Grid-Size Design Strategy for FEM–DEM Coupled Flow Simulations with Application to a Flow Diverter Stent Model

In fluid analysis of stent models with a braided structure, conventional modeling using Finite Element Method (FEM) boundaries requires extremely fine fluid mesh resolution. The objective of this study is to propose a grid size design strategy for FEM–Discrete Element Method (DEM) coupled analysis. In the proposed method, the fluid is modeled using FEM, while the stent is modeled using a continuous arrangement of DEM particles. The volume-force-based coupling method eliminates the need for node sharing between the FEM and DEM, thereby reducing the modeling workload. In this study, we derived grid sizes based on flow analysis around a single strand and verified the flow analysis around a 3D braided stent model. The results showed that the proposed method reduced the number of fluid grids by approximately 44% compared to conventional methods. In this case, the maximum errors in velocity and pressure were 0.0064 m/s and 17.07 Pa, respectively, and high correlations of 0.9 or higher were obtained for both distributions. Furthermore, the maximum relative error in the drag coefficient was 4.332%. This study provides guidelines for a fluid grid size design method that enables the reduction in computational cost and modeling burden in fluid flow analysis around stents.