UC San Diego

The characterization of the pressure-related turbulence terms including pressure–rate-of-strain, pressure diffusion and velocity–pressure-gradient tensor in the Reynolds stress transport equation in canonical turbulent flows is of critical importance for calibrating and improving turbulence models for RANS (Reynolds-Averaged Navier Stokes) based flow simulation. It demands very accurate measurements of the instantaneous velocity fields and the instantaneous pressure fields, which require precise measurement systems and techniques. A water tunnel facility was built at the San Diego State University with the necessary flow quality to perform the measurement of the instantaneous velocity fields using Time-Resolved Tomographic PIV. To ensure the accuracy of the pressure measurement a PIV-based pressure technique called rotating parallel ray omnidirectional integration was developed and it was shown to be very robust and accurate. The rotating parallel ray omnidirectional integration was applied to several cases from the instantaneous pressure measurement around a rising bubble, water surface elevation mapping, density reconstruction and analytical model validation showing a wide scope of applications. Those developments enabled the measurement of all the terms of the Reynolds stress equation for a turbulent shear layer flow impinging on a cavity trailing corner at a 4.0×10^4 including the velocity–pressure-gradient tensor. This new data on the cavity flow provides the opportunity to test and develop Reynolds stress models to improve flow simulation.