Experimental and computational study of pulsatile flow characteristics in Romanesque and gothic aortic arch models.

Romanesque and Gothic are two types of deformed aortic arch geometries after surgical repair of coarctation of the aorta. The abnormal arch geometry and hemodynamics are associated with late systemic hypertension, aortic aneurysms, and other cardiovascular complications. To understand the fluid dynamic signatures of such flow, a combined experimental and computational fluid dynamic (CFD) study has been conducted to quantitatively compare the main (axial) and secondary flow characteristics. In the experiments, a pulsatile flow simulator was used to generate the pulsatile flow conditions. Phase-locked planar and tomographic particle image velocimetry techniques were employed to quantitatively study the flow fields. Three-dimensional CFD simulations were also performed and compared with the experimental data. The results show that in the Romanesque arch, the flow first accelerates along the inner wall and then becomes more uniform in the cross-section after the peak systole. A pair of wall vortices and Dean-type vortices develop during the systolic phase. The coherent structures are continuously extended into the descending aorta and persist throughout the cycle. In comparison, the Gothic arch exhibits a highly skewed velocity distribution with high velocity around the arch apex. The sharp curvature causes flow separation, jet impingement, and stagnant flow near the top. The coherent structures in the Gothic arch are less continuous in the descending aorta, which also differ from those observed in the Romanesque model. The distinct flow characteristics of the Gothic arch lead to more temporal and spatial variations of wall shear stress in the descending aorta, implying hemodynamic risks for aortic complications.