Control over multiscale mixing in broadband-forced turbulence

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    Abstract

    The effects of explicit flow modulation on the dispersion of a passive scalar field are studied. Broadband forcing is applied to homogeneous isotropic turbulence to modulate the energy cascading and alter the kinetic energy spectrum. Consequently, a manipulation of turbulent flow can be achieved over an extended range of scales beyond the directly forced ones. This modifies transport processes and influences the physical-space turbulent mixing of a passive scalar field. We investigate by direct numerical simulation the stirring-efficiency associated with turbulence modified by forcing. This is quantified by monitoring the surface-area and wrinkling of a level-set of the passive scalar field. We consider different forcing to manipulate the quality and rate of mixing. The instantaneous mixing efficiency measured in terms of surface-area or wrinkling is found to increase when additional energy is introduced at the smaller scales. The increased intensity of small scales significantly influences the small-scale mixing characteristics depicted by wrinkling, while the forcing of large scales primarily affects the surface-area. Evaluation of geometrical statistics in broadband-forced turbulence indicates that the self-amplification process of vorticity and strain is diminished. This leads generally to smaller extremal values of the velocity gradients but higher average values as a result of the competition between the natural cascading processes and the explicit small-scales forcing.
    Original languageUndefined
    Title of host publicationIUTAM symposium on computational physics and new perspectives in turbulence
    Place of PublicationNetherlands
    PublisherSpringer
    Pages131-136
    Number of pages6
    ISBN (Print)978-1-4020-6472-2
    DOIs
    Publication statusPublished - 2008
    EventIUTAM symposium on computational physics and new perspectives in turbulence - Nagoya, Japan
    Duration: 11 Sep 200614 Sep 2006

    Publication series

    NameIUTAM Bookseries
    PublisherSpringer Verlag
    Number11
    Volume4
    ISSN (Print)1875-3507
    ISSN (Electronic)1875-3493

    Conference

    ConferenceIUTAM symposium on computational physics and new perspectives in turbulence
    Period11/09/0614/09/06
    Other11-14 September, 2006

    Keywords

    • EWI-14732
    • IR-65255
    • METIS-238752

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