DEVELOPMENT OF TURBULENCE MODELS FOR SHEAR FLOWS BY A DOUBLE EXPANSION TECHNIQUE

Turbulence models are developed by supplementing the renormalization group (RNG) approach of Yakhot & Orszag with scale expansions for the Reynolds stress and production of dissipation terms. Th, additional expansion parameter,, (---K / i) is the ratio of the turbulent to mean strain time scale. While 'low-order expansions appear to provide an adequate description for the Reynolds stress, no finite truncation of the expansion for the production of dissipation term in powers of;r suffices- terms of all orders must be retained. Based on these ideas, a new two-equation model and Reynolds stress transport model are developed for turbulent shear flows. The models are tested for homogeneous shear flow and flow over a backward facing step. Comparisons between the model predictions and experimental data are excellent. Aceos2:,a Y-r •~~~ ~ r aIIone " ' Iji-'ty CcdO