The potential role of hemodynamics on atherogenesis and lesion progression in coronary arteries has been widely studied both experimentally and numerically. Clinical and postmortem examinations have provided valuable insight on the location of these lesions and the impact of flow disturbance and wall shear stress on their development. The determination of the exact conditions at the entrance of the coronary arteries as required for accurate numerical simulation of intracoronary flow pattern is difficult due to the inherent flow unsteadiness and the complexity of the ostium geometry. Thus, most previous theoretical analyses have often assumed uniform or parabolic spatial distribution of the entrance velocity. Such assumption severely limits the scope of validity of these studies because the strong curvature of the ostium and the relatively short length of the epicardial coronary artery do not allow for adequate flow development upstream of the coronary branches or regions of curvature where lesions occur.
This problem is further exacerbated by the non-uniqueness of the location of the ostium. It has been shown that the rate of blood flow in the coronary artery depends on the ostium location which in turn affects the flow characteristics, wall shear stress distribution and lesion proliferation on the arterial wall.
The objective of this paper is to predict the entrance velocities in human coronary arteries through a numerical model of flow in the aortic root. Specifically, we perform a detailed investigation of the flow pattern in a model human aortic root with two adjoining arteries. At this initial phase of model development, we consider the flow behavior only at diastole, the period of maximum coronary artery flow. A range of ostium curvatures and locations and coronary flow Reynolds numbers are considered. Emphasis is placed on characterizing the flow separation and recirculation resulting from the complex geometry of the aortic root-ostium assembly. The conservation equations governing the transport of mass and momentum are written in curvilinear coordinate system and solved using a fully-implicit finite domain numerical scheme. The predictions are checked for numerical accuracy through systematic grid refinement. The predicted flow pattern at the entrance of the coronary artery is subsequently used as an input for calculation of flow and wall shear stress characteristics in stenosed coronary artery curvatures and bifurcations. The predictions are compared with the experimental data and existing numerical results where available.