Spatio-temporal Analysis of Macro-instability in a Stirred Tank Reactor via Digital Particle Image Velocimetry (DPIV)

Jianhua Fan, Qi Rao, Yundong Wang, Weiyang Fei

Research output: Contribution to journalJournal articleResearchpeer-review


To characterize the flow instability in mechanically agitated vessels, digital particle image velocimetry (DPIV) was used to measure the near-instantaneous flow fields in a baffled, stirred vessel, equipped with a Rushton turbine impeller of large impeller and vessel diameter ratio. From the measured near-instantaneous flow fields, distinct large-scale flow patterns were identified and the formation mechanisms of the patterns were explored via multi-scale analysis. Further investigations show that the flow patterns are rather complex and unsteady. Macro-instability (MI) appears as a switch among those flow patterns. Spectra distribution function P(f), equivalent to probability distribution function from a purely mathematical point of view, was introduced to extract information on MI from the time series of the vorticity of the fluctuating velocity field. The two-dimensional distribution of MI and its dependence on Reynolds number and measuring plane were studied. Results show that probability analysis via spectra distribution function can be successfully used to quantify the relative intensity of macro-instabilities. Low–frequency, large-scale fluctuations of flow patterns were much intensive in the lower and upper corner of the vessel than in the rest parts of the vessel. The fluctuations of flow patterns also had an offset to the core of the vessel due to the influence of baffles. Compared with visual observation technique, this new analysis method via DPIV is more objective and can be used to give much understanding to the spatio-temporal properties of macro-instability. Keywords: Stirred vessel; Macro-instability (MI); Spatio-temporal analysis; Probability distribution function; Digital particle image veloctimetry (DPIV); Multi-scale complex system
Original languageEnglish
JournalChemical Engineering Science
Issue number8-9
Pages (from-to)1863-1873
Publication statusPublished - 2004
Externally publishedYes


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