Characterization and evolution of poststenotic flow disturbances

Khalifa, A.M.A.; Giddens, Don P.

doi:10.1016/0021-9290(81)90038-5

Cited by 120 publications

(39 citation statements)

References 14 publications

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“…The increased pressure losses associated with flow separation can reduce the flow rate and produce ischemia (localized anoxia/absence of oxygen) which is typically used as an indicator for surgical interventions such as stenting, angioplasty and bypass operations. Over the past three to four decades there have been a number of published works on the topic of flow within stenotic pipes, beginning with experimental studies of flows in idealized axisymmetric stenotic tubes (Cassanova & Giddens 1978;Khalifa & Giddens 1981;Ahmed & Giddens 1983, 1984Ojha et al 1989;Ahmed 1998). More recently, computational fluid dynamics has begun to have an impact, through numerical simulations in idealized stenoses, both axisymmetric and non-axisymmetric (Long et al 2001;Mallinger & Drikakis 2002), and of stenotic flows with two-dimensional planar geometries derived from MRI measurements of individual patient geometries (Stroud, Berger & Saloner 2002).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows

2005

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A straight tube with a smooth axisymmetric constriction is an idealized representation of a stenosed artery. We examine the three-dimensional instabilities and transition to turbulence of steady flow, steady flow plus an oscillatory component, and an idealized vascular pulsatile flow in a tube with a smooth 75 % stenosis using both linear stability analysis and direct numerical simulation. Steady flow undergoes a weak Coanda-type wall attachment and turbulent transition through a subcritical bifurcation, leading to hysteretic behaviour with respect to changes in Reynolds number. The pulsatile flows become unstable through a subcritical period-doubling bifurcation involving alternating tilting of the vortex rings that are ejected from the throat with each pulse. These tilted vortex rings rapidly break down through a self-induction mechanism within the confines of the tube. While the linear instability modes for pulsatile flow have maximum energy well downstream of the stenosis, we have established using direct numerical simulation that breakdown can gradually propagate upstream until it occurs within a few tube diameters of the constriction, in agreement with previous experimental observations. At the Reynolds numbers employed in the present study, transition is localized, with relaminarization occurring further downstream. A non-exhaustive investigation has also been undertaken into the receptivity of the axisymmetric shear layer in the idealized physiological pulsatile flow, with the results suggesting it has localized convective instability over part of the pulse cycle.

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Section: Introductionmentioning

confidence: 99%

Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows

2005

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“…This finding is consistent with those obtained in model experiments. 16,17 Before graft occlusion in the second protocol ( figure 8 and table 2), the LAD flow velocity distal to the graft insertion represented a diastolic-predominant pattern, indicating that enough perfusion into myocardium was achieved by the bypass graft. In contrast, a transient graft occlusion caused a marked reduction in the diastolic velocity, while the systolic velocity remained almost unchanged.…”

Section: Therapy and Prevention-coronary Artery Diseasementioning

confidence: 99%

Analysis of flow characteristics in poststenotic regions of the human coronary artery during bypass graft surgery.

et al. 1987

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Poststenotic blood flow velocities were evaluated in nine patients with 75% to 99% stenosis of the left anterior descending coronary artery (LAD) No. 5, 1092No. 5, -1100No. 5, , 1987 PHASIC FLOW in the left coronary artery of animals is high during diastole and remains low during systole. This pattern is thought to be caused by transmural compression of the intramyocardial vessels during systole and by release of the compression force during diastole." 2 Partial obstruction of the left coronary artery in the dog reduced the ratio of diastolic-to-systolic flow as measured by an electromagnetic flowmeter. 3 However, measurements of phasic poststenotic blood flow velocity in a human native coronary artery have been hampered by methodologic limitations. In addition, the velocity profile across the vessel in the poststenotic region has not been clarified in man or in animals.

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“…In healthy vessels in generally we have a laminar flow, but in the narrowed vessel can lead to relatively highReynolds numbers and disturbed flow. A large number of experimental studies [12][13][14] and computational [15][16][17] studies of the hemodynamics in diseased arteries exhibit disordered and turbulent flows in such vessels. Turbulence can significantly affect the pressure and shear stress downstream of the stenosis [18].…”

Section: Computational Fluid Dynamicsmentioning

confidence: 99%

Blood flow simulations in patient-specific coronary bypass grafts

Bernad¹,

Craina²,

Bernad

2013

WIT Transactions on Information and Communication Technologies

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The purpose of this paper was to investigate the hemodynamic parameters associated with the blood flow in failed coronary venous bypass grafts using a computational fluid dynamics (CFD) technique. A narrowed section creates bypass graft constriction and disturbed flow. This change of the flow direction alters significantly the local hemodynamic parameters. In this paper, a patient specific three-dimensional bypass model is used to investigate blood flow in narrowed venous bypass grafts so as to understand the detailed flow physics of the transition to turbulence downstream of the graft narrowed section. Results of the simulation show that successive curvature and sudden narrowing of the bypass graft induce disturbance of the flow profile that produces high local wall shear stress (WSS) and large recirculation regions. Both these parameters create favorable conditions for the initiation of graft failure.

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Characterization and evolution of poststenotic flow disturbances

Cited by 120 publications

References 14 publications

Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows

Three-dimensional instabilities and transition of steady and pulsatile axisymmetric stenotic flows

Analysis of flow characteristics in poststenotic regions of the human coronary artery during bypass graft surgery.

Blood flow simulations in patient-specific coronary bypass grafts

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