Ice-basin experiments and computational modeling of frazil ice ingestion by submerged water intakes.

摘要

Submerged, offshore water intakes are used commonly for withdrawing water from lake and coastal waters. They typically serve to meet the diverse water supply needs. A variety of intake designs are used, but they commonly are conical in shape. A prominent concern for intake in cold regions, however, is intake ingestion and blockage by frazil ice under frigid winter conditions. Frazil ice poses a considerable threat to the intake operation. Minimizing frazil ice ingestion is an important design issue for intakes to operate in frigid waters. Despite the issue's importance, there have not been quantitative insights to aid in the design of conical submerged intakes to minimize frazil ice ingestion.; This study provides insights illuminating the processes whereby frazil ice is drawn into an intake and its pipe link to an onshore pump stations. The insights are based on the findings from laboratory experiments conducted with a large ice basin, and on the findings from computational models simulating flow and frazil ice ingestion by an intake. The laboratory experiments are the first known quantitative series of frazil ice experiments conducted using a large basin (20 m x 5 m x 0.5 m). Prior to the present study, laboratory investigations of frazil ice involved small volume of water, typically less than about 1 m3.; The computational model of frazil ice transport represents the first such effort for simulating frazil particle transport into a submerged intake. The model includes a component that simulated frazil ice adhesion to the intake.; Findings from the ice basin experiments and the computational model concur sufficiently to facilitate development of the guidance to aid intake design. A larger diameter of the intake rim with a cap and a smaller cap height, results in larger horizontal velocity component and smaller vertical velocity component, thus reduces the amount of frazil ice ingested by the intake. For an intake of diameter D (D = 3.05m), a cap placed at a height 0.3D above the intake's rim reduces frazil ice ingestion by about 70%. As the cap height decreases, the amount of frazil ice ingestion decreases. An acceptable maximum flow velocity at the intake rim for concerns of debris and fish larvae prohibits cap height lower than 0.18D.