Title High-speed video recording of basal shear layers in snow chute flows
Author Schaefer, M.; Rösgen, T.; Kern, M.
Author Affil Schaefer, M., Institute for Snow and Avalanche Research, Davos, Switzerland. Other: Eidgenössische Technische Hochschule Zürich, Switzerland; Institute for Natural Hazards and Alpine Timberline, Austria
Source Cold Regions Science and Technology, 64(2), p.182-189, ; International snow science workshop 2009, Davos, Switzerland, Sept. 27-Oct. 2, 2009, edited by J. Schweizer. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0165-232X
Publication Date Nov. 2010
Notes In English. Based on Publisher- supplied data GeoRef Acc. No: 309820
Index Terms avalanche mechanics; avalanches; layers; mass movements (geology); rheology; shear strain; snow; turbulence; velocity; chutes; flows; high-resolution methods; layered materials; mass movements; shear; video methods
Abstract Run-out distances and flow velocities of snow avalanches are mainly determined by frictional processes originating from the interaction with the ground. At the SLF snow chute at the Weissfluhjoch near Davos, a setup was developed which allowed us to record high-speed movies of the basal shear layer of small-scale avalanches with a frame rate of 1000 frames per second. Shear processes could be observed in high- resolution slow motion. Downstream velocity profiles were extracted by a pattern matching algorithm. The comparison of computed profiles with velocity profiles obtained from optical sensors showed good agreement. However, the temporal and spatial resolutions are much higher for the high-speed video data. Because the optical velocity sensors are one-dimensional, we found that they overestimate the velocities when a flow- normal velocity component exists as well. All measured velocity profiles exhibited very high shear rates near the ground. The maximum shear rates were up to 600/s for dry snow and 200/s for wet snow avalanches. The observations of the video images suggested a turbulent motion of the snow in the basal shear layer.
URL http://hdl.handle.net/10.1016/j.coldregions.2010.08.014
Publication Type conference paper or compendium article
Record ID 65006945