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Please use this identifier to cite or link to this item: http://hdl.handle.net/1993/5109

Title: A Theoretical and Experimental Study of the Evolution of Surface Ice
Authors: Unduche, Fisaha Solomon
Supervisor: Dr. J.C. Doering, Engineering Department, Faculty of Engineering
Examining Committee: Dr. P. Rasmussen, Engineering Department, Faculty of Engineering; Dr. R.W. Carson, Adjunct Professor, Civil Engineering Department, Faculty of Engineering; Dr. M. Tachie, Associate Head, Graduate Studies, Department of Mechanical and Manufacturing Engineering
Graduation Date: May 2008
Keywords: Surface ice
Issue Date: 24-Jan-2012
Abstract: The theory of the formation of surface ice is not fully understood, yet its presence on water surface affects the operation of many different kinds of hydraulic structures. It is known that when the water surface temperature reaches supercooling ice particles are formed at the water surface. If the intensity of turbulence is low these ice particles will be suspended on the surface forming a surface ice. Herein, an experimental study that incorporates the effect of depth, velocity, roughness and air temperature is carried out in a counter-rotating flume to investigate the formation of surface ice in relation to these parameters. The experimental result is supported by a mathematical model based on the theory of formation of surface ice. A mathematical model is developed based on a comprehensive theory and is solved using Matlab. The mathematical model integrates the effect of the heat balance on the water surface with the degree of turbulent mixing and the rate of growth of surface ice. The two calibrating parameters for the model are the magnitude of the initial seeding and the surface heat loss coefficient. The developed mathematical model is calibrated for the different types of surface ice formations for the data obtained from the experiment. The experimental analysis shows that there are four main types of surface ice formations and their formation is mainly dependent on the degree of turbulence. It is also found that the types of these ice formations are dependent on the minimum supercooling temperature at an average depth. Moreover, it is demonstrated that skim ice particles are those ice particles that nucleate on the water surface during low to medium turbulent intensities and can have four different types of shapes, namely needle shapes, finger shapes, hexagonal shapes and irregular shapes. The sizes and relative quantities of these ice particles on the water surface are also dependent on the degree of turbulence.
URI: http://hdl.handle.net/1993/5109
Appears in Collection(s):FGS - Electronic Theses & Dissertations (Public)

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