VELOCITY AND ANGLE DISTRIBUTIONS OF DRIFTING SNOW PARTICLES NEAR THE LOSSE SNOW SURFACE

概要

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Drifting snow experiments in a cold wind tunnel were conducted to investigate impact and ejection velocities and angles of snow particles as functions of friction velocity from 0.15 to 0.39m/s. Disintegrated particles of natural compact snow were used. Trajectories of snow particles were illuminated with a laser sheet cut with a rotary shutter and were recorded with a video camera system. Both average impact and ejection velocities increased with the friction velocity. However, average impact and ejection angles decreased. Standard deviations of the ejection angles were larger than those of the impact angles. Average horizontal components of both the impact and ejection velocities increased with the friction velocity, while average vertical components did not change much. In general, faster particles had smaller impact angles and slower particles had larger angles. The ratio of the average ejection velocity to the average impact velocity, that is the restitution coefficient, increased with the friction velocity. The vertical restitution coefficient ranged from 1.5 to 2.3,showing the increase of vertical ejection velocity at each impact. The results were discussed in comparison with those of previous studies including sand particles, and it was concluded that the overall characteristics of a loose snow surface at impact are similar to those of a sand surface in spite of different materials.
国立極地研究所の論文