Numerical Study of the Unsteady Flow in Simplified and Realistic Iliac Bifurcation Models

Violeta Carvalho,Filipa Carneiro,José C Teixeira,Ana C Ferreira,Vasco Gama,Senhorinha Teixeira

doi:10.3390/fluids6080284

Abstract

Cardiovascular diseases are a major cause of death and disability worldwide and they are commonly associated with the occurrence of atherosclerotic plaque deposition in the vessel walls, a process denoted as atherosclerosis. This is a chronic and progressive inflammatory disease of large-/medium-sized blood vessels that affects blood flow profiles, with the abdominal aorta and its branches being one of the locations prone to the development of this pathology, due to their curvatures and bifurcations. In this regard, the effect of flow patterns was studied and compared for both a simplified three-dimensional model of aorta bifurcation on the iliac arteries and a realistic model of iliac bifurcation, which was constructed from a computational tomography medical image. The flow patterns were analyzed in terms of velocity and wall shear stress distribution, but a special focus was given to the size and location of the recirculation zone. The simulations were performed using the Computational Fluid Dynamics software, FLUENT, taking into account the cardiac cycle profile at the infrarenal aorta. The shear stress and the velocity distribution observed for both models indicated that higher shear stress occurred along the flow divider wall (inner wall) and low shear stress occurred along the outer walls. In addition, the results demonstrated that the wall shear stress profiles were deeply affected by the transient profile of the cardiac cycle, with the deceleration phase being the most critical phase to the occurrence of backflow.

Highlights

Cardiovascular diseases are a major cause of death and disability worldwide and they are commonly associated with the occurrence of atherosclerotic plaque deposition in the vessel walls, a process denoted as atherosclerosis
Phase of the cardiac cycle is more likely to lipidic deposition. These effects indicate that the development of atherosclerosis is, deeply correlated with the transient character of the cardiac cycle, mainly in the deceleration phase, where the recirculation expands all over the iliac artery
A simplified CFD model and a realistic one based on anatomical geometry were implemented in order to simulate the blood flow dynamics in the abdominal aorta bifurcation into the iliac arteries

Summary

Introduction

Cardiovascular diseases are a major cause of death and disability worldwide and they are commonly associated with the occurrence of atherosclerotic plaque deposition in the vessel walls, a process denoted as atherosclerosis This is a chronic and progressive inflammatory disease of large-/medium-sized blood vessels that affects blood flow profiles, with the abdominal aorta and its branches being one of the locations prone to the development of this pathology, due to their curvatures and bifurcations. There has been a growing interest in understanding the biomechanics of its formation, detection, and treatment of atherosclerotic lesions, with computational simulations being one of the main tools applied to better understand the disease and to develop new treatments [5,6,7,8] Over the years, this pathology has been deeply studied; the focus has essentially been on the carotid [9,10,11,12] and coronary arteries [13,14,15,16], since these are the most commonly affected arteries. Patients with atherosclerotic lesions in the iliac arteries will probably show published maps and institutional affiliations

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