Shun'ichi Kobayashi

Interaction Between Wind and Snow Surface

The horizontal and vertical wind velocity fluctuations were measured using two sonic anemometers at a height of 135 em above a snow surface under a transverse snow wave-forming condition. A snow-wave was formed when the wind at a height of 1 m blew at a speed of more than 7 m s−1 after an approximate accumulation of from 10 to 20 cm of new snow on a snowfield. For example, when a snow-wave had a wavelength of 10 m and a wave height of 15 to 20 cm, the measured horizontal and vertical velocity components showed that they had a frequency peak of 0.7 Hz in coherence and co-spectrum corresponding to this wavelength. The results suggest that wind turbulence and snow-wave formation interact with each other.

The effect of wind direction on drift control by snow fences

Abstract Snowdrifting processes and the wind-velocity profiles around a collector and a blower snow fence were investigated in a cold wind tunnel. The purpose was to ascertain the effect of wind direction on drift control by snow fences. Three different cases were studied for both types of snow fence, and the resultant snowdrifts were compared. In the first case, the snow fence was perpendicular to the wind direction. In the second and third cases, it was tilted by 30° and 45°. When the collector snow fence was tilted, the amounts of snowdrift were much less than when the fence was perpendicular to the wind direction, because the area with low wind velocity was reduced to half behind the tilted fence. On the other hand, the blowing effect of the blower snow fence increased when it was set up at an angle to the wind direction. It is necessary to investigate the position where the blown snow is deposited by the tilted blower snow fence.

Snow avalanche chute experiments. III: Prediction of impact pressure waves for snow blocks with low density.

これまで雪崩実験シュートを用いて測定された,雪塊の壁,杭および小円板に対する衝撃波形は,いずれも衝突直後に最大値が出現して,その後しだいに減衰するというものであった.本報告では,初期密度380kg/m3までの低密度の雪塊の衝撃現象に塑性圧縮理論を適用させ,かつ破砕された雪粒子がその後に及ぼされた衝撃力積により圧密されるという新しい観点を導入することにより,初期密度および衝突速度から衝撃波形を簡便に予測する手法を提案した.またこの際,実測された衝突速度,初期密度および最大衝撃圧から塑性波前面での破砕雪の密度を推定したところ,それは初期密度の1.45倍という直線関係で表されることが判明した.

Prediction of avalanche paths deviated from the stream by center-of-mass model

Abstract We developed a method that predicts avalanche paths deviating from a stream on complex surfaces. This method is based on Nohguchi’s center-of-mass model with simple dynamic resistance. Avalanche paths from many starting points were calculated at two sites in Japan where avalanche disasters have occurred, and paths causing unexpected disaster are presented. The characteristics of avalanche paths at these sites are shown. Small differences of the release positions sometimes cause great changes in avalanche meanderings.