Evaluation of Turbulence Mix Model Constants for Low Atwood Number Rayleigh-Taylor Flows

Progress on evaluation of turbulence mix model constants for the \textit{$\kappa $}-\textit{$\varepsilon $} and BHR mix models will be presented. Our detailed measurements of Rayleigh-Taylor (RT) mixing at low Atwood number ($A_{t}$ = 0.04) in the Texas A{\&}M air-helium gas channel facility has allowed us to evaluate several mix model constants used in the \textit{$\kappa$}-\textit{$\varepsilon $} and BHR models. We have measured the various terms allowing us to compute (measure) the model constant C$_{\mu}$. The measured value of C$_{\mu}$ is 0.3, significantly higher that the usual value of 0.09 assigned for shear flows. In addition, model constants are evaluated based on a self similar analytical solution using top-hat and parabolic profiles, and then compared with a detailed one-dimensional transient numerical solution. Various assumptions at the low Atwood limit that have been used for evaluating the various model constants will be discussed.