The Wall Shear Stress （WSS） generated by blood flow and Circumferential Stress （CS） driven by blood pressure have been thought to play an important role in blood flow-dependent phenomena such as angiogenesis, vasc...The Wall Shear Stress （WSS） generated by blood flow and Circumferential Stress （CS） driven by blood pressure have been thought to play an important role in blood flow-dependent phenomena such as angiogenesis, vascular remodeling, and atherosgenesis. The WSS and CS in straight arteries were calculated by measuring the blood pressure, center-line velocity, wall thickness, and radius of vessels. The WSS and CS in the time domain were then decomposed into the amplitude and phase in the frequency domain. The CS amplitude to the WSS amplitude ratio （referred as stress ampli tude ratio, Zs ） and the phase difference between the CS and the WSS （referred as stress phase difference, SPA） in the fre quency domain were calculated to characterize the synergy of the CS and WSS. Numerical results demonstrated that the CS is not in phase with the WSS, a time delay in the time domain or a stress phase difference in the frequency domain between the WSS and the CS exists. Theoretical analysis demonstrated that the Zs and SPA are primarily determined by the local fac tors （blood viscosity, local inertial effects, local geometry, loeal elasticity） and the input impedance of whole downstream arterial beds. Because the arterial input impedance has been shown to reflect the physiological and pathological states of whole downstream arterial beds, the stress amplitude ratio Zs and stress phase difference SPA would be thought to be the appropriate indices to reflect the effects of states of whole downstream arterial beds on the local blood flow dependent phenomena such as angiogenesis, vascular remodeling, and atherosgenesis.展开更多
目的先天性心脏病相关性肺动脉高压(pulmonary arterial hypertension related to congenital heart disease,PAH-CHD)是肺动脉血流动力学异常所致的一种疾病。研究肺循环血流动力学特异性,有助于了解PAH-CHD发生发展的生物力学因素。...目的先天性心脏病相关性肺动脉高压(pulmonary arterial hypertension related to congenital heart disease,PAH-CHD)是肺动脉血流动力学异常所致的一种疾病。研究肺循环血流动力学特异性,有助于了解PAH-CHD发生发展的生物力学因素。方法对5例PAH-CHD患儿和5例无PAH(Non-PAH)的先天性心脏病患儿通过临床及影像资料收集,重建三维血管模型,利用计算流体动力学模拟肺动脉血液流动,对比分析肺动脉血流动力学相关速度流线、壁面剪切力(wall shear stress,WSS)及单位体表面积平均能量损失(·E)差异。结果血流动力学相关指标显示,PAH-CHD患儿左右肺动脉分支处流速和WSS明显升高,主肺动脉处WSS明显降低,·E呈显著增加趋势且与肺动脉直径及入口流量呈明显正相关。结论PAH-CHD患儿较Non-PAH患儿肺动脉分支处流速和WSS明显升高,主肺动脉WSS降低,·E增加,表明这些血流动力学因素与PAH-CHD密切相关,是临床评估PAH-CHD的潜在血流动力学指标。展开更多
The asymmetric inlet velocity profile has been observed in phantom model using LDA and in health subjects using Magnet Resonance （MR）. The effects of asymmetric inlet axial velocity profile on the flow field and the...The asymmetric inlet velocity profile has been observed in phantom model using LDA and in health subjects using Magnet Resonance （MR）. The effects of asymmetric inlet axial velocity profile on the flow field and the Wall Shear Stress （WSS） of carotid bifurcation were numerically studied herein with the TF-AHCB model, The results show that the Wall Shear Stress Gradient （WSSG） in the front part of the sinus for inward-tilting inlet axial velocity profile is nearly 2 times of that for the symmetric one in the beginning of systole, the end of systole, and diastole, respectively. The area of WSS below 5× 10^-3 Pa at the outer wall of the sinus for outward-tilting inlet axial velocity profile is 1.5 times of that for the inward-tilting one during diastole of the cardiac cycle. The asymmetric inlet velocity profiles can reduce the flow velocity near the inner wall of the sinus, which has been normally considered a high velocity region. It is concluded that besides bifurcation geometry and flow waveform, the asymmetry of inlet velocity profile is probably a factor influencing atherosclerosis.展开更多
目的通过计算流体动力学(computational fluid dynamics,CFD)分析右冠状动脉起源于左冠状窦(anomalous origin of the right coronary artery from the left coronary artery sinus,AORL)的血流动力学参数,从而有效评估疾病。方法选取...目的通过计算流体动力学(computational fluid dynamics,CFD)分析右冠状动脉起源于左冠状窦(anomalous origin of the right coronary artery from the left coronary artery sinus,AORL)的血流动力学参数,从而有效评估疾病。方法选取正常右冠状动脉(right coronary artery,RCA)和AORL两例个体病例,在Mimics软件中重建两个病例的血管模型,并将模型导入ANSYS CFX软件中进行血流动力学模拟计算,比较正常和AORL两种模型的血流动力学情况。结果AORL模型右冠状动脉入口截面具有较小的血流量(9.35 cm^3/s),有可能会导致右冠状动脉下游供血不足;AORL模型右冠状动脉急性拐角处的压力(13.78 kPa)相比于正常模型右冠状动脉(14.9 kPa)较低;AORL模型壁面剪切力(12.83 Pa)大于正常模型(9.74 Pa);AORL模型血管壁变形量较大。结论AORL入口流速及拐角处压力均比正常RCA小,从而可能导致缺血症状发生。研究结果对临床上有效评估缺血等疾病具有理论指导意义。展开更多
Emphysema and influenza directly affect alveolar sacs and cause problems in lung performance during the breathing cycle. In this study, the effects of Emphysema and Influenza on alveolar sac’s air flow characteristic...Emphysema and influenza directly affect alveolar sacs and cause problems in lung performance during the breathing cycle. In this study, the effects of Emphysema and Influenza on alveolar sac’s air flow characteristics are investigated through Computational Fluid Dynamics (CFD) simulation. Both normal and Emphysemic alveolar sac models with varying collapsed volumes resulting from influenza virus replication were developed. Maximum, area average pressure, and wall shear stress (WSS) in collapsed and open alveolar sacs models were compared. It was found that a collapse at half of the volume at the bottom of the alveolar sacs’ models would cause a decrease in average and maximum pressure values and yield higher WSS values for fluid flow during the breathing cycle. On the other hand, a quarter volume collapse at the bottom and side of the model resulted in higher values for average and maximum pressure and WSS. Additionally, results also showed that a combination of alveolar sacs closure and Emphysema would generally lead to an increase in fluid pressure and average WSS during breathing. Maximum WSS was observed during exhalation and maximum WSS decrease occurred during inhalation. Findings are in good agreement with previous studies and suggest that emphysema and influenza virus affect fluid flow and may contribute to alveolar sac closure. However, more realistic simulations should include the fluid-solid interaction studies.展开更多
目的通过在FLUENT计算流体动力学分析软件中调用自主开发的用户自定义函数(user defined function,UDF)动网格程序,实现网格节点根据壁面切应力(wall shear stress,WSS)判据进行移动更新,并将此方法应用于模拟动脉粥样硬化(atherosclero...目的通过在FLUENT计算流体动力学分析软件中调用自主开发的用户自定义函数(user defined function,UDF)动网格程序,实现网格节点根据壁面切应力(wall shear stress,WSS)判据进行移动更新,并将此方法应用于模拟动脉粥样硬化(atherosclerosis,AS)的发展过程中。方法二次开发的UDF程序能够在计算过程中提取壁面各节点处WSS结果,若满足阈值判据条件则进行移动调整。采用弹性光顺与局部重构相结合的网格再生方法调控网格模型的更新,保证变形过程中的网格质量。结果 UDF程序成功提取出WSS并调整网格进行相应变形。初始狭窄造成的尾部涡流导致血管壁出现近端局部扩张,远端再狭窄的形貌特征,临床血管造影存在相似形貌。结论自主开发的UDF程序达到了预期效果,勾勒出了WSS影响下AS的形貌特征。在今后研究中可以考虑在动网格的变形控制方面添加更多影响因素,为AS临床预后及风险评测提供数值依据。展开更多
Numerical models of carotid bifurcation were constructed using a combination of tuning-fork bifurcation and straight or curved common carotid. The different inlet velocity profiles of the common carotid were generated...Numerical models of carotid bifurcation were constructed using a combination of tuning-fork bifurcation and straight or curved common carotid. The different inlet velocity profiles of the common carotid were generated for Bloch flow waveform and Holdsworth flow waveform, respectively. The effects of the different flow waveform for the common carotid on Wall Shear Stress （WSS） and Oscillatory Shear Index （OSI） of carotid bifurcation were studied by CFD method. The results show that the physiological flow waveform of curved common carotid has a significant effect on OSI. In particular, the OSI on the outer walls of carotid sinus and external carotid becomes higher in the inward-curved common carotid for Holdsworth flow waveform. But, in both cases of low WSS and high OSI, the effects of flow waveforms are smaller than those of the curved common carotid. The study reveals that the exact knowledge of the physiological flow waveform, vascular geometry and inlet velocity profile is important for hemodynamic numerical simulation of artery bifurcation.展开更多
Intracranial atherosclerotic disease(ICAD)is an important cause for ischemic stroke and transient ischemic stroke(TIA)throughout the world,especially in Asians,which is not fully appreciated,partly due to its inaccess...Intracranial atherosclerotic disease(ICAD)is an important cause for ischemic stroke and transient ischemic stroke(TIA)throughout the world,especially in Asians,which is not fully appreciated,partly due to its inaccessibility and limitations of current neuroimaging methods.The computational fluid dynamics(CFD)modeling technique provides a novel approach to reveal the hemodynamic characteristics in ICAD,e.g.,the distributions of pressure,wall shear stress and flow velocity.In this review article,we aim to provide an overview of the general methodology of CFD modeling in arterial stenotic diseases,the established application of this technique in coronary artery disease,and more importantly,perspectives and challenges of this technique in the investigation of ICAD.Promising findings of preliminary studies using a CFD model for hemodynamic analysis in ICAD warrant verifications.Further studies in this area will help rectify loopholes in the current secondary prevention strategy,and inform individualized treatment for ICAD patients in the near future.展开更多
文摘The Wall Shear Stress （WSS） generated by blood flow and Circumferential Stress （CS） driven by blood pressure have been thought to play an important role in blood flow-dependent phenomena such as angiogenesis, vascular remodeling, and atherosgenesis. The WSS and CS in straight arteries were calculated by measuring the blood pressure, center-line velocity, wall thickness, and radius of vessels. The WSS and CS in the time domain were then decomposed into the amplitude and phase in the frequency domain. The CS amplitude to the WSS amplitude ratio （referred as stress ampli tude ratio, Zs ） and the phase difference between the CS and the WSS （referred as stress phase difference, SPA） in the fre quency domain were calculated to characterize the synergy of the CS and WSS. Numerical results demonstrated that the CS is not in phase with the WSS, a time delay in the time domain or a stress phase difference in the frequency domain between the WSS and the CS exists. Theoretical analysis demonstrated that the Zs and SPA are primarily determined by the local fac tors （blood viscosity, local inertial effects, local geometry, loeal elasticity） and the input impedance of whole downstream arterial beds. Because the arterial input impedance has been shown to reflect the physiological and pathological states of whole downstream arterial beds, the stress amplitude ratio Zs and stress phase difference SPA would be thought to be the appropriate indices to reflect the effects of states of whole downstream arterial beds on the local blood flow dependent phenomena such as angiogenesis, vascular remodeling, and atherosgenesis.
文摘目的先天性心脏病相关性肺动脉高压(pulmonary arterial hypertension related to congenital heart disease,PAH-CHD)是肺动脉血流动力学异常所致的一种疾病。研究肺循环血流动力学特异性,有助于了解PAH-CHD发生发展的生物力学因素。方法对5例PAH-CHD患儿和5例无PAH(Non-PAH)的先天性心脏病患儿通过临床及影像资料收集,重建三维血管模型,利用计算流体动力学模拟肺动脉血液流动,对比分析肺动脉血流动力学相关速度流线、壁面剪切力(wall shear stress,WSS)及单位体表面积平均能量损失(·E)差异。结果血流动力学相关指标显示,PAH-CHD患儿左右肺动脉分支处流速和WSS明显升高,主肺动脉处WSS明显降低,·E呈显著增加趋势且与肺动脉直径及入口流量呈明显正相关。结论PAH-CHD患儿较Non-PAH患儿肺动脉分支处流速和WSS明显升高,主肺动脉WSS降低,·E增加,表明这些血流动力学因素与PAH-CHD密切相关,是临床评估PAH-CHD的潜在血流动力学指标。
基金the National Natural Science Foundation of China (Grant No. 10672104).
文摘The asymmetric inlet velocity profile has been observed in phantom model using LDA and in health subjects using Magnet Resonance （MR）. The effects of asymmetric inlet axial velocity profile on the flow field and the Wall Shear Stress （WSS） of carotid bifurcation were numerically studied herein with the TF-AHCB model, The results show that the Wall Shear Stress Gradient （WSSG） in the front part of the sinus for inward-tilting inlet axial velocity profile is nearly 2 times of that for the symmetric one in the beginning of systole, the end of systole, and diastole, respectively. The area of WSS below 5× 10^-3 Pa at the outer wall of the sinus for outward-tilting inlet axial velocity profile is 1.5 times of that for the inward-tilting one during diastole of the cardiac cycle. The asymmetric inlet velocity profiles can reduce the flow velocity near the inner wall of the sinus, which has been normally considered a high velocity region. It is concluded that besides bifurcation geometry and flow waveform, the asymmetry of inlet velocity profile is probably a factor influencing atherosclerosis.
文摘目的通过计算流体动力学(computational fluid dynamics,CFD)分析右冠状动脉起源于左冠状窦(anomalous origin of the right coronary artery from the left coronary artery sinus,AORL)的血流动力学参数,从而有效评估疾病。方法选取正常右冠状动脉(right coronary artery,RCA)和AORL两例个体病例,在Mimics软件中重建两个病例的血管模型,并将模型导入ANSYS CFX软件中进行血流动力学模拟计算,比较正常和AORL两种模型的血流动力学情况。结果AORL模型右冠状动脉入口截面具有较小的血流量(9.35 cm^3/s),有可能会导致右冠状动脉下游供血不足;AORL模型右冠状动脉急性拐角处的压力(13.78 kPa)相比于正常模型右冠状动脉(14.9 kPa)较低;AORL模型壁面剪切力(12.83 Pa)大于正常模型(9.74 Pa);AORL模型血管壁变形量较大。结论AORL入口流速及拐角处压力均比正常RCA小,从而可能导致缺血症状发生。研究结果对临床上有效评估缺血等疾病具有理论指导意义。
文摘Emphysema and influenza directly affect alveolar sacs and cause problems in lung performance during the breathing cycle. In this study, the effects of Emphysema and Influenza on alveolar sac’s air flow characteristics are investigated through Computational Fluid Dynamics (CFD) simulation. Both normal and Emphysemic alveolar sac models with varying collapsed volumes resulting from influenza virus replication were developed. Maximum, area average pressure, and wall shear stress (WSS) in collapsed and open alveolar sacs models were compared. It was found that a collapse at half of the volume at the bottom of the alveolar sacs’ models would cause a decrease in average and maximum pressure values and yield higher WSS values for fluid flow during the breathing cycle. On the other hand, a quarter volume collapse at the bottom and side of the model resulted in higher values for average and maximum pressure and WSS. Additionally, results also showed that a combination of alveolar sacs closure and Emphysema would generally lead to an increase in fluid pressure and average WSS during breathing. Maximum WSS was observed during exhalation and maximum WSS decrease occurred during inhalation. Findings are in good agreement with previous studies and suggest that emphysema and influenza virus affect fluid flow and may contribute to alveolar sac closure. However, more realistic simulations should include the fluid-solid interaction studies.
基金supported by the National Natural Science Foundation of China (Grant No.10672104,10772120)the Shanghai Leading Academic Discipline Project (Grant No.B206)
文摘Numerical models of carotid bifurcation were constructed using a combination of tuning-fork bifurcation and straight or curved common carotid. The different inlet velocity profiles of the common carotid were generated for Bloch flow waveform and Holdsworth flow waveform, respectively. The effects of the different flow waveform for the common carotid on Wall Shear Stress （WSS） and Oscillatory Shear Index （OSI） of carotid bifurcation were studied by CFD method. The results show that the physiological flow waveform of curved common carotid has a significant effect on OSI. In particular, the OSI on the outer walls of carotid sinus and external carotid becomes higher in the inward-curved common carotid for Holdsworth flow waveform. But, in both cases of low WSS and high OSI, the effects of flow waveforms are smaller than those of the curved common carotid. The study reveals that the exact knowledge of the physiological flow waveform, vascular geometry and inlet velocity profile is important for hemodynamic numerical simulation of artery bifurcation.
文摘Intracranial atherosclerotic disease(ICAD)is an important cause for ischemic stroke and transient ischemic stroke(TIA)throughout the world,especially in Asians,which is not fully appreciated,partly due to its inaccessibility and limitations of current neuroimaging methods.The computational fluid dynamics(CFD)modeling technique provides a novel approach to reveal the hemodynamic characteristics in ICAD,e.g.,the distributions of pressure,wall shear stress and flow velocity.In this review article,we aim to provide an overview of the general methodology of CFD modeling in arterial stenotic diseases,the established application of this technique in coronary artery disease,and more importantly,perspectives and challenges of this technique in the investigation of ICAD.Promising findings of preliminary studies using a CFD model for hemodynamic analysis in ICAD warrant verifications.Further studies in this area will help rectify loopholes in the current secondary prevention strategy,and inform individualized treatment for ICAD patients in the near future.
