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TECHNICAL PAPERS

Experimental Investigation of the Fluid Motion in a Cylinder Driven by a Flat-Plate Impeller

[+] Author and Article Information
Douglas Bohl

Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY 13699-5725

J. Fluids Eng 129(6), 737-746 (Nov 16, 2006) (10 pages) doi:10.1115/1.2734186 History: Received November 01, 2005; Revised November 16, 2006

The flow field in a cylindrical container driven by a flat-bladed impeller was investigated using particle image velocimetry (PIV). A range of Reynolds numbers (0.005–7200), based on the container radius rw, were investigated using four Newtonian fluids: water (Re=7200,6800), 85/15 glycerin/water mixture (Re=108), pure glycerin (Re=8), and corn syrup (Re=0.02,0.005). Two impellers with a radius of 0.43rw and 0.95rw were used to drive the flow. The 0.43rw impeller was shown to generate a vortex near the tip of the blades. The peak magnitude of the vortices and the size of the vortices in the radial direction decreased with increasing Reynolds number. Additionally, the vortex generated at the high Reynolds number was unsteady with a trailing shear layer that periodically shed vorticity into the flow field. The structure of the flow in the region between the blade and the cylinder wall showed a Reynolds number dependence, though the two lowest Reynolds number (0.02 and 8) flows investigated had quantitatively similar flow structures. These cases were found to have a closed region of reverse flow between the blade tip and the cylinder wall. No recirculating flow was indicated for the Re=108 and 7200 cases. These data indicate that there may be a critical condition below which there is little dependence in the flow structure on the Reynolds number.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 2

Phase-averaged vorticity and velocity vectors for the low, mid, and high Reynolds number cases, half blade. Lined contours show ⟨ωz⟩rw∕Vw=±1,2,3…. Blade rotation is in the counterclockwise direction.

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Figure 3

Phase-averaged tangential velocity and vorticity profiles for the half-blade cases. Blade position (black line) shown schematically with respect to profile location (dashed). Blade tip location indicated by dashed line in plot. Dashed-dotted line in plot is linear velocity profile based on rotational frequency and radial location. Error levels indicated by symbol size.

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Figure 4

Phase-averaged vorticity and velocity vectors for the low, mid, and high Reynolds number cases, full blade. Lined contours show ⟨ωz⟩rw∕Vw=±1,2,3…. Blade rotation is in the counterclockwise direction.

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Figure 5

Phase-averaged tangential velocity and vorticity profiles for the full-blade cases. Blade position (black line) shown schematically with respect to profile location (dashed). Blade tip location indicated by dashed line in plot. Dashed-dotted line in plot is linear velocity profile based on rotational frequency and radial location. Error levels indicated by symbol size.

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Figure 6

Average tangential velocity and vorticity. Blade tip location indicated by dashed line. Linear velocity profile shown by solid black line in velocity profile plot.

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Figure 7

Flow type for the lowest Re cases. Phase indicated. Dashed line indicates mixing blade tip location.

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Figure 8

Mean flow type. Blade tip location indicated by dashed lines.

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Figure 1

Schematic representation of flat-plate mixer apparatus

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