Effect of spiral flow on the transport of oxygen in the aorta: a numerical study.

To test the hypothesis that the spiral flow pattern in the human aorta may play a beneficial role in the transport of oxygen, hence sparing the ascending aorta from atherosclerosis, a comparative study on the distribution of oxygen flux to the arterial wall was carried out numerically for three aorta models. The first one (Model 1) was constructed based on MRI images of a human aorta acquired in vivo. The second (Model 2) was made the same as Model 1 but without the three branches. The third (Model 3) was similar to Model 2 only with the aortic torsion removed. The results showed that without the torsion, the flow fashion in Model 3 was very different from the swirling flows in Models 1 and 2 and exhibited the typical characteristics of Dean flow with two symmetrical helical structures. In Models 1 and 2, the average Sherwood number (Sh) in the ascending aorta with the presence of a strong spiral flow was not only higher than that in the inner wall of the descending aorta where the spiral flow faded out, but also generally higher than that in Model 3. The comparison between Models 2 and 3 demonstrated that the averaged Sh from ascending aorta to aortic arch was relatively higher for Model 2. In conclusion, the spiral or swirling flow may have certain physiological significance in the aorta and play a positive role in the transport of oxygen by enhancing oxygen flux to the arterial wall.