Author(s): Lennart Billfalk; Robert M. Desmond
Linked Author(s): Lennart Billfalk
Keywords: No Keywords
Abstract: Some experiments regarding frazil ice production in aerated spillway discharges are reported. Water at a temperature just above 0C was pumped from an ice-covered river into the air, run through a collecting basin and observed for the formation of frazil and for the change in its temperature. It was apparent from the experiments that the cooling of the water was greatly dependent upon the surface area of the water in contact with air (droplet size). The heat transfer from a droplet travelling through the air was estimated. In view of the estimated initial temperature decrease it is reasonable to suggest that some small droplets froze and subsequently dropped into the water. Such a process would appear to explain the formation of frazil ice in the experiments. This result also supports the theory for frazil ice formation in a river, put forth by Osterkamp et al. (1974); namely that airborne ice crystals form in the supercooled fog above the stream and fall into the stream and act as a nuclei for frazil ice crystals. Based on our results it would appear that the adoption of jet deflectors as a mean of improving energy dissipation downstream of a spillway suffers from the drawback that frazil ice formation is greatly enhanced during cold periods.
Year: 1978