Pressure-velocity correlations in a flow upstream of a forward-facing step

The 2-dimensional velocity field upstream of a forward step was determined experimentally using Particle Image Velocimetry. A total of 4 seconds of data was acquired at $8000\rm{Hz}$. The flow velocity was $10\rm{ms^{-1}}$ with an $\rm{Re}_h$ of 20000, where $h=0.03\rm{m}$ is the step height. The boundary layer thickness relative to step height was $\delta/h=1.6$. The upstream surface pressure fluctuations were simultaneously measured using an array of 9 microphones embedded in tunnel floor. These pressure fluctuations are shown to have a direct linear correlation to the velocity perturbations. The correlation has a maximum of approximately 0.3 at upstream stations $x/h>2$ and reduces toward background noise levels as the flow approaches separation at $0.5