scholarly journals A Computational Model for Biomechanical Effects of Arterial Compliance Mismatch

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Fan He ◽  
Lu Hua ◽  
Li-jian Gao
Keyword(s):  
Blood Flow ◽  
Computational Model ◽  
Arterial Compliance ◽  
Wall Stress ◽  
Shear Stresses ◽  
Wall Shear ◽  
Stress And Deformation ◽  
Wall Interaction ◽  
Comparison Of The Results ◽  
Compliance Mismatch

Background. Compliance mismatch is a negative factor and it needs to be considered in arterial bypass grafting.Objective. A computational model was employed to investigate the effects of arterial compliance mismatch on blood flow, wall stress, and deformation.Methods. The unsteady blood flow was assumed to be laminar, Newtonian, viscous, and incompressible. The vessel wall was assumed to be linear elastic, isotropic, and incompressible. The fluid-wall interaction scheme was constructed using the finite element method.Results. The results show that there are identical wall shear stress waveforms, wall stress, and strain waveforms at different locations. The comparison of the results demonstrates that wall shear stresses and wall strains are higher while wall stresses are lower at the more compliant section. The differences promote the probability of intimal thickening at some locations.Conclusions. The model is effective and gives satisfactory results. It could be extended to all kinds of arteries with complicated geometrical and material factors.

A BIOMECHANICAL COMPARISON OF BLOOD FLOW AND MECHANICAL CHARACTERISTICS OF THE EARLY ARTERIOSCLEROTIC AND HEALTHY ARTERIES USING A FLUID-WALL INTERACTION MODEL

2014 ◽  
Vol 26 (02) ◽  
pp. 1450028
Author(s):  
Fan He
Keyword(s):  
Blood Flow ◽  
Flow Characteristics ◽  
Interaction Model ◽  
Cyclic Strain ◽  
Wall Stress ◽  
Strain Ratio ◽  
Shear Stresses ◽  
Stress And Deformation ◽  
Wall Interaction ◽  
Biomechanical Comparison

A fluid-wall interaction model was introduced to investigate and compare the properties of blood flow, wall stress and deformation of the early arteriosclerotic and healthy arteries. The unsteady blood flow was assumed to be laminar, Newtonian, viscous and incompressible. The vessel wall was assumed to be linear-elastic, isotropic and incompressible. The fluid-wall interaction algorithm was constructed using a finite element method. The results show that the blood flow, wall stress and strain distributions of both arteries are similar. The blood flow characteristics of the diseased artery are similar to those of the healthy artery, which may be the main reason that the early arteriosclerosis could be reversible and treated by itself. The values of velocities, wall shear stresses, pressures and wall stresses of the diseased artery are approximately equal to those of the healthy artery, however the values of wall strains of both arteries are different and the cyclic strain ratio of the diseased artery is higher than that of the healthy artery. A high cyclic strain ratio is thought to be disadvantageous for arterial tissue. A new parameter anti-fatigue index (AFI) is introduced to evaluate mechanical fatigue of artery in the study. AFI is effective in characterizing the anti-fatigue ability of artery.

scholarly journals Numerical Simulation of Dispersed Particle-Blood Flow in the Stenosed Coronary Arteries

2018 ◽  
Vol 2018 ◽  
pp. 1-16 ◽  
Author(s):  
Mongkol Kaewbumrung ◽  
Somsak Orankitjaroen ◽  
Pichit Boonkrong ◽  
Buraskorn Nuntadilok ◽  
Benchawan Wiwatanapataphee
Keyword(s):  
Numerical Simulation ◽  
Blood Flow ◽  
Shear Stress ◽  
Coronary Artery ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Stokes Equations ◽  
Spherical Shape ◽  
Shear Stresses ◽  
Wall Shear

A mathematical model of dispersed bioparticle-blood flow through the stenosed coronary artery under the pulsatile boundary conditions is proposed. Blood is assumed to be an incompressible non-Newtonian fluid and its flow is considered as turbulence described by the Reynolds-averaged Navier-Stokes equations. Bioparticles are assumed to be spherical shape with the same density as blood, and their translation and rotational motions are governed by Newtonian equations. Impact of particle movement on the blood velocity, the pressure distribution, and the wall shear stress distribution in three different severity degrees of stenosis including 25%, 50%, and 75% are investigated through the numerical simulation using ANSYS 18.2. Increasing degree of stenosis severity results in higher values of the pressure drop and wall shear stresses. The higher level of bioparticle motion directly varies with the pressure drop and wall shear stress. The area of coronary artery with higher density of bioparticles also presents the higher wall shear stress.

Intra-Aneurysmal Flow With Helix and Mesh Stent Placement Across Side-Wall Aneurysm Pore of a Straight Parent Vessel

2004 ◽  
Vol 126 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Tong-Miin Liou ◽  
Shun-Nan Liou ◽  
Kai-Lung Chu
Keyword(s):  
Average Velocity ◽  
Side Wall ◽  
Reynolds Numbers ◽  
Shear Stresses ◽  
Parent Vessel ◽  
The Mean ◽  
Wall Shear ◽  
Comparison Of The Results ◽  
Flow Stasis ◽  
Aneurysm Model

Pulsatile flow fields in a cerebrovascular side-wall aneurysm model with a wide ostium after stenting are presented in terms of particle tracking velocimetry measurements and flow visualization. Among the stent parameters the shape, helix versus mesh, was selected to study its effect on the changes of intraaneurysmal hemodynamics for the reference of minimally invasive endovascular aneurysm treatment. The blocking ratio of the stents was fixed at 30%. The Womersley number was 3.9 and the mean, peak, and minimal Reynolds numbers based on the bulk average velocity and diameter of the parent vessel were 600, 850, and 300, respectively. Four consecutive flow-rate phases were selected to characterize the intra-aneurysmal flow. The results are characterized in terms of velocity vector field, regional average velocity, and intra-aneurysmal vorticity/circulation/wall shear stress. It is found that the hemodynamic features inside the aneurysm alter markedly with the shape of the stent and the size of the orifice. Both stents investigated induce favorable changes in the intra-aneurysmal flow stasis as well as direction and undulation of wall shear stresses. A comparison of the results of the helix to mesh stent shows that the former is more favorable for endovascular treatment.

Blood Flow Manipulation in the Aorta With Coarctation and Arch Narrowing for Pediatric Subjects

2020 ◽  
Vol 88 (2) ◽  
Author(s):  
Yuxi Jia ◽  
Kumaradevan Punithakumar ◽  
Michelle Noga ◽  
Arman Hemmati
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Aortic Arch ◽  
Flow Direction ◽  
Upper Body ◽  
Patient Specific ◽  
Shear Stresses ◽  
Wall Shear

Abstract The characteristics of blood flow in an abnormal pediatric aorta with an aortic coarctation and aortic arch narrowing are examined using direct numerical simulations and patient-specific boundary conditions. The blood flow simulations of a normal pediatric aorta are used for comparison to identify unique flow features resulting from the aorta geometrical anomalies. Despite flow similarities compared to the flow in normal aortic arch, the flow velocity decreases with an increase in pressure, wall shear stress, and vorticity around both anomalies. The presence of wall shear stresses in the trailing indentation region and aorta coarctation opposing the primary flow direction suggests that there exist recirculation zones in the aorta. The discrepancy in relative flowrates through the top and bottom of the aorta outlets, and the pressure drop across the coarctation, implies a high blood pressure in the upper body and a low blood pressure in the lower body. We propose using flow manipulators prior to the aortic arch and coarctation to lower the wall shear stress, while making the recirculation regions both smaller and weaker. The flow manipulators form a guide to divert and correct blood flow in critical regions of the aorta with anomalies.

Reduced Effect of Aspirin on Thrombus Formation at High Shear and Disturbed Laminar Blood Flow

1996 ◽  
Vol 75 (05) ◽  
pp. 827-832 ◽  
Author(s):  
R Marius Barstad ◽  
Una Ørvim ◽  
Maria J A.G Hamers ◽  
Geir E Tjønnfjord ◽  
Frank R Brosstad ◽  
...  
Keyword(s):  
Blood Flow ◽  
Thrombus Formation ◽  
Secondary Prophylaxis ◽  
Significant Inhibition ◽  
Von Willebrand Disease ◽  
Shear Stresses ◽  
High Shear ◽  
Cross Sectional ◽  
Wall Shear ◽  
Von Willebrand

SummaryAspirin is the most commonly used antithrombotic drug in primary and secondary prophylaxis against cardio- and cerebrovascular disease. In previous studies from our laboratory it was demonstrated that the effect of aspirin on collagen-induced thrombus formation in a parallelplate perfusion device with laminar blood flow is shear rate dependent. Although aspirin did not affect collagen-induced thrombus formation at 650 s-1 (medium sized arteries), a significant inhibition of thrombus formation by approximately 38% at 2,600 s-1 (moderately stenoses in medium sized arteries) was observed. At present we have extended these studies to thrombus formation at the apex of eccentric stenoses in a parallel-plate perfusion chamber device. The stenoses reduced the cross-sectional area of the blood flow channel of the perfusion chambers by 60 or 80%, introducing disturbed laminar flow and apex wall shear rates of 2,600 and 10,500 s-1, respectively. The corresponding wall shear stresses were 80 and 315 dynes/cm2, respectively.Aspirin reduced the platelet thrombus volume at the 60% stenosis by 45% (p <0.03), and the fibrin deposition by 70% (p <0.004). However, none of these parameters were affected by aspirin at the 80% stenosis. These observations may at least partly explain why aspirin has a limited clinical effect in preventing arterial thrombus formation in atherosclerotic vessels at high shear and disturbed blood flow. In contrast, thrombus formation in blood from one patient with Glanzmann’s thrombasthenia and two patients with von Willebrand disease subtype 2M was almost abolished at this blood flow condition. Thus, blocking the function of either von Willebrand factor or glycoprotein IIb/IIIa may represent better antithrombotic approaches for such critical events than blocking the prostaglandin metabolism by aspirin. The lack of effect of aspirin on thrombus formation at the 80% stenosis may reflect shear-induced platelet activation at the stenosis inlet region, since shear-induced platelet aggregation in rotational viscometers is not affected by aspirin at shear stresses exceeding 100 dynes/cm2.

The Localized Hemodynamics of Drug-Eluting Stents Are Not Improved by the Presence of Magnetic Struts

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
P. R. S. Vijayaratnam ◽  
T. J. Barber ◽  
J. A. Reizes
Keyword(s):  
Blood Flow ◽  
Stent Thrombosis ◽  
Separated Flow ◽  
Drug Eluting Stents ◽  
Magnetic Flux Density ◽  
Drug Eluting Stent ◽  
Shear Stresses ◽  
Stent Strut ◽  
Drug Eluting ◽  
Wall Shear

The feasibility of implementing magnetic struts into drug-eluting stents (DESs) to mitigate the adverse hemodynamics which precipitate stent thrombosis is examined. These adverse hemodynamics include platelet-activating high wall shear stresses (WSS) and endothelial dysfunction-inducing low wall shear stresses. By magnetizing the stent struts, two forces are induced on the surrounding blood: (1) magnetization forces which reorient red blood cells to align with the magnetic field and (2) Lorentz forces which oppose the motion of the conducting fluid. The aim of this study was to investigate whether these forces can be used to locally alter blood flow in a manner that alleviates the thrombogenicity of stented vessels. Two-dimensional steady-state computational fluid dynamics (CFD) simulations were used to numerically model blood flow over a single magnetic drug-eluting stent strut with a square cross section. The effects of magnet orientation and magnetic flux density on the hemodynamics of the stented vessel were elucidated in vessels transporting oxygenated and deoxygenated blood. The simulations are compared in terms of the size of separated flow regions. The results indicate that unrealistically strong magnets would be required to achieve even modest hemodynamic improvements and that the magnetic strut concept is ill-suited to mitigate stent thrombosis.

scholarly journals The Influence of Non-Newtonian Model on Properties of Blood Flow Through a Left Coronary Artery with Presence of Different Double Stenosis

2021 ◽  
Vol 39 (3) ◽  
pp. 895-905
Author(s):  
Saleem K. Kadhim ◽  
Mohammed G. Al-Azawy ◽  
Sinan Abdul-Ghafar Ali ◽  
Mina Qays Kadhim
Keyword(s):  
Blood Flow ◽  
Coronary Artery ◽  
Left Coronary Artery ◽  
Calculated Data ◽  
Shear Stresses ◽  
Numerical Investigations ◽  
Newtonian Model ◽  
Flow Through ◽  
Wall Shear ◽  
Flow States

Cardiovascular diseases were the main cause for loosing lives in the last decades due to the restricted blood flow states in the blood vessels areas. Numerical investigations have been conducted as the aim of this work to examine the blood flow, and wall shear stresses adjacent to the mono stenosis up to different degrees involved in the main, side and distal main branches as well as observe the pulsatile flow of blood in the left coronary artery through various percentage of stenosis. Both the Carreau non-Newtonian rheological model and the Newtonian model were utilized to model the blood fluid and wall shear stresses of left coronary artery, in a row, all the calculated data were validated with the previously published papers. It was found that the blood flow inside areas of the artery lie within the range of non-Newtonian rheological effects can be present, verifying the need to treat blood as non-Newtonian fluid; especially, with the case of 90% blockage.

On the Calculation of Fluid Shear Stresses at the Wall of Dilated Large Arteries: Part II—Application to 3D Computational Models

2000 ◽  
Author(s):  
Ender A. Finol ◽  
Cristina H. Amon
Keyword(s):  
Blood Flow ◽  
Stress Tensor ◽  
Computational Models ◽  
Numerical Study ◽  
Aortic Aneurysms ◽  
Shear Stresses ◽  
Numerical Predictions ◽  
Aneurysm Wall ◽  
Pulsatile Flows ◽  
Wall Shear

Abstract Experimental and numerical investigations of pulsatile flows in artery models have been numerous during the last two decades. For 3D artery models, numerical predictions of wall shear stresses can be rather difficult to make due to the six independent stress tensor components that may be evaluated at any particular time during the blood flow pulse. The only 3D numerical study of blood flow in Abdominal Aortic Aneurysms (AAAs) known to the authors is that of Taylor and Yamaguchi (1994), in which iso-shear stress contours are reported for an asymmetric aneurysm model. However, the projection of these stresses at the aneurysm wall is not reported. This paper presents an extension of the plane stress formulation outlined in Part I, combined with a transformation of the stress tensor, as an alternative procedure for the calculation of wall shear stresses in 3D dilated artery models, with application to asymmetric aneurysms.

A COMPUTATIONAL MODEL OF BLOOD FLOW AND AORTIC WALL STRESS IN ABDOMINAL AORTIC ANEURYSMS

ASAIO Journal ◽  
1999 ◽  
Vol 45 (2) ◽  
pp. 197
Author(s):  
P J Cabrales ◽  
J E Gómez ◽  
J Camacho ◽  
C Espinel ◽  
J C Briceño
Keyword(s):  
Blood Flow ◽  
Computational Model ◽  
Aortic Wall ◽  
Wall Stress ◽  
Abdominal Aortic Aneurysms ◽  
Aortic Aneurysms ◽  
Abdominal Aortic

Finite Element Simulation of Blood Flow in a Flexible Carotid Artery Bifurcation

2011 ◽  
Author(s):  
Sang Hoon Lee ◽  
Hyoung Gwon Choi ◽  
Jung Yul Yoo
Keyword(s):  
Finite Element ◽  
Blood Flow ◽  
Carotid Artery ◽  
Flow Separation ◽  
Solid Mechanics ◽  
Incompressible Flows ◽  
Stokes Equations ◽  
Shear Stresses ◽  
Artery Wall ◽  
Wall Shear

To investigate the effect of the flexible artery wall on the flow field and to determine the wall shear stresses in the carotid artery wall, numerical simulations for the blood flow are carried out. For solving the equation of motion for the structure in typical fluid-structure interaction (FSI) problems, it is necessary to calculate the fluid force on the surface of the structure explicitly. To avoid the complexity due to the necessity of additional mechanical constraints, we use the combined formulation which includes both the fluid and structure equations of motion into single coupled variational equation. The Navier-Stokes equations for fluid flow are solved using a P2P1 Galerkin finite element method (FEM) and mesh movement is achieved using arbitrary Lagrangian-Eulerian (ALE) formulation. The Newmark method is employed for solving the dynamic equilibrium equations for linear elastic solid mechanics. The time-dependent, three-dimensional, incompressible flows of Newtonian fluids constrained in the flexible wall are analyzed. The study shows strongly skewed axial velocity and flow separation in the internal carotid artery (ICA). Flow separation results in locally low wall shear stress. Further, strong secondary motion in the ICA is observed.

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