Streamwise Evolution of Turbulent Boundary Layer Response to Active Control Actuator

摘要

In these studies, a plasma based active flow control device was used to introduce periodic motions into the wake region of the turbulent boundary layer. The boundary layer Reynolds number was low enough, Re_τ = 683 that no natural large-scale structure was present. Through actuation, a synthetic large-scale periodic shear-layer-like structure was introduced into the boundary layer, and the boundary layer response to this synthetic structure at various wall-normal and streamwise locations downstream of the actuator was studied using a single hot-wire. Due to the periodic nature of the forcing, a phase-locked triple Reynolds decomposition of velocity was used to analyze the data. The evolution of near-wall residual turbulence modulated by the synthetic structure in the inner and log regions of the boundary layer was analyzed. The dynamics of the synthetic structure and small-scale structures were then quantified using several modulation coefficients. These modulation coefficients show a strong positive correlation in the inner and log region of the boundary layer. The evolution of the synthetic large-scale structure and its modulating effect on the near-wall turbulence at several streamwise locations was described.