The three-dimensional turbulent boundary layer in a free vortex diffuser

Abstract

Experimental velocity profiles and static pressure measurements were obtained from the flow in a free vortex diffuser. The purpose of the study was to obtain additional three dimensional boundary layer data and to compare it with existing theories. Free vortex diffuser behavior under varying inlet angles was also studied. The boundary layer profiles correlated well with an existing model for three dimensional boundary layers generated by transverse pressure gradients. From this model boundary layer cross flow can be approximately predicted using a shearless flow analysis for the outer part of the boundary layer and an empirical correlation for the inner portion. At high inlet swirl angles, a separation ring followed by reattachment was found in the diffuser.