Two-equation turbulence modeling for internal flows with non-equilibrium and rotating effects

There are numerous modifications and “improvements” proposed in the literature for the k-ɛ two-equation model originally developed by Launder and Spalding (1974) (currently the “standard” used in complex flow computations). Even though many deficiencies have been reported in the literature, this family of the turbulence models is by far most adopted one for practical flow computations. In the present work, we will offer assessments of the non-equilibrium and rotating flow aspects of the model, aided by a systematic investigation for three complex flow problems. The approach taken herein is to fully retain the original k-ɛ two-equation model where the modeling assumption are valid, and to extend it to the domain where they are not. By adopting this approach, we need to expand the expression of the original model, making it more compatible with complex flow conditions. However, since the original model does perform well in certain flows, we prefer that the modified model reduces to the original model in domains where it works well. It is well established that for complex flows the original k-ɛ two-equation model does not work well because the reasoning used to deduce the modeling coefficients is not valid; in such situations, the model needs to be modified. Specifically, in the present work, the nonequilibrium and rotating flow effects will be investigated.