Direct numerical simulation of a turbulent boundary layer over an oscillating wall

Abstract

Direct Numerical Simulations have been performed to study the effect of a partially oscillating wall on the turbulent boundary layer. Even though the Reynolds number is three times lower than in previous experimental investigations, many of the characteristic flow features are confirmed. The drag reduction is of the same magnitude as for higher Reynolds number flows, and the spatial development follows closely earlier experimental findings. The reduction of Reynolds shear stress is more pronounced than the decrease in streamwise and normal velocity fluctuations. In addition, comparisons are made with earlier numerical studies of channel flow. The sensitivity of the Reynolds shear stress on the time allowed for statistics collection is scrutinised, and the discrepancy in results from earlier experiments are, thus, explained.

Keywords:

• direct numerical simulation
• turbulent boundary layer
• oscillating wall