COMPUTATION OF CONFINED COFLOW JETS WITH 3 TURBULENCE MODELS

A numerical study of confined jets in a cylindrical duct is carried ou t to examine the performance of two recently proposed turbulence model s: an RNG-based K-epsilon model and a realizable Reynolds stress algeb raic equation model. The former is of the same form as the standard K- epsilon model but has different model coefficients. The latter uses an explicit quadratic stress-strain relationship to model the turbulent stresses and is capable of ensuring the positivity of each turbulent n ormal stress. The flow considered involves recirculation with unfixed separation and reatachment points and severe adverse pressure gradient s, thereby providing a valuable test of the predictive capability of t he models for complex flows. Calculations are performed with a finite volume procedure. Numerical credibility of the solutions is ensured by using second-order-accurate differencing schemes and sufficiently fin e grids. Calculations with the standard K-epsilon model are also made for comparison. Detailed comparisons with experiments show that the re alizable Reynolds stress algebraic equation model consistently works b etter than does the standard K-epsilon model in capturing the essentia l flow features, while the RNG-based K-epsilon model does not seem to give improvements over the standard K-epsilon model under the flow con ditions considered.