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Research Papers

Analysis of Flow Patterns in a Patient-Specific Aortic Dissection Model

[+] Author and Article Information
Z. Cheng, F. P. P. Tan, N. B. Wood

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

C. V. Riga, C. D. Bicknell, M. S. Hamady, R. G. J. Gibbs

Vascular Surgical Unit, St. Mary’s Hospital, Imperial College Healthcare NHS Trust, London W2 1NY, UK

X. Y. Xu1

Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UKyun.xu@imperial.ac.uk

1

Corresponding author.

J Biomech Eng 132(5), 051007 (Mar 29, 2010) (9 pages) doi:10.1115/1.4000964 History: Received March 06, 2009; Revised January 07, 2010; Posted January 11, 2010; Published March 29, 2010; Online March 29, 2010

Aortic dissection is the most common acute catastrophic event affecting the thoracic aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent aneurysmal dilatation of the thoracic aorta. This study aimed at gaining more detailed knowledge of the flow phenomena associated with this condition. Morphological features and flow patterns in a dissected aortic segment of a presurgery type B dissection patient were analyzed based on computed tomography images acquired from the patient. Computational simulations of blood flow in the patient-specific model were performed by employing a correlation-based transitional version of Menter’s hybrid k-ε/k-ω shear stress transport turbulence model implemented in ANSYS CFX 11 . Our results show that the dissected aorta is dominated by locally highly disturbed, and possibly turbulent, flow with strong recirculation. A significant proportion (about 80%) of the aortic flow enters the false lumen, which may further increase the dilatation of the aorta. High values of wall shear stress have been found around the tear on the true lumen wall, perhaps increasing the likelihood of expanding the tear. Turbulence intensity in the tear region reaches a maximum of 70% at midsystolic deceleration phase. Incorporating the non-Newtonian behavior of blood into the same transitional flow model has yielded a slightly lower peak wall shear stress and higher maximum turbulence intensity without causing discernible changes to the distribution patterns. Comparisons between the laminar and turbulent flow simulations show a qualitatively similar distribution of wall shear stress but a significantly higher magnitude with the transitional turbulence model.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

A cross-sectional CT image with arrows indicating the tear between true and false lumen, the ascending aorta, and the spine

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Figure 2

Geometrical description of the aortic dissection model. Panels (a)–(c) show the reconstructed model from different oblique view angles (R-A: right-anterior, L-P: left-posterior, R-P: right-posterior), and (d) shows the transparent view of the model and locations of the tear and the outlet plane

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Figure 3

Volumetric flow rate used at the inlet of the aortic dissection model (data extracted from Ref. 34)

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Figure 4

Particle paths of blood flow in the aortic dissection model (left: right-anterior view, right: left-posterior view)

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Figure 5

Path lines of four particles released from different cross sections of the ascending aorta. (a)–(f) present the path lines and locations of particles at the end of fifth cycle from six cross sections, respectively, in the order of distance from the model inlet.

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Figure 6

TAWSS contours in the aortic dissection model (maximum value of 17.98 Pa) (left: right-anterior view; right: left-posterior view)

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Figure 7

OSI contours in the aortic dissection model (left: right-anterior view; right: left-posterior view)

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Figure 8

Turbulence intensity isosurfaces of Newtonian model in the aortic dissection at midsystolic deceleration

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Figure 9

Pressure contours in the aortic dissection model at peak systole (left: right-anterior view; right: left-posterior view)

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Figure 10

Turbulence intensity isosurfaces of non-Newtonian model in the aortic dissection at midsystolic deceleration

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Figure 11

TAWSS contours of the laminar flow model (left) and transitional model (right). The scales have been chosen to show direct comparison between laminar and transitional flows, but the differing peak levels have been highlighted.

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