Control over multiscale mixing by broadband-forced of turbulence

A.K. Kuczaj, B.J. Geurts

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

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 languageEnglish
Title of host publicationProceedings of the IUTAM Symposium on Computational Physics and New Perspectives in Turbulence, September 11-14, 2006, Nagoya, Japan
EditorsY. Kaneda
Place of PublicationDordrecht
PublisherSpringer
Pages131-136
ISBN (Print)978-1-4020-6471-5
DOIs
Publication statusPublished - 2006
Eventconference; The IUTAM Symposium on Computational Physics and New Perspectives in Turbulence, 2006, Nagoya, Japan; 2006-09-11; 2006-09-14 -
Duration: 11 Sep 200614 Sep 2006

Publication series

NameIUTAM Bookseries
Volume4
ISSN (Print)1875-3507

Conference

Conferenceconference; The IUTAM Symposium on Computational Physics and New Perspectives in Turbulence, 2006, Nagoya, Japan; 2006-09-11; 2006-09-14
Period11/09/0614/09/06
OtherThe IUTAM Symposium on Computational Physics and New Perspectives in Turbulence, 2006, Nagoya, Japan

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