A major aim of the present study is to understand and thoroughly document the fluid dynamics in three-dimensional branching networks when an intermediate branch is partially or completely obstructed. Altogether, 26 different three-dimensional networks each comprising six generations of branches (involving 63 straight portions and 31 bifurcation modules) are constructed and appropriately meshed to conduct a systematic study of the effects of varying the locations of a blockage of a given relative extent and varying the extent of a blockage at a fixed location. The side-by-side consideration of two branching configurations (in-plane and $$90^{\circ }$$ 90 ∘ out-of-plane) gives a quantitative assessment of the dependence of flow alteration due to blockage on the three-dimensional arrangement of the same individual branches. A blockage in any branch affects the flow in both downstream and upstream branches. The presence of a blockage can make three-dimensional asymmetric alteration to the flow field, even when the blockage itself is geometrically symmetric. The overall mass flow rate entering the network is found to remain nearly unaltered if a blockage is shifted within the same generation but is progressively reduced if the blockage is shifted to upstream generations. A blockage anywhere in the network increases the degree of mass flow asymmetry $$\delta _{\mathrm{G}n} $$ δ G n in any generation. The order of magnitude disparity in $$\delta _{\mathrm{G}n} $$ δ G n between the in-plane and out-of-plane configurations, characteristic of unobstructed networks, can be significantly reduced in the presence of a single blockage. The present three-dimensional computations show that the effects of blockage on the mass flow distribution in a large network are complex, often non-intuitive and sometimes dramatic, and cannot be captured by any simple one-dimensional model.

中文翻译：

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三维分支网络阻塞的系统研究，并应用于模拟人类支气管树

本研究的一个主要目的是了解并彻底记录中间分支部分或完全阻塞时三维分支网络中的流体动力学。总共构建了 26 个不同的 3D 网络，每个网络包含 6 代分支（涉及 63 个直线部分和 31 个分叉模块）并进行适当的网格划分，以对给定相对范围的阻塞位置变化的影响进行系统研究和改变固定位置的堵塞程度。并排考虑两个分支配置（平面内和 $$90^{\circ }$$ 90 ∘ 平面外）给出了由于阻塞而导致的流动改变对三个-同一个分支的维度排列。任何分支的堵塞都会影响下游和上游分支的流量。阻塞的存在可以使流场发生三维不对称的改变，即使阻塞本身是几何对称的。如果堵塞在同一代内转移，进入网络的总质量流量几乎保持不变，但如果堵塞转移到上游代，则逐渐减少。网络中任何地方的阻塞都会增加任何代中质量流量不对称的程度 $$\delta _{\mathrm{G}n} $$ δ G n。$$\delta _{\mathrm{G}n} $$ δ G n 在面内和面外配置之间的数量级差异，无障碍网络的特征，可以在存在以下情况时显着减少单一的阻塞。