Pressure-Rate-of-Strain, Pressure Diffusion, and Velocity-Pressure-Gradient Tensor Measurements in a Cavity Flow

Pressure-related turbulence statistics in a two-dimensional open cavity shear layer flow was investigated experimentally at a Reynolds number of 4.0 x 10(4) based on a cavity length of 38.1mm. Time-resolved particle image velocimetry sampled at 4500 frames per second and 25 x 25 mm field of view was used to simultaneously measure the instantaneous velocity and pressure distributions. Direct estimate results of the pressure-rate-of-strain, pressure diffusion, and velocity-pressure-gradient tensor components based on 140,000 measurement samples were presented after a brief review of the theory about the pressure-related terms in the context of turbulence modeling and a discussion about their role in determining an accurate mean flow. The analysis is also augmented with comparisons with experimental data obtained at a higher Reynolds number of 3.4 x 10(5). The pressure and stream wise velocity correlation changes its sign from negative values far upstream in the shear layer to positive ones near the trailing corner due to the strong adverse pressure gradient imposed by the corner. The distribution patterns of the pressure diffusion and the turbulence diffusion are considerably different, indicating that the conventional practice of modeling the transport terms all together as Laplacians of the turbulent kinetic energy is not justifiable, at least for the turbulent shear layer flow past a cavity. In the shear layer, turbulence fluctuation energy is redistributed from streamwise to lateral components. This intercomponent energy transfer is reversed on top of the trailing corner, indicating the complexity of the flow, especially around the corner area.