Effects of three geometrical parameters on pulsatile blood flow in complete idealised coronary bypasses

Vimmr, Jan; Jonášová, Alena; Bublík, Ondřej

doi:10.1016/j.compfluid.2012.08.007

Cited by 11 publications

(31 citation statements)

References 29 publications

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“…As the degree of stenosis increased, the use of the bypass became more effective. These findings were consistent with those of Ko et al 14 and Vimmr et al, 19 who asserted that stenosis degree smaller than 50% was commonly described as hemodynamically insignificant because there was no impact on the blood supply to downstream tissues. Furthermore, according to Fan et al, 21 the resistance and induce a small pressure gradient from the inlet of a bypass, causing a competitive flow through it and reducing its long-term patency.…”

Section: Velocity Fieldssupporting

confidence: 92%

“…These results showed that the diameter ratio D 1 /D had a more significant effect on the pressure drop than α. The prominent influence of the D 1 /D ratio compared to the α angle had been confirmed experimentally 45 and numerically [17][18][19] in idealized steady and pulsatile stenotic flows. Tsukui et al 45 also confirmed that a smaller junction angle (α) yielded lower energy loss at bypass graft.…”

Section: Model Verificationmentioning

confidence: 72%

“…Because of this phenomenon bypass surgery tends to fail after some years, being well recognized that nonuniform hemodynamics contributes to restenosis and the risk of thrombosis due to the possibility of blood cell accumulation. 19,46 Jet blood flow was observed in the poststenotic region (x̃= 0), especially at severe degrees of stenosis (S = 75%) and when D 1 /D had lower values. The complexity of these flow patterns had been analyzed in the most recent studies in the hemodynamic area at stenotic arteries without bypass graft.…”

Section: Velocity Fieldsmentioning

confidence: 98%

“…Blood is modeled as an incompressible Newtonian fluid with density of ρ = 1000 kg/m³ and dynamic viscosity of μ = 0.0035 Pa.s. 14 The assumption of blood as Newtonian fluid is acceptable and used by other studies in the hemodynamic area, for example, Ko et al, 14,16 Xiong and Chong, 17 and Vimmr et al 19 Constructal theory assumes that living systems evolve limited by space. 31 Accordingly, constructal theory systems must evolve in order to provide easier access to its flows.…”

Section: Introductionmentioning

confidence: 99%

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Constructal design of an arterial bypass graft

et al. 2020

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Section: Velocity Fieldssupporting

confidence: 92%

Section: Model Verificationmentioning

confidence: 72%

Section: Velocity Fieldsmentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

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Constructal design of an arterial bypass graft

et al. 2020

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“…The space discretisation of the system of Equations is performed with the cell‐centred finite volume method for hybrid unstructured tetrahedral grids . The hybrid grid system defines the values of pressure and Cartesian velocity components in the centre of the control volume Ω k , and the values of face‐normal velocity V m , which have the direction of outward unit vector

n_{k}^{m}

normal to the m th face

Γ_{k}^{m}

of the control volume Ω k , are defined in the middle of the face

Γ_{k}^{m}

(Figure ).…”

Section: Methodsmentioning

confidence: 99%

Numerical analysis of non‐Newtonian blood flow and wall shear stress in realistic single, double and triple aorto‐coronary bypasses

Vimmr

Jonášová

Bublík

2013

Numer Methods Biomed Eng

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Considering the fact that hemodynamics plays an important role in the patency and overall performance of implanted bypass grafts, this work presents a numerical investigation of pulsatile non-Newtonian blood flow in three different patient-specific aorto-coronary bypasses. The three bypass models are distinguished from each other by the number of distal side-to-side and end-to-side anastomoses and denoted as single, double and triple bypasses. The mathematical model in the form of time-dependent nonlinear system of incompressible Navier-Stokes equations is coupled with the Carreau-Yasuda model describing the shear-thinning property of human blood and numerically solved using the principle of the SIMPLE algorithm and cell-centred finite volume method formulated for hybrid unstructured tetrahedral grids. The numerical results computed for non-Newtonian and Newtonian blood flow in the three aorto-coronary bypasses are compared and analysed with emphasis placed on the distribution of cycle-averaged wall shear stress and oscillatory shear index. As shown in this study, the non-Newtonian blood flow in all of the considered bypass models does not significantly differ from the Newtonian one. Our observations further suggest that, especially in the case of sequential grafts, the resulting flow field and shear stimulation are strongly influenced by the diameter of the vessels involved in the bypassing.

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A computational fluid dynamics study on hemodynamics for different locations of the distal anastomosis of a bypass nearby a collateral vessel in the femoropopliteal area

Rivera

Graaf

Escudero

et al. 2014

Numer Methods Biomed Eng

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Revascularization of the femoropopliteal sector is often performed by the placement of a bypass. In this paper, we have studied the effects of hemodynamics on patency of the bypass for different positions of the distal anastomosis close to a collateral artery. Computational fluid dynamics (CFD) are used for this study. The cardiac cycle-averaged wall shear stress (WSS) and oscillation index (OSI) have been analyzed. Low WSS and high OSI may increase the risk of intimal hyperplasia (IH), which may reduce bypass patency. From the CFD simulations, spots of low WSS and high OSI are found within and near the entrance of the collateral artery, near the suture line, at the floor, toe, and heel. We regarded flow ratios of 20:80 and of 35:65. It is found that for the high flow ratio anastomosis located proximal to the collateral artery is clearly more advantageous. However for the low flow ratio anastomosis located distal to the collateral artery seems to be slightly more advantageous, the results are less conclusive. One of the studied flow geometries has been validated by in vitro experiments using a time resolved particle image velocimetry technique. Velocity fields from these experiments are in good agreement with the CFD results.

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Effects of three geometrical parameters on pulsatile blood flow in complete idealised coronary bypasses

Cited by 11 publications

References 29 publications

Constructal design of an arterial bypass graft

Constructal design of an arterial bypass graft

Numerical analysis of non‐Newtonian blood flow and wall shear stress in realistic single, double and triple aorto‐coronary bypasses

A computational fluid dynamics study on hemodynamics for different locations of the distal anastomosis of a bypass nearby a collateral vessel in the femoropopliteal area

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