Numerical Study of Purely Viscous Non-Newtonian Flow in an Abdominal Aortic Aneurysm
Numerical Study of Purely Viscous Non-Newtonian Flow in an Abdominal Aortic Aneurysm
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DOI：
10.1115/1.4027488
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发表时间：
2014-10-01
影响因子：
1.7
通讯作者：
Jansen, Kenneth E.
中科院分区：
文献类型：
--
作者：
Marrero, Victor L.;Tichy, John A.;Jansen, Kenneth E.
众所周知，血液具有非牛顿性质，但通常认为血液在高于100 s（-1）的剪切速率下表现为牛顿流体。然而，在瞬态条件下，存在剪切速率远低于100 s（-1）的时间和位置，并且可以合理地推断非牛顿效应可能变得重要。在该研究中，血液的纯粘性非牛顿（广义牛顿）性质被并入Taylor等人开发的用于心血管手术规划的基于模拟的框架中（1999，“Predictive Medicine：Computational Techniques in Therapeutic Decision Making，”Comput.辅助外科，第4页。231-247; 1998，“动脉中血流的有限元建模”，计算。方法应用机械工程，158，pp. 155-196）。描述血流的方程在稳定和生理流动条件下在基于患者的腹主动脉瘤模型中求解。直接数值模拟（DNS）被用来，和复杂的流动被发现不断过渡层流和湍流之间的空间和时间的意义。它被发现的情况下模拟，使用非牛顿粘度修改的解决方案，在微妙的方式，产生一个网格独立的解决方案，比牛顿对应的自由度更少。似乎在分离流的区域中，较低的剪切速率产生较高的粘度，具有非牛顿模型，这降低了相关的分辨率需求。当考虑脉动流的真实的情况时，相对于非牛顿情况，牛顿情况下的高剪切层导致更大的不稳定性。这反过来又导致非牛顿模型倾向于需要更少的计算资源，即使它必须对粘度进行额外的计算。它还表明，这两个粘度模型预测可比的壁面剪切应力分布。这项工作表明，使用非牛顿粘度模型可能是有吸引力的，以解决心血管流量，因为它可以提供模拟结果，大概是物理上更现实的，至少有相当的计算工作量为一个给定的精度水平。
It is well known that blood has non-Newtonian properties, but it is generally accepted that blood behaves as a Newtonian fluid at shear rates above 100 s(-1). However, in transient conditions, there are times and locations where the shear rate is well below 100 s(-1), and it is reasonable to infer that non-Newtonian effects could become important. In this study, purely viscous non-Newtonian (generalized Newtonian) properties of blood are incorporated into the simulation-based framework for cardiovascular surgery planning developed by Taylor et al. (1999, "Predictive Medicine: Computational Techniques in Therapeutic Decision Making," Comput. Aided Surg., 4, pp. 231-247; 1998, " Finite Element Modeling of Blood Flow in Arteries," Comput. Methods Appl. Mech. Eng., 158, pp. 155-196). Equations describing blood flow are solved in a patient-based abdominal aortic aneurysm model under steady and physiological flow conditions. Direct numerical simulation (DNS) is used, and the complex flow is found to be constantly transitioning between laminar and turbulent in both the spatial and temporal sense. It is found for the case simulated that using the non-Newtonian viscosity modifies the solution in subtle ways that yield a mesh-independent solution with fewer degrees of freedom than the Newtonian counterpart. It appears that in regions of separated flow, the lower shear rate produces higher viscosity with the non-Newtonian model, which reduces the associated resolution needs. When considering the real case of pulsatile flow, high shear layers lead to greater unsteadiness in the Newtonian case relative to the non-Newtonian case. This, in turn, results in a tendency for the non-Newtonian model to need fewer computational resources even though it has to perform additional calculations for the viscosity. It is also shown that both viscosity models predict comparable wall shear stress distribution. This work suggests that the use of a non-Newtonian viscosity models may be attractive to solve cardiovascular flows since it can provide simulation results that are presumably physically more realistic with at least comparable computational effort for a given level of accuracy.