Reduction in the Turbulent Instabilities in a Boundary Layer using Micro-cavities

Abstract

The turbulence intensities and shear stresses in a turbulent boundary layer (TBL) are primarily associated with the presence of coherent structures, such as sweep and ejection events. Recent experiments using a passive method of controlling the TBL using micro-cavities have reported reduction in the coherent structures by ∼ 7%. However, the mechanism behind the reduction has not been identified due to the complexity of the near-wall small scale interactions. The present work presents outcomes of the direct numerical simulations of the turbulent boundary layer over the bottom surface of a channel with the aim of focussing on the effects on the velocity fluctuations and the shear stresses. It is found that the application of microcavities on the surface results in the reduced turbulent instabilities in the near-wall flow region.