Measurements of pressure-velocity correlations in variable density round jets*

Flows in which the density ratio and gradients are large create what is known as variable density turbulence. These physics are important to natural and engineered processes at many scales from the astrophysical (stellar evolution, supernovae) to the very small (inertial confinement fusion). We have been studying these problems at the Turbulent Mixing Tunnel at Los Alamos National Laboratory using simultaneous planar velocity and density measurements acquired via Particle Image Velocimetry and Laser Induced Fluorescence. However, an important part of the physics in these problems is the interaction of the velocity field with the instantaneous pressure, which has traditionally been very difficult to acquire with sufficient spatial resolution and accuracy for successful turbulence budget analysis. Building off measurements acquired with jets in air and SF₆ at matching Reynolds numbers (At = 0.1 & 0.6, Re = 20,000), (Charonko and Prestridge, JFM 2016) we have applied recently developed GPU-accelerated omni-directional pressure integration schemes (Zigunov and Charonko, MST 2024) along with Taylor's frozen turbulence hypothesis to estimate the fluctuating pressure fields. Using this data, we have computed the resulting pressure-velocity terms in the turbulent kinetic energy budget. Differences caused by variable density conditions will be explored, and the experimentally measured values will be compared to models such as one proposed by Lumley for pressure-velocity correlations.