Floc rupture and re-flocculation in turbulent shear flow

Juha Salmela, Markku Kataja

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review


    The dynamics of fibre suspension flow, especially breakup and re-formation of fibre flocs in a closed channel flow past a forward facing step was studied experimentally using fast CCD camera imaging and image analysis techniques that allow for simultaneous measurement of floc size and turbulent flow field of fibres. The recirculation eddy downstream of the expansion step was found to exist only if the step height exceeds the mean fibre length. When existing, the behavior of the eddy is similar to that of Newtonian fluis flows. Experimental correlations between floc size and turbulent flow quantities were found indicating that the ratio of the minimum floc sizefound at the end of the recirculation region and the size upstream of the step is strongly correlated with the size of the largest scales of the turbulent field and less directly with the total turbulent intensity of the flow immediately after the step. In addition, an approximate power law scaling behavior of the floc size with the turbulent intensity was found within the decaying turbulence region downstream of the recirculation eddy.
    Original languageEnglish
    Title of host publicationAdvances in Paper Science and Technology
    Subtitle of host publicationTransactions of the 13th Fundamental Research Symposium
    EditorsS.J. l'Anson
    PublisherPulp & Paper Fundamental Research Society
    Number of pages15
    ISBN (Print)978-0-9545272-3-5, 0-9545272-3-2
    Publication statusPublished - 2005
    MoE publication typeA4 Article in a conference publication
    Event13th Fundamental Research Symposium - Cambridge, United Kingdom
    Duration: 11 Sept 200516 Sept 2005


    Conference13th Fundamental Research Symposium
    Country/TerritoryUnited Kingdom


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