We have chosen to study wet-snow avalanches in order to be able to run simulations with Telemac2d.

Globally, you can describe the forces which are acting on a pack of snow as follows:

Then you obtain the following equation:

where U  is the speed of the solid of weight m (here U is the average speed of the avalanche)
and F is the sum of the external forces which are acting on this solid.

  • Fp represents the driving forces (drawn in blue)
  • Fn represents the drag forces (drawn in red)
  • The only driving force is of course the driving part of the gravity, which can be written as:

    The drag forces, linked to different wasting processes, are difficult to modelize, depending on the rheological model chosen. Otherwise, many authors agree to express this force as follows:

  • The first term represents the solid rubbing:
  • The second term is due to the viscosity forces, linked to speed gradient in the flow. Those forces are predominant in very slow flows and can be in consequence negligible in many models.
  • The third term represents the flow turbulence. The coefficient of turbulence rubbing, c, can be defined as follows:
  • Finaly, you obtain this basis equation: