锥度角对弯曲动脉血管的血流动力学影响

运用血流动力学的基本原理和计算流体力学方法,对具有锥度角的弯曲血管内的血液二维定常流动流场进行数值模拟和分析.计算出具有锥度角的弯曲动脉内血液流动的压力和速度的分布情况.计算结果表明由于弯曲血管的曲率和沿血管渐缩的锥度角使得血管截面血流速度分布尤其是径向速度分布发生较大畸变;锥度角对弯曲动脉血管的血流动力学影响主要体现在对血流径向速度分布的影响.     

动脉中的发展流动与其锥度角的关系

本文推导了动脉血管流动的速度分布和压力分布公式，并从数学上论证出动脉血管中之所以总是发展流动的主要原因是动脉血管存在着锥度角，此外，还讨论了锥度角对动脉血液流动的速度分布的影响问题。     

人体主动脉弓内三维血流动力学数值分析

目的阐明基于核磁共振数据进行数值建模的关键技术,利用计算流体动力学方法对人体主动脉弓内的血液流场进行了三维数值模拟。方法通过对临床核磁共振成像进行图像处理完成主动脉弓及分支血管的三维数字化重构,结合相关脉动血流量,模拟主动脉弓在心动周期不同时刻的血液流动细节。结果计算得到了人体主动脉弓内的血液流动在心动周期不同时刻的速度场、压力、壁面剪切应力的分布特征。结论基于核磁共振数据进行数值建模的关键技术有利于生物流体力学研究的深入开展,对主动脉弓进行血液流场的数值模拟有利于临床动脉粥样硬化、主动脉夹层的诊断和治疗。     

锥度角对非定常的动脉血流的压力分布的影响

应用Navier-Stokes方程和质量连续原理对具有锥度角的动脉血管中非定常状态下的血液发展流动建立了一组数学模型，采用贝塞尔函数方法进行了解析求解，获得了非定常状态下的动脉血液发展流动的速度分布和压力分布公式。并与定常状态下动脉血管中的血液发展流动做了比较。结果表明，非定常状态下动脉血液发展流动的压力分布和定常状态下的动脉血管中的血液发展流动的压力分布差别很大。     

弯曲动脉中非线性脉动流的计算机模拟

非线性脉搏波在主动脉弓及任意弯曲动脉内传播的问题是生物流体力学中尚未很好地研究解决的重大课题之一。作为研究非线性脉搏波在弯曲动脉血管内传播问题的第一步,我们对主动脉弓内的非线性脉动流进行了计算机模拟。在本研究中做如下基本假设：将主动脉弓模拟为等圆截面的圆环形刚性管;血液为不可压缩牛顿流体;主动脉弓内的血液流动为发展中的层流,且在下游远处（出口处）变为充分发展的流动。我们利用SIMPLE方法对狗主动脉弓内的生理脉动流进行了数值模拟,得到了主动脉弓内的速度场和压力场的全部数值解。数值计算结果表明,血液…     

锥形血管内血液脉动流的数值模拟

将锥形血管与人体血液的脉动流动联系起来研究发展中的血液流动问题 ,给出了锥形血管的几何模型、血液流动的理论模型、生理边界条件以及计算条件 ;根据人体生理脉动流条件 ,建立了血流平均速度函数 ,并就此对三维锥形血管内的血液脉动流动进行了数值模拟 ,获得心动周期不同时刻的轴向速度、径向速度、断面压力和轴向压力分布曲线。将数值模拟计算结果与实验和分析计算结果进行对照 ,讨论了锥形血管内血液脉动流的特点。     

考虑流固耦合作用的主动脉弓血液流动分析

流固耦合作用对血液的流动速度、回流速度和壁面剪应力有较大的影响。但迄今已有的研究工作较少考虑血液．血管相互作用和生理脉动作用的影响，可能难以真实地反映血液在主动脉弓中的流动情况。将升主动脉、主动脉弓和降主动脉联系起来，根据生理脉动流条件，利用有限元软件，分析流固耦合作用下主动脉弓中的血液流动问题。研究表明，流固耦合作用对血液流动速度、回流速度和壁面剪应力的变化趋势影响较小，对血液回流速度幅值、壁面剪应力幅值影响较大。结果表明：在心脏收缩与舒张转换期，主动脉内的血液向心室方向反流；考虑流固耦合作用总体上降低血液回流速度的幅值；在流固耦合作用下，壁面最大剪应力幅值比非流固耦合偏低约25％。     

动脉锥度角对非定常血流速度分布的影响

从动脉血管具有1°左右的锥度角的实际情况出发,应用Navier-Stokes方程和质量连续原理对非定常状态下动脉中血液流动的锥度角效应问题建立了一组数学模型,继而采用贝塞尔函数方法进行了解析求解,获得了非定常状态下的动脉血液发展流动的速度分布公式.和无锥度角的动脉血管中的血液发展流动做了比较.得出了一些颇为新颖而重要的结论.     

主动脉弓内脉动流的有限元分析

将升主动脉和主动脉弓联系起来研究发展中的血液流动问题,给出了血液流动的理论模型、边界条件以及计算条件;根据生理脉动流条件,对狗的升主动脉和主动脉弓内血液流动进行有限元数值模拟,并对计算结果进行了可视化分析。     

基于CT重建颅内动脉瘤非稳态血流分析

选择Navier-Stokes方程作为颅内动脉瘤三维重建模型的不可压缩血液流动的数学模型,使用计算流体力学(Computational fluid dynamics,CFD)的方法对颅内动脉瘤模型进行非牛顿(non-Newtonian fluid)模型的非定常流的数值模拟。计算3个心跳脉动周期的数值,认为第三个心跳脉动周期为稳定周期并选择第三个周期为研究对象。分析了稳定周期内不同时刻血液动力学特性参数分布情况对颅内动脉瘤的形成、生长和破裂的影响。并将此结果与牛顿(Newtonian fluid)血液模型的流线、壁面剪切力、壁面压力分布特性进行对比。结果显示,非牛顿流体血液模型比牛顿血液模型更有可信度,比较符合真实血液的流动特性,在血液流动的心跳脉动周期内,非牛顿流体的(速度、压力、壁面剪切力等)分布更加平滑。过高的壁面剪切力会直接造成动脉瘤区域处破裂,过低的壁面剪切力会使血液的营养成为和代谢物遗留在血管区域导致血液粥样化的形成。     

Aortic Arch Morphogenesis and Flow Modeling in the Chick Embryo

Morphogenesis of the “immature symmetric embryonic aortic arches” into the “mature and asymmetric aortic arches” involves a delicate sequence of cell and tissue migration, proliferation, and remodeling within an active biomechanical environment. Both patient-derived and experimental animal model data support a significant role for biomechanical forces during arch development. The objective of the present study is to quantify changes in geometry, blood flow, and shear stress patterns (WSS) during a period of normal arch morphogenesis. Composite three-dimensional (3D) models of the chick embryo aortic arches were generated at the Hamburger–Hamilton (HH) developmental stages HH18 and HH24 using fluorescent dye injection, micro-CT, Doppler velocity recordings, and pulsatile subject-specific computational fluid dynamics (CFD). India ink and fluorescent dyes were injected into the embryonic ventricle or atrium to visualize right or left aortic arch morphologies and flows. 3D morphology of the developing great vessels was obtained from polymeric casting followed by micro-CT scan. Inlet aortic arch flow and cerebral-to-lower body flow split was obtained from 20 MHz pulsed Doppler velocity measurements and literature data. Statistically significant variations of the individual arch diameters along the developmental timeline are reported and correlated with WSS calculations from CFD. CFD simulations quantified pulsatile blood flow distribution from the outflow tract through the aortic arches at stages HH18 and HH24. Flow perfusion to all three arch pairs are correlated with the in vivo observations of common pharyngeal arch defect progression. The complex spatial WSS and velocity distributions in the early embryonic aortic arches shifted between stages HH18 and HH24, consistent with increased flow velocities and altered anatomy. The highest values for WSS were noted at sites of narrowest arch diameters. Altered flow and WSS within individual arches could be simulated using altered distributions of inlet flow streams. Thus, inlet flow stream distributions, 3D aortic sac and aortic arch geometries, and local vascular biologic responses to spatial variations in WSS are all likely to be important in the regulation of arch morphogenesis. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

3D CFD Simulation of Pulsatile Blood Flow in the Human Aorta

INTRODUCTION　　The human aorta is the majorblood vessel of complex geometry including curva-tures in multiple planes,branches at the apex of the arch,significant tapering andwith distensible vessel wall ( as shown in Fig.1 ) . The blood flow structures in theaorta are very complex and attribute a lot to the development of atherosclerotic le-sions,which always occur in the vicinity of arterial branches,curvatures and bifur-cations〔1～ 5〕.In order to understand the complex nature of the …     

支架治疗主动脉弓内侧动脉瘤的仿真研究

血管内支架是治疗主动脉弓动脉瘤的一种新技术。目前还没有人对具有局部突起的动脉瘤支架治疗血流动力学进行过研究。基于这样的事实,本仿真研究对主动脉弓内侧动脉瘤的支架治疗进行血流动力学分析。为便于比较,分别建立了有支架和无支架的主动脉弓动脉瘤模型。利用计算流体力学的方法对两个模型中的生理性血液流动进行了仿真。对流动情形、压力和壁面切应力分布进行了比较和分析,以便评价血管内支架对主动脉弓动脉瘤治疗的效果。结果表明,有支架的模型和无支架的模型,在瘤腔内的流动情形具有显著的不同。有支架模型瘤腔内的流动受到明显的抑制,特别是局部突起处的压力和壁面切应力大大地减小了。这些现象使我们有理由推断,血管内支架可以促进瘤腔内血栓的形成,并能减小动脉瘤破裂的危险。     

左心室辅助装置与主动脉吻合角度对主动脉瓣膜影响的血流动力学研究

目的 探究左心室辅助装置(left ventricular assist device, LVAD)与主动脉吻合角度对主动脉瓣膜的血流动力学影响。方法 分别构建LVAD与主动脉吻合角度为45°、60°、90°的3个主动脉模型和主动脉瓣膜模型,搭建体外搏动台用于体外实验。运用粒子图像测速(particle image velocimetry, PIV)系统,选取心动周期中的3个时刻(T₁收缩峰值期,T₂瓣膜快速闭合时期和T₃舒张峰值期)探究主动脉瓣膜处血流动力学状态。结果 采用速度矢量、涡量、黏性剪切力指标评价LVAD吻合角度对主动脉瓣膜血流动力学的影响。瓣膜快速闭合时期,吻合角度增大时,瓣膜近壁面血流速度、平均涡量和最大黏性剪切力均增大。结论 吻合角度较低时,血流对主动脉瓣膜的冲击速度较小,瓣膜受到较小的剪切力,使瓣膜处于较好的血流动力学环境。研究结果为临床手术中吻合角度的选择提供参考。     

Comparison of the reflex vasomotor responses to separate and combined stimulation of the carotid sinus and aortic arch baroreceptors by pulsatile and non-pulsatile pressures in the dog

1. In the anaesthetized dog the carotid sinuses and aortic arch were isolated from the circulation and separately perfused with blood by a method which enabled the mean pressure, pulse pressure and pulse frequency to be varied independently in each vasosensory area. The systemic circulation was perfused at constant blood flow by means of a pump and the systemic venous blood was oxygenated by an extracorporeal isolated pump-perfused donor lung preparation.2. When the vasosensory areas were perfused at non-pulsatile pressures within the normal physiological range of mean pressures, the reflex reduction in systemic vascular resistance produced by a given rise in mean carotid sinus pressure was significantly greater than that resulting from the same rise of aortic arch pressure.3. On the other hand, when the vasosensory areas were perfused at normal pulsatile pressures and within the normal physiological range of mean pressures, there was no difference in the size of the reflex vascular responses elicited by the same rise in mean pressure in the carotid sinuses and in the aortic arch.4. Whereas the vasomotor responses elicited reflexly by changes in mean carotid sinus pressure are modified by alterations in pulse pressure, those evoked by the aortic arch baroreceptors through changes of mean pressure are only weakly affected by modifications in pulse pressure. Evidence for this was obtained from single stepwise changes of mean pressure in each vasosensory area during pulsatile and non-pulsatile perfusion, and from curves relating the mean pressure in the carotid sinuses or aortic arch and systemic arterial perfusion pressure.5. The vasomotor response elicited by combined stimulation of the carotid sinus and aortic arch baroreceptors was greater than either response resulting from their separate stimulation.6. When the mean perfusion pressures in the two vasosensory areas are changed together, the curve relating mean pressure to systemic arterial pressure during pulsatile perfusion of the areas is considerably flatter than that for non-pulsatile perfusion.7. Increasing the pulse pressure in the carotid sinuses or aortic arch caused a decrease in systemic vascular resistance, the response elicited from the carotid sinuses being the larger.8. Altering the phase angle between the pulse pressure waves in the carotid sinuses and aortic arch had no effect on systemic vascular resistance.9. In both vasosensory areas, increasing the pulse frequency caused a reduction in systemic vascular resistance.     

The responses of aortic arch and right subclavian baroreceptors to changes of non-pulsatile pressure and their modification by hypothermia

1. A method is described for isolation of the aortic arch and right subclavian-carotid angle in situ in the rabbit and perfusion with Krebs-Henseleit solution or blood under controlled conditions of pressure and temperature.2. The characteristics of the baroreceptors of the aortic arch and right subclavian-carotid angle were studied by recording from single or few-fibre preparations of the left and right aortic nerves respectively. Curbes were plotted to show the relationship between the frequency of baroreceptor impulse activity and intra-aortic pressure during non-pulsatile perfusion under steady-state conditions.3. The aortic arch and right subclavian-carotid angle baroreceptors were found to have similar characteristics. Three types of response of the baroreceptors at the threshold pressure to a steady intra-aortic pressure are described.4. Increasing the intra-aortic pressure increased the frequency of impulses in fibres previously active and caused recruitment of other fibres in multi-fibre preparations. The relationship was linear at low pressures and a point of inflexion occurred at higher pressures in the majority of fibres.5. Lowering the temperature of the perfusate reduced the impulse frequency at any given pressure.6. The curves obtained during stepwise increases and decreases in intra-aortic arch pressure were dissimilar, particularly at the lower end of the pressure range. This phenomenon is probably due to properties of the arterial wall.7. When the aortic arch preparation was excised, changes occurred in the shape of the impulse frequency-pressure curves from baroreceptors in both areas. The point of inflexion was elevated and a higher percentage of fibres failed to reach a point of inflexion in the pressure range studied.     

Effects of graded pulsatile pressure on the reflex vasomotor responses elicited by changes of mean pressure in the perfused carotid sinus-aortic arch regions of the dog

1. In the anaesthetized dog, the carotid sinuses and aortic arch were isolated from the circulation and separately perfused with blood by a method which enabled the mean pressure, pulse pressure and pulse frequency to be varied independently in each vasosensory area. The systemic circulation was perfused at constant blood flow by means of a pump and the systemic venous blood was oxygenated by an extracorporeal isolated pump-perfused donor lung preparation.2. We have confirmed our previous observations that under steadystate conditions the vasomotor responses elicited reflexly by changes in mean carotid sinus pressure are modified by alterations in carotid sinus pulse pressure, whereas those evoked by changes of mean aortic arch pressure are only weakly affected by modifications of aortic pulse pressure.3. When the carotid sinus and aortic arch regions are perfused in combination at constant pulse frequency (110 c/min), the relationship between mean carotid sinus-aortic arch pressure and systemic arterial perfusion pressure is dependent on the size of the pulse pressure.4. Increasing the pulse pressure alters the curve relating the mean carotid sinus-aortic arch pressure to systemic arterial perfusion pressure in such a way that the perfusion pressure is lower at a given carotid sinus-aortic arch pressure within the range 80-150 mm Hg. The larger the pulse pressure, up to about 60 mm Hg, the greater the fall in systemic arterial perfusion pressure. Above a mean carotid sinus-aortic arch pressure of about 150 mm Hg, alterations of pulse pressure have little effect.5. There is a family of curves representing the relation between mean carotid sinus-aortic arch pressure and systemic vascular resistance, depending on the pulse pressure.