Computational fluid dynamics investigation of turbulent separated flows in axisymmetric diffusers

Abstract

This study discusses about numerical investigation of the turbulent flow (Re = 5~104) through axisymmetric expansion having different diffuser half-angles (6‹<ƒ¿<90‹) experimentally found in literature. The diffuser inlet flow is a two-dimensional, turbulent, and fully-developed one. Commercial code GAMBIT is used for geometry and grid generation and FLUENT 6.3 is used for flow simulation. Grid cells are selected based on ramp angle, which ranges from 99500 to 135000. Space 3D formulation with implicit function approach is adopted in the solution scheme along with RNG k-ƒÃ turbulence model in
consideration. The main attention is given to flow separation as well as to downstream reattachment. It is found that the pressure
distribution becomes uniform and separation is getting delayed as ƒ¿ decrease.