CFD-DEM: A Multiresolution Framework for Modeling Multiphase Geophysical Flows

Geophysical flows such as debris flows, avalanches and floods pose significant geohazards in mountainous areas, likely worsened by impending global climate change.The multi-phase and multi-scale nature of these flows shapes their initiation, transportation, erosion, impact and runout dynamics, and makes them challenging to predict and model.We present a multiresolution framework for modeling multiphase geophysical flows by coupling computational fluid dynamics with the discrete element method.Two modules, resolved and unresolved CFD-DEM, have been developed to model multiscale and multiphase particulate systems at varying resolutions.The resolved module probes fluid-arbitrary-shaped solids-structure interactions in geophysical flows, enabling high-fidelity modeling of debris flows carrying driftwood and boulders against forests.Shapes of driftwood, boulders, and trees are captured from reduced-scale samples using X-ray CT techniques, and the CFD and DEM models utilizing the immersed boundary (IB) and signed distance field (SDF) methods, respectively.Conversely, the unresolved module simulates debris flows interacting with erodible beds across full-scale terrains, facilitating comprehensive modeling of debris flows, avalanches and floods impacting various countermeasures.As a result, the multiresolution CFD-DEM framework provides a unified treatment of multiscale and multiphase particulate systems, offering a promising tool for understanding and predicting geophysical flow dynamics and mitigations.Notably, this framework represents a pioneering advancement in geohazard modeling and holds promise for applications in diverse fields such as nature, engineering, and industry involving multiscale, multiphase particulate systems.