A coupling discrete element and lattice Boltzmann method model for simulating fluid–structure interactions involving deformable and breakable solids

Although fluid–flexible structure interaction problems have been extensively studied, the fracture behavior of solid systems remains largely unexplored. This study presents a coupled computational framework based on the discrete element method (DEM), immersed moving boundary (IMB) method, and lattice Boltzmann method (LBM) that integrates numerical models for fluid dynamics, solid elastic deformation, and fracture of slender, flexible structures. The approach leverages the LBM for efficiently handling complex flow phenomena and employs the DEM with rectangular particles and a parallel bond model to capture deformation and failure of flexible plates. Large eddy simulation is incorporated to model the turbulence. Fluid–solid interface dynamics are resolved using the IMB method, and the solid volume fraction in the coupled system is analytically computed to accurately capture two-way fluid–solid interactions (FSIs). Consequently, the proposed approach is capable of simulating the complete transition from continuous to discontinuous fracture in slender solid systems. The framework is validated against several benchmarks to demonstrate its accuracy and reliability. The results demonstrate the framework's effectiveness in simulating the transition from elastic deformation to fracture in slender structures and in capturing complex two-way FSI, confirming its potential for engineering applications such as the analysis of submarine risers.