Fluid Mechanics and Transport Phenomena

On the Manifestation and nature of macroinstabilities in stirred vessels

  1. Zacharias Doulgerakis1,
  2. Michael Yianneskis1,
  3. Andrea Ducci2,*

Article first published online: 3 FEB 2011

DOI: 10.1002/aic.12519

Issue

AIChE Journal

AIChE Journal

Volume 57, Issue 11, pages 2941–2954, November 2011

Additional Information

How to Cite

Doulgerakis, Z., Yianneskis, M. and Ducci, A. (2011), On the Manifestation and nature of macroinstabilities in stirred vessels. AIChE J., 57: 2941–2954. doi: 10.1002/aic.12519

Author Information

  1. 1

    Experimental and Computational Laboratory for the Analysis of Turbulence (ECLAT), Div of Engineering King's College London, Strand WC2R 2LS, U.K.

  2. 2

    Dept. of Mechanical Engineering, University College London, Torrington Place, WC1E 7JE, U.K.

*Dept. of Mechanical Engineering University College London, Torrington Place, WC1E 7JE, U.K.

Publication History

  1. Issue published online: 10 OCT 2011
  2. Article first published online: 3 FEB 2011
  3. Accepted manuscript online: 23 DEC 2010 09:47AM EST
  4. Manuscript Revised: 7 DEC 2010
  5. Manuscript Received: 10 MAY 2010

Funded by

  • Engineering and Physical Sciences Research Council (EPSRC) of the UK. Grant Numbers: EP/D032539, EP/E055958

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Keywords:

  • mixing;
  • macroinstability;
  • Pitched blade impeller;
  • stirred vessels

Abstract

The flow variations or macroinstabilities (MIs) occurring in a vessel stirred by a pitched blade turbine (PBT) are studied through particle image velocimetry (PIV) experiments. Proper orthogonal decomposition and fast Fourier transform techniques are applied to the PIV velocity data at one vertical and nine horizontal planes below the impeller, to identify and characterize the flow structures present in the vessel. It is shown that the PBT MI is manifested as a precessional movement around the impeller axis and an oscillation in the direction of the axial mean stream around the shaft axis. The identified flow structures are similar to those previously observed in vessels stirred by Rushton impellers and are characterized by two dominant frequencies, equal to one-tenth and one-fifth of the impeller rotational speed. The nature and extent of these structures and their interaction with the trailing vortices emanating from the turbine blades are discussed. © 2011 American Institute of Chemical Engineers AIChE J, 2011

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