Cheng Z, Tan F P P, Riga C V, Bicknell C D, Hamady M S, Gibbs R G J, Wood N B, Xu X Y
Department of Chemical Engineering, Imperial College London, London, UK.
J Biomech Eng. 2010 May;132(5):051007. doi: 10.1115/1.4000964.
Aortic dissection is the most common acute catastrophic event affecting the thoracic aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent aneurysmal dilatation of the thoracic aorta. This study aimed at gaining more detailed knowledge of the flow phenomena associated with this condition. Morphological features and flow patterns in a dissected aortic segment of a presurgery type B dissection patient were analyzed based on computed tomography images acquired from the patient. Computational simulations of blood flow in the patient-specific model were performed by employing a correlation-based transitional version of Menter's hybrid k-epsilon/k-omega shear stress transport turbulence model implemented in ANSYS CFX 11. Our results show that the dissected aorta is dominated by locally highly disturbed, and possibly turbulent, flow with strong recirculation. A significant proportion (about 80%) of the aortic flow enters the false lumen, which may further increase the dilatation of the aorta. High values of wall shear stress have been found around the tear on the true lumen wall, perhaps increasing the likelihood of expanding the tear. Turbulence intensity in the tear region reaches a maximum of 70% at midsystolic deceleration phase. Incorporating the non-Newtonian behavior of blood into the same transitional flow model has yielded a slightly lower peak wall shear stress and higher maximum turbulence intensity without causing discernible changes to the distribution patterns. Comparisons between the laminar and turbulent flow simulations show a qualitatively similar distribution of wall shear stress but a significantly higher magnitude with the transitional turbulence model.
主动脉夹层是影响胸主动脉的最常见急性灾难性事件。大多数表现为单纯B型夹层的患者接受药物治疗，但其中25%的患者随后会出现胸主动脉瘤样扩张。本研究旨在更详细地了解与这种情况相关的血流现象。基于从一名术前B型夹层患者获取的计算机断层扫描图像，分析了该患者解剖主动脉段的形态特征和血流模式。通过采用在ANSYS CFX 11中实现的基于相关性的Menter混合k-ε/k-ω剪切应力输运湍流模型的过渡版本，对患者特异性模型中的血流进行了计算模拟。我们的结果表明，解剖后的主动脉以局部高度紊乱且可能为湍流的血流为主，伴有强烈的回流。大约80%的主动脉血流进入假腔，这可能会进一步增加主动脉的扩张。在真腔壁撕裂处周围发现了高壁面剪切应力值，这可能增加了撕裂扩大的可能性。在收缩中期减速阶段，撕裂区域的湍流强度最高达到70%。将血液的非牛顿行为纳入相同的过渡流模型中，得到的峰值壁面剪切应力略低，最大湍流强度更高，但未对分布模式造成明显变化。层流和湍流模拟之间的比较表明，壁面剪切应力的分布在定性上相似，但过渡湍流模型的壁面剪切应力大小明显更高。
