Improved Model for Granular Avalanches

Avalanches and debris flows are typically modeled as flow processes in granular media. Sarno et al. proposed a mathematically well-posed multilayer model for these complex systems and compared computational results from this model to several laboratory experiments.

The model describes the evolution of granular avalanches in a computationally efficient way by using a multilayer approach. The flow domain is discretized into several miscible layers evolving according to a specified rheology. The model also incorporates a dilatancy law to consider the dynamical effects of variable volume fraction.

“This is the latest in a series of contributions about granular flows in the framework of the Marie-Curie project ‘Stratified Granular,’” said author Luca Sarno. “The main goal of the current work is to assess the ability of the proposed multilayer model to practically describe a variety of granular flows.”

Frictional effects of the sidewalls were also included, allowing the investigators to compare computational results from their model to three different experimental scenarios. Specifically, the model results compared favorably with the velocity measurements of unsteady surface flows, dam-break flows in an inclined narrow flume, and steady flows over an erodible bed. In this third investigation, volume fraction measurements were also obtained using a stochastic-optical method and compared to simulations by the model.

“Comparison with various laboratory experiments encompassing different geometries and flow conditions showed that the proposed multilayer model is a reliable and computationally cost-effective tool for practically describing granular flows,” Sarno said.

The authors also suggested that the proposed model is a good alternative to fully three-dimensional models with similar rheologies, especially considering that its mathematical properties ensure the convergence of numerical simulations.

Source: “A well-posed multilayer model for granular avalanches: comparison with laboratory experiments,” by L. Sarno, Y. Wang, Y.-C. Tai, M. N. Papa, P. Villani, and M. Oberlack, Physics of Fluids (2022) The article can be accessed at https://doi.org/10.1063/5.0106908 .