Computational study on the swirling turbulent flow with recirculation

Abstract

A computational investigations on swirling turbulent flows with and without recirculation are presented. The emphasis is given to computational turbulence models, especially algebraic stress model. In order to develop a new version of the algebraic stress model for swirling flows, algebraic stress equations are incorporated with conventional k- $\varepsilon$ model by the use of anisotropic eddy viscosities. For slender swirling shear flows without recirculation, the algebraic stress equations are reduced to constitutive equations which are similar to those used in the k- $\varepsilon$ model. This approach lead to a new simple correction method for the k- $\varepsilon$ model to be used for swirling flows without recirculation. The computational results show that present algebraic stress model remarkably improves the prediction of single swirling jet with recirculation over the conventional isotropic k- $\varepsilon$ model. Significant anisotropy in the turbulent diffusivity, induced by the strong swirl accompanied by flow recirculation, is correctly reproduced by the algebraic stress model. On the other hand, results of calculations of single and coaxial swirling jets without recirculation and swirling flow in an annulus with rotating inner cylinder, show that the new correction method for k- $\varepsilon$ model is superior to previous correction methods in the computational accuracy in addition to its sound theoretical background. The new k- $\varepsilon$ model yields very good agreement with experimental data, especially on decay rates of centerline velocity of swirling jets. The stabilizing and destabilizing effects of swirl on turbulent transport are correctly reflected in the new correction method.