The influence of out-of-plane geometry on pulsatile flow within a distal end-to-side anastomosis

Papaharilaou, Yannis; Doorly, D. J.; Sherwin, Spencer J.

doi:10.1016/s0021-9290(02)00072-6

Cited by 81 publications

(46 citation statements)

References 35 publications

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“…A prismatic boundary-layer mesh was used at the wall to enhance the modelling of viscous flows (Papaharilaou et al 2002); in all cases, it had a thickness of 0.3D. For the simple, single-branch geometry, a mesh of 452 prismatic and 2116 tetrahedral elements was generated.…”

Section: Methodsmentioning

confidence: 99%

Effect of Reynolds number and flow division on patterns of haemodynamic wall shear stress near branch points in the descending thoracic aorta

Kazakidi

Sherwin

Weinberg

2008

J. R. Soc. Interface.

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Atherosclerotic lesions are non-uniformly distributed at arterial bends and branch sites, suggesting an important role for haemodynamic factors, particularly wall shear stress (WSS), in their development. The pattern of lesions at aortic branch sites depends on age and species. Using computational flow simulations in an idealized model of an intercostal artery emerging perpendicularly from the thoracic aorta, we studied the effects of Reynolds number and flow division under steady conditions. Patterns of flow and WSS were strikingly dependent on these haemodynamic parameters. With increasing Reynolds number, WSS, normalized by the fully developed aortic value, was lowered at the sides of the ostium and increased upstream and downstream of it. Increasing flow into the side branch exacerbated these patterns and gave rise to a reversing flow region downstream of the ostium. Incorporation of more realistic geometric features had only minor effects and patterns of mean WSS under pulsatile conditions were similar to the steady flow results. Aspects of the observed WSS patterns correlate with, and may explain, some but not all of the lesion patterns in human, rabbit and mouse aortas.

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Section: Methodsmentioning

confidence: 99%

Effect of Reynolds number and flow division on patterns of haemodynamic wall shear stress near branch points in the descending thoracic aorta

Kazakidi

Sherwin

Weinberg

2008

J. R. Soc. Interface.

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“…4 Flow separation and static zones may occur in arteries and investigation of the issue continues. 5 Notably, however, no attempt appears to have been made in any of the above studies to determine whether a correlation existed between suggested sites of wall damage, or flow separation and actual sites of occurrence of atherosclerosis.…”

Section: Fluid Mechanics and Pathologymentioning

confidence: 99%

Discovery of the Role of Wall Shear in Atherosclerosis

Caro

2009

ATVB

175

114

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Abstract-The suggestion was made in the 1870s that mechanical irritation of the arterial wall is a cause of atherosclerosis, because the changes were chiefly found at points "exposed to the full stress and impact of the blood." The mechanical damage theory persisted until well into the 20th century when, with interest increasing in multidisciplinary research, two fluid mechanical proposals were advanced for the patchy distribution of the lesions. One advocated high-and the other low-wall shear. Arterial wall shear stress levels appeared, however, insufficiently high to damage the endothelium. In contrast, examination of cadaver human arteries, combined with flow studies in models and casts of arteries, implied that the lesions occurred preferentially in regions expected to experience low-wall shear; a mechanism, involving arterial wall lipid metabolism and shear-dependent blood-wall mass transport, was suggested to account for that distribution. These proposals helped stimulate extensive investigation of arterial fluid mechanics/mass transport and vascular biology/pathology, revealing mechanisms that may explain the now widely confirmed preferred occurrence of atherosclerosis in low wall shear regions in adult human beings. Fluid Mechanics and PathologyPolymaths, including Leonhard Euler (1707-1783) and Thomas Young (1773-1829), studied wave propagation in arteries, but they do not appear to have investigated the arterial flow field. Interest in atherosclerosis and the mechanisms that underlay its patchy distribution in arteries increased from the later 19th century onward. However, in contrast to the polymath approach, there was then a tendency toward specialization in engineering and biology/pathology/ medicine, a development unfavorable to research in the essentially multidisciplinary field of arterial fluid dynamics. The specialization largely persisted until the middle of the 20th century, when interest increased in multidisciplinary research. Therefore, it was against a background of specialization that much of the research of the 19th century and first half of the 20th century on blood flow and atherosclerosis was undertaken.It is important to appreciate that wall shear stress and wall shear rate are characteristics of the local flow field. The former is the force applied parallel, or tangential, to a boundary, and the latter is the gradient of velocity normal to the boundary. The wall shear stress is the product of the wall shear rate and the viscosity of the fluid. In citing relevant studies, we comment, where indicated, on instances of incomplete understanding of the fluid mechanics.Several workers suggested that flow separation might occur in the arterial system at, for example, sites of curvature, branching or expansion of the cross-section. Suggested links between flow separation and the development of atherosclerosis included mechanical damage to the wall, 1,2 platelet deposition, 3 and fibrin deposition. 4 Flow separation and static zones may occur in arteries and investigation of the issue conti...

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“…In our case the critical zone of the bypass near the upper wall has lower mean velocity. The introduction of the upstream curvature has been discussed also in Papaharilaou et al [16]. Results in Figure 14 (right) refers to a graft angle of 45…”

Section: A Output Sensitivitymentioning

confidence: 89%

Numerical solution of parametrized Navier–Stokes equations by reduced basis methods

Quarteroni

Rozza

2007

Numerical Methods Partial

143

113

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We apply the reduced basis method to solve Navier-Stokes equations in parametrized domains. Special attention is devoted to the treatment of the parametrized nonlinear transport term in the reduced basis framework, including the case of nonaffine parametric dependence that is treated by an empirical interpolation method. This method features (i) a rapid global convergence owing to the property of the Galerkin projection onto a space W N spanned by solutions of the governing partial differential equation at N (optimally) selected points in the parameter space, and (ii) the offline/online computational procedures that decouple the generation and projection stages of the approximation process.This method is well suited for the repeated and rapid evaluations required in the context of parameter estimation, design, optimization, and real-time control. Our analysis focuses on: (i) the pressure treatment of incompressible Navier-Stokes problem; (ii) the fulfillment of an equivalent inf-sup condition to guarantee the stability of the reduced basis solutions. The applications that we consider involve parametrized geometries, like e.g. a channel with curved upper wall or an arterial bypass configuration.

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The influence of out-of-plane geometry on pulsatile flow within a distal end-to-side anastomosis

Cited by 81 publications

References 35 publications

Effect of Reynolds number and flow division on patterns of haemodynamic wall shear stress near branch points in the descending thoracic aorta

Effect of Reynolds number and flow division on patterns of haemodynamic wall shear stress near branch points in the descending thoracic aorta

Discovery of the Role of Wall Shear in Atherosclerosis

Numerical solution of parametrized Navier–Stokes equations by reduced basis methods

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