Development of a One Equation Eddy Viscosity Model Based on K-Epsilon and RAS Turbulence Models

A reformulated version of the RAS (Rahman-Agarwal-Siikonen) turbulence model is presented, facilitating its range of applicability significantly to near-wall turbulence and non-equilibrium flows. Revisions include the addition of a free-stream strain-rate correction and an adjustment of the stress-limiter to the eddy-viscosity formulation. In addition, the RAS model is re-derived from k-epsilon equations, emerging naturally extra diffusion/destruction terms which have significant influence on the RAS model; associated coefficients are paramaterized with original RAS model coefficients, resulting in a new RAS-based one-equation model. Computations of few well documented turbulent flows demonstrate an enhanced capability, showing the advantage of new RAS model in simulating the flow transition from separation to reattachment in wall bounded flows.