Journal of the Japanese Society of Snow and Ice

Friction experiments were done to measure the kinetic friction coefficient between ice and ice at velocities from 10^-4 to 10^-1 m/s and temperatures from-1 to-27°C. It was found that at all temperatures tested, the ice-ice friction coefficient increased with the decrease in velocity;e.g., from 0.01 at 10^-1m/s to 0.15 at 10^-4m/s at -12°C, and that the friction coefficient showed minimum values at -5°C. The stick-slip phenomenon was observed at lower velocities than 5×10^-4m/s(-12°C)and 10^-3 m/s(-27°C). No dependence on the load, that is the normal stress applied between ice and ice, was noted in the range tested in the experiment, 2.9 to 6.7 kPa. Most of the obtained results can be explained by the theory of lubrication of water produced by frictional heating.

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Preventing snow buildup on an inclined roof using a falling water film is studied in this paper. A cluster of physical models for a gas-water-snow system has been developed and solved with a fully implicit control-volume finite-difference procedure. The contact flow pattern of a turbulent water film and a laminar gas stream was used in the simulation. The temperatures of the ambient saturated atmosphere and the falling snow were assumed to be equal and below zero Celsius. The outlet temperature of the water film was set at zero Celsius for the critical state. The effects of various parameters on heat transfer and water film temperature drop were investigated. The results revealed that it is feasible to use a falling water film to prevent snow buildup on an inclined roof. It was clarified numerically that among the factors influencing water film temperature drop, the snowfall intensity, the water film flow rate, the roof length and inclination play important roles. Of course the ambient temperature and wind speed also contribute to the water film temperature drop. The critical states of the inlet temperature and flow rate of the water film for various parameters were calculated in the present paper. The intensive heat transfer occurs in a very thin layer near the free surface of the water film in response to snow melting at the gas-water interface. The numerical results were correlated in terms of effective Nusselt number, and Reynolds number, Prandtl number and Gukhman number for simplified predicting. The maximum deviation of the numerical data from the regression line is approximately 15.6%, which causes an uncertainty of less than 3% in simple prediction.

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