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TECHNICAL PAPERS

Numerical Analysis of Wall Slip Effects on Flow of Newtonian and Non-Newtonian Fluids in Macro and Micro Contraction Channels

[+] Author and Article Information
Alfeus Sunarso

Department of Mechanical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japanalfnarso@rheol.mech.eng.osaka-u.ac.jp

Takehiro Yamamoto, Noriyasu Mori

Department of Mechanical Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan

J. Fluids Eng 129(1), 23-30 (Jun 08, 2006) (8 pages) doi:10.1115/1.2375127 History: Received September 11, 2005; Revised June 08, 2006

We performed numerical simulation to investigate the effects of wall slip on flow behaviors of Newtonian and non-Newtonian fluids in macro and micro contraction channels. The results show that the wall slip introduces different vortex growth for the flow in micro channel as compared to that in macro channel, which are qualitatively in agreement with experimental results. The effects of slip on bulk flow behaviors depend on rheological property of the fluid. For Newtonian fluid, the wall slip always reduces the vortex length, while for non-Newtonian fluid, the strength of the slip determines whether the vortex length is reduced or increased. Analyses on the velocity and stress fields confirm the channel size dependent phenomena, such as the reduction of wall shear stress with the decrease in channel size. With the increase in average shear rate, the Newtonian fluid shows the reduction of wall shear stress that increases in the same trend with slip velocity-wall shear stress function, while for non-Newtonian fluid, the effect of the slip is suppressed by shear thinning effect and, therefore, the reduction of wall shear stress is less sensitive to the change in average shear rate and slip velocity-wall shear stress function.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Channel geometry and boundary conditions

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Figure 2

Shear viscosity η and first normal stress difference N1

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Figure 3

Slip velocity vs as a function shear stress τ for various slip models

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Figure 4

Values of slip velocity (a) and shear stress (b) at the wall for the flow in micro channel at γ̇avg=5s−1. Distance r is measured from the contraction corner (r=1−y for the upstream wall, r=x for the downstream wall).

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Figure 5

Contours of variables near the corner for the flow of non-Newtonian fluid in micro channel at γ̇avg=5s−1, (a) velocity u, (b) shear stress τxy

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Figure 6

Stream line patterns of flow in micro channel at γ̇avg=5s−1 for Newtonian fluid (a) and non-Newtonian fluid (b)

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Figure 7

Effect of wall slip on vortex growth for Newtonian fluid (a) and non-Newtonian fluid (b)

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Figure 8

Profiles of velocity in the flow direction along the centerline at γ̇avg=0.25s−1 for Newtonian fluid (a) and non-Newtonian fluid (b)

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Figure 9

Profiles of velocity in the flow direction along the centerline at γ̇avg=5s−1 for Newtonian fluid (a) and non-Newtonian fluid (b)

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Figure 10

Profiles of velocity in the flow direction at cross section of x=20H at γ̇avg=5s−1 for Newtonian fluid (a) and non-Newtonian fluid (b)

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Figure 11

Profiles of shear stress τxy at cross section of x=20H at γ̇avg=5s−1 for Newtonian fluid (a) and non-Newtonian fluid (b)

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Figure 12

Wall shear stress τw at x=20H as a function of average shear rate γ̇avg for Newtonian fluid (a) and non-Newtonian fluid (b)

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