Ice-Tank and Numerical Study of Frazil Ingestion by Submerged Intakes

Abstract

This paper addresses the problem of frazil ingestion by submerged water intakes located offshore in frigid water. It is well known that intakes under such conditions are prone to blockage by frazil, small ice crystals that commonly occur when water, agitated by wind or current, supercools. However, little quantitative information exists delineating how intake shape and size influence intake ingestion of frazil ice. Presented herein are insights and quantitative trends associated with those influences. The insights and trends were obtained from observations of frazil in a set of unique ice-tank experiments of a common intake configuration. The experiments were extended through numerical simulation. The essential intake layout considered herein comprises a conical inlet connected by pipe to an onshore pump station, and fitted with an elevated cap. The study’s findings show how either a cap or larger intake-rim diameter reduce the rate of frazil ingestion. Reducing the rate of frazil ingestion may enable an intake to operate longer during periods of water supercooling, and thereby reduce the possibility of blockage by frazil.