Author(s): F. D. Haynes; G. D. Ashton; P. R. Johnson
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Keywords: No Keywords
Abstract: Air bubbler systems are used to suppress ice formation and prevent ice damage to structures. Injection of air into the slightly more dense, warm water at the bottom of a body of fresh water raises the warm water to the surface. A bubbler system provides a simple and inexpensive means of suppressing ice if the body of water has the necessary thermal reserve. A study was conducted with a point source bubbler to examine its performance when installed under an existing layer of thick lake ice. When a small hole existed in the ice above the bubbler, the induced flow caused rapid melting of the sides of the hole at and below the water level. Melting progressed outward until the ice cavity reached a radius of 3m, at which time the unsupported ice sheet above the cavity collapsed. The outer edge of this thin ice plate remained in place but the center sagged into the water and melted. When the bubbler was placed under a solid ice sheet without an escape hole, the air escaped laterally under the ice toward the shore. After one day the air began to escape through the ice directly above the bubbler. A cavity was formed to the hydrostatic water level and then enlarged as with the earlier test. Again, the unsupported ice above the free water level failed, sagged into the water, and melted. The radial flow at the surface melted the ice sheet on the periphery of the cavity. After the ice above the cavity collapsed, melting continued at the periphery of the open water. The melting front of the cavity was approximately vertical with minor irregularities in the side wall. Little evidence was found of thinning of the ice sheet beyond the edge of the open pond. The mixing of the water by the bubbler disturbed the stratified thermal regime in the vicinity of the bubbler. Velocity and temperature profiles are given for the bubbler plume and radial flow pattern. A heat transfer analysis is also included.
Year: 1981