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1.
目的比较分析应用弹性血管壁的流固耦合计算流体力学(CFD)方法和刚性血管壁的CFD方法模拟获得的正常主动脉弓内血流动力学参数,同时比较两种方法的优劣,为深入研究血液流动状态与动脉疾病的关系提供帮助。方法取46岁男性,胸主动脉正常CT图像,格式为Dicom,层间距为0.5mm,每片图像的平面分辨率为512×512,像素大小为0.5mm。应用医学图像后处理软件,对通过临床获得正常人体主动脉CT二维医学图像数据进行重构,得到主动脉血流及血管壁的三维立体模型并应用于模拟计算。结果在设定边界条件和初始条件的基础上,经多次迭代耦合计算,获得血管壁形变、等效应力、血流速度、壁面振荡切应力等相关血流动力学参数。结论在心动周期内弹性血管壁的主动脉内血流情况较刚性血管壁主动脉内血流情况更为复杂,管壁等效压力变化较大,血管壁的振荡切应力更高,表明弹性血管壁的流固耦合的CFD模拟更能体现真实主动脉内复杂血流情况,为深入研究血流动力学与心脑血管疾病的关系提供了一定的技术支持。  相似文献   

2.
目的应用基于CT图像的三维重构技术,分别构建血管壁3层模型和单层模型,并应用流固耦合计算流体力学方法对这两种模型进行数值模拟。通过比较两者的血流动力学结果,讨论了两种应力模型的优劣,为深入研究血液流动状态与动脉疾病的关系提供帮助。方法采集腹主动脉瘤(AAA)临床CT图像,格式为DICOM,层间距为0.5mm,每片图像的平面分辨率为512×512,像素大小为0.5mm。应用医学图像后处理软件构建血管壁3层模型和单层模型,并应用流固耦合方法进行血流动力学模拟计算。结果经过多次迭代耦合计算,获得血管壁形变、等效应力等相关血流动力学参数。血管壁位移比较,单层血管壁模型B部分区域的血管壁变形情况略高于3层血管壁模型A,如腹主动脉分叉处模型A变形为1.041×10-3m,而模型B变形为1.171×10-3 m。血管壁应力分布比较,相同位置的3层血管壁模型的Von Mises值明显高于单层血管壁模型。结论通过对血管壁的变形及等效压力的分析,以及与单层血管壁模型的流固耦合模拟结果对比,得出了血管壁中层结构的变形和受力情况是AAA的形成和破裂的关键,为深入研究血流动力学与AAA疾病的关系提供帮助。  相似文献   

3.
目的简化基于临床采集的增强CT图像数据进行人体腹主动脉及髂动脉真实三维解剖结构的过程,提高计算流体力学(CFD)计算结果的可靠性,并对比分析正常髂动脉和髂动脉血栓后血管内血流情况,为阐明动脉粥样硬化血栓的形成机制提供理论依据。方法患者A为40岁男性,腹主动脉及髂动脉正常;患者B为60岁女性,腹主动脉正常,但左髂主动脉部分血栓及左髂内动脉血栓。CT图像为医学数字成像与通信标准(DICOM)格式,层间距为0.5 mm,每片图像的平面分辨率为512×512,像素大小为0.5mm。应用医学后处理软件对通过临床采集的增强CT二维图像数据进行三维重构,然后在通用有限元分析软件ANSYS中转换成可用于数值计算的计算机辅助设计(CAD)模型并直接进行CFD模拟计算。结果通过计算可得到A、B研究对象在心动周期内不同时刻的血流动力学参数。B研究对象左和右髂动脉感兴趣区域的平均壁面切应力(0.576 6±0.009 0,3.260 2±0.032 0)明显区别于A研究对象左和右髂动脉感兴趣区域的平均壁面切应力(1.269 8±0.008 0,1.393 2±0.011 0)。结论通过CFD模拟方法的改进,得到更加接近生理解剖特征的血栓后不规则血管三维立体模型,并通过对比A、B研究对象的计算结果,分析了复杂的血流情况如低流速、低壁面切应力等现象与动脉粥样硬化血栓的形成机制存在一定的关系。  相似文献   

4.
目的:基于血液和弹性血管壁相互作用的流固耦合方法,探究1例椎动脉颅内段狭窄的临床病例支架植入前后椎基底动脉的血流动力学特性。方法:应用医学建模软件对二维CT数据进行三维重建,得到支架植入前后的椎基底动脉血管模型,采用流固耦合方法对支架植入前后的椎基底动脉血流特性进行数值模拟,分析椎基底动脉的血流动力学特性。结果:支架植入前后椎基底动脉的血液流场、血液压力、血管壁面切应力以及管壁形变量有显著的变化。在支架植入后,基底动脉中间部位两侧受力变得均匀,椎基底动脉内血流速度明显增大,支架植入处压力增大,支架上游压力和支架处切应力减小。结论:在介入治疗后,椎基底动脉内的血流环境及受力情况得到明显改善,当椎动脉发生狭窄后应及时干预治疗,避免累及基底动脉和后循环系统。  相似文献   

5.
动脉中管壁的脉动低切应力在动脉粥样硬化形成中起始动和主要的决定作用.本文比较了几种计算血管壁切应力的方法,认为采用有约束的弹性管模型计算获得的动脉壁切应力更适合于临床应用.根据检测得到的正常人和动脉硬化性脑血管病患者的颈动脉血流速度、血管管径等数据,计算两者的颈动脉壁面切应力.研究发现动脉硬化性脑血管病患者的壁面切应力比正常人显著减小.这表明,颈动脉的壁面切应力可以作为动脉硬化性脑血管疾病的早期诊断的重要参考指标.  相似文献   

6.
背景:颅内动脉瘤病死率高,有限元分析预测其破裂风险目前成了一个热门课题。有限元分析需要可靠的流固耦合模型,动脉瘤的血液模型很易得到,而血管壁模型无法直接获得,只能人为设置,这可能对计算结果造成影响。目的:探讨有限元建模时血管壁厚度的设置对复杂颅内动脉瘤流固耦合分析的影响,为颅内动脉瘤的数值模拟研究提供更可靠的建模方法。方法:通过3D脑血管造影取得一67岁男性患者左侧颈内动脉颅内段串联动脉瘤的三维数值模型。术后通过管壁增厚的方法构建出血管壁模型,人为设置的壁厚为0.3,0.4,0.5,0.6 mm,得到4个流固耦合模型。根据术中测得的数据,利用有限元法模拟分析流固耦合作用下颈内动脉串联动脉瘤的血液动力学特征,比较4个模型计算结果之间的差异。结果与结论:4个模型的血液流线图、血液压力降图、血管内壁壁面切应力均无差异(P0.05)。4个模型血管壁变形最明显处均在颈内动脉C2段,但血管壁越厚者最大变形量越小(P0.01)。4个模型血管壁Von Mises应力均在I,J两点处达到局部最大值,血管壁越薄者局部最大值越大(P0.01)。证实血管壁厚度的设置会对复杂颅内动脉瘤的流固耦合分析结果造成影响,欲得到准确计算结果需根据实际情况设置合适厚度。  相似文献   

7.
目的在考虑血管壁弹性条件下,分析颈内动脉血液流动和壁面切应力的分布特性,探讨动脉瘤破裂的生物力学因素。方法依据二维医学扫描图像构建三维个性化颈内动脉瘤模型。依据人体生理统计数据构建出血管壁模型。根据人体颈内动脉生理流动条件,利用有限体积法和有限元法模拟分析流固耦合作用下颈内动脉瘤中的血流动力学。结果在动脉瘤腔中有一个明显的涡旋存在,此涡旋流动的方向在心动周期内没有改变;在动脉瘤颈和动脉瘤壁面处存在一个壁面切应力值相对较大区域;在动脉瘤颈和动脉瘤顶有两个区域的Von Mises应力处于局部最大值。从材料强度角度考虑,这几个区域都是动脉瘤容易破裂的地方。结论通过流固耦合计算可以获得血管壁面应力分布特性,进而推断动脉瘤破裂的可能位置。  相似文献   

8.
目的研究沙疗对人体弯曲股动脉血流动力学的影响,从血流动力学角度进一步揭示沙疗的疗效机理。方法以人体主动脉CT图像为依据,建立弯曲股动脉三维有限元模型,并以实验所测受试者心率、股动脉血流速度峰值和内径作为初始条件和边界条件进行有限元数值模拟,对比分析在流固耦合条件下沙疗前后弯曲血管血液流场血流速度、压力和壁面切应力。结果与沙疗前相比,沙疗后血管弯曲段纵向速度有较大提高,增幅为22.76%;二次回流速度明显减弱,减少了18.26%;壁面切应力减少2.01%。结论沙疗会使血液流动性效果显著,并提高股动脉血液的流动性,预防动脉内血小板的沉积;沙疗后二次回流速度流动现象明显减弱,避免血液中物质产生沉积,临床上对预防动脉粥样硬化、血栓等各种血管疾病有积极作用。  相似文献   

9.
目的:探讨锁骨下动脉、颈总动脉和椎动脉分叉处的血流动力学特性,分析该处发生血管狭窄引起大脑供血不足的 血流动力学原因。方法:采用内蒙古民族大学附属医院神经内科提供的CT数据,应用医学建模软件MIMICS20.0将患者 二维CT数据进行三维血管重建,经过网格划分及边界条件设置后导入计算流体力学软件FLUENT14.5中。计算和分析 不同血液入口速度的锁骨下动脉、颈总动脉和椎动脉分叉处的血流动力学特性。结果:在血液入口速度不同的情况下,锁 骨下动脉、颈总动脉和椎动脉分叉处的血液流场分布、血液压力分布和血管壁面切应力分布有显著变化。在血液入口速 度增大时,锁骨下动脉分叉处和颈总动脉分叉处的血液流速快、血管壁压力大,颈总动脉内侧血管壁面切应力大,但锁骨 下动脉分叉处和颈总动脉分叉处血管壁面切应力数值和变化幅度小,属于低切应力区。结论:通过血流动力学数值模拟 研究,分析锁骨下动脉、颈总动脉和椎动脉分叉处易发生粥样斑块病变导致大脑供血不足的血流动力学原因。  相似文献   

10.
考虑动脉锥形血管为弹性血管,应用流固耦合方法研究锥形血管在人体血液脉动流动状态下变形问题。在运用血液流动连续性方程、血液运动方程、血管壁运动方程和给定的血压波形函数的基础上,根据流固边界耦合条件建立血管壁变形与应力的关系,揭示血管相应参数变化对血管弹性变形的影响:(1)当血管弹性模量增大到一定程度时,血管壁弹性变形将会很小,失去弹性,导致动脉硬化的发生;(2)当血管壁的厚度增大时,血管壁变形与应力就会增大,如果此时血管某处变薄,则会导致血管破裂;(3)当血压越高时,血管壁变形与应力越大,血压增大到一定程度,会导致脑出血等疾病;(4)当血管半径越大时,血管壁变形与应力会变大,且变化幅度很大。反之,血管壁变形与应力会变小,但变化幅度不明显。通过分析锥形血管弹性变形,为医学工作者研究动脉硬化和脑出血等疾病发病机理提供理论参考。  相似文献   

11.
A nonlinear three-dimensional thick-wall model with fluid-structure interactions is introduced to simulate blood flow in carotid arteries with an asymmetric stenosis to quantify the effects of stenosis severity, eccentricity, and pressure conditions on blood flow and artery compression (compressive stress in the wall). Mechanical properties of the tube wall are measured using a thick-wall stenosis model made of polyvinyl alcohal hydrogel whose mechanical properties are close to that of carotid arteries. A hyperelastic Mooney–Rivlin model is used to implement the experimentally measured nonlinear elastic properties of the tube wall. A 36.5% pre-axial stretch is applied to make the simulation physiological. The Navier–Stokes equations in curvilinear form are used for the fluid model. Our results indicate that severe stenosis causes critical flow conditions, high tensile stress, and considerable compressive stress in the stenosis plaque which may be related to artery compression and plaque cap rupture. Stenosis asymmetry leads to higher artery compression, higher shear stress and a larger flow separation region. Computational results are verified by available experimental data. © 2003 Biomedical Engineering Society. PAC2003: 8719Uv, 8710+e  相似文献   

12.
缓变狭窄幅度径向振荡血管内血流动力学   总被引:10,自引:4,他引:6  
本文研究缓变狭窄幅度径向振荡血管内血液脉动流。求解线化的Navier-St-okes血流方程和管壁方程,得出速度剖面和管壁切庆力。结果表明狭窄参数的变化对流动有很大影响。在狭窄区仙,速度变化和狭窄程度及狭窄幅度振荡频率的耦合作用有关。当狭窄幅度振荡频率接近血流基频时,血液速度变化较大,并且狭窄区最大壁切应力达到峰值。  相似文献   

13.
目的探索将血流储备分数(fractional flow reserve,FFR)引入颈动脉狭窄评估的可行性,并且分析血管壁弹性模量对颈动脉狭窄中血液动力学参数和FFR计算结果的影响。方法利用计算机辅助设计软件建立颈动脉分叉标准模型并获得不同狭窄率的模型。假设血管壁为线弹性材料,血液为不可压缩牛顿流体,在脉动流条件下,利用有限元分析软件进行颈动脉狭窄模型中血液流动的流固耦数值模拟,获得各种血液动力学参数,并计算相应的FFR值。结果当弹性模量固定时,随着狭窄率增加,模型中狭窄部位的FFR逐渐减小,且此时其弹性壁与刚性壁的FFR相对差异随着狭窄率的增加而增加;当狭窄率固定为70%时,随着弹性模量增加,FFR会逐渐减小。结论采用FFR对颈动脉狭窄程度进行功能性评估需要考虑血管壁弹性的影响;狭窄率越大,血管壁弹性模量对FFR的影响越大。  相似文献   

14.
Atherosclerotic plaque can cause severe stenosis in the artery lumen. Blood flow through a substantially narrowed artery may have different flow characteristics and produce different forces acting on the plaque surface and artery wall. The disturbed flow and force fields in the lumen may have serious implications on vascular endothelial cells, smooth muscle cells, and circulating blood cells. In this work a simplified model is used to simulate a pulsatile non-Newtonian blood flow past a stenosed artery caused by atherosclerotic plaques of different severity. The focus is on a systematic parameter study of the effects of plaque size/geometry, flow Reynolds number, shear-rate dependent viscosity and flow pulsatility on the fluid wall shear stress and its gradient, fluid wall normal stress, and flow shear rate. The computational results obtained from this idealized model may shed light on the flow and force characteristics of more realistic blood flow through an atherosclerotic vessel.  相似文献   

15.
Numerical simulations of unsteady flows in a stenosed coronary bypass graft   总被引:7,自引:0,他引:7  
Using the finite element method, physiological blood flows through a three-dimensional model of a coronary graft are numerically analysed. The model includes a stenosis shape in the host artery upstream from the anastomosis. Recirculating areas, secondary flows, wall shear stress (WSS) and spatial wall shear stress gradients (WSSGs) are studied for different flow repartitions and at different times in the cycle. The temporal and spatial evolutions of the recirculating areas downstream from the stenosis, their interactions with the flow issued from the graft and their associated WSSs highlight that the presence of the stenosis in the recipient artery is essential for prediction of the evolution of a grafting at the beginning of its implantation. The areas downstream from the stenosis expansion, non-existent for a host artery without stenosis, are submitted to low and oscillating WSS between −0.5 and 0 Nm−2. The stagnation point on the recipient artery floor is subjected to high positive and negative WSSGnd values, and its location is dependent on the residual flow through the stenosis.  相似文献   

16.
Arterial stenoses may cause critical blood flow and wall conditions leading to clinical complications. In this paper computational models of stenotic carotid arteries are proposed and the vessel wall collapse phenomenon is studied. The models are based on fluid-structure interactions (FSI) between blood and the arterial walls. Coupled finite element and computational fluid dynamics methods are used to simultaneously solve for stress and displacement in the solid, and for pressure, velocity and shear stress in the fluid domain. Results show high wall shear stress at the stenosis throat and low (negative) values accompanied by disturbed flow patterns downstream of the stenosis. The wall circumferential stress varies abruptly from tensile to compressive along the stenosis with high stress concentration on the plaque shoulders showing regions of possible plaque rupture. Wall compression and collapse are observed for severe cases. Post-stenotic collapse of the arterial wall occurs for stenotic severity as low as 50%, with the assumption that a given amount of blood flow needs to pass the stenotic artery; whereas if constant pressure drop should be maintained across a constriction, then collapse happens at severity of 75% and above. The former assumption is based on the requirement of adequate blood supply to the downstream organs/tissue, while the latter stems from the fact that the pumping mechanism of the body has a limited capacity in regulating blood pressure, in case a stenosis appears in the vasculature.  相似文献   

17.
The influence of stenosis on the pulsatile blood flow pattern in curved arteries with stenosis at inner wall was investigated by computer simulations. Numerical calculations were performed with various values of physiological parameters to examine the effect of a stenosis on the hemodynamic characteristics such as secondary flow, flow separation, wall shear stress (WSS) and pressure drop. The results demonstrated that when the severity of a stenosis at the inner wall of a curved artery reaches a certain level, the flow pattern in the downstream of the artery shows a dramatic change compared to that of a curved artery with no stenosis. According to previous studies, a flow separation occurs at the inner wall of the bend in a curved artery. The present work reports an analysis of such a flow separation area at the inner wall of the post stenosis region in curved arteries with a stenosis. In addition, another area of flow separation with low and oscillating WSS and blood pressure at the outer wall in a downstream tube was also found and investigated. The observed characteristic change of the flow downstream may suggest a formation of a new plaque at the outer wall downstream.  相似文献   

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