Development and validation of a turbulent-mix model for variable-density and compressible flows

Area of Science:

• Fluid Dynamics and Turbulence Modeling
• Computational Physics

Background:

• Buoyancy-driven turbulent flows, including Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM), and Kelvin-Helmholtz (KH) instabilities, are crucial in various scientific and engineering disciplines.
• Accurate modeling of these complex, variable-density, and compressible flows remains a significant challenge in computational fluid dynamics.
• Existing turbulence models often struggle to capture the intricate mixing dynamics inherent in these phenomena.

Purpose of the Study:

• To implement and evaluate the advanced Besnard-Harlow-Rauenzahn (BHR) k-S-a turbulence model for buoyancy-driven flows.
• To assess the model's performance against experimental data and direct numerical simulations (DNS) for RT, RM, and KH driven mixing.
• To advance the development of turbulence models for buoyancy-driven flows to a level comparable to single-phase shear flows.

Main Methods:

• Implementation of the BHR k-S-a turbulence mix model within the RAGE hydro-code.
• Evaluation of model constants using analytical self-similar solutions of the BHR k-S-a model equations.
• Comparison of simulation results with a comprehensive database of experimental and DNS data for RT, RM, and KH mixing.

Main Results:

• Successful implementation of the BHR k-S-a model in the RAGE hydro-code.
• Model constants were effectively determined using analytical solutions.
• The BHR k-S-a model demonstrated good agreement with experimental and DNS data for various buoyancy-driven mixing scenarios.

Conclusions:

• The BHR k-S-a model shows significant promise for accurately simulating variable-density and compressible turbulent flows.
• The research contributes to improving the fidelity of turbulence modeling for buoyancy-driven phenomena.
• This work advances the state-of-the-art in modeling complex turbulent mixing processes.