无心跳供体肺支气管内气体三维流动的数值模拟研究

Simulation on 3D Flow Characteristics inside Bronchia of Non-Heart Beating Donor Lung

无心跳供体肺(NHBD)有望解决临床供肺严重不足的问题,肺内低温通气被公认为是NHBD肺在体低温保护的有效方法之一,可提高供肺的利用率。通过建立三维非对称四级支气管模型,运用计算流体动力学(CFD)方法对支气管内的气流流动特性进行数值模拟,并通过试验对数值模拟的边界条件进行验证。研究结果表明:在被动呼吸的吸气和呼气时,支气管截面上的无量纲速度分布不同,左肺支气管和右肺支气管截面上的速度分布也存在较大差异,其中左肺下叶支气管内中心线上的无量纲速度峰值最大,达到1.7,而右肺上叶支气管内中心线上的无量纲速度峰值最小,仅为0.8;由于分叉角度和管径不同,导致吸气过程中流入左主支气管内和右主支气管内的流量分别占55%和45%,而左肺下叶支气管内的流量比率在各肺叶支气管内的流量比率最高,约为35%;通过分析支气管内的流动压力损失,得出支气管的平均压降系数与Re的关系为珔Cp∝Re-0.6。可见,由于支气管的非对称结构以及分叉处空间旋转角度的存在,使得支气管内的气体流动结构比较复杂,这对于无心跳供体肺原位通低温保存的临床实验研究有一定的参考价值。

Non-heart beating donor （NHBD） lung is expected to be the most potential donor source for clinical lung transplantation,and the low temperature ventilation is normally thought to effectively protect the donor lung in vivo.A 3D asymmetric bronchial model with four levels was formed in this work; computational fluid dynamics （CFD） technique was adopted for investigating the 3D flow characteristics inside NHBD lung bronchia.Results show that there were some differences of dimensionless velocity distribution between inhaling and exhaling,the velocity distribution was also different on the left lung bronchus and the right lung bronchus sections.In particular,the dimensionless velocity of left lobar bronchus was 1.7 but the right upper lobar was 0.8.The flow ratios of left and right bronchia were 55％ and 45％,respectively.The flow ratio of left inferior lobar bronchus was the largest one,about 35％.This is related to bifurcation angles and diameters changing with varied levels.The average pressure drop coefficients inside bronchia were also obtained here,which was the function of Re as-Cp] ∝ Re-0.6.Because of the existence of asymmetric structure of bronchial and bifurcation space rotation angle,the gas flow in the bronchus became complicated,which is valuable for clinical and experimental study on NHBD lung in situ through cryopreservation.