Assessment of Pulsatile Blood Flow Models for the Descending Aorta Using CFD

The objective of this research is to develop a computational fluid dynamics (CFD) model of a healthy human aorta from the aortic arch to the femoral arteries to allow for a better understanding of blood flow characteristics in this significant vessel. The increasing number of patients suffering from vascular diseases has accelerated the research in this field. Pulsatile blood flow through the descending aorta has numerous mechanisms that influence the flow characteristics, including non-Newtonian fluid effects, transient effects of the cardiac cycle, and geometries within the aortic vessel, among others. Although CFD has been used to predict flow effects of rather complicated systems, the use of CFD in vascular flow is still largely not understood. This paper compares non-Newtonian fluid effects in the flow of a natural aorta as well as flow effects within the descending aorta, including the ostium flow diverter, which regulates blood flow from the aorta to the renal arteries and was discovered within the last five years. Utilizing Creo Parametric, a 3-dimensional representation of the aorta was created including physical portrayals of the renal, superior mesenteric, common iliac and celiac arteries. This geometry was imported, meshed, and analyzed using a commercially available CFD solver. Using fluid properties of blood previously characterized in prior research, pulsatile flow models were investigated using constant viscosity and the Carreau-Yasuda Non-Newtonian viscosity model. This research compares the Oscillating Shear Index results of the constant viscosity model versus non-Newtonian. Shear stress and velocity profiles are used to study the effects of each assumption on the flow of blood through the descending aorta. This will be done by using a scalar result of the shear stress and the calculated Oscillating Shear Index. Based on previous work, the boundary layers created at the entrance of the renal arteries should be reduced by the presence of the ostium flow diverter. The model with the ostium flow diverter is used in both simulations. Ultimately, the simulation may predict the effects of changes or interventions to the descending aorta caused by assuming constant viscosity or non-Newtonian.