Avalanches can be simulated using the free surface modeling capabilities of FLOW-3D. The avalanche model below is based on FLOW-3D's drift model for two-phase flow, which was customized to handle dense flow avalanche problems.
Modeling & Customization of the Avalanche Model
The avalanche model is based on the assumption that dense flow of snow exhibits Non-Newtonian behavior. In this model the effective dynamic viscosity is modeled using the Cross Model:
The Cross model is a generic rheological model where the non-Newtonian viscosity, μ, varies between μo and μ∞ with the shear rate, γ. For the simulation shown in the animation, the parameter α is set to 1.1 and the rheological exponent m is set to one.
Modeling of solidification was included to account for the change from flowing fluid phase to solid phase in the run out zone. This enables the modeler to simulate the stopping process and evaluate the run out distances of the avalanche. Initiating the movement of the snow, and the transition from solid to fluid phase, was a function of increasing a certain shearing stress or angle, for the given snow conditions.
This avalanche model has not been fully evaluated or compared with experimental data, because such data is lacking. The nature of an avalanche is very complex. Full scale avalanche experiments are expensive, demanding and difficult to perform, which makes numerical modeling an attractive option. However based on avalanche observations, the front velocities and run out length seem to be within the range of what would typically be expected.