Numerical Investigation of Cavitation Shedding in a Multiphase Flow with Sharp Density Gradient

The numerical simulation of transient three-dimensional cavitating flow in ejectors is still an open challenge in the fluid mechanics domain due to the complexities associated with sharp density gradient and phase-transition. In this article, the effects of Reynold Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) turbulence models on the non-equilibrium homogeneous relaxation model (HRM) are discussed. A carbon dioxide (CO₂) ejector has been experimentally tested at different operating conditions. The high pressure (motive flow) inlet condition of the ejector is maintained at pressure and temperature at 63.5 bar and 296 K, respectively, where CO₂ is in the critical region. The pressure and temperature boundary conditions at the low pressure (suction) inlet are 25 bar and 287 K respectively, providing a pressure lift ratio of 1.2 at the outlet. A three-dimensional numerical model of the ejector is developed with traditional standard, RNG, realizable k-epsilon; standard and SST k-omega (RANS based), and dynamic structure sub-grid scale (LES based) turbulence models. These models are individually validated utilizing appropriate experimental data with an error of < 1% for different flow parameters. Implementing LES turbulence model successfully captured the effects of cavitation shedding over a wide length scale at the diffuser zone of the ejector, whereas the RANS model failed to capture the physics.