StratifiedGRANULAR · Modelling of rheologically stratified granular flows by a multi-layer depth-averaged approach

Geophysical granular flows, like rock avalanches and debris flows, represent a serious hazard to life and infrastructures in Europe. Yet their dynamics is still far from being completely understood. Recent experimental investigations on granular flows showed that velocity and solid volume fraction exhibit a stratified pattern along the flow depth. This indicates the superimposition of different rheological regimes. Moreover, non-local rheological theories have been recently proposed for capturing momentum exchanges, driven by the occurrence of force chains.The present multidisciplinary project aims at developing a computationally cost-effective multi-layer depth-averaged model for describing rheologically stratified granular flows. The model, having much lower computational costs than three-dimensional models, will be designed to capture the essential physics of granular flows in the depth-wise direction. To properly take into account the curvature effects due to basal topography, the model equations will be derived in curvilinear coordinates attached to the topography. Moreover, a suitable non-local constitutive law will be incorporated. The resulting equations will be numerically integrated by a proper finite volume scheme, taking into account their main mathematical properties, i.e. non-strict hyperbolicity and non-conservative form. The model validation will be carried out by using a wide experimental data set, previously gathered by the applicant on dry granular flows. The last stage of the project is devoted to extending the multi-layer approach to cases with dense interstitial fluid, so as to allow its application to debris flows.In line with H2020 priorities, especially as regards sustainable human settlements and their resilience to natural hazards due to climate changes, the project has the potential to provide an advanced mathematical-numerical tool for better identifying the hazardous areas associated with avalanches and debris flows.