Interactions of Shear Layer Vortices with the Trailing Corner in an Open   Cavity Flow
  This fluid dynamics video provides sample experimental results focusing on the interactions of shear layer vortices with the trailing corner in a 2D open cavity shear layer. These interactions were investigated experimentally in a water tunnel at a Reynolds number of 40,000. Time-resolved particle image velocimetry (PIV) with an image sampling rate of 4500 frames per second was used to simultaneously measure the instantaneous velocity, material acceleration and pressure distributions. The latter was calculated by integrating the spatial distribution of in-plane components of the material acceleration. A large database of instantaneous realizations visualized the dynamic changes to the shear layer vortices, such as deformation and breakup as they impinged and climbed over the cavity trailing corner. These interactions cause time-dependent formation of a pressure maximum as the flow impinges on the forward facing surface of the trailing corner, and a minimum above the corner, where large local pressure gradients dominate the generation of fresh vorticity. Data analysis shows that interactions with the corner involve two time scales. Intermediate Strouhal numbers (0.6-3.2) are associated with interaction of the shear layer vortices with the corner, while vertical flapping of the shear layer occurs at low Strouhal numbers (0.1-0.6). 
Xiaofeng Liu, Joseph Katz
physics.flu-dyn physics.ao-ph