An experimental investigation of hanging ice dam formation
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Date
2020-02-21
Authors
Ahsan Badhan, Mahid
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Abstract
Understanding the formation of hanging ice dams could reduce energy losses, and consequent financial losses, experienced at northern hydroelectric generating stations. Despite several studies that focused on hanging ice dams, a lack of research has been identified in the literature, and no comprehensive study on the factors influencing hanging ice dam formation has been conducted. No previous studies have been conducted to simulate a real world geometric condition that influences the evolution of hanging ice dam. The research presented in this thesis attempts to address this gap. A better comprehension of dynamics beneath a hanging ice dam will help river ice engineers to reduce economic, environmental, and ecological damages. Experimental investigations were conducted in a fixed-bed, with flat (zero sloped) flume in the Hydraulics Research & Testing Facility (HRTF) at the University of Manitoba. Experiments were conducted to investigate the formation of a hanging ice dam and its evolution in terms of areal extent, average thickness, length and maximum width under different flow conditions (e.g., Froude number and ice volume). The effect of various ice concentrations on the same variables was also tested. The whole investigation was divided into two primary conditions; firstly, experiments were conducted to investigate the effects of different Froude numbers on the evolution of hanging ice dam where ice concentration was kept constant. Additional experiments were later conducted to observe the effect of different ice concentrations on hanging ice dam formation keeping the Froude number at a fixed value.
A high-resolution GoPro camera was installed above the flume to get top-down photographs at regular intervals during the experiments. Emphasis was also given on how a hanging ice dam develops under a thin ice cover for a certain flow condition. An underwater laser scanner was deployed to observe the approximate shape of hanging ice dams and the changes of maximum thickness. The results indicate that Froude number has a significant impact on the mentioned parameters during hanging ice dam formation. Flow from a narrow channel that outfalls into a wider lake (higher cross sectional area) acts as a surface jet. The evolution and decay of the surface jet are directly related to the streamwise and lateral development of hanging ice dams. Ice concentration also plays an important role in hanging ice dam development. The formation of a hanging ice dam depends on the ice transport capacity and the result of the experiments from this study supports this concept developed by Shen and Wang (1995). It is believed that the results from this experiment will improve our fundamental understanding of hanging ice dam formation, and can be used for validation of subsequent numerical models.
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Keywords
Hanging Ice Dam