Experimental investigation of the effects of turbulence intensity on frazil ice characteristics

The counter-rotating flume at the University of Manitoba was used to conduct a series of 21 laboratory experiments to investigate the effects of turbulence intensity on frazil ice formation and evolution. A detailed study of the velocity and turbulence intensity distributions within the counter-rotating flume was initially conducted using a constant-temperature anemometer equipped with a one-dimensional conical hot-film probe. Five levels of turbulence intensity were generated by five different sets of bed plates and flume wall rotation rates in order to study how turbulence affected the frazil particle size distributions and the statistics related to clear disk-shaped particles. It was found that a lognormal distribution could not be rejected when describing the frazil particle size distributions, regardless of the turbulence intensity of the water. The variation of the mean and standard deviation of particle diameter with turbulence intensity are well described by a parabolic shape. A preliminary equation to describe the variation of the mean and standard deviation of particle diameter as a function of turbulence intensity and time is presented.

Development of a mathematical model of frazil ice evolution based on laboratory tests using a counter-rotating flume

A mathematical model to simulate the supercooling process and frazil ice evolution in a counter-rotating flume was developed. It considers the effect of frazil ice thermal growth while neglecting several complicated physical processes such as secondary nucleation, flocculation, and (or) break up. The supercooling process, vertical distribution of flow turbulence parameters, and frazil ice number concentration were simulated, as well the variation of the mean size of frazil ice during the supercooling process was modeled. The simulation results from this model show good agreement with experimental data.Key words: frazil ice, turbulence, numerical models, counter-rotating flume, supercooling.

Simulation of the supercooling process and frazil evolution in turbulent flows

A model to simulate the supercooling process and frazil ice evolution in a counter-rotating flume is developed based on a series of laboratory experiments. The characteristics of the supercooling process were found to be related to air temperature and flow turbulence. Frazil ice growth was observed to follow a log-normal distribution model. The model avoids the need to simulate seeding, secondary nucleation, flocculation–breakup, and gravitational removal. Only the overall heat balance is considered during the entire process. The simulations show good agreements with experimental time–temperature curves and frazil evolution.Key words: supercooling, frazil ice, size distribution, concentration, turbulence, simulation.

A laboratory study of frazil evolution in a counter-rotating flume

A series of experiments was carried out using a counter-rotating flume that is housed in a computer-controlled cold room. A digital image process system (DIPS) was used to observe frazil ice processes. In particular, the effects of air temperature and flow velocity on the supercooling and frazil ice processes were examined. The super cooling process was found to be strongly related to air temperature and water depth, but only weakly related to water velocity. The water velocity has a strong influence on frazil evolution, frazil size, and number of the particles, however. The measured frazil size distribution by volume was found to be reasonably well approximated by a log-normal distribution. Frazil growth continues in number and size during supercooling and appears to reach a stable state at the end of the principal period of supercooling. All characteristic parameters of the supercooling processes and frazil size distribution were found to be related to the Reynolds number, an index of the intensity of flow turbulence. This information can be used in the development of models of frazil ice dynamics.Key words: supercooling, frazil ice, distribution, flow velocity, air temperature, turbulence.