PIV Investigation of the Turbulent Boundary Layer Response to Active Control Actuator

Abstract

It has been established that the dynamics of large-scale structures (LSS) in the outer region of turbulent boundary layers (TBL) and the near-wall small-scale turbulence are correlated. In the study reported here, a plasma-based active flow control device was placed within the TBL to introduce periodic motions into the outer region. The boundary layer Reynolds number was low enough, Re_τ=700 that no naturally occurring energetic coherent large-scale structure was present. Via actuation, a periodic synthetic large-scale structure was introduced into the TBL, and the TBL’s response to this structure in the near-wall region was studied using both hot-wire anemometry and planar PIV. In previous experiments, it was shown that this large-scale structure had a strong modulating effect on the near-wall turbulence downstream of the actuator. In this study an optimized actuator design is tested, and changes to the modulating effect are discussed. In addition, planar PIV is implemented to measure the spatially and temporally resolved two-dimensional velocity field downstream of the actuator. The PIV measurements are shown to be consistent with the hot-wire measurements and capable of capturing the synthetic LSS dynamics and their modulating effect on the near wall turbulence. Ongoing PIV work and the benefits of supplementing the original hot-wire measurements with PIV are discussed.