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Rapid diagnosis of flow separation around an axial impeller in a mixing vessel

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Abstract

The relative flows around a flat plate axial impeller in a mixing vessel were visualized directly using a combined image shifting and image de-rotation technique. The image shifting technique used a rotating mirror to produce a velocity bias equal to the blade velocity so that the relative flow field could be studied in a co-axial plane cutting through the 2-dimensional blade section. The technique provides a rapid means of locating local flow separation on the blade. To visualize the relative flow field in the plane of the blade span, an image de-rotation method was used. The method includes using a dove-shaped prism which, when rotated, produce a rotation of an image about the optical axis. It was observed in the relative frame of reference through the prism that a new vortex structure, not reported previously, with vorticity sign opposite to that of the rotation of the shaft, exists near the hub at the high pressure side of the blade.

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Abbreviations

C:

blade chord length (m)

D:

impeller diameter (m)

h:

liquid level measured from impeller centreline (m)

Lb :

separation bubble length (m)

r:

radius (m)

rt :

the impeller tip radius (m)

R:

the distance from the mirror’s rotational axis to the laser sheet (m)

ω:

impeller rotational speed (1/s)

ωm :

mirror rotational speed (1/s)

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Author information

Authors and Affiliations

  1. CSIRO Division of Building, Construction and Engineering, PO Box 56 Highett,, 3190, Victoria, Australia

    J. Wu, L. Pullum & M. C. Welsh

  2. Department of Mechanical Engineering, University of Western Australia, Australia

    R. Yunken

Authors
  1. J. Wu
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  2. L. Pullum
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  3. R. Yunken
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  4. M. C. Welsh
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Additional information

The authors wish to thank the technical assistance provided by A. Kilpatrick, B. Dunstan and M. Scott.

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Wu, J., Pullum, L., Yunken, R. et al. Rapid diagnosis of flow separation around an axial impeller in a mixing vessel. Experiments in Fluids 22, 519–522 (1997). https://doi.org/10.1007/s003480050079

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  • DOI: https://doi.org/10.1007/s003480050079

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