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

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 fiel...

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Bibliographic Details
Published in:Experiments in fluids 1997, Vol.22 (6), p.519-522
Main Authors: WU, J, PULLUM, L, YUNKEN, R, WELSH, M. C
Format: Article
Language:English
Subjects:
Applied sciences
Chemical engineering
Exact sciences and technology
Flat plates
Flow separation
Image shifting
Impellers
Local flow
Mixing
Rotating mirrors
Rotating shafts
Vessels
Vorticity
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Summary: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.
ISSN:0723-4864
1432-1114
DOI:10.1007/s003480050079