Importance of flow division on transition to turbulence within an arteriovenous graft.
Importance of flow division on transition to turbulence within an arteriovenous graft.
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动静脉移植物内流动分配对湍流过渡的重要性。
DOI：
10.1016/j.jbiomech.2006.03.024
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发表时间：
2007
影响因子：
2.4
通讯作者：
Bassiouny,HishamS
中科院分区：
文献类型：
--
作者：
Lee,Sang-Wook;Smith,DavidS;Loth,Francis;Fischer,PaulF;Bassiouny,HishamS
通过直接数值模拟研究了不同分流条件下动静脉移植物中的过渡血流。该连接处由以锐角 (21.6°) 连接到宿主血管（静脉）的入口血管（假体移植物）组成。基于平均速度和移植物入口直径的入口雷诺数范围为 800 至 1400。考虑了宿主血管两端（即近端静脉段 PVS 和远端静脉段 DVS）之间的各种流量分配（PVS:DVS 比率为 100:0、85:15、70:30 和 115:(15)）。数值技术采用谱元法，这是一种高阶离散化方法，非常适合复杂域中过渡流的模拟。在 PVS:DVS=70:30 和 85:15 的情况下观察到高速度和压力波动，而在 100:0 和 115:(15) 的情况下则没有观察到；结果表明，分流对于该交界处湍流发展的重要性。在85:15和70:30的分流下，雷诺数分别低至1000和800，明显低于临界值2100，观察到向湍流的转变。速度波动的频谱表明，在交汇处下游～300Hz的频率范围内有显着的强度。当移植物流入在连接处分成相反方向时，PVS 中会形成不利的压力梯度。这种压力梯度对流动产生不稳定影响，并增强了 PVS 中向湍流的转变。这些发现表明，入口和出口处体内流速的测量对于准确预测动静脉血流动力学至关重要。这些结果的潜在临床应用可能是在移植物构建过程中关闭 DVS，以确保 100:0 的流量分配。
Transitional blood flow in an arteriovenous graft under various conditions of flow division was examined through direct numerical simulation. This junction consists of an inlet vessel (prosthetic graft) connected to a host vessel (vein) at an acute angle (21.6°). Inlet Reynolds numbers, based on mean velocity and graft inlet diameter, ranged from 800 to 1400. Various flow divisions between the two ends of the host vessel (i.e., the proximal venous segment, PVS, and distal venous segment, DVS) were considered (PVS:DVS ratios of 100:0, 85:15, 70:30 and 115:(15)). The numerical technique employed the spectral element method which is a high-order discretization ideally suited to the simulation of transitional flows in complex domains. High velocity and pressure fluctuations were observed for the PVS:DVS=70:30 and 85:15 cases and absent from the 100:0 and 115:(15) cases; the results indicate the importance of flow division on the development of turbulence in this junction. Transition to turbulence was observed at Reynolds numbers as low as 1000 and 800 under flow divisions of 85:15 and 70:30, respectively, significantly lower than the critical value of 2100. The frequency spectra of velocity fluctuations indicated a significant intensity within the frequency range of ∼300Hz downstream of the junction. An adverse pressure gradient developed in the PVS when graft inflow divided into opposite directions in the junction. This pressure gradient had a destabilizing effect on the flow and enhanced transition to turbulence in the PVS. These findings suggest that measurements of in vivo flow rates at the inlet and outlets are critical for the accurate prediction of arteriovenous hemodynamics. A potential clinical application of these results might be to close off the DVS during graft construction to ensure a 100:0 flow division.