Immiscible two-phase model for air blasts created during natural avalanches

An immiscible two-phase model based on the incompressible Navier-Stokes (N-S) equations is used to simulate the air blast generated by an avalanche. For simplicity, the avalanche is treated as an assembly of monodisperse spherical grains and described as a continuous media. The constitutive law of local µ(I) rheology is introduced to model the moving granular material. The motion of the avalanche and the induced air blast fits into a unified framework that combines the N-S−type governing equations with a µ(I)-rheology−based kinematic viscosity and a constant viscosity. The avalanche-air interface is treated using the volume-of-fluid method. A numerical program was developed on the open-source platform OpenFOAM specifically for this model to simulate the entire evolutionary process of the avalanche as well as the air blast generated. The model was validated by comparing the results of numerical simulations with those from inclined-plane laboratory experiments. With terrain input from the Shuttle Radar Topography Mission data, the model was further applied to simulate the air blast generated in two natural avalanches, namely, the Baige and Wenjia valley avalanches fo China, which occurred in 2008 and 2018, respectively. The simulation results were found to be consistent with field observations following a statistical analysis of the properties of the air blast including flow speed and area of impact of the above-mentioned natural events.