Multiscale modeling of multiphase flow interaction with mitigation structures

Debris flows are multiphase flows consisting of water, fine-grained, and coarse-grained sediments, whose complex behavior poses challenges for understanding the process dynamics, and mitigating the effects on the territory. Standards for designing effective protection measures are lacking, and are unlikely to become available soon. A variety of simulation methods exist, ranging from microscopic to macroscopic scales, offering tools to model multiphase flows and address the above challenges. Discrete methods represent flows as assemblies of colliding particles. They are useful for studying particle clogging, but appear inadequate for capturing the entirety of events due to computational demands. Continuum-based numerical methods, such as depth-averaged and three-dimensional models, offer more comprehensive simulations. Depth-averaged models efficiently simulate the entire process, but struggle with flow-structure interactions. In contrast, three-dimensional models, while more complex, excel at studying specific aspects like the impact of debris flow against mitigation structures. This study focuses on the Gran Valley catchment, leveraging historical data and existing mitigation structures. It explores how different modeling approaches contribute to understanding the dynamics of debris flows and their interaction with protective measures. By examining both the process dynamics and structural interactions, the research aims to provide insights into effective mitigation strategies