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TECHNICAL PAPERS: Fluids/Heat/Transport

Pulsatile Flow and Mass Transport Over an Array of Cylinders: Gas Transfer in a Cardiac-Driven Artificial Lung

[+] Author and Article Information
Kit Yan Chan, Hideki Fujioka, James B. Grotberg

Department of Biomedical Engineering, The University of Michigan, Ann Arbor, Michigan 48109

Robert H. Bartlett, Ronald B. Hirschl

Department of Surgery, The University of Michigan Medical School, Ann Arbor, Michigan 48109

J Biomech Eng 128(1), 85-96 (Sep 14, 2005) (12 pages) doi:10.1115/1.2133761 History: Received May 04, 2005; Revised September 14, 2005

The pulsatile flow and gas transport of a Newtonian passive fluid across an array of cylindrical microfibers are numerically investigated. It is related to an implantable, artificial lung where the blood flow is driven by the right heart. The fibers are modeled as either squared or staggered arrays. The pulsatile flow inputs considered in this study are a steady flow with a sinusoidal perturbation and a cardiac flow. The aims of this study are twofold: identifying favorable array geometry/spacing and system conditions that enhance gas transport; and providing pressure drop data that indicate the degree of flow resistance or the demand on the right heart in driving the flow through the fiber bundle. The results show that pulsatile flow improves the gas transfer to the fluid compared to steady flow. The degree of enhancement is found to be significant when the oscillation frequency is large, when the void fraction of the fiber bundle is decreased, and when the Reynolds number is increased; the use of a cardiac flow input can also improve gas transfer. In terms of array geometry, the staggered array gives both a better gas transfer per fiber (for relatively large void fraction) and a smaller pressure drop (for all cases). For most cases shown, an increase in gas transfer is accompanied by a higher pressure drop required to power the flow through the device.

Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 8

Concentration profile and instantaneous streamlines: squared array. The upper plot indicates the concentration contours lines and the lower plot shows the instantaneous streamlines pattern. (a) t=14cycle; (b) t=34cycle; (c) U(t) (α=1; Re=10; A=0.5; ε=0.8036).

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Figure 11

Concentration profile and instantaneous streamlines. The upper plot indicates the concentration contours lines and the lower plot shows the instantaneous stream lines pattern. (a) t=0cycle; (b) t=12cycle; (c) U(t) (α=2; Re=10; A=0.5; ε=0.8036).

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Figure 12

(a) A influence on the surface-average Sherwood number time cycle. (b) A influence on the ΔP∕L time cycle (α=1; Re=10; ε=0.8036).

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Figure 13

(a) Re influence on the surface-average Sherwood number time cycle. (b) Re influence on the ΔP∕L time cycle (α=1; A=0.5; ε=0.8036).

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Figure 14

(a) ε influence on the surface-average Sherwood number time cycle. (b) ε influence on ΔP∕L time cycle (α=1; Re=10; A=0.5).

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Figure 15

Streamline patterns of staggered array with different ε(t=14cycle). (a) ε=0.4973; (b) ε=0.8036.

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Figure 16

Concentration profile and instantaneous stream lines with cardiac U(t): squared array. (a) t=14cycle; (b) t=11∕20cycle; (c) U(t).

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Figure 17

Concentration profile and instantaneous stream lines with cardiac U(t): staggered array. t=14cycle; (b) t=11∕20cycle; (c) U(t).

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Figure 18

The log-log plot of space-average Sherwood vs Reynolds number. The solid symbols represent actual data; the solid line is the least-square fit. (Re=10, ε=0.4986).

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Figure 1

Artificial lung device (reproduced with permission from Michigan Critical Care Consultant Inc., Ann Arbor, MI)

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Figure 2

Fiber arrangement. The unit cell is marked by the dashed lines

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Figure 3

Example of unit cells

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Figure 4

Two functional forms of pulsatile input U(t)

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Figure 5

Gas concentration computational domain and boundary conditions. Dash rectangle represents the computational domain.

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Figure 7

Plot of time-averaged Sherwood number and gas concentration vs fiber layer number. (Square array: α=1; Re=10; A=0.5; ε=0.8036.)

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Figure 9

Concentration profile and instantaneous streamlines: staggered array. The upper plot indicates the concentration contours lines and the lower plot shows the instantaneous streamlines pattern. (a) t=14cycle; (b) t=34cycle; (c) U(t) (α=1; Re=10; A=0.5; ε=0.8036).

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Figure 10

(a) α influence on the surface-average Sherwood number time cycle. (b) α influence on ΔP∕L time cycle (Re=10; A=0.5; ε=0.8036).

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