Flow field and wall shear stress (WSS) in an idealized model of a human aorta with a coarctation and a post-stenotic dilatation, Figure 1, were investigated with large eddy simulation. A physiologic pulse was prescribed at the inlet, Figure 1. Phase averages of axial WSS, from 30 consecutive pulses, were determined between the throat (x=0) and the exit (x=0.2 m) along lines where the x-y plane and x-z plane cross the vessel wall. Figure 2 shows these values at late systole; the pattern is representative for the entire systolic phase. WSS peaks in the stenosis, as expected, but also at the end of the dilatation (x=0.06 m). In the dilatation backflow causes a negative peak. Diastolic WSS is characterised by low amplitude oscillations. Also noticeable is the asymmetric pattern between the inner (y>0) and outer (y<0) sides caused by the flow through the arch. Thus, large spatial, temporal, and probably asymmetric WSS gradients in the already diseased region suggest increased risk for further endothelial dysfunction [1]. This reflects a complex, partly turbulent, flow pattern that may disturb the blood flow in the abdominal aorta.

Figure 1

Geometry with flow direction and inlet pulse profile.

Figure 2

Phase averaged axial WSS along four lines between the throat (x=0) and the exit (x=0.2 m).