Item: A mixed flowing/powder snow avalanche model
Title: A mixed flowing/powder snow avalanche model
Proceedings: Proceedings of the 2000 International Snow Science Workshop, October 1-6, Big Sky, Montana
Authors: P.A. Bartelt; M.A. Kern and M. Christen Swiss Federal Institute of Snow and Avalanche Research (SLF), CH-7260 Davos, Swizerland
Abstract: One-dimensional layer-averaged equations describing the mechanics of mixed flowing/powder snow avalanches are- formulated and solved. The equations describe the volume, mass and momentum balance of the powder and flowing parts of the avalanche. The powder cloud of changing density is assumed to be incompressible and the suspended ice particles inert with respect to small scale turbulent fluctuations in the air. Normalized velocity and density profiles are based on experiments and supplement .the depth-averaged equations. The dense flowing avalanche is of constant flow density. Longitudinal straining of the granular flow mass is formulated with an active/passive pressure with cohesion. The mass exchange between the flowing and powder avalanche is assumed to be velocity dependent. Air entrainment into the powder cloud is governed by a dimensionless form factor. Therefore, the initiation and eventual self-acceleration of the powder cloud from a full flowing avalanche is modelled. It is possible to simulate the evolution of a large powder cloud from a dense flowing avalanche. Deceleration of the powder cloud is due to conversion of kinetic flow energy into potential energy and turbulent energy in the air which is eventually dissipated. The stagnant powder cloud left behind the flowing parts is modelled as a mass loss at the tail of the avalanche. Several calculation examples of mixed flowing parts is avalanches are presented showing the practicality of the new model.
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Keywords: density, model, snow, powder, flowing
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