Article

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: 1.75). 09/2003; 125(4):445-60. DOI: 10.1115/1.1589774
Source: PubMed

ABSTRACT 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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Available from: Steven H Frankel, Aug 13, 2015
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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.
    Journal of Mechanical Science and Technology 03/2015; 29(8):3549-3560. DOI:10.1007/s12206-015-0752-3 · 0.70 Impact Factor
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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.
    02/2014; 38(2):140-146. DOI:10.5916/jkosme.2014.38.2.140
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    • "On the other hand, since obtaining simultaneous hemodynamic parameters such as the WCS and WSS pulses through in-vivo or even other experimental methods is not an easy task, thus considering FSI and the obtained boundary conditions through experimental methods, based on similar to real physiological conditions, is a very important matter. In studies conducted with regard to arterial stenosis as of yet, some simplifications such as rigidity of the wall (Varghese and Frankel, 2003; Long et al., 2001; Stroud et al., 2002; Chaturani and Ponnalagarsamy, 1986; Chaturani and Ponnalagarsamy, 1985), Newtonian model (Bathe and Kamm, 1999; Tang et al., 1999a, b, 2001a, b), steady flow and constant inlet and outlet pressure (Tang et al., 1999a, b, 2001a, b) were used. However, in this study, the effects of increasing stenosis severity on the variations of WSS and WCS and the correlation between the low mean WSS, high OSI and the large negative SPA are studied. "
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    ABSTRACT: To study the effects of increase in the degree of stenosis severity and subsequent complexity of hemodynamic patterns on hemodynamic parameters, experimental investigations and numerical simulations were performed. The correlations between the large negative Stress Phase Angle (SPA), the low mean Wall Shear Stress (WSS) and high Oscillatory Shear Index (OSI) were investigated at the distal shoulder and post-stenotic regions as the outcomes of elevated stenosis severity. Models included non-Newtonian fluid flow in stenotic arteries with 30-80% symmetrical stenoses. To study the interactions between pulsatile WSS and pulsatile wall circumferential stress (WCS) acting on endothelial cells, SPA as the phase difference between WSS and WCS waves was used. Moreover, the distribution of SPA on the lumen axis was compared to the distributions of the mean WSS and OSI that have been regarded until now as the determinants of atherosclerosis-prone regions. Results indicate that an increase in stenosis severity, not only affects the mean WSS, mean WCS and pulse amplitudes, but also influences the phase difference between them. The SPA is large negative on the distal shoulder and post-stenotic areas where atherosclerotic plaque develops. The increasing stenosis severity and the subsequent increasing complexity of hemodynamic patterns affect the correlation between any of the low mean WSS and high OSI with large negative SPA, such that it not only leads to create and develop some regions where the correlation between any of the low mean WSS and high OSI with large negative SPA is well but also leads to create and develop other regions where such correlations fail.
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