Effects of Meridional Divergence on Vortex Evolution in Annular Cascades

The flow process of concentrated vortex occurrence and development was investigated in the meridian with considerable divergence.The distributions of aerodynamic parameters along pitch and span in the 12 measurement sections were surveyed.The results show that the divergence of the diffused meridian passage thickens the inlet boundary layer,so saddle point separation intensifies,and pressure side and suction side branches of high-strength and large-scale horseshoe vortex are formed,low energy gas around them enhances the paired effect,delays the formation and development of passage vortex.The strength and scale of passage vortex are proportional to the divergent angle of the passage.Due to the influence of radial positive pressure gradient,low-energy gas moves along trailing area to hub.That causes rapid dissipation and weakening of downstream passage vortex.