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Flow and mixing in swirling flow in a sudden expansion
Author(s) -
Hallett W. L. H.,
Günther R.
Publication year - 1984
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.5450620123
Subject(s) - backflow , mixing (physics) , mechanics , precession , flow (mathematics) , turbulence , tracer , mean flow , isothermal flow , physics , thermodynamics , materials science , geology , open channel flow , inlet , nuclear physics , condensed matter physics , geomorphology , quantum mechanics
Experiments have been performed on swirling air flow in a sudden expansion in a model of a chemical reactor to study the effect of swirl intensity on flow and mixing. At the highest swirl tested a central recirculation zone was formed, while at swirl intensities below the critical value required for central backflow a precession of the flow was discovered in which the flow entering the expansion was deflected away from the axis of symmetry and caused to precess around it. The effect of these flow patterns on the mixing of a tracer gas with the main flow was studied by measuring both time‐mean values and turbulent fluctuations of the concentration. The time‐mean measurements indicated mixing at all swirl levels to be about equally fast, but measurements of fluctuation intensities showed a much higher unmixedness at low swirl, corresponding to the large‐scale motions of the precessing flow.