Sub-Boundary Layer Vortex Generator Control of a Separated Diffuser Flow

Abstract

*† ‡ § The application of sub-boundary layer vortex generators to control flow separation in a diffuser with an opening angle of 10 degrees has been studied using the computational fluid dynamics (CFD) code Fluent 6™. Experimental data is available for the uncontrolled flow in the diffuser. The section of the duct upstream of the diffuser has a height H equal to 15 mm; its length and breadth are 101H and 41H respectively; the diffuser has an expansion ratio of 4.7:1. Fully developed flow is achieved upstream of the diffuser. Sub-boundary layer vortex generators with a trailing edge span of 2 mm (13.3% of the duct height) have been considered. A parametric study was performed in which generator spacing, angle of incidence, configuration (counter and co-rotating) and streamwise position were varied. The best results were obtained with a counter-rotating array of generators at 18° incidence with a spacing equal to 2.5 times the generator trailing edge span (5H/16) and placed just upstream of the entrance to the diffuser.