Optimum micro-vortex generator design for planar symmetric diffuser under fully developed turbulent flow

A systematic parametric investigation to determine the optimal micro-vortex generator (MVG) design for a large-opening-angle planar symmetric diffuser with an area ratio of 4.7, operating under steady, fully developed turbulent inlet flow conditions is reported. This numerical study explores the relationship between geometric and performance parameters to meet specific design criteria. computational fluid dynamics simulations were performed by solving the Reynolds-averaged Navier-Stokes equations coupled with the shear stress transport k-omega turbulence model. The investigation covered diffuser opening angles (2 theta) ranging from 10 degrees to 20 degrees, with inflow speeds varying from 7.76 to 38.8 m/s. The study systematically analyzed the effects of three-dimensional isotropic geometric scaling of the diffuser at different opening angles mounted with a row of optimally sized MVG blade pairs, benchmarking against both unscaled and baseline (without MVG) cases. Careful selection of MVG geometrical parameters effectively mitigates adverse pressure gradient-induced boundary layer separation from the diffuser walls, thereby enhancing performance and improving exit flow quality. For the diffusers evaluated, a symmetrically located row of counter-rotating vane-type MVGs with parameters h/delta similar to 0.275-0.325, g/h = 1, e/h = 8, beta = 18 degrees and x(vg)/H = 0.15-0.2 is proposed as the optimal design choice.