The influence of two different dihedral angles on diffuser performance based on LES

Abstract The influence of two different dihedral angles on diffusion capability and flow separation in a diffuser was investigated in this study. Geometric models of straight-walled diffusers with dihedral angles of 90° and 108° were established. The mean and transient flow fields were obtained by using the large eddy simulation (LES) method. The research results show that increasing the dihedral angle enhances the diffusion capability of the diffuser and reduces the volume fraction of the mean separation zones for the diffusers with dihedral angles of 90° and 108°. Besides, hairpin vortexes are observed near the onset of divergent sections of the two diffusers. The findings regarding the effect of dihedral angle on flow separation provide some guidance for corner designing, which can be summarized as increasing dihedral angle reasonably can suppress corner separation and reduce flow losses.