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Investigation of Coherent Stuctures in Active Flow Control over a Backward-Facing step by PIV

Ma, Xingyu and Geisler, Reinhard and Agocs, Janos and Schröder, Andreas (2014) Investigation of Coherent Stuctures in Active Flow Control over a Backward-Facing step by PIV. 16th International Symposium on Flow Visualization, 24. - 28. June 2014, Okinawa, Japan.

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An acoustic tube was designed and implemented in turbulent shear flow over a backward-facing step at Re = 2.0×10^4 with respect to the step height. As an active flow control device, the acoustic tube generated periodic small perturbations at 100 Hz which educed coherent structures into the shear layer to reduce the size of the flow separation. Standard particle image velocimetry (2D-2C- PIV) was employed and the region of interest was 310×70 mm2 in x- and ydirection respectively, which covered the turbulent boundary layer in the step region, the separated shear layer and the reattachment area. In the controlled case, it is shown that the flow separation was suppressed and the reattachment length was reduced by 43.0%. The consecutive phaselocked results presented the generation, entrainment and dissipation of shedding vortices and the development of periodic motions in the turbulent shear layer. Besides, two-point spatial crosscorrelations revealed the shape of growing shear layer and the coherent features. The Reynolds shear stress was increased correspondingly where coherent structures were educed, entrained and dissipated. The associated organized structures extracted by Proper Orthogonal Decomposition (POD) based on their kinetic energy evolve as traveling waves. These coherent structures eventually convey kinetic energy from the mean flow to the fluctuating motions and consequently enhance the momentum transfer in the separated shear layer.

Item URL in elib:https://elib.dlr.de/88401/
Document Type:Conference or Workshop Item (Speech, Poster)
Additional Information:Paper-Nr.: ISFV16-1052
Title:Investigation of Coherent Stuctures in Active Flow Control over a Backward-Facing step by PIV
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Ma, Xingyuxingyu.ma (at) dlr.deUNSPECIFIED
Geisler, Reinhardreinhard.geisler (at) dlr.deUNSPECIFIED
Agocs, Janosjanos.agocs (at) dlr.deUNSPECIFIED
Schröder, Andreasandreas.schroeder (at) dlr.deUNSPECIFIED
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:No
Page Range:pp. 1-21
Series Name:Conference Proceedings on CD-ROM
Keywords:active flow control, coherent structure, turbulent separated flow, backward-facing step, standard Particle Image Velocimetry, phase average, Reynolds shear stress, Proper Orthogonal Decomposition
Event Title:16th International Symposium on Flow Visualization
Event Location:Okinawa, Japan
Event Type:international Conference
Event Dates:24. - 28. June 2014
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:fixed-wing aircraft
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Simulation and Validation
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Experimental Methods
Deposited By: Micknaus, Ilka
Deposited On:30 Jul 2014 17:00
Last Modified:18 Feb 2015 10:39

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