Coupling depth-averaged and 3D numerical models for the simulation of granular flows

Continuum-based numerical models are widely used to simulate debris flows due to their reliability in predicting the movement path, depth and velocity, which are key parameters to design mitigation structures. Nowadays, two main families of continuum-based models exist: depth-averaged (DA) models and three-dimensional (3D) models. If the former are already able to determine the key flow parameters, only the latter allow a detailed investigation of a flow-structure interaction. The study of the whole propagation path with a 3D model would be extremely complex and time-consuming, but the whole process influences the flow-structure interaction. Therefore, this work aims to couple a DA model and a 3D model (DA-3D). The first model simulates the flow in the upper part of the propagation path, where no structure exists. The second model takes over upstream of the structure to be analysed. At the transition from one model to the other, the coupling requires that outputs of the DA model become inputs of the 3D model. The validation of the DA-3D model is made through numerical simulations of the experimental results obtained on a flume apparatus at laboratory scale. The obtained numerical results confirmed the successful coupling of the two models.