Implementation and assessment of the renormalization group (RNG), quadratic and cubic non-linear eddy viscosity k-(epsilon) models in GOTHIC

In GOTHIC, the standard k-(epsilon) model is used to model turbulence. However, for practical reasons, one usually employs relatively large meshes near physical boundaries (walls). In an attempt to enhance the turbulence modelling in the code for simulation of mixing driven by highly buoyant discharges, in the framework of this simplified approach appropriate for containment analysis codes, we have implemented three additional models which are modifications/extensions of the standard k-(epsilon) model: the renormalization group k-(epsilon) model, and the non-linear (quadratic and cubic) eddy viscosity k-e models. These models which for the time being, are only implemented in the ʹgasʹ phase, were tested with different simple test-problems and their predictions were compared to the corresponding ones of the standard k-(epsilon) model. Furthermore, a simple study was performed to assess the sensitivity of the predictions to the mesh size.