A non-linear eddy viscosity/diffusivity model for confined swirling flows

A non-linear eddy viscosity/diffusivity model for turbulent flows is presented, featuring quadratic constituive relationships for both Reynolds stresses and scalar fluxes. Model coefficients are defined by enforcing compliance with fundamental experimental evidence, and realizability of both the velocity and scalar fields, which is achieved by making coefficients depend upon an appropriately defined strain parameter. The model is also shown to satisfy joint-realizability. The model is extensively tested against experimental results for confined swirling flows, encompassing a wide range of values of the swirl number, momentum and density ratios. The results unambiguously indicate a remarkable, uniform improvement over standard modelling. Further, previous work on the subject of nonlinear models is reviewed.