Surface Vortex Mitigation at Submerged Intakes

Surface vortices at submerged intakes entrain air, convey debris, and reduce efficiency. This research investigates the effect of lid geometry on mitigation of surface vortices at submerged intakes in the context of still reservoirs. Six lid geometries were evaluated: three solid lids of increasing diameter, two lids with perforations, and one lid fitted with a downward curtain. Vortex severity was measured by Alden’s vortex type rating scale, surface-dimple diameter, and qualitative video analysis. The perforated lid extension and the curtain configurations were most effective at mitigating vortices. The curtain configuration negated all surface swirling by redirecting a portion of the flow to the subsurface and spreading out streamlines, effectively thickening the shear layer. This introduced trade-offs including reduced discharge capacity, subsurface vortex formation, and potential sediment uptake. The perforated lid extension and curtain both forced streamline convergence which introduced turbulence, effectively weakening vortex strength.