Model studies of the flow in abdominal aortic aneurysms during resting and exercise conditions
Model studies of the flow in abdominal aortic aneurysms during resting and exercise conditions
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DOI：
10.1016/s0021-9290(99)00134-7
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发表时间：
1999-12-01
影响因子：
2.4
通讯作者：
Johansen, KH
中科院分区：
文献类型：
--
作者：
Egelhoff, CJ;Budwig, RS;Johansen, KH
为了了解可能有助于 AAA 生长的血流动力学，我们对腹主动脉瘤 (AAA) 模型中的脉动血流进行了检查。模型研究是通过实验（血流可视化和激光多普勒测速）以及使用生理真实的休息和运动血流条件的数值模拟来进行的。我们描述了两种 AAA 模型形状和尺寸的特征，通过适度的 AAA 生长来模拟早期 AAA 的发育（平均和峰值雷诺数为 362 < Re-mean < 1053 和 3308 < Re-peak < 5696，Womersley 参数 16.4 < alpha < 21.2）。我们的研究结果表明，AAA 流可分为三种流态：(i) 静止条件下小型 AAA 中整个循环的附着流，(ii) 静止条件下中等大小 AAA 中的涡流形成和平移，以及 (iii) 运动条件下中等大小 AAA 中的涡流形成、平移和湍流。后两种方案在医学文献中被分类为与动脉粥样硬化形成以及血栓形成相关的血流紊乱状况。因此，AAA 的血流动力学紊乱可能通过加速动脉壁的退化而成为 AAA 生长的一个促成因素。我们的调查还得出结论，不对称 AAA 中涡流的发展要弱得多。此外，在非对称模型中没有观察到湍流。最后，我们的研究提出了一种过渡到湍流的新模式：涡环不稳定和爆发到湍流。转变过程取决于脉动流条件和管横截面积变化的组合。 (C) 1999 Elsevier Science Ltd. 保留所有权利。
Pulsatile flow in abdominal aortic aneurysm (AAA) models has been examined in order to understand the hemodynamics that may contribute to growth of an AAA. The model studies were conducted by experiments (flow visualization and laser Doppler velocimetry) and by numerical simulation using physiologically realistic resting and exercise flow conditions. We characterize the how for two AAA model shapes and sizes emulating early AAA development through moderate AAA growth (mean and peak Reynolds numbers of 362 < Re-mean < 1053 and 3308 < Re-peak < 5696 with Womersley parameter 16.4 < alpha < 21.2). The results of our investigation indicate that AAA flow can be divided into three flow regimes: (i) Attached flow over the entire cycle in small AAAs at resting conditions, (ii) vortex formation and translation in moderate size AAAs at resting conditions, and (iii) Vortex formation, translation and turbulence in moderate size AAAs under exercise conditions. The second two regimes are classified in the medical literature as disturbed flow conditions that have been correlated with atherogenesis as well as thrombogenesis. Thus, AAA disturbed hemodynamics may be a contributing factor to AAA growth by accelerating the degeneration of the arterial wall. Our investigation also concluded that vortex development is considerably weaker in an asymmetric AAA. Furthermore, turbulence was not observed in the asymmetric model. Finally, our investigation suggests a new mode of transition to turbulence: vortex ring instability and bursting to turbulence. The transition process depends on a combination of the pulsatile flow conditions and the tube cross-sectional area change. (C) 1999 Elsevier Science Ltd. All rights reserved.