Fluid–Solid Interaction Analysis on Iliac Bifurcation Artery: A Numerical Study

Abstract

Atherosclerosis, which is commonly seen at regions with low wall shear stress (WSS) level in bifurcations, is a kind of fibro-fatty plaque accumulated on arterial walls. Aortic and iliac bifurcations have the highest proportion of patients among all atherosclerosis cases, thus it is necessary to numerically analyze the flow distribution and predict plaque positions in these bifurcations. Furthermore, using fluid–solid interaction (FSI) method could obtain a more exact flow pattern in arteries. In this study, a patient-specific model of aortic and iliac bifurcations was simulated with both FSI and rigid-wall cases. We analyzed the vessel deformation, WSS and flow distribution of this model. Computed tomography (CT) angiography was used in our study to create patient-specific model of aorto-iliac arteries. Real material properties and pulsatile fluid boundary conditions were applied in solid and fluid zones, respectively. We performed FSI and ordinary computational fluid dynamics (CFD) simulations with AYSYS 15.0 software (ANSYS Inc., Canonsburg, PA), and compared the diameter change, WSS and flow field between these two results. The diameter change between systolic phase and diastolic phase is 8–9% on abdominal aorta, and 3% on external and internal iliac arteries. The compliance of vessels corresponds to in-vivo observations. At peak systolic phase, the average WSS obtained in FSI simulation is 10% lower than in rigid-wall result, area of low-WSS region ([Formula: see text]) also increases by 78%. Wall deformation has a greater impact on WSS of those vessels with larger diameter, but hardly changes the shear level in smaller branches. Our result also shows that iliac bifurcations reveal more complicated secondary flow in systolic phase, comparing to other vessels, and stenosed iliac artery has more severe secondary flow than healthy artery. We obtained a feasible method for hemodynamic FSI research. The material parameters, boundary conditions and mesh could be used for further simulations, while the WSS and flow distribution may support clinical diagnosis and treatment. We concluded that compliance is a must-consider factor for simulating an accurate wall shear stress, because the vessel deformation in FSI simulation will significantly change the distribution of low-WSS zones. Moreover, more complicated secondary flow is detected in iliac arteries because it may interact between bifurcations. Stenosis in artery may also have a blocking effect on downstream blood flow.