O'Rourke M J, McCullough J P
School of Electrical, Electronic and Mechanical Engineering, Room 304, Centre for Material Science and Engineering, University College Dublin, Belfield, Dublin, Ireland.
Proc Inst Mech Eng H. 2010;224(8):971-88. doi: 10.1243/09544119JEIM694.
The flow fields within three patient-specific models of an abdominal aortic aneurysm (AAA) were investigated under steady laminar inflow conditions over a range of Reynolds numbers. Each model extended from the renal arteries to downstream of the iliac bifurcation. The aneurysms (referred to as models A, B, and C) are mature, with D/d ratios of 1.83, 1.57, and 1.95 respectively. The mass flowrates in each of the iliac arteries were equal. Using flow visualization it was observed that the flow proximally in the aneurysm was characterized by a primary jet that separated from either the posterior wall or the lateral wall or both, producing large recirculating zones. The primary jet impinged either normally or obliquely upon the anterior or right lateral wall in the distal half of the aneurysm, the flow distally in the aneurysm having been greatly disturbed. Measurements of the turbulence intensity along the median lumen centre-line showed that in each model the onset of transition and full turbulence occurred at Reynolds numbers much lower than those previously measured in idealized models. Computational fluid dynamics showed substantial differences in the velocity and stress fields when using the shear stress transport turbulence model as opposed to a laminar viscous model. It was also observed that turbulence was largely produced along the shear layers surrounding the primary jet and, in particular, at interfaces between the jet and the recirculating zones. In conclusion, turbulence may be expected to exist at Reynolds numbers typically encountered within an AAA, and it must be taken account of in an analysis of the flow field.
在一系列雷诺数的稳定层流流入条件下，对三个腹主动脉瘤（AAA）患者特异性模型内的流场进行了研究。每个模型从肾动脉延伸至髂动脉分叉下游。这些动脉瘤（分别称为模型A、B和C）已成熟，D/d比分别为1.83、1.57和1.95。每条髂动脉中的质量流量相等。通过流动可视化观察到，动脉瘤近端的血流特征是一股从后壁或侧壁或两者分离的主射流，产生大的回流区。主射流垂直或倾斜撞击动脉瘤远端半部的前壁或右外侧壁，动脉瘤远端的血流受到极大干扰。沿中腔中心线的湍流强度测量表明，在每个模型中，转捩起始和完全湍流发生时的雷诺数远低于先前在理想化模型中测得的雷诺数。计算流体动力学表明，与层流粘性模型相比，使用剪切应力输运湍流模型时速度场和应力场存在显著差异。还观察到，湍流主要在围绕主射流的剪切层中产生，特别是在射流与回流区之间的界面处。总之，在AAA内通常遇到的雷诺数下可能会存在湍流，在流场分析中必须予以考虑。
