scholarly journals Hemodynamic Analysis on the Anastomosis Angle in Arteriovenous Graft Using Multiphase Blood Model

2021 ◽  
Vol 11 (17) ◽  
pp. 8160
Author(s):  
Ji Tae Kim ◽  
Hyangkyoung Kim ◽  
Hong Sun Ryou
Keyword(s):  
Computed Tomography ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Arteriovenous Graft ◽  
Venous Anastomosis ◽  
Vein Wall ◽  
High Wall Shear Stress ◽  
Anastomosis Site ◽  
Wall Shear ◽  
Tomography Data

Numerical analysis was performed for the effect of the venous anastomosis angle in a forearm arteriovenous graft for hemodialysis using a multiphase blood model. The geometry of the blood vessel was generated based on the patient-computed tomography data. The anastomosis angles were set at 15°, 30°, and 45°. The hematocrit was set at 34%, 45%, and 58%. The larger anastomosis angle, high wall shear stress area >11 Pa, increases to the side of the vein wall away from the anastomosis site. Further, the relatively low wall shear stress area, <3 Pa, occurs near the anastomosis site in larger anastomosis angles. Therefore, the effect of high wall shear stress has advantages in the vicinity of the anastomosis, as the anastomosis angle is larger, but disadvantages as the distance from the anastomosis increases. Moreover, patients with low hematocrit are advantageous for WSS area.

Quantifying Turbulent Wall Shear Stress in an Arteriovenous Graft Using Large Eddy Simulation

2012 ◽  
Author(s):  
L. D. Browne ◽  
P. Griffin ◽  
M. T. Walsh
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Large Eddy Simulation ◽  
Secondary Patency ◽  
Arteriovenous Graft ◽  
Venous Anastomosis ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Wall Shear ◽  
Turbulent Wall

Hemodialysis patients require a vascular access capable of accommodating the high blood flow rates required for effective dialysis treatment. The arteriovenous graft is one such access. However, this access type suffers from reduced one year primary & secondary patency rates of 59–90% and 50–82% respectively [1]. The main contributor to the failure of this access is stenosis via the development of intimal hyperplasia (IH) that predominately occurs at the venous anastomosis. It is hypothesized that the resulting transitional to turbulent flow regime within the venous anastomosis contributes to the development of IH. The aim of this study is to investigate the influence of this transitional to turbulent behavior on wall shear stress within the venous anastomosis via the use of large eddy simulation.

scholarly journals TCT CONNECT-401 Stent Underexpansion Is Associated With High Wall Shear Stress: A Biomechanical Analysis of the Shear Stent Study

2020 ◽  
Vol 76 (17) ◽  
pp. B172
Author(s):  
Sonali Kumar ◽  
David Molony ◽  
Kaylyn Crawford ◽  
Ryan Dunn ◽  
Elizabeth Thompson ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Biomechanical Analysis ◽  
High Wall Shear Stress ◽  
Wall Shear

scholarly journals Targeting functionalized nanoparticles to activated endothelial cells under high wall shear stress

2019 ◽  
Vol 5 (2) ◽  
Author(s):  
Hila Zukerman ◽  
Maria Khoury ◽  
Yosi Shammay ◽  
Josué Sznitman ◽  
Noah Lotan ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Shear Stress ◽  
Wall Shear Stress ◽  
Functionalized Nanoparticles ◽  
High Wall Shear Stress ◽  
Wall Shear

Non-Newtonian Flow Behavior in Microchannels for Emulsion Formation

2006 ◽  
Author(s):  
Ravi Arora ◽  
Eric Daymo ◽  
Anna Lee Tonkovich ◽  
Laura Silva ◽  
Rick Stevenson ◽  
...  
Keyword(s):  
Shear Stress ◽  
Pressure Drop ◽  
Wall Shear Stress ◽  
Power Law ◽  
Flow Behavior ◽  
Scale Up ◽  
High Wall Shear Stress ◽  
Shear Rates ◽  
Wall Shear ◽  
Low Shear

Emulsion formation within microchannels enables smaller mean droplet sizes for new commercial applications such as personal care, medical, and food products among others. When operated at a high flow rate per channel, the resulting emulsion mixture creates a high wall shear stress along the walls of the narrow microchannel. This high fluid-wall shear stress of continuous phase material past a dispersed phase, introduced through a permeable wall, enables the formation of small emulsion droplets — one drop at a time. A challenge to the scale-up of this technology has been to understand the behavior of non-Newtonian fluids under high wall shear stress. A further complication has been the change in fluid properties with composition along the length of the microchannel as the emulsion is formed. Many of the predictive models for non-Newtonian emulsion fluids were derived at low shear rates and have shown excellent agreement between predictions and experiments. The power law relationship for non-Newtonian emulsions obtained at low shear rates breaks down under the high shear environment created by high throughputs in small microchannels. The small dimensions create higher velocity gradients at the wall, resulting in larger apparent viscosity. Extrapolation of the power law obtained in low shear environment may lead to under-predictions of pressure drop in microchannels. This work describes the results of a shear-thinning fluid that generates larger pressure drop in a high-wall shear stress microchannel environment than predicted from traditional correlations.

Positive and Negative Wall Shear Stress Gradients Have Different Effects on Endothelial Phenotype Under High Wall Shear Stress

2011 ◽  
Author(s):  
Jennifer Dolan ◽  
Frasier Sim ◽  
Hui Meng ◽  
John Kolega
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Vessel Wall ◽  
Cerebral Aneurysms ◽  
In Vivo Studies ◽  
Spatial Gradient ◽  
Cerebral Vasculature ◽  
High Wall Shear Stress ◽  
Wall Shear

In both human and animal models, cerebral aneurysms tend to develop at the apices of bifurcations in the cerebral vasculature where the blood vessel wall experiences complex hemodynamics. In vivo studies have recently revealed that the initiation of cerebral aneurysms is confined to a well-defined hemodynamic microenvironment [1,2]. Metaxa et al. [2] found that early aneurysm remodeling initiates where the vessel wall experiences high wall shear stress (WSS) and flow is accelerating, thus creating a positive spatial gradient in WSS (WSSG). Closer examination of such in vivo studies reveals that exposure of the vessel wall to equally high WSS in the presence of decelerating flow, that is, negative WSSG, does not result in aneurysm-like destruction.

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