Small-Scale Forcing of a Turbulent Boundary Layer

Abstract

In order to understand the effect of small scale forcing on turbulent flows and its implications on control, an experimental investigation is made into the forcing of the inertial scales in the wall region of a turbulent boundary layer. A wall-mounted resonant actuator is used to produce a local vortical structure in the streamwise direction which is convected downstream by the boundary layer flow. The frequency associated with this structure is governed by the resonant frequency of the device and falls in the range of the inertial scales at the Reynolds number of the experiment (Re[theta] [is approximately equal to] 1200). Single and multiple point measurements have been made to determine mean and fluctuating statistics as well as dual-point correlations. These data can be used to infer changes in the structure of the near wall region of the boundary layer that are due to the actuator forcing and subsequently, to construct transfer functions between the actuator and the fluid necessary for active control.