Equation for the force experienced by a wall overflowed by a granular avalanche: experimental verification.

The present paper deals with the force experienced by a wall overflowed by a granular avalanche. First, we briefly report laboratory tests on dry granular avalanches overflowing a wall down a rough channel. In the first step, the thickness and velocity of the control flows without a wall are measured. In the second step, a wall is mounted to obstruct the flow and the normal force experienced by the wall is measured. Then a set of equations based on depth-averaged momentum conservation, making it possible to derive the time-varying force on the wall, is described. The model was proposed and calibrated in two-dimensional (2D) discrete numerical simulations in an earlier work [Chanut, Faug, and Naaim, Phys. Rev. E 82, 041302 (2010)]. This model takes into account the fact that a quasistatic stagnant zone is established upstream of the wall and coexists with an inertial flowing zone above. For a large range of slopes, the model's prediction is successfully compared to experimental data with a reasonable estimation of the incoming flow density and in spite of some rough assumptions made to describe the dynamics of the dead zone. Finally, the results are analyzed with regard to previous 2D discrete numerical simulations and we discuss future work to be undertaken on the dynamics of the dead zone established upstream of the wall.