Computational study on turbulent recirculating flows

Abstract

Two dimensional turbulent recirculating flows are numerically investigated. The phenomena considered in this kind of flows are ; cross injection of fluid into a channel flow, flow over a fence in a channel, cross injection on the top of a vertical fence in a channel flow and cross injection into an annular jet. The k-$\varepsilon$ turbulence model is used with model constants which are not modified the particular flows in order to test the capability of the existing k-$\varepsilon$ model for the recirculating flows. The governing partial differential equations are solved by the finite difference method. Present calculations are compared with the available measurements. Qualitative features of the numerical predictions are not quite different from the experimental measurements. However, the computed recirculating zone size and the turbulent kinetic energy are rather small compared to the measurements. These may be attributed to the inability of the k-$\varepsilon$ model near the wall region where the local Reynolds number is very small and the fact Reynolds stress components are predominantly anisotropic. Particularly, the wall shear stress is overpredicted in the separated recirculating bubble zones.