Spanwise wall forcing can reduce turbulent heat transfer more than drag