PHD POSITION: INVESTIGATION OF INTERACTIONS BETWEEN DEBRIS FLOWS AND OBSTACLES THROUGH COUPLED DEM-SPH MODELLING

Debris flows are fast flowing landslides, i.e., mixtures of coarse grains and mud. They are extremely destructive. Engineers thus regularly seek to stop them with barriers. This involves complex granular and viscoplastic fluid mechanics’ interactions. So far, debris flows are modelled either with pure fluid mechanics approaches (e.g., depth-averaged models, SPH - smooth particle hydrodynamics) or with granular approaches e.g., using DEM - discrete elements modelling.

This project seek to explore the process of debris flow stopping using advanced numerical models coupling DEM with computational fluid dynamics, likely SPH through the plateform DualSPHysics.

DEM enables to capture the behaviour of coarse grains, i.e., rocky boulders transported by debris flows, while coupling it with SPH will allow, for the first time, to explore how non-Newtonian properties of interstitial fluid located between coarse grains influences the bulk dynamics of debris flows. The complex interplay between angular coarse grains of various sizes and the viscoplastic interstitial fluid during debris flow propagation and stopping remains generally poorly explored. This work will address a comprehensive exploration of:

1. How do coupled discrete element model–computational flow dynamics perform in computing debris flows propagating under regimes actually observed in the field?

2. How does the interplay between force chains within the granular skeleton and viscoplastic interstitial fluid dynamics drive the fluid–solid transition and thus the flowing and eventual stopping of debris flow surges during impact with an obstacle?

In essence, in the line of Canelas et al. (2017, Journal of Hydraulic Engineering 143:6017012) and Wang et al. (2016, Natural Hazards 81:1981–1998), this project will seek to improve coupled DEM-CFD models by incorporating non-Newtonian rheology of the fluid phase to study flow before and during impacts of debris flows against obstacles. After rigorous implementation of complex fluid rheology and solid–fluid coupling, it will enable to study in detail the fluid-solid transition at the impact and the flow behaviour near obstacles to finally provide recommendations on ways to compute these phenomena in larger-scale models, e.g., depth-averaged.

This project involves a collaboration between Dr Guillaume PITON from the INRAE (center of Grenoble - STREAM team) and Dr Vincent RICHEFEU from Laboratory 3SR.

More details about the job offer in the downloadable PDF document.

Deadline for the application: June 30, 2020