Numerical Modeling of Pulsatile Turbulent Flow in Stenotic Vessels

School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA.
Journal of Biomechanical Engineering (Impact Factor: 1.78). 09/2003; 125(4):445-60. DOI: 10.1115/1.1589774
Source: PubMed


Pulsatile turbulent flow in stenotic vessels has been numerically modeled using the Reynolds-averaged Navier-Stokes equation approach. The commercially available computational fluid dynamics code (CFD), FLUENT, has been used for these studies. Two different experiments were modeled involving pulsatile flow through axisymmetric stenoses. Four different turbulence models were employed to study their influence on the results. It was found that the low Reynolds number k-omega turbulence model was in much better agreement with previous experimental measurements than both the low and high Reynolds number versions of the RNG (renormalization-group theory) k-epsilon turbulence model and the standard k-epsilon model, with regard to predicting the mean flow distal to the stenosis including aspects of the vortex shedding process and the turbulent flow field. All models predicted a wall shear stress peak at the throat of the stenosis with minimum values observed distal to the stenosis where flow separation occurred.

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    • "To check the validity of the solution, the numerical results of the current study were compared with the experimental results of Ahmed and Giddens [15] and the numerical results of Banks and Bressloff [16] and Varghese and Frankel [17], as shown in Fig. 1. Results showed that the numerical results of the current study had better match with the results of Ahmed and Giddens [15] than the numerical results of Banks and Bressloff [16] and Varghese and Frankel [17]. Furthermore, the comparative results indicated that the k-ε standard model was more consistent with the experimental results; therefore, k-ε standard was used in this study. "
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    ABSTRACT: This article investigates the pulsatile and turbulent blood flows in flexible artery with single and double stenoses. The changes in pressure drop, mean wall shear stress (WSS), radial displacement of the artery, and oscillating shear index are investigated. Similar to experimental data, the results of the present study show that a laminar flow occurs for stenosis of up to 70%, and for 80% stenosis the flow is turbulent. The mean WSS analysis shows that assuming the flow is laminar causes more errors than assuming the walls are solid. The comparison of the results for single stenosis with those for double stenosis reveals that the dilation in the arterial walls in double stenoses is much more common than in single stenosis. Therefore, the maximum mean WSS in double stenoses is less than that in single stenosis. The results also indicate that the axial pressure drop in double stenoses is higher than that in single stenosis.
    Full-text · Article · Mar 2015 · Journal of Mechanical Science and Technology
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    • "While blood passes through a stenotic conduit, recirculation zones are generated in the downstream side of the stenosis by an abrupt variation in velocity and pressure. These recirculation zones may damage endothelial cells, leading to a rupture of the blood vessels depending on the flow conditions and morphology of the stenotic structure [2][3]. Therefore, studying the formation of these recirculation zones under different pathological and physiological conditions is very important. "
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    ABSTRACT: Stenosis is the drastic reduction in the cross-sectional area of blood vessel caused by accumulations of cholesterol. It affects the blood flow property and structure from the fluid dynamic point of view. To understand the flow phenomenon more clearly, a particle image velocimetry method is used and the fluid dynamic characteristics in a circular channel containing stenosis structure is investigated experimentally in this study. Different stenotic-structured models made of acrylic material are subjected to a pulsatile flow generated by an in-house designed pulsatile pump. The inner diameter of the tube inlet is 20 mm and the length of reduced area for stenosis ranges between 35mm and 40mm. It is circulated continuously through a circular channel by the pump system. Pressure is measured at four different sections during systolic and diastolic phase changes. The phase-averaged velocity field distribution shows a recirculation regime after the stenotic structure. The effects of the stenotic obstructions are found to be more severe when the aspect ratio is varied.
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    • "In addition, we considered a laminar flow. However, close to the bifurcation and especially in the stenosis region, turbulences, secondary flow, and even flow separation might occur [46]. Due to the grid resolution only larger eddies are considered in our study. "
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    ABSTRACT: Contrast-enhanced first-pass magnetic resonance imaging (MRI) in combination with a tracer kinetic model, for example, MMID4, can be used to determine myocardial blood flow (MBF) and myocardial perfusion reserve (MPR). Typically, the arterial input function (AIF) required for this methodology is estimated from the left ventricle (LV). Dispersion of the contrast agent bolus might occur between the LV and the myocardial tissue. Negligence of bolus dispersion could cause an error in MBF determination. The aim of this study was to investigate the influence of bolus dispersion in a simplified coronary bifurcation geometry including one healthy and one stenotic branch on the quantification of MBF and MPR. Computational fluid dynamics (CFD) simulations were combined with MMID4. Different inlet boundary conditions describing pulsatile and constant flows for rest and hyperemia and differing outflow conditions have been investigated. In the bifurcation region, the increase of the dispersion was smaller than inside the straight vessels. A systematic underestimation of MBF values up to -16.1% for pulsatile flow and an overestimation of MPR up to 7.5% were found. It was shown that, under the conditions considered in this study, bolus dispersion can significantly influence the results of quantitative myocardial MR-perfusion measurements.
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