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Research Papers

Investigation of Coriolis Forces Effect of Flow Structure and Heat Transfer Distribution in a Rotating Dimpled Channel

[+] Author and Article Information
Mohammad A. Elyyan1

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

Danesh K. Tafti2

Department of Mechanical Engineering, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061

The notation (aj)k is used to denote the kth component of vector aj, (aj)k=ξj/xk.

Henceforth, all usage is in terms of nondimensional quantities unless qualified with an asterisk.

1

Currently a technical services engineer at ANSYS Inc.

2

Corresponding author.

J. Turbomach 134(3), 031007 (Jul 14, 2011) (8 pages) doi:10.1115/1.4003027 History: Received July 08, 2010; Revised July 22, 2010; Published July 14, 2011; Online July 14, 2011

Large-eddy simulations are used to investigate Coriolis forces effect on flow structure and heat transfer in a rotating dimpled channel. Two geometries with two dimple depths are considered, δ=0.2 and 0.3 of channel height, for a wide range of rotation number, Rob=0.00.70, based on mean bulk velocity and channel height. It is found that the turbulent flow is destabilized near the trailing side and stabilized near the leading side, with secondary flow structures generated in the channel under the effect of Coriolis forces. Higher heat transfer levels are obtained at the trailing surface of the channel, especially in regions of flow reattachment and boundary layer regeneration at the dimple surface. Coriolis forces showed a stronger effect on the flow structure for the shallow dimple geometry (δ=0.2) compared with the deeper dimple where the growth and shrinkage of the flow recirculation zone in the dimple cavity with rotation were more pronounced than the deep dimple geometry (δ=0.3). Under the action of rotation, heat transfer augmentation increased by 57% for δ=0.2 and by 70% for δ=0.3 on the trailing side and dropped by 50% for δ=0.2 and by 45% for δ=0.3 on the leading side from that of the stationary case.

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Figures

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Figure 1

Rotating dimpled channel geometry

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Figure 2

2D view of the selected computational domain

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Figure 3

Mean velocity streamlines at a streamwise plane located at the center of the dimple (z=−0.81) for the rotating channel cases for dimple depth δ=0.2 and 0.3 at selected rotation numbers

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Figure 4

Secondary flow at spanwise plane located 0.2D downstream of the dimple for dimple depth δ=0.2 and 0.3 at selected rotation numbers

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Figure 5

Normalized TKE contours at a spanwise plane located 0.2D downstream of the dimple for dimple depth δ=0.2 and 0.3 at selected rotation numbers

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Figure 6

Volume averaged TKE profile for both dimple depths

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Figure 7

Nusselt number augmentation distribution on the trailing surface at Rob=0.0, 0.14, 0.40, 0.60, and 0.71, for dimple depth δ=0.3

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Figure 8

Nusselt number augmentation distribution on the leading surface at Rob=0.0, 0.14, 0.40, 0.60, and 0.71, for dimple depth δ=0.3

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Figure 9

Variation in surface-averaged Nusselt number augmentation versus rotation number on the leading and trailing surfaces for δ=0.2 and 0.3

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Figure 10

Cf/Cfo variation with rotation number for both dimple depths, δ=0.2 and 0.3

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Figure 11

Comparison of Nusselt number augmentation with experimental results of typical surface roughness at (a) trailing side (b) leading side

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