Snow Chute Experiments

SLF snow chute at Weissfluhjoch

Motivation

Frictional processes in the basal sliding and shear layers of snow avalanches are not yet understood. As nearly all of the energy in flowing avalanches dissipates in these basal layers, the understanding of the physical processes is crucial for proper avalanche modeling and hazard mitigation.

Methods

We gain direct insight into the shearing processes in the basal layer using a modern high-speed camera installed in a sharp half wedge at the center-line of the chute. The camera is able to capture 1000 images in one second. Flow processes can be observed in a high-resolution slow motion. By means of an appropriate pattern matching algorithm two dimensional velocity fields in the shear layer can be extracted from the high-speed video images.

Measuring setup: high-speed camera, stroboscopes and optical velocity sensors for comparison.

First results

Extremely high shear rates could be measured in the lower one to three centimeters of the flow. The strongly fluctuating velocities in the shear layer have signs of a turbulent motion.

Videos of experiments

Side view
Video from the bridge