Unsteady and Three-Dimensional Simulation of Blood Flow in the Human Aortic Arch

Abstract

A three-dimensional and pulsatile blood flow in a human aortic arch and its three major branches has been studied numerically for a peak Reynolds number of 2500 and a frequency (or Womersley) parameter of 10. The simulation geometry was derived from the three-dimensional reconstruction of a series of two-dimensional slices obtained in vivo using CAT scan imaging on a human aorta. The numerical simulations were obtained using a projection method, and a finite-volume formulation of the Navier-Stokes equations was used on a system of overset grids. Our results demonstrate that the primary flow velocity is skewed towards the inner aortic wall in the ascending aorta, but this skewness shifts to the outer wall in the descending thoracic aorta. Within the arch branches, the flow velocities were skewed to the distal walls with flow reversal along the proximal walls. Extensive secondary flow motion was observed in the aorta, and the structure of these secondary flows was influenced considerably by the presence of the branches. Within the aorta, wall shear stresses were highly dynamic, but were generally high along the outer wall in the vicinity of the branches and low along the inner wall, particularly in the descending thoracic aorta. Within the branches, the shear stresses were considerably higher along the distal walls than along the proximal walls. Wall pressure was low along the inner aortic wall and high around the branches and along the outer wall in the ascending thoracic aorta. Comparison of our numerical results with the localization of early atherosclerotic lesions broadly suggests preferential development of these lesions in regions of extrema (either maxima or minima) in wall shear stress and pressure.

Effect of Reynolds number and flow division on patterns of haemodynamic wall shear stress near branch points in the descending thoracic aorta

“…We wished to determine whether patterns of WSS can also vary. The values of Re that we studied are appropriate for species ranging from mice to people (Buchanan et al 1999;Shahcheraghi et al 2002;Feintuch et al 2007). Flow partitions have not been measured accurately at intercostal branch sites in any species.…”

Influence of Differential Calcification in the Descending Thoracic Aorta on Aortic Pulse Pressure

“…Multiple mechanisms have been proposed, including altered low-density-lipoprotein cholesterol transportation 20,21 and increased turbulence and wall shear stress, especially in the location of the descending aorta, which has many more branches than the other segments. [22][23][24] For instance, the ascending aorta only has two branches (right and left coronary artery), and the arch has three branches (brachiocephalic, right subclavian, right common carotid). However, the descending aorta has multiple branches, including 11 pairs of posterior intercostal arteries and multiple arteries originating anteriorly, including bronchial, mediastinal, esophageal and pericardial branches as well as superior phrenic arteries.…”

Left Ventricular Assist Devices: Engineering Design Considerations

“…Although not always the case, steady or near steady flow characterizes the flow regime in many patient with LVAD support (Shahcheraghi et al, 2002;Tokuda et al, 2008;and Drummond et al, 2008). Continuous-flow LVADs have predominantly become the device of choice.…”