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Mixing Layers in Sink Flow: Effect of Length of Flight on Mixing in a Channel Downstream
KTH, School of Engineering Sciences (SCI), Mechanics.ORCID iD: 0000-0002-2906-9306
2009 (English)In: Flow Turbulence and Combustion, ISSN 1386-6184, E-ISSN 1573-1987, Vol. 82, no 3, 407-433 p.Article in journal (Refereed) Published
Abstract [en]

We have experimentally and analytically studied transport of a passive scalar in the wake of a thin flat plate located at the centerline of a planar contraction with flat walls. The constant Launder parameter in the contraction, K = 6.25 x10 (-aEuro parts per thousand 6), was twice the value required for a turbulent boundary layer to relaminarize. In addition to the mixing analysis inside the contraction, layer mixing is also investigated downstream, where the flow continues inside a constant cross-section channel. In order to generate the passive scalar, the airflow above the plate was heated and the temperature stratification in the wake was traced by measuring the temperature field using constant current anemometry. Using different plate lengths, we found that the degree of mixing, obtained at a given position in the straight channel, is a function of the distance from the plate trailing edge to the contraction outlet. For a plate which does not protrude into the straight channel, we demonstrate the existence of an optimal trailing edge-contraction outlet distance that results in the lowest possible degree of mixing at a given downstream position in the straight channel. This finding is also supported by a semi-empirical relationship based on our developed self-similar solution for mixing layers in planar contractions.

Place, publisher, year, edition, pages
2009. Vol. 82, no 3, 407-433 p.
Keyword [en]
Flat plate wake, Planar contraction, Favorable pressure gradient, Mixing layer, Passive scalar, Hot-wire anemometry, turbulent boundary-layers, plane wakes, self-similarity, contraction, equilibrium, laminar
URN: urn:nbn:se:kth:diva-18283DOI: 10.1007/s10494-008-9185-8ISI: 000264519900007ScopusID: 2-s2.0-63049097458OAI: diva2:336329
QC 20100525Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2011-01-13Bibliographically approved

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