Deciphering controls for the impact of geophysical flows on a flexible barrier: Insights from coupled CFD-DEM modeling

Geophysical flows impacting a flexible barrier can create complex flows and solid-fluid-structure interactions, which are challenging to quantify and characterize towards a unified description. Here, we examine the common physical laws of multiphase, multiway interactions during debris flows, debris avalanches and rock avalanches against a flexible barrier system using a coupled computational fluid dynamics and discrete element (CFD-DEM) method. This model captures essential physics observed in experiments and fields. The bi-linear, positive correlations are found between peak impact load and Fr or maximum barrier deflection, with inflection points due to the transitions from trapezoid- to triangle-shaped dead zones. Our findings quantitatively elucidate how flow materials (wet versus dry) and impact dynamics (slow versus fast) control the patterns of the identified bi-linear correlations. This work offers a physics-based reference and insights for improving widely-used impact solutions for geophysical flows against flexible barriers.