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Research Papers

Numerical Simulation of Bubble Transport in a Bifurcating Microchannel: A Preliminary Study

[+] Author and Article Information
J. Poornima

S. Vengadesan1

Fluid Mechanics Laboratory,Department of Applied Mechanics,  Indian Institute of Technology Madras, Chennai – 600036, Tamil Nadu, Indiavengades@iitm.ac.in

1

Corresponding author.

J Biomech Eng 134(8), 081005 (Aug 06, 2012) (10 pages) doi:10.1115/1.4006975 History: Received January 12, 2012; Revised June 16, 2012; Posted June 25, 2012; Published August 06, 2012; Online August 06, 2012

In this paper, we present the computational fluid dynamics (CFD) simulations of bubble transport in a first generation bifurcating microchannel. In the present study, the human arteriole is modeled as a two-dimensional (2D) rectangular bifurcating microchannel. The microchannel is filled with blood and a single perfluorocarbon (PFC) bubble is introduced in the parent channel. The simulations are carried out to identify the lodging and dislodging pressures for two nondimensional bubble sizes, Ld (ratio of the dimensional bubble length to the parent tube diameter), that is for Ld  = 1 and Ld  = 2. Subsequently, the bubble transport and splitting behavior due to the presence of symmetry and asymmetry in the daughter channels of the microchannel is studied for these bubble sizes. The splitting behavior of the bubble under the effect of gravity is also assessed and reported here. For the symmetric bifurcation model, the splitting ratio (SR) (ratio of bubble volume in bottom daughter channel to bubble volume in top daughter channel), of the bubble was found to be 1. For the asymmetric model, the splitting ratio was found to be less than 1. The loss in the bubble volume in the asymmetric model was attributed to surface tension effects and the resistance offered by the flow, which led to the bubble sticking and sliding along the walls of the channel. With the increase in roll angle, Φ (angle which the plane makes with the horizontal to study the effects of gravity), there was a decline in the splitting ratio.

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Copyright © 2012 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of the first generation bifurcation symmetric geometry where: W0  = 77.1 μm; L0 , L1  = 462.6 μm; L2 , L3  = 360.828 μm; W1 , W2  = 60.138 μm; θ = 78 deg

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Figure 2

Schematic of the validation microchannel geometry where: θ1 , θ2 , θ3  = 120 deg

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Figure 3

Streamwise velocity plot at 115 μm from the bifurcation point for different mesh sizes

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Figure 4

Volume fraction contours of PFC obtained for different mesh sizes for symmetric geometry

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Figure 5

Volume fraction contours of PFC for Ld  = 1 at a pressure of 852.87 Pa for symmetric geometry

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Figure 6

Volume fraction contours of bubble transport before and after the bifurcation junction for Ld  = 1 at its dislodging pressure of 897.76 Pa for symmetric geometry

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Figure 7

Schematic of the first generation bifurcation asymmetric geometry where: W0  = 77.1 μm; L1  = 462.645 μm; L2  = 510.425 μm; L3  = 373.836 μm; L4  = 336.704 μm; W1  = 60.138 μm; W2  = 30.069 μm; θ = 78 deg

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Figure 8

Volume fraction contours of bubble transport of Ld  = 1 to visualize the bubble sticking and sliding along the walls of the channel for asymmetric geometry

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Figure 9

Illustration of the bubble transport for Ld  = 1 at its lodging pressure of 852.87 Pa for different roll angles, Φ = 0 deg, 30 deg, and 45 deg for symmetric geometry

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