Abstract
ABSTRACTNumerical simulations of pulsatile flow in a feline aorta for hypertrophic cardiomyopathy (HCM) heart conditions are performed to predict flow details and to evaluate possible thrombus trajectory patterns. The study demonstrates that average flow rate boundary conditions (QBC) at artery outlets act as a resistance-type boundary condition for pulsatile flow. For simulations when the exact artery outflows are not known, specification of estimated values from physiological conditions is a plausible approach. This boundary condition is further improved using an iterative method (I-QBC) to accurately satisfy outflow conditions when expected outflow is known. The approach is validated against experimental data for the prediction of iliac artery flow and wall stresses in a human abdominal aorta. The feline aorta simulations including Lagrangian particle transport are performed on grids with up to 11M cells for a generalized feline aorta. It is found that LES on larger grids performs significantly better than URANS for the prediction of vortical structures. Simulations for both healthy and HCM conditions show similar flow patterns in the upper abdominal aorta. However, the HCM condition shows the presence of large recirculation regions in the thoracic aorta resulting in 50% lower flow through the iliac arteries and increased entrapment of fluid-borne particles near the trifurcation region compared to the healthy condition.
Highlights
Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiac diseases among humans and affects about 1 in 500 individuals
HCM is caused by the thickening of the left ventricular muscle wall, which results in decreased relaxation and increased diastolic pressure in the left ventricle and increased stasis of blood in the left atrium
The computer-aided design (CAD) model is generated using the dimensions of the feline aorta of Samii, Biller, and Koblik (1998), and any missing information is estimated by scaling the dimensions of the human aorta (Moore et al, 1992)
Summary
Hypertrophic cardiomyopathy (HCM) is one of the most common inherited cardiac diseases among humans and affects about 1 in 500 individuals. Khanafer and Berguer (2009) studied the effect of pulsatile cardiac flow on the aortic wall stresses (and deformation) using fluid-structure interaction. In contrast to the constant pressure boundary condition, some studies have specified cardiac cycle averaged expected flow rate at artery outlets (in terms of % of inlet flow). We denote such an approach here as QBC. The objectives of this study are to perform simulations of pulsatile feline aortic flow with Lagrangian thrombus transport for HCM heart conditions, to understand the effect of cardiac outflow changes on the aortic and abdominal artery flows, and to investigate the effect of HCM on the probability of thrombogenesis. The linkage between the probabilities of thrombogenesis as related to potential thrombi trajectories through the aorta and the roles of aortic flow in the entrapment of thrombi are discussed
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