Numerical simulation of air bubbler systems

Abstract

The use of air bubbler systems to suppress ice formation is a technique that has been applied in a variety of situations with varying degrees of success. In 1974, two-dimensional line source bubbler systems were analyzed by G. D. Ashton in an effort to make available a tool that may be used in the design of a bubbler installation. That analysis was a steady-state evaluation of the melting rate of an ice cover above a bubbler system predicted on the basis of the input variables (depth, air discharge rate, water temperature). In actual operation, however, a bubbler 'sees' changing conditions such as diurnal and longer-term weather conditions, varying water temperatures and depletion of the available thermal reserve.The simulation presented herein uses the steady-state analysis developed earlier by Ashton and steps it in time with each new condition determined from the results of the previous time step. In this sense the analysis herein may be considered quasi-steady.Results of the simulation are presented for an example case for a winter in Superior, Wisconsin, and illustrate the variation in width of open water area with changing weather conditions with good comparison to field observations.