The formation of frazil ice is an important stage in the river freeze-up process, yet little is known about many of its properties. It forms only in turbulent water during the brief period of time prior to freeze-up when the water becomes supercooled. Frazil particles are predominately discoid in shape and, in the active state, will easily adhere to almost any surface. This adhesion causes many problems as the particles can accumulate quickly on trash racks or other grates used to prevent debris from entering fresh water intakes along the river, severely reducing or even halting the flow of water. Intakes must then be shut down until the accumulation of frazil ice can be removed, either by thermal or mechanical means. The size distribution of frazil ice particles was studied using experiments performed in the University of Alberta Civil Engineering Cold Room Facility. Frazil ice was produced in a custom designed tank and high resolution digital images were taken of the particles as they passed between two cross polarizing filters, backlit by an array of LED lights. A MATLAB code was written to process the images by identifying each individual particle and determining its size. Particles less than 0.04 mm to greater than 5 mm in diameter were observed, with a mean diameter of approximately 0.8 mm.
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