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Research Papers

Analysis of Flow Disturbance in a Stenosed Carotid Artery Bifurcation Using Two-Equation Transitional and Turbulence Models

[+] Author and Article Information
F. P. Tan, G. Soloperto, N. B. Wood, X. Y. Xu

Department of Chemical Engineering, Imperial College London, South Kensington Campus, London, SW7 2AZ, UK

S. Bashford, S. Thom, A. Hughes

National Heart and Lung Institute, International Centre for Circulatory Health, Imperial College London, 59-61 North Wharf Road, Paddington, London, W2 1LA, UK

J Biomech Eng 130(6), 061008 (Oct 10, 2008) (12 pages) doi:10.1115/1.2978992 History: Received October 05, 2007; Revised March 01, 2008; Published October 10, 2008

In this study, newly developed two-equation turbulence models and transitional variants are employed for the prediction of blood flow patterns in a diseased carotid artery where the growth, progression, and structure of the plaque at rupture are closely linked to low and oscillating wall shear stresses. Moreover, the laminar-turbulent transition in the poststenotic zone can alter the separation zone length, wall shear stress, and pressure distribution over the plaque, with potential implications for stresses within the plaque. Following the validation with well established experimental measurements and numerical studies, a magnetic-resonance (MR) image-based model of the carotid bifurcation with 70% stenosis was reconstructed and simulated using realistic patient-specific conditions. Laminar flow, a correlation-based transitional version of Menter’s hybrid kϵkω shear stress transport (SST) model and its “scale adaptive simulation” (SAS) variant were implemented in pulsatile simulations from which analyses of velocity profiles, wall shear stress, and turbulence intensity were conducted. In general, the transitional version of SST and its SAS variant are shown to give a better overall agreement than their standard counterparts with experimental data for pulsatile flow in an axisymmetric stenosed tube. For the patient-specific case reported, the wall shear stress analysis showed discernable differences between the laminar flow and SST transitional models but virtually no difference between the SST transitional model and its SAS variant.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 2

Comparison of inlet velocity waveforms between numerical simulations and the experimental work of Ahmed and Giddens (15). T1–T5 were the time points selected for analysis.

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Figure 3

Velocity waveform used as the inlet boundary condition for the patient-specific model

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Figure 4

Geometry of the idealized stenosed tube with shown axial positions used for the comparison of flow parameters

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Figure 5

Geometry of the patient-specific carotid artery model and locations of cross sections where comparisons were made

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Figure 6

Axial velocity profiles of the idealized stenosed tube at different axial positions taken at peak velocity, T5

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Figure 7

Axial velocity flow profiles of the idealized stenosed tube at different axial positions taken at midacceleration, T2

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Figure 8

Axial wall shear stress profiles of the idealized stenosed tube at the peak velocity. The wall shear stress was normalized by the blood density and the square of the mean velocity.

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Figure 9

Turbulence intensity profiles of the idealized stenosed tube at different axial positions taken at the peak velocity, T5

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Figure 11

Isosurfaces of the flow separation zone and possible reattachment points of the patient-specific model. As both transitional models gave similar results, only one representation is shown.

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Figure 12

OSI contours of the patient-specific model. As both transitional models gave similar results, only one representation is shown.

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Figure 13

Turbulence intensity profiles of the patient-specific model at different cross sections taken at the (a) peak velocity and (b) at mid-deceleration

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Figure 1

Turbulence intensity profiles at three axial positions (Z=2.5, 4.0, and 6.0) of the idealized model for different inlet Tu. The flow was steady with an inlet Re of 1000. Experimental data of Ahmed and Giddens (24) are shown for comparison.

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Figure 10

TAWSS contours of the patient-specific carotid artery model. As both transitional models gave similar results, only one representation is shown. The scale for the inset figure is on the upper left.

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