过载负荷下分叉血管的流动数值模拟
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摘要
背景:人体对于过载负荷的大小具有一定的耐受极限,超过一定强度时会对人体造成损伤,过载对人体血管流动过程的影响是载人航天医学研究的一个重要课题。目的:针对典型的颈部动脉简化分叉三维血管模型进行了非常规重力载荷下的脉动流血管流动形态数值模拟分析。方法:根据人体的正常脉搏周期,计算过程设定0.85 s为一个血液脉动供给周期。对于分叉血管(基于人体颈部动脉分支血管的几何特征进行刚性简化),假设正常状态下主血管与分支血管流量分配为7∶3。基于Fluent计算流体力学软件,通过在控制方程动量源项中添加重力载荷的方法(过载方向X+,过载大小为1 G;过载方向Y+,过载大小为2 G),分析重力过载效应对人体典型血管流动特征的影响。结果与结论:(1)获得了重力过载下的瞬态流场结构、壁面剪切应力的变化情况。由于受到Y+方向过载的影响,分叉血管在不同时刻在流速分布、回流区域大小、剪切应力分布上存在明显差异;(2)超重负荷效应下,分叉位置分支血管内壁面处形成了明显的分离区域且血液流量明显变大,造成主血管段内血液流量减少且发生严重的回流现象;(3)在超重负荷的影响下分支血管段壁面剪切应力明显大于主血管段壁面剪切应力。
BACKGROUND: Human body has a certain tolerance limit to overload, so load beyond certain strength will cause damage to the human body. The effect of overload on the flow of blood vessels is an important medical topic in manned space.OBJECTIVE: To study the flow patterns of pulsating blood vessels under unconventionally gravity load in a typical three-dimensional model of cervical artery.METHODS: Based on normal pulse cycle, we considered 0.85 seconds as pulsating blood supply cycle. The blood flow ratio of main vessels and branch vessels was 7:3. Based on Fluent software, the effects of gravity overload on the flow characteristics of typical blood vessels were analyzed by adding gravity load(1 G of overload at direction of X+; 2 G of overload at direction of Y+) to the momentum source of the control equation.RESULTS AND CONCLUSION: The changes of transient flow field structure and shear stress of wall under gravity overload were obtained.Because of the influence of Y+ direction of overload, the bifurcating vessels had obvious difference in velocity distribution, size of reflux region and shear stress distribution at different time. Under the effect of overweight load, the blood flow in the main blood vessel decreased and serious reflux occurred. The shear stress on the wall of the branching blood vessel was obviously higher than that on the main blood vessel.
BACKGROUND: Human body has a certain tolerance limit to overload, so load beyond certain strength will cause damage to the human body. The effect of overload on the flow of blood vessels is an important medical topic in manned space.OBJECTIVE: To study the flow patterns of pulsating blood vessels under unconventionally gravity load in a typical three-dimensional model of cervical artery.METHODS: Based on normal pulse cycle, we considered 0.85 seconds as pulsating blood supply cycle. The blood flow ratio of main vessels and branch vessels was 7:3. Based on Fluent software, the effects of gravity overload on the flow characteristics of typical blood vessels were analyzed by adding gravity load(1 G of overload at direction of X+; 2 G of overload at direction of Y+) to the momentum source of the control equation.RESULTS AND CONCLUSION: The changes of transient flow field structure and shear stress of wall under gravity overload were obtained.Because of the influence of Y+ direction of overload, the bifurcating vessels had obvious difference in velocity distribution, size of reflux region and shear stress distribution at different time. Under the effect of overweight load, the blood flow in the main blood vessel decreased and serious reflux occurred. The shear stress on the wall of the branching blood vessel was obviously higher than that on the main blood vessel.
引文
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[2]钟国徽,李玉恒,凌树宽,等.太空微重力环境对人体的影响及防护措施[J].生物学通报,2016,51(10):1-4.
[3]孙联文,庄逢源.微重力导致航天员骨质疏松的研究进展[J].中华航空航天医学杂志.2004,15(1):54-58.
[4]刘洋,冯娜,张曦,等.失重环境下人体心血管功能失调及对抗措施的仿真设计研究[J].医疗卫生装备,2015,36(7):16-19,33.
[5]张昭.冲击过程中脑组织力学行为的数值模拟[J].中国生物医学工程学报,2008,27(6):882-886,893.
[6]张立辉,金朝,徐艳,等.持续性加速度生理与防护研究进展[J].中华航空航天医学杂志,2014,25(4):299-307.
[7]金朝,耿喜臣,李茜,等.重复+Gz暴露后血清心肌损伤标志物浓度的变化[J].解放军预防医学杂志,2005,23(2):82-85.
[8]金朝,耿喜臣,苏迅,等.高+Gz暴露时血小板功能的变化[J].中华航空航天医学杂志,2004,15(1):8-10.
[9]赵金萍.重力改变对人体心血管循环系统影响的仿真研究[D].株洲:湖南工业大学,2014.
[10]王汉青,赵金萍,陈娟.重力应激下心血管循环系统建模仿真研究进展[J].湖南工业大学学报,2014,28(3):99-102.
[11]Fry DL.Acute vascular endothelial changes associated with increased blood velocity gradients.Circ Res.1968;22(2):165-197.
[12]邓小燕.动脉狭窄内低密度脂蛋白传输的数值研究:LDL的浓度极化现象[J].计算力学学报,2002,19(3):253.
[13]Malek AM,Alper SL,Izumo S.Hemodynamic shear stress and its role in atherosclerosis.JAMA.1999;282(21):2035-2042.
[14]Fry DL.Certain histological and chemical responses of the vascular interface to acutely induced mechanical stress in the aorta of the dog.Circ Res.1969;24(1):93-108.
[15]徐跃平,杨金有,俞航,等.应用计算流体力学方法分析人体腹主动脉分叉内血液流动[J].中国现代医学杂志,2012,22(8):36-40.
[16]Iyer EM,Malik WCH,Dikshit GCM.Serum creatine phosphokinase isoenzyme changes in pilots during+Gz training in human centrifuge.Ind J Aerospace Med.2000;44(1):12-15.
[17]Ozturk C,Ilbasmis S,Dulkadir Z,et al.Cardiac effects of chronic+Gz exposure on military pilots.Aviat Space Environ Med.2011;82(3):218-219.
[18]Tetsuya H,Kimura M,Inui T,et al.Patterns of premature ventricular contractions occurrence during high Gz training.Aviat Space Environ Med.201.82(3):219.
[19]罗惠兰,李茜,耿喜臣,等.正加速度暴露对兔动脉粥样硬化过程中的内源性一氧化碳及血清脂质代谢的影响[J].中华航空航天医学杂志,2006,20(3):206-211.
[20]李茜,耿喜臣,金朝,等.在高+Gz应激下人体血清睾酮和皮质醇水平的变化[J].中华航空航天医学杂志,2003,14(1):22-25.