Simulation of atherosclerosis-related thrombus evolution in representative vascular geometries using Immersed...

Thrombus formation in atherosclerosis-related vascular regions is influenced by complex and spatially varying hemodynamic conditions. While low shear stress and flow recirculation have been widely associated with increased thrombotic risk, the mechanisms by which geometry-induced hemodynamic features translate into distinct thrombus evolution outcomes remain insufficiently understood, partly due to the lack of quantitatively validated closed-loop models. In this study, we develop a two-dimensional fluid-structure interaction framework that resolves the bidirectional coupling between thrombus growth and the surrounding flow field, as a mechanism-oriented computational model for comparative analysis. Based on the IB2d (Immersed Boundary 2D) framework, a two-stage simulation strategy is implemented in three representative vascular geometries: straight, curved, and bifurcated vessels. In the first stage, thrombus formation is suppressed to obtain a thrombus-free baseline flow field, from which a geometry-dependent risk score is constructed to provide an a priori ranking of thrombotic susceptibility. In the second stage, thrombus formation is activated to systematically simulate thrombus evolution, extract key phenotypic metrics, and construct detachment critical phase diagrams through parametric control. The results indicate that, under identical inlet conditions, bifurcated vessels tend to exhibit earlier thrombus nucleation and a greater propensity for rapid accumulation leading to occlusion, whereas straight and curved geometries preferentially undergo detachment after reaching a critical growth scale. The resulting phase diagrams further delineate distinct phenotypic regimes of thrombus evolution within parameter space and define their critical boundaries, thereby enabling mechanism-based comparative analysis and characterization of critical conditions.