Three-dimensional inspiratory flow in a double bifurcation airway model
Three-dimensional inspiratory flow in a double bifurcation airway model
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DOI：
10.1007/s00348-016-2234-5
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发表时间：
2016-09-01
影响因子：
2.4
通讯作者：
Coletti, Filippo
中科院分区：
文献类型：
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作者：
Jalal, Sahar;Nemes, Andras;Coletti, Filippo
针对稳态吸入情况，研究了理想气道模型中的流动问题。几何由一个对称的平面双分叉组成，它反映了人类支气管树的解剖比例，并考虑了广泛的生理相关雷诺数(Re=100-5000)。利用磁共振测速仪，我们分析了三维速度场和涡量场，以及表征纵向和横向弥散的流动描述符。与前人的研究一致，即使在较低的雷诺数下，流动分配的对称性也被破坏，并且在第二次分叉时，流体有利于内侧分支而不是侧分支。这一趋势在Re=2000左右达到平台期，超过这一平台值时，湍流流入将导致平滑的平均速度梯度。这也减少了流向动量通量，它是平均流量纵向弥散的量度。由于局部曲率的存在，在第一代子体分支中观察到典型的Dean型对旋涡。然而，在孙子支流中，二次流只在较低的流型(Re 500)下由局部曲率决定，在内侧的子支流可能比上游的子支流更强。对于真实的气道模型，理想化的几何形状会产生较弱的二次流，这表明现实的解剖特征可能比规范的对称模型产生更多的侧向弥散。
The flow in an idealized airway model is investigated for the steady inhalation case. The geometry consists of a symmetric planar double bifurcation that reflects the anatomical proportions of the human bronchial tree, and a wide range of physiologically relevant Reynolds numbers (Re = 100-5000) is considered. Using magnetic resonance velocimetry, we analyze the three-dimensional fields of velocity and vorticity, along with flow descriptors that characterize the longitudinal and lateral dispersion. In agreement with previous studies, the symmetry of the flow partitioning is broken even at the lower Reynolds numbers, and at the second bifurcation, the fluid favors the medial branches over the lateral ones. This trend reaches a plateau around Re = 2000, above which the turbulent inflow results in smoothed mean velocity gradients. This also reduces the streamwise momentum flux, which is a measure of the longitudinal dispersion by the mean flow. The classic Dean-type counter-rotating vortices are observed in the first-generation daughter branches as a result of the local curvature. In the granddaughter branches, however, the secondary flows are determined by the local curvature only for the lower flow regimes (Re 500 they can become stronger in the medial granddaughter than in the upstream daughter branches. With respect to realistic airway models, the idealized geometry produces weaker secondary flows, suggesting that realistic anatomical features may generate more lateral dispersion than canonical symmetric models.