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Research Papers

Numerical Study of Blood Flow at the End-to-Side Anastomosis of a Left Ventricular Assist Device for Adult Patients

[+] Author and Article Information
Ning Yang

Department of Bioengineering, Pennsylvania State University, University Park, PA 16802

Steven Deutsch

Applied Research Laboratory and Department of Bioengineering, Pennsylvania State University, University Park, PA 16802

Eric G. Paterson

Applied Research Laboratory and Department of Mechanical Engineering, Pennsylvania State University, University Park, PA 16802

Keefe B. Manning1

Department of Bioengineering, Pennsylvania State University, University Park, PA 16802kbm10@psu.edu

1

Corresponding author.

J Biomech Eng 131(11), 111005 (Oct 16, 2009) (9 pages) doi:10.1115/1.3212114 History: Received October 16, 2008; Revised May 28, 2009; Published October 16, 2009

We use an implicit large eddy simulation (ILES) method based on a finite volume approach to capture the turbulence in the anastomoses of a left ventricular assist device (LVAD) to the aorta. The order-of-accuracy of the numerical schemes is computed using a two-dimensional decaying Taylor–Green vortex. The ILES method is carefully validated by comparing to documented results for a fully developed turbulent channel flow at Reτ=395. Two different anastomotic flows (proximal and distal) are simulated for 50% and 100% LVAD supports and the results are compared with a healthy aortic flow. All the analyses are based on a planar aortic model under steady inflow conditions for simplification. Our results reveal that the outflow cannulae induce high exit jet flows in the aorta, resulting in turbulent flow. The distal configuration causes more turbulence in the aorta than the proximal configuration. The turbulence, however, may not cause any hemolysis due to low Reynolds stresses and relatively large Kolmogorov length scales compared with red blood cells. The LVAD support causes an acute increase in flow splitting in the major branch vessels for both anastomotic configurations, although its long-term effect on the flow splitting remains unknown. A large increase in wall shear stress is found near the cannulation sites during the LVAD support. This work builds a foundation for more physiologically realistic simulations under pulsatile flow conditions.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of a LVAD anastomosis

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Figure 2

(a) Healthy aorta; (b) proximal configuration with the cannula attached on the ascending aorta; (c) distal configuration with the cannula attached on the aortic arch

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Figure 3

Normalized average velocity error over the computational domain versus normalized grid resolution for different numerical schemes at t=1 s. |US−UA|mean is the mean velocity error between the simulation and analytical results over the computational domain, Umax is the maximum velocity magnitude, Δx is the grid spacing, and Δxfinest is the finest grid spacing.

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Figure 4

(a) Mean streamwise velocity profile and (b) RMS velocity fluctuations in the fully developed turbulent channel flow at Reτ=395

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Figure 5

(a) The effect of grid size on the mean velocity magnitude near the distal cannulation site under operating condition III at the position of r∗=[(Ro∗+Ri∗)/2], ϕ=45 deg; (b) the effect of grid size on the temporal energy spectra at probe 1 for the distal configuration under operating condition II

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Figure 6

Summary of the plane and probe locations used in this study

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Figure 7

Mean velocity contour: (a) condition I; (b) condition II, proximal configuration; (c) condition III, proximal configuration; (d) condition II, distal configuration; and (e) condition III, distal configuration

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Figure 8

Power spectra of the fluctuating velocities at probe 2 for the distal configuration

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Figure 9

The maximum principal normal Reynolds stress at z∗=−0.3, z∗=0, and z∗=0.3 planes for flow condition II: (a) proximal and (b) distal configurations

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Figure 10

Distribution of mean WSS magnitude: (a) condition I; (b) condition II, proximal configuration; (c) condition III, proximal configuration; (d) condition II, distal configuration; and (e) condition III, distal configuration

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