Surface pressure and flow field behind an oscillating fence submerged in turbulent boundary layer

Multiple flow diagnostic techniques have been used for better understanding of a complex unsteady flow. In particular, phase-locked PSP and PIV measurements have been used to study the evolution of three-dimensional disturbances produced by an oscillating fence actuator that is immersed in a zero pressure gradient turbulent boundary layer. Finite fence effects, introduced due to reducing aspect ratio of the fence during its oscillations, appear to be the reason for the strong three dimensionality and non-uniform growth of the structure across the span. Strong suction pressures are observed on the surface due to an intense vortex closer to the edge of the fence. At the midspan, the structure grows rapidly and weakens, limiting the magnitude of low pressure region. Additionally, strong suction pressures were observed when the vortex stays closer to the plate surface, which occurs for a longer time period near the side edge of the fence. The use of multiple diagnostics provided a link between flow field and surface pressure footprints, yielding an understanding of the flow that would have not been possible with any one technique.