Effects of intake geometry on the occurrence of a free-surface vortex

Abstract

Both the profile and orientation of an intake entrance basically determine the characteristics of the flow (especially the velocity distribution and therefore the hydraulically developed subsurface depressions) toward the intake. The profile and orientation of the intake affect (1)the process of accumulation and growth of vorticity (circulation) along the pathway axis of the swirling vortex from the free surface to the intake; (2)position of the pathway of the swirling-vortex filament; and (3)location of the point of entry of the free-surface or subsurface vortex at the entrance of the intake. Test results indicate that the intake-entrance profile has limited effects on the occurrence of the air-core vortex and critical submergence. Regardless of the profile of the intake entrance, one common physical mechanism exists for development of free vortices occurring at intake entrances of different profiles. It is proven that spherical sink surface sectors (SSSSs) are essential for the vortex to exist.