Adel M Malek

Alexandra Lauric

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Copyright © 2012 by ASME 1 
Introduction 
Research by the Malek  Computational Hemodynamics Laboratory has 
focused on using computational fluid dynamic (CFD) tools to gain an 
improved insight of the mechanical environment faced by endothelial 
cells in and around cerebrovascular atherosclerotic and aneurysmal 
lesions.  More recently, we have been interested in studying the effect 
of endovascular therapies such as aneurysm-occluding coils and 
intravascular stents on local microhemodynamics.    
 
Methods 
Meshing was performed using three different methods: 1) by using the 
commercial meshing capability of Star-CCM (CD-Adapco) to obtain a 
polyhedral mesh (988,000 faces / 128,000 polyhedral elements) with 
prismatic enhancement on the wall, 2) by using the commercial 
mesher Harpoon (Sharc) to generate a tetrahedral mesh (3,400,000 
faces / 1,640,000 tetrahedral elements) with boundary layer 
enhancement on the wall using 3 layers at a 1.2 expansion ratio and 
local refinement based on Gaussian curvature and proximity, 3) by 
using the mesh generated in 2) and performing a polyhedral domain 
conversion using Fluent (Ansys) to obtain a final polyhedral mesh 
containing (2,200,000 faces / 351,000 polyhedral elements). 
Solver used was the finite volume solver Fluent v.13 in all cases 
running in double precision mode on a quad-core Intel Core i7 or dual 
quad-core Intel Xeon workstation in the Microsoft Windows 64 
environment.  Solver was pressure-based using Simple pressure-
velocity coupling with using node-based (for tetrahedral) and cell-
based (for polyhedral) standard pressure and second-order upwind 
spatial discretization.  Transient analysis was by fixed-time stepping 
was used with 200 uniform steps of 0.005 second.  Convergence 
criteria was for residual reaching below 10e-3 for continuity and all 
three components. 
 
 
 
Figure 1: Isovelocity contour (left column; v=50 cm/sec) and Pressure contour 
(right column) for low flow (Q=9.14 mL/sec, top) and high flow (Q=11.42 
mL/sec) using the polyhedral mesh 
 
Results 
Evaluation of the flow pattern within the dome showed a subtle but 
definite dependence of the flow pattern on the mesh density with a 
main vortex near the inflow zone of the aneurysm which led to a 
second less prominent but incomplete vorticial pattern near the more 
 
Adel M. Malek, M.D., Ph.D. and Alexandra Lauric, Ph.D. 
Department of Neurosurgery 
Tufts Medical Center 
Boston, MA 02111 
U.S.A. 
Tufts University School of Medicine 
Boston, MA 02111 
U.S.A. 
 
CFD CHALLENGE: SOLUTIONS USING THE COMMERCIAL FINITE VOLUME SOLVER 
FLUENT ON TETRAHEDRAL AND POLYHEDRAL MESHES 
Proceedings of the ASME 2012 Summer Bioengineering Conference 
SBC2012 
June 20-23, 2012, Fajardo, Puerto Rico 
SBC2012-80938
Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use
Copyright © 2012 by ASME 2 
distal prominence of the dome.  As expected, the higher density 
polyhedral mesh resulted in improved spatial resolution.  Both 
polyhedral meshes converged significantly faster and more completely 
when compared to the tetrahedral mesh resulting in significant 
shortened computational time on the order of 2-4 fold.  
 
 
Figure 2: Centerline pressures at peak systole for the pulsatile cases at (Q = 
9.14 and 11.42 mL/sec). Results from high-density polyhedral mesh. 
 
 
Figure 3: Cycle-averaged centerline pressures along with pressures from the 
two corresponding steady flow cases (Q = 5.13 and 6.41 mL/sec). Results from 
high-density polyhedral mesh. 
 
Discussion 
Analysis using three different types of mesh configurations led to very 
similar centerline pressures with near identical profiles.  In contrast, 
there was greater variability within the aneurysm dome with respect to 
the flow patterns and accordingly, the resulting wall shear stress, 
depending on the type of mesh and density used.  This is an important 
dependence which needs further exploration when determining an 
approch to evaluate wall shear stress pattern and aneurysm 
pathophysiology.   
 
Acknowledgments: 
This work was supported by grant NIH 5R21HL102685-02. 
 
 
 
 
 
 
References: 
[1] Baharoglu, M.I., Schirmer, C.M., Hoit, D.A., Gao, B.L, and Malek, 
A.M., 2010, “Aneurysm Inflow-Angle As A Discriminant For Rupture 
In Sidewall Cerebral Aneurysms: Morphometric and Computational 
Fluid Dynamic Analysis,” Stroke, 41, pp. 1423-1430.  
 
[2] Schirmer, C.M., and Malek, A.M, 2010,  “Critical Influence Of 
Framing Coil Orientation On Intra-Aneurysmal And Neck Region 
Hemodynamics,” Neurosurgery, 67(6), pp 1692-1702.  
 
 
Downloaded From: https://proceedings.asmedigitalcollection.asme.org on 06/29/2019 Terms of Use: http://www.asme.org/about-asme/terms-of-use


CFD Challenge: Solutions Using the Commercial Finite Volume Solver Fluent on Tetrahedral and Polyhedral Meshes

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CFD Challenge: Solutions Using the Commercial Finite Volume Solver Fluent on Tetrahedral and Polyhedral Meshes

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