Numerical Simulation of Wall Shear Stress and Particle-Based Hemodynamic Parameters in Pre-Cuffed and Streamlined End-to-Side Anastomoses

2005 ◽  
Vol 33 (12) ◽  
pp. 1752-1766 ◽  
Author(s):  
P. Worth Longest ◽  
Clement Kleinstreuer ◽  
Abe Deanda
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Hemodynamic Parameters ◽  
Wall Shear

scholarly journals Hemodynamic parameters and vessel tortuosity: an investigation with a mesenterial vascular network

2017 ◽  
Vol 1 (4) ◽  
pp. 62-68
Author(s):  
Roberto Annunziata ◽  
Bettina Reglin ◽  
Axel Pries ◽  
Emanuele Trucco
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Oxygen Saturation ◽  
Wall Thickness ◽  
Blood Velocity ◽  
Vascular Network ◽  
Hemodynamic Parameters ◽  
Vessel Tortuosity ◽  
Wall Shear ◽  
Quantitative Definition

Purpose: The effect of hemodynamic parameters on vessel tortuosity remains un-clear. Here we investigate the correlation of tortuosity with a set of hemodynamicparameters in a mesenterial vascular network.Methods: A mesenterial vascular network of 389 vessels (131 arteries, 132 veins, and 126 capillaries) was imaged. Eleven hemodynamic parameters were measured (pressure, wall shear stress, diameter, blood velocity and flow, viscosity, haematocrit, partial oxygen saturation, oxygen saturation, wall thickness, and local vessel density). Tortuosity was assessed quantitatively with a validated algorithm and correlation computed with subsets of hemodynamic parameters selected by a lasso regressor.Results: Results suggest that tortuosity is related to pressure, wall shear stress, diameter, blood velocity, viscosity, partial but not full oxygen saturation, and wall thickness for the arteries; diameter, blood flow, hematocrit, and density for the veins; and viscosity (but not hematocrit), partial and full oxygen saturation, and density for the capillaries. The combination of hemodynamic parameters correlating best with tortuosity is the set of all parameters except density (r = 0.64, p < 0.01), using as tortuosity definition the set of tortuosity features (geometric measures) correlating best with a single hemodynamic factor for the arteries.Conclusion: This pilot suggests two general conclusions. First, the quantitative definition of tortuosity (i.e., the set of geometric features adopted) should be tuned to the specific data and problem considered. Second, tortuosity is caused by a combination of hemodynamic factors, not a single one.

A Review On the Effect of Temporal Geometric Variations of the Coronary Arteries On the Wall Shear Stress and Pressure Drop

2021 ◽  
Author(s):  
Navid Freidoonimehr ◽  
Rey Chin ◽  
Anthony C. Zander ◽  
Maziar Arjomandi
Keyword(s):  
Shear Stress ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Coronary Arteries ◽  
Cardiac Cycle ◽  
Temporal Variations ◽  
Hemodynamic Parameters ◽  
Clinical Environment ◽  
Cross Sectional ◽  
Wall Shear

Abstract Temporal variations of the coronary arteries during a cardiac cycle are defined as the superposition of the changes in the position, curvature, and torsion of the coronary artery axis markers and the variations in the lumen cross-sectional shape due to the distensible wall motion induced by the pulse pressure and contraction of the myocardium in a cardiac cycle. This review discusses whether the modelling the temporal variations of the coronary arteries is needed for the investigation of the hemodynamics specifically in time critical applications such as a clinical environment. The numerical modellings in the literature which model or disregard the temporal variations of the coronary arteries on the hemodynamic parameters are discussed. The results in the literature show that neglecting the effects of temporal geometric variations is expected to result in about 5\% deviation of the time-averaged pressure drop and wall shear stress values and also about 20\% deviation of the temporal variations of hemodynamic parameters, such as time-dependent wall shear stress and oscillatory shear index. This review study can be considered as a guide for the future studies to outline the conditions in which temporal variations of the coronary arteries can be neglected, while providing a reliable estimation of hemodynamic parameters.

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.

Longitudinal Effect of Wall Shear Stress on the Amount of Intimal-Medial Thickening of Venous Wall in Arteriovenous Fistula

2012 ◽  
Author(s):  
Ehsan Rajabi-Jaghargh ◽  
Prabir Roy-Chaudhury ◽  
Mahesh K. Krishnamoorthy ◽  
Yang Wang ◽  
Rupak K. Banerjee
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Arteriovenous Fistula ◽  
Hemodynamic Parameters ◽  
Temporal Gradient ◽  
Post Surgery ◽  
Venous Stenosis ◽  
Venous Diameter ◽  
Consistent Increase ◽  
Wall Shear

Arteriovenous fistula (AVF) maturation failure is mainly due to venous stenosis characterized by significant amount of intima-media thickening (IMT). Although hemodynamic endpoints are believed to play a crucial role in pathogenesis of venous stenosis, the exact mechanism behind this is unclear. Our hypothesis is that longitudinal (temporal) changes of hemodynamic parameters, specifically wall shear stress (WSS), influences amount of IMT in maturation process of AVF. AVFs were created in curved (C-AVF) and straight (S-AVF) configurations between femoral artery and vein of 3 pigs. CT-scans and ultrasound were utilized to calculate WSS at 2D (D: days), 7D, and 28D post-surgery. IMT was measured at 4 histological blocks along the vein of AVFs. It was found that C-AVF underwent outward remodeling characterized by consistent increase in venous diameter and larger IMT. This remodeling process was governed by negative temporal gradient of WSS (τ′) [−0.99 ± 0.60 dyn/cm2/day]. In contrast, S-AVF underwent inward remodeling characterized by temporal decrease in venous diameter and relatively smaller IMT. This remodeling process was governed by positive τ′ (0.42 ± 0.6 dyn/cm2/day). In summary, temporal gradient of WSS influences IMT. Temporal decrease of WSS in C-AVF resulted in vasodilation and outward growth of wall (favorable to maturation). However, temporal increase in WSS in S-AVF leaded to vasoconstriction and inward growth of wall (detrimental to maturation). Thus, clinically it can be of great importance to surgeons to create AVF in a configuration that can result in favorable hemodynamic parameters and histological end-points.

Numerical Simulation of Flow-Induced Wall Shear Stress of a One Strand Tundish Design

2011 ◽  
Vol 402 ◽  
pp. 85-89 ◽  
Author(s):  
Zhi Bing Tian ◽  
Yan Jin ◽  
Hong Yu Li
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Shear Stress ◽  
Service Life ◽  
Wall Shear Stress ◽  
Design Parameters ◽  
Horizontal Distance ◽  
Wall Shear

In this paper, the flow-induced wall shear stress on the wall of a one Strand tundish has been computed by a 3-D mathematical model. Different design parameters of the tundish such as HB(the height of the dam) and DB(the horizontal distance between the dam and the outlet of the tundish) are studied by analyzing the flow-induced wall shear stress. After a series of calculation, A modification in design parameters (DB and HB )of the tundish can reduce the wall shear stress, thus may help to improve the service life of the tundish.

scholarly journals Developing Pulsatile Flow in a Deployed Coronary Stent

2005 ◽  
Vol 128 (3) ◽  
pp. 347-359 ◽  
Author(s):  
Divakar Rajamohan ◽  
Rupak K. Banerjee ◽  
Lloyd H. Back ◽  
Ashraf A. Ibrahim ◽  
Milind A. Jog
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Pulsatile Flow ◽  
Thrombus Formation ◽  
Three Dimensional ◽  
Tissue Growth ◽  
Coronary Stent ◽  
Stress Distributions ◽  
Hemodynamic Parameters ◽  
Wall Shear

A major consequence of stent implantation is restenosis that occurs due to neointimal formation. This patho-physiologic process of tissue growth may not be completely eliminated. Recent evidence suggests that there are several factors such as geometry and size of vessel, and stent design that alter hemodynamic parameters, including local wall shear stress distributions, all of which influence the restenosis process. The present three-dimensional analysis of developing pulsatile flow in a deployed coronary stent quantifies hemodynamic parameters and illustrates the changes in local wall shear stress distributions and their impact on restenosis. The present model evaluates the effect of entrance flow, where the stent is placed at the entrance region of a branched coronary artery. Stent geometry showed a complex three-dimensional variation of wall shear stress distributions within the stented region. Higher order of magnitude of wall shear stress of 530dyn∕cm2 is observed on the surface of cross-link intersections at the entrance of the stent. A low positive wall shear stress of 10dyn∕cm2 and a negative wall shear stress of −10dyn∕cm2 are seen at the immediate upstream and downstream regions of strut intersections, respectively. Modified oscillatory shear index is calculated which showed persistent recirculation at the downstream region of each strut intersection. The portions of the vessel where there is low and negative wall shear stress may represent locations of thrombus formation and platelet accumulation. The present results indicate that the immediate downstream regions of strut intersections are areas highly susceptible to restenosis, whereas a high shear stress at the strut intersection may cause platelet activation and free emboli formation.

Sensitivity of Hemodynamic Parameters to Waveform, Flow Division, and Head Rotation in the Human Carotid Bifurcation

2008 ◽  
Author(s):  
Yannis Papaharilaou ◽  
Ioannis Seimenis ◽  
John Ekaterinaris ◽  
Georgios Georgiou ◽  
Eleni Eracleous ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Head Rotation ◽  
Carotid Bifurcation ◽  
Hemodynamic Parameters ◽  
Flow Waveform ◽  
Temporal Gradient ◽  
Wall Shear ◽  
Flow Division ◽  
Human Carotid

Hemodynamic parameters such as time averaged wall shear stress (TAWSS), wall shear stress temporal gradient (WSSTG) and Oscillatory Shear Index (OSI) have previously been cited as parameters associated with the development of atherosclerotic disease at the human carotid bifurcation [1,2]. The sensitivity of these important parameters however, with variations of driving flow waveform, flow division and posture changes are not well known. To investigate these changes, we have used image based CFD, to analyze the flowfield of the carotid bifurcation of a healthy volunteer for five different input waveforms, three flow division ratios and two head postures.

Numerical Simulation of Flow Distribution and Wall Shear Stress Downstream from an Orifice

2016 ◽  
Vol 2016.21 (0) ◽  
pp. D113
Author(s):  
Shungo MATSUMURA ◽  
Takahiro KIWATA ◽  
Atsusi KAWAI ◽  
Yoichi UTANOHARA ◽  
Takaaki KONO
Keyword(s):  
Numerical Simulation ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Flow Distribution ◽  
Wall Shear
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