Objective To observe value of 0D-1D coupling model and 3D fluid-structure interaction(FSI)model based on coronary CT angiography(CCTA)for displaying hemodynamic characteristics of coronary artery stenosis.Methods Base...Objective To observe value of 0D-1D coupling model and 3D fluid-structure interaction(FSI)model based on coronary CT angiography(CCTA)for displaying hemodynamic characteristics of coronary artery stenosis.Methods Based on CCTA data of the stenosed left anterior descending branch(LAD)in a patient with coronary heart disease,an 0D-1D coupling model and 3D FSI model were built,respectively.Then hemodynamic characteristic indexes,including the pressure,flow velocity and wall shear stress(WSS)were obtained in every 0.01 s during 1 s at 5 sampling points(i.e.sampling point 1—5)using these 2 models,respectively,and the consistencies of the results between models were evaluated with Spearman correlation coefficient r s.Results The time consuming for construction of 0D-1D coupling model and 3D FSI model was 0.033 min and 704 min,respectively.Both models showed basically distribution of the pressure,flow velocity and WSS of the stenosed LAD.For more details,the pressure at the stenosed segment of LAD and the proximal segment of stenosis were both higher,which gradually decreased at the distal segment of stenosis,and the flow velocity at the proximal segment of stenosis was in a relatively slow and uniform condition,with significantly increased flow velocity and WSS at the stenosed segment.Compared with 3D FSI model,0D-1D vascular coupling model was relatively unrefined and lack of distal flow lines when displaying blood flow velocity.For sampling point 2 at the stenosed segment of LAD,no significant consistency for pressure between 2 models was found(P=0.118),but strong consistency for the flow velocity and WSS(r s=0.730,0.807,both P<0.05).The consistencies of pressure,flow velocity and WSS between 2 models at the proximal and distal segment of stenosis,i.e.1,3—5 sampling points were week to moderate(r s=0.237—0.669,all P<0.05).Conclusion 0D-1D coupling model exhibited outstanding computational efficiency and might provide relatively reasonable results,while 3D FSI model showed higher accuracy for details and streamline when simulating LAD stenosis.展开更多
Pulse detonation engine (PDE) is expected for a next-generation propulsion system. PDE is a promising engine that can generates power and thrust by using intermittent detonation. Promotion of deflagration to detonatio...Pulse detonation engine (PDE) is expected for a next-generation propulsion system. PDE is a promising engine that can generates power and thrust by using intermittent detonation. Promotion of deflagration to detonation transition (below DDT) is a key issue to realize this system. PDE has experimentally been investigated, and it was confirmed that detonation tubes with U-shaped bends are useful for fast DDT. However, the mechanism of DDT promotion due to U-bends has not been well clarified. In the present study, the influence of a U-bend on detona-tion wave propagation is researched with computational fluid dynamics (CFD). The numerical results show that detonation wave disappears once near the U-bend inlet and restarts after passing through it. In addition, it was found that the use of the U-bend with small channel width and curvature radius can induce fast DDT.展开更多
The present work is concerned with the analysis of an axi-symmetric flow of blood through coaxial tubes where the outer tube has an axially symmetric mild stenosis and the inner tube has a balloon which is axi-symmetr...The present work is concerned with the analysis of an axi-symmetric flow of blood through coaxial tubes where the outer tube has an axially symmetric mild stenosis and the inner tube has a balloon which is axi-symmetric in nature. The mild stenosis approximation is used to solve the present problem. The effect of the volume fraction density of the particles, the maximum height attained by the balloon, the radius of the inner tube, which keeps the balloon in position k, and the axial displacement of the balloon have been studied. Flow parameters such as the resistive impedance, the wall shear stress distribution in the stenotic region and its magnitude at the stenosis throat have been computed for different parameters. It is observed that the resistance to flow decreases with increasing values of the axial displacement of the balloon, while the resistance to flow increases with the volume fraction density of the particles, the radius of the inner tube, which keeps the balloon in position k, and the maximum height attained by the balloon. The wall shear stress distribution in the stenotic region possesses a character similar to the resistance to flow with respect to any parameter.展开更多
Analytical solutions are obtained for steady flow of an incompressible second grade fluid in an axisymmetric channel of varying width. Three approximate methods are used depending upon three different geometrical conf...Analytical solutions are obtained for steady flow of an incompressible second grade fluid in an axisymmetric channel of varying width. Three approximate methods are used depending upon three different geometrical configuration. The results obtained are applied to study the flow of a second grade fluid through a smooth constriction. To understand the flow behavior near stenosis, resistance to the flow, shear stress at the wall and stress at the stenosis throat are calculated. The results obtained are numerically evaluated for different values of dimensionless non-Newtonian parameters λ1 and λ2 and maximum height of the stenosis δm. It is observed that as we increase the value of these parameters the resistance to the flow, wall shear stress and stress at the stenosis throat increase.展开更多
A theoretical investigation concerning the influence of slip velocity on the flow of blood through an artery having its wall permeable has been carried out. Here blood is treated as a homogeneous Newtonian fluid. The ...A theoretical investigation concerning the influence of slip velocity on the flow of blood through an artery having its wall permeable has been carried out. Here blood is treated as a homogeneous Newtonian fluid. The flow is characterized by three parameters： /3 the ratio of radius to length of the arterial segment, Re the characteristic Reynolds number associated with the pressure outside the arterial segment and c the filtration coe^cient. The problem has been solved by the use of a perturbation technique, e is considered to be very small, ensuring the validity of the perturbation method. The computed numerical results are presented graphically to depict the variations in velocity, volumetric flow rate, wall shear stress and flow resistance.展开更多
文摘Objective To observe value of 0D-1D coupling model and 3D fluid-structure interaction(FSI)model based on coronary CT angiography(CCTA)for displaying hemodynamic characteristics of coronary artery stenosis.Methods Based on CCTA data of the stenosed left anterior descending branch(LAD)in a patient with coronary heart disease,an 0D-1D coupling model and 3D FSI model were built,respectively.Then hemodynamic characteristic indexes,including the pressure,flow velocity and wall shear stress(WSS)were obtained in every 0.01 s during 1 s at 5 sampling points(i.e.sampling point 1—5)using these 2 models,respectively,and the consistencies of the results between models were evaluated with Spearman correlation coefficient r s.Results The time consuming for construction of 0D-1D coupling model and 3D FSI model was 0.033 min and 704 min,respectively.Both models showed basically distribution of the pressure,flow velocity and WSS of the stenosed LAD.For more details,the pressure at the stenosed segment of LAD and the proximal segment of stenosis were both higher,which gradually decreased at the distal segment of stenosis,and the flow velocity at the proximal segment of stenosis was in a relatively slow and uniform condition,with significantly increased flow velocity and WSS at the stenosed segment.Compared with 3D FSI model,0D-1D vascular coupling model was relatively unrefined and lack of distal flow lines when displaying blood flow velocity.For sampling point 2 at the stenosed segment of LAD,no significant consistency for pressure between 2 models was found(P=0.118),but strong consistency for the flow velocity and WSS(r s=0.730,0.807,both P<0.05).The consistencies of pressure,flow velocity and WSS between 2 models at the proximal and distal segment of stenosis,i.e.1,3—5 sampling points were week to moderate(r s=0.237—0.669,all P<0.05).Conclusion 0D-1D coupling model exhibited outstanding computational efficiency and might provide relatively reasonable results,while 3D FSI model showed higher accuracy for details and streamline when simulating LAD stenosis.
文摘Pulse detonation engine (PDE) is expected for a next-generation propulsion system. PDE is a promising engine that can generates power and thrust by using intermittent detonation. Promotion of deflagration to detonation transition (below DDT) is a key issue to realize this system. PDE has experimentally been investigated, and it was confirmed that detonation tubes with U-shaped bends are useful for fast DDT. However, the mechanism of DDT promotion due to U-bends has not been well clarified. In the present study, the influence of a U-bend on detona-tion wave propagation is researched with computational fluid dynamics (CFD). The numerical results show that detonation wave disappears once near the U-bend inlet and restarts after passing through it. In addition, it was found that the use of the U-bend with small channel width and curvature radius can induce fast DDT.
文摘The present work is concerned with the analysis of an axi-symmetric flow of blood through coaxial tubes where the outer tube has an axially symmetric mild stenosis and the inner tube has a balloon which is axi-symmetric in nature. The mild stenosis approximation is used to solve the present problem. The effect of the volume fraction density of the particles, the maximum height attained by the balloon, the radius of the inner tube, which keeps the balloon in position k, and the axial displacement of the balloon have been studied. Flow parameters such as the resistive impedance, the wall shear stress distribution in the stenotic region and its magnitude at the stenosis throat have been computed for different parameters. It is observed that the resistance to flow decreases with increasing values of the axial displacement of the balloon, while the resistance to flow increases with the volume fraction density of the particles, the radius of the inner tube, which keeps the balloon in position k, and the maximum height attained by the balloon. The wall shear stress distribution in the stenotic region possesses a character similar to the resistance to flow with respect to any parameter.
文摘Analytical solutions are obtained for steady flow of an incompressible second grade fluid in an axisymmetric channel of varying width. Three approximate methods are used depending upon three different geometrical configuration. The results obtained are applied to study the flow of a second grade fluid through a smooth constriction. To understand the flow behavior near stenosis, resistance to the flow, shear stress at the wall and stress at the stenosis throat are calculated. The results obtained are numerically evaluated for different values of dimensionless non-Newtonian parameters λ1 and λ2 and maximum height of the stenosis δm. It is observed that as we increase the value of these parameters the resistance to the flow, wall shear stress and stress at the stenosis throat increase.
文摘A theoretical investigation concerning the influence of slip velocity on the flow of blood through an artery having its wall permeable has been carried out. Here blood is treated as a homogeneous Newtonian fluid. The flow is characterized by three parameters： /3 the ratio of radius to length of the arterial segment, Re the characteristic Reynolds number associated with the pressure outside the arterial segment and c the filtration coe^cient. The problem has been solved by the use of a perturbation technique, e is considered to be very small, ensuring the validity of the perturbation method. The computed numerical results are presented graphically to depict the variations in velocity, volumetric flow rate, wall shear stress and flow resistance.
