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Research Papers

Evaluation of Different Meshing Techniques for the Case of a Stented Artery

[+] Author and Article Information
Azadeh Lotfi

Department of Mechanical and
Manufacturing Engineering,
University of New South Wales,
Sydney, NSW 2052, Australia
e-mail: a.lotfi@unsw.edu.au

Anne Simmons

Department of Mechanical and
Manufacturing Engineering,
University of New South Wales,
Sydney, NSW 2052, Australia
e-mail: a.simmons@unsw.edu.au

Tracie Barber

Department of Mechanical and
Manufacturing Engineering,
University of New South Wales,
Sydney, NSW 2052, Australia
e-mail: t.barber@unsw.edu.au

Manuscript received September 18, 2015; final manuscript received December 17, 2015; published online January 29, 2016. Assoc. Editor: Ender A. Finol.

J Biomech Eng 138(3), 031005 (Jan 29, 2016) (8 pages) Paper No: BIO-15-1465; doi: 10.1115/1.4032502 History: Received September 18, 2015; Revised December 17, 2015

The formation and progression of in-stent restenosis (ISR) in bifurcated vessels may vary depending on the technique used for stenting. This study evaluates the effect of a variety of mesh styles on the accuracy and reliability of computational fluid dynamics (CFD) models in predicting these regions, using an idealized stented nonbifurcated model. The wall shear stress (WSS) and the near-stent recirculating vortices are used as determinants. The meshes comprise unstructured tetrahedral and polyhedral elements. The effects of local refinement, as well as higher-order elements such as prismatic inflation layers and internal hexahedral core, have also been examined. The uncertainty associated with individual mesh style was assessed through verification of calculations using the grid convergence index (GCI) method. The results obtained show that the only condition which allows the reliable comparison of uncertainty estimation between different meshing styles is that the monotonic convergence of grid solutions is in the asymptotic range. Comparisons show the superiority of a flow-adaptive polyhedral mesh over the commonly used adaptive and nonadaptive tetrahedral meshes in terms of resolving the near-stent flow features, GCI value, and prediction of WSS. More accurate estimation of hemodynamic factors was obtained using higher-order elements, such as hexahedral or prismatic grids. Incorporating these higher-order elements, however, was shown to introduce some degrees of numerical diffusion at the transitional area between the two meshes, not necessarily translating into high GCI value. Our data also confirmed the key role of local refinement in improving the performance and accuracy of nonadaptive mesh in predicting flow parameters in models of stented artery. The results of this study can provide a guideline for modeling biofluid domain in complex bifurcated arteries stented in regards to various stenting techniques.

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Figures

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Fig. 1

Stented artery with a single repeating unit of stent used for simulation

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Fig. 2

Different mesh configurations used to discretize the geometry of stented vessel

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Fig. 3

Comparison of grid solutions obtained based on awa_WSS values: (a) results are normalized by the extrapolated value for tetrahedral mesh styles with or without prism layer and (b) percentage of actual fractional error for all the mesh styles considered

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Fig. 4

Variation of error with grid refinement factor obtained on the three finest grid solutions using Conv_Tet mesh

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Fig. 5

(a) Schematic view of the stent strut exposed to elevated WSS (locations over the stent strut surface) and recirculating vortices (locations between and beyond the stent struts) and (b)–(d) WSS distribution on two lines (lines A and B, shown in the schematic view) in the axial direction of the flow using various mesh configurations

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Fig. 6

Percentage of arterial surface exposed to near-stent recirculation using various mesh styles

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