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Effect of uniform blowing/suction in a turbulent boundary layer at moderate Reynolds number
KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
KTH, School of Engineering Sciences (SCI), Mechanics, Fluid Physics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0002-1663-3553
KTH, School of Engineering Sciences (SCI), Mechanics, Stability, Transition and Control. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.ORCID iD: 0000-0001-9627-5903
2015 (English)In: International Journal of Heat and Fluid Flow, ISSN 0142-727X, E-ISSN 1879-2278, Vol. 55, 132-142 p.Article in journal (Refereed) Published
Abstract [en]

A number of well-resolved large-eddy simulations (LES) of a spatially evolving turbulent boundary layer with uniform blowing or suction is performed in order to investigate the effect on skin friction drag as well as turbulence statistics and spectral composition at moderate Reynolds numbers up to Reθ=2500, based on the free-stream velocity and the momentum-loss thickness. The amplitude of uniform blowing or suction is set to be 0.1% of the free-stream velocity with different streamwise ranges of the controlled region.The boundary layer is thickened by blowing and thinned by suction. The Reynolds shear and normal stresses are increased by blowing and decreased by suction, most prominently, in the outer region. Through spectral analysis of the streamwise velocity and cross-spectra of the Reynolds shear stress, the enhancement and reduction of the fluctuation energy in the outer region by blowing and suction are found, respectively. It is also found that the emergence of a second peak in the outer region is promoted by blowing, while it is inhibited in the case of suction.In spite of the weak amplitude of the control, more than 10% of drag reduction and enhancement are achieved by means of blowing and suction, respectively. In the case of blowing, where drag reduction is achieved, the mean drag reduction rate increases as the blowing region extends because the local reduction rate, i.e.the streamwise gradient of the mean drag reduction rate, grows in the streamwise direction. The net-energy saving rate and the control gain have the same trends. It is found that a more effective skin friction drag reduction and control efficiency can be achieved with a wider control region that starts at a more upstream location.

Place, publisher, year, edition, pages
Elsevier, 2015. Vol. 55, 132-142 p.
Keyword [en]
Drag reduction, Large-eddy simulation, Turbulent boundary layer, Boundary layer flow, Boundary layers, Buoyancy, Drag, Energy conservation, Friction, Large eddy simulation, Reynolds equation, Reynolds number, Shear flow, Shear stress, Skin friction, Spectrum analysis, Turbulence, Fluctuation energies, Free-stream velocity, Moderate Reynolds numbers, Reynolds shear stress, Stream-wise velocities, Streamwise directions, Turbulence statistics, Turbulent boundary layers, Atmospheric thermodynamics
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-175094DOI: 10.1016/j.ijheatfluidflow.2015.05.019ISI: 000364732400014ScopusID: 2-s2.0-84945456169OAI: oai:DiVA.org:kth-175094DiVA: diva2:881813
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20151211. QC 20160113

Available from: 2015-12-11 Created: 2015-10-09 Last updated: 2016-01-13Bibliographically approved

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Kametani, YukinoriÖrlü, RamisSchlatter, Philipp
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