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Title:
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Coherent structures in oscillatory flows within the laminar-to-turbulent transition regime for smooth and rough walls
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Author:
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Mujal Colilles, Anna; Christensen, Kenneth T.; Bateman Pinzón, Allen; Garcia, Marcelo Horacio
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Other authors:
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Universitat Politècnica de Catalunya. Departament d'Enginyeria Civil i Ambiental; Universitat Politècnica de Catalunya. LIM/UPC - Laboratori d'Enginyeria Marítima; Universitat Politècnica de Catalunya. GITS - Modelització Integral de Conques i Transport de Sediments |
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Abstract:
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This is an Accepted Manuscript of an article published by Taylor & Francis Group in [Journal of hydraulic research] on [2016], available online at: http://www.tandfonline.com/10.1080/00221686.2016.1174960 |
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Abstract:
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We investigate coherent structures present in oscillatory boundary layers over smooth and rough beds for Reynolds numbers between 103 and 104, in the transition to turbulence regime. A two-camera 2D- particle image velocimetry (PIV) system was used to visualize coherent structures in an oscillatory-flow tunnel. The obtained results show that smooth-bed flow is populated by vortex-tube structures that are formed due to the Kelvin–Helmholtz instability. Three types of coherent structures are observed in the rough-wall experiments: vortices randomly distributed in space; turbulent bursts – spatial structures without a clear shape compared to vortices but with a longer life than the former; and shear layers of vortices originating due to flow separation from some of the grains on the bed. The reported study contributes to the description of coherent structures in oscillatory flows that are captured with the PIV technique, particularly a new structure in flows over rough beds in the transition to turbulence regime. |
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Abstract:
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Peer Reviewed |
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Subject(s):
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-Àrees temàtiques de la UPC::Física::Física de fluids::Flux de fluids
-Turbulence--Measurement
-Boundary layer turbulence
-coherent structures
-oscillatory flows
-particle image velocimetry (PIV)
-transition to turbulence
-Turbulència -- Mesurament |
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Rights:
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Document type:
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Article - Submitted version
Article |
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