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Title: PIV study of the flow field generated by a sawtooth impeller
Authors: Unadkat, Heema
Rielly, Chris D.
Nagy, Zoltan K.
Keywords: Particle image velocimetry
Stirred vessels
Energy dissipation
Turbulence
Intermittency
Multifractal model
Issue Date: 2011
Publisher: © Elsevier
Citation: UNADKAT, H., RIELLY, C.D. and NAGY, Z.K., 2011. PIV study of the flow field generated by a sawtooth impeller. Chemical Engineering Science, 66 (21), pp. 5374-5387.
Abstract: Stereoscopic and high-speed particle image velocimetry (PIV) techniques have been employed to study the flow field induced by a sawtooth (EkatoMizer) impeller, operated in the fully turbulent flow regime at an impeller speed of 1500 rpm. Ensemble-averaged mean flow fields and turbulence quantities were calculated for a region close to the impeller blades. The flow was found to be anisotropic near the impeller and exhibited return-to-isotropy behaviour further away from it. Macroinstabilities were found to have a high probability of occurrence in the discharge stream. All three velocity components from the stereo-PIV measurements were used to estimate the dissipation rate, by adopting a large eddy simulation (LES) analogy. Spurious vectors distorting the dissipation rate calculation were identified, and various standard deviation filters were applied for vector validation. By evaluating the filtered dissipation rate profiles against the multi-fractal intermittency model of Meneveau and Sreenivasan (1991), the global standard deviation filter was found to be the most suitable type. The ratio of the maximum to the mean dissipation rate for the EkatoMizer discharge stream was found to be similar to that reported for Rushton disk turbine and pitched-blade turbine impellers in the literature, raising questions about the reported high-shear advantage of sawtooth impellers.
Description: This is the author’s version of a work that was accepted for publication in the journal Chemical Engineering Science. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published at: http://dx.doi.org/10.1016/j.ces.2011.07.046
Version: Accepted for publication
DOI: 10.1016/j.ces.2011.07.046
URI: https://dspace.lboro.ac.uk/2134/11471
Publisher Link: http://dx.doi.org/10.1016/j.ces.2011.07.046
ISSN: 0009-2509
Appears in Collections:Published Articles (Chemical Engineering)

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