Velocity–Pressure-Gradient tensor measurements in a turbulent shear layer flow impinging on a cavity trailing corner by Time-Resolved Tomographic PIV*

The velocity–pressure-gradient measured by time-resolved tomographic PIV for a turbulent shear layer flow over an open cavity at a Reynolds number of 40,000 will be presented. The velocity–pressure-gradient is decomposed into the pressure diffusion and the pressure-rate-of-strain tensors, with the latter term necessary for the characterization of the intercomponent turbulence fluctuation energy transfer in both the shear layer and the impingement regions around the cavity trailing corner. We acquired 138,000 Tomo-PIV images at a sample rate of 4500 frames per second and a 42mm × 11mm field of view with a 7mm depth of the measurement volume. The pressure gradient is obtained from the pseudo-Lagrangian tracking based on the consecutive time-resolved three-dimensional velocity fields, and it is further integrated using the rotating parallel ray Omni-directional integration method to obtain the pressure field. The quality of the measurements is ensured by evaluating the curl-free property of the measured pressure gradient and the divergence-free property of the velocity field. The quality of the measured pressure-related terms is also cross-checked with the balance of the Reynolds stress transport budget. The three-dimensional measurement of the pressure-related turbulence terms by time-resolved Tomo-PIV will be used to verify the conjectures raised by Liu and Katz (2018, https://doi.org/10.2514/1.J056168) regarding the magnitude of the spanwise intercomponent energy transfer based on their planar PIV data.