Department of Mechanical Engineering, North Dakota State University, Fargo, ND, USA.
Department of Mechanical Engineering, North Dakota State University, Fargo, ND, USA.
Med Eng Phys. 2022 Apr;102:103784. doi: 10.1016/j.medengphy.2022.103784. Epub 2022 Feb 25.
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.
罗曼式和哥特式是主动脉缩窄手术后两种变形的主动脉弓几何形状。异常的弓几何形状和血液动力学与晚期系统性高血压、主动脉瘤和其他心血管并发症有关。为了了解这种流动的流体动力学特征，进行了一项结合实验和计算流体动力学（CFD）的研究，以定量比较主要（轴向）和二次流动特征。在实验中，使用脉动流模拟器产生脉动流条件。采用锁相平面和层析粒子图像测速技术对流场进行定量研究。还进行了三维 CFD 模拟并与实验数据进行了比较。结果表明，在罗曼式弓中，血流在峰值收缩期后首先在内壁加速，然后在横截面上变得更加均匀。在收缩期形成一对壁涡和迪恩型涡。相干结构在整个心动周期内不断延伸到降主动脉并持续存在。相比之下，哥特式弓显示出高度偏斜的速度分布，弓顶周围的速度较高。急剧的曲率导致在顶部附近发生流动分离、射流冲击和停滞流。哥特式弓中的相干结构在降主动脉中连续性较差，这也与罗曼式模型中观察到的不同。哥特式弓的明显流动特征导致降主动脉壁切应力的时间和空间变化更大，暗示了主动脉并发症的血流动力学风险。
