The flow of incompressible couple stress fluid in a circular tube with stenosis and dilatations has been investigated. The stenosis was assumed to be axially symmetric and mild. The flow equations have been linearized...The flow of incompressible couple stress fluid in a circular tube with stenosis and dilatations has been investigated. The stenosis was assumed to be axially symmetric and mild. The flow equations have been linearized and the expressions for the resistance to the flow, velocity, pressure drop, wall shear stress have been derived. The effects of various parameters on these flow variables have been investigated. It is found that the resistance to the flow and pressure drop increase with height of the stenosis and decrease with post stenotic dilatation. Pressure drop decreases with couple stress fluid parameter for both stenosis and post stenotic dilatation. Further, the wall shear stress increases with height of the stenosis and couple stress parameter but decreases with post stenotic dilatation and couple stress fluid parameter.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
A numerical analysis of Newtonian and non-Newtonian flow in an axi-symmetric tube with a local constriction simulating a stenosed artery under steady and pulsatile flow conditions war carried out. Bared on these resul...A numerical analysis of Newtonian and non-Newtonian flow in an axi-symmetric tube with a local constriction simulating a stenosed artery under steady and pulsatile flow conditions war carried out. Bared on these results, the concentration fields of LDL ( (low-density lipoprotein) and Albumin were discussed. According to the results, in great details the macromolecule transport influences of wall shear stress, non-Newtonian fluid character and the scale of the molecule etc are given. The results of Newtonian fluid flow and non-Newtonian fluid flow, steady flow and pulsatile flow are compared. These investigations can provide much valuable information about the correlation between the flow properties, the macromolecule transport and the development of atherosclerosis.展开更多
目的基于流固耦合(FSI)力学的方式,分析不同血液黏滞系数对重度狭窄颈动脉的血液流速及壁面剪切力(WSS)的影响。方法选取2015年8月于天津市第四中心医院经CT血管成像(CTA)检查诊断为颈内动脉重度狭窄(狭窄程度为75%)的1例62岁男性病人,...目的基于流固耦合(FSI)力学的方式,分析不同血液黏滞系数对重度狭窄颈动脉的血液流速及壁面剪切力(WSS)的影响。方法选取2015年8月于天津市第四中心医院经CT血管成像(CTA)检查诊断为颈内动脉重度狭窄(狭窄程度为75%)的1例62岁男性病人,将其CTA影像数据制作模型,导入FSI分析软件中,分别设定血液黏滞系数为1、3.5、6、8.5、11 c P并进行运算。在运算结果中测量并分析颈总动脉末端(A1)、颈动脉窦水平(A2)、颈内动脉狭窄处(A3)、颈内动脉狭窄处远端(A4)截面的血液流速和WSS值。结果随着血液黏滞系数的升高,A1、A2、A3、A4的血流速度均值降低,WSS均值增大;A4的中心血液流速降低,A1、A2和A3的中心血流速度升高。结论随着颈动脉重度狭窄病人的血液黏滞系数升高,其脑部供血不足趋于严重化,从而导致急性脑卒中的发生,而且造成狭窄位置斑块的破损概率和面积进一步增大,因此应引起临床的高度重视并及时干预。展开更多
Based on the VOF model,CFD simulations were carried out for wall shear stress in gas-liquid vertical and inclined upward slug flow.The simulation results showed that the thickness of the falling film in the vertical u...Based on the VOF model,CFD simulations were carried out for wall shear stress in gas-liquid vertical and inclined upward slug flow.The simulation results showed that the thickness of the falling film in the vertical upward slug flow was always smaller than that in the inclined upward slug flow.In the vertical tubes,wall shear stress increased gradually from Taylor bubble nose to the falling liquid film until it became stable in the developed falling liquid film,but in the wake zone the wall shear stress appeared irregular.In the inclined tubes,the tip of the Taylor bubble nose was above the centerline of the tube and the smaller the angle,the greater the thickness of the falling liquid film.Meanwhile,for the wall shear stress of slug flow in an inclined tube,when FrTB was small,the shear stress profile of falling liquid film on the top wall fluctuated significantly,but it was smooth on the bottom wall.With increasing FrTB, the difference between the shear stress profile on the top wall and the shear stress profile on the bottom wall gradually disappeared.展开更多
文摘The flow of incompressible couple stress fluid in a circular tube with stenosis and dilatations has been investigated. The stenosis was assumed to be axially symmetric and mild. The flow equations have been linearized and the expressions for the resistance to the flow, velocity, pressure drop, wall shear stress have been derived. The effects of various parameters on these flow variables have been investigated. It is found that the resistance to the flow and pressure drop increase with height of the stenosis and decrease with post stenotic dilatation. Pressure drop decreases with couple stress fluid parameter for both stenosis and post stenotic dilatation. Further, the wall shear stress increases with height of the stenosis and couple stress parameter but decreases with post stenotic dilatation and couple stress fluid parameter.
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.
文摘A numerical analysis of Newtonian and non-Newtonian flow in an axi-symmetric tube with a local constriction simulating a stenosed artery under steady and pulsatile flow conditions war carried out. Bared on these results, the concentration fields of LDL ( (low-density lipoprotein) and Albumin were discussed. According to the results, in great details the macromolecule transport influences of wall shear stress, non-Newtonian fluid character and the scale of the molecule etc are given. The results of Newtonian fluid flow and non-Newtonian fluid flow, steady flow and pulsatile flow are compared. These investigations can provide much valuable information about the correlation between the flow properties, the macromolecule transport and the development of atherosclerosis.
文摘目的基于流固耦合(FSI)力学的方式,分析不同血液黏滞系数对重度狭窄颈动脉的血液流速及壁面剪切力(WSS)的影响。方法选取2015年8月于天津市第四中心医院经CT血管成像(CTA)检查诊断为颈内动脉重度狭窄(狭窄程度为75%)的1例62岁男性病人,将其CTA影像数据制作模型,导入FSI分析软件中,分别设定血液黏滞系数为1、3.5、6、8.5、11 c P并进行运算。在运算结果中测量并分析颈总动脉末端(A1)、颈动脉窦水平(A2)、颈内动脉狭窄处(A3)、颈内动脉狭窄处远端(A4)截面的血液流速和WSS值。结果随着血液黏滞系数的升高,A1、A2、A3、A4的血流速度均值降低,WSS均值增大;A4的中心血液流速降低,A1、A2和A3的中心血流速度升高。结论随着颈动脉重度狭窄病人的血液黏滞系数升高,其脑部供血不足趋于严重化,从而导致急性脑卒中的发生,而且造成狭窄位置斑块的破损概率和面积进一步增大,因此应引起临床的高度重视并及时干预。
文摘Based on the VOF model,CFD simulations were carried out for wall shear stress in gas-liquid vertical and inclined upward slug flow.The simulation results showed that the thickness of the falling film in the vertical upward slug flow was always smaller than that in the inclined upward slug flow.In the vertical tubes,wall shear stress increased gradually from Taylor bubble nose to the falling liquid film until it became stable in the developed falling liquid film,but in the wake zone the wall shear stress appeared irregular.In the inclined tubes,the tip of the Taylor bubble nose was above the centerline of the tube and the smaller the angle,the greater the thickness of the falling liquid film.Meanwhile,for the wall shear stress of slug flow in an inclined tube,when FrTB was small,the shear stress profile of falling liquid film on the top wall fluctuated significantly,but it was smooth on the bottom wall.With increasing FrTB, the difference between the shear stress profile on the top wall and the shear stress profile on the bottom wall gradually disappeared.
