Experimental and Numerical Investigation of Controlled, Small-Scale Motions in a Turbulent Shear Layer

Abstract

Abstract The effects of high-frequency fluidic actuation on the evolution of small-and large-scale motions in a turbulent shear layer downstream of a backward-facing step are investigated experimentally and numerically. The flow behind the step is characterized in the spatial and spectral domain by high-resolution diagnostic tools. Model stability problems with increasing complexity mimic the experimental setup and actuations and describe local and global flow behaviour. It is demonstrated that dissipative, high-frequency actuation effects the shear layer evolution through three domains: I -a localized dissipative, small scales domain having enhanced turbulent kinetic energy production and dissipation rate, II -a stabilized domain marked by concomitant suppression of turbulent kinetic energy production and dissipation rate, and III -a domain of re-emerging inviscid instability at lower natural frequencies and larger scales