Eighth International Symposium on Turbulence and Shear Flow Phenomena
DOI: 10.1615/TSFP8
SPANWISE OSCILLATORY WALL MOTION IN CHANNEL FLOW: DRAG-REDUCTION MECHANISMS INFERRED FROM DNS-PREDICTED PHASE-WISE PROPERTY VARIATIONS AT Reτ = 1000
pages 1-6
DOI: 10.1615/TSFP8.1310
ABSTRACT
A DNS-based study is presented, which focuses on the response of near-wall turbulence and skin friction to the imposition of an oscillatory spanwise wall motion in channel flow. The main focus is on transients in the drag, at Reτ=1000, that are in the form of moderate oscillatory variations in the phase-averaged skin friction and near-wall turbulence around the low-drag state at non-optimal actuation conditions at which the drag reduction margin does not reach the highest possible level. The study reveals a distinctive hysteresis in the periodic fall and rise of the drag, and the results allow the interaction between drag and the turbulence response to the unsteady Stokes strain to be illuminated.