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Superstructures in a Turbulent Boundary Layer Under the Influence of an Adverse Pressure Gradient Investigated by Large-Scale PIV

Schanz, Daniel and Knopp, Tobias and Schröder, Andreas and Dumitra, Michnea and Kähler, Christian (2014) Superstructures in a Turbulent Boundary Layer Under the Influence of an Adverse Pressure Gradient Investigated by Large-Scale PIV. In: New Results in Numerical and Experimental Fluid Mechanics IX Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 124. Springer Verlag, Cham Heidelberg New York Dordrecht London. pp. 143-151. ISBN 978-3-319-03157-6. ISSN 1612-2909

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Official URL: http://link.springer.com/chapter/10.1007/978-3-319-03158-3_15

Abstract

The flow of a turbulent boundary layer under the influence of an adverse pressure gradient was investigated using a large-scale, high-resolution PIV setup. Wall-normal vector fields with a length of 1.7m (ultimately over 3.0m) and a resolution below one mm were stitched from multiple camera views. Reθ was measured to be 4,600 at the end of a long flat plate preceding the pressure gradient.Within this dataset long, stretched regions with positive or negative streamwise velocity fluctuations can be observed in singular snapshots. These so-called ‘super-structures’ (or ‘very large-scale motions’) were already identified in undisturbed turbulent boundary layers [1], pipe flows [2], and in flows under the influence of an adverse pressure gradient [3, 4]. These measurements either used PIV with a limited measurement region or probe-measurements assuming frozen turbulence. As already described in other publications, a reliable capture of very long flow henomena proved to be problematic due to spanwise meandering. The structures move in and out of the twodimensional measurement plane used in the presented experiment, reducing their perceived extent. However, in many snapshots the meandering is of a low scale, so that large parts of the structures could be imaged. In order to characterize the occurring flow structures, two-point-correlations were performed, yielding the average structure size in the course of the adverse pressure gradient for different heights above the wall. Average sizes of 1.6–3.2 δ were found, with an increase in structure length with the advance of the pressure gradient. Especially smaller-scale structures near the model wall increase in size as they are driven from the wall,being stretched in the process. Further measures to identify singular super-structures instead of applying statistical approaches—which are biased by the huge number of small structures and the meandering of the large ones—are discussed.

Item URL in elib:https://elib.dlr.de/78731/
Document Type:Contribution to a Collection
Additional Information:DOI: 10.1007/978-3-319-03158-3_15, Online ISBN: 978-3-319-03158-3, ISSN 1860-0824 (electronic), Library of Congress Control Number: 2013957123
Title:Superstructures in a Turbulent Boundary Layer Under the Influence of an Adverse Pressure Gradient Investigated by Large-Scale PIV
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Schanz, Danieldaniel.schanz (at) dlr.deUNSPECIFIED
Knopp, Tobiastobias.knopp (at) dlr.deUNSPECIFIED
Schröder, Andreasandreas.schroeder (at) dlr.deUNSPECIFIED
Dumitra, MichneaUniBw MünchenUNSPECIFIED
Kähler, ChristianUniBw MünchenUNSPECIFIED
Date:2014
Journal or Publication Title:New Results in Numerical and Experimental Fluid Mechanics IX
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Volume:124
Page Range:pp. 143-151
Editors:
EditorsEmail
Dillmann, AndreasDLR
Heller, GerdAirbus Deutschland
Krämer, EwaldUni Stuttgart
Kreplin, Hans-PeterDLR
Nitsche, WolfgangTU-Berlin, Germany
Rist, UlrichUni Stuttgart
Publisher:Springer Verlag, Cham Heidelberg New York Dordrecht London
Series Name:Notes on Numerical Fluid Mechanics and Multidisciplinary Design
ISSN:1612-2909
ISBN:978-3-319-03157-6
Status:Published
Keywords:Turbulent boundary layer, Super-structures, Adverse Pressure Gradient, Turbulente Grenzschicht, Super-Strukturen, Positiver Druckgradient, PIV
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research (old)
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Simulation & Validation (old)
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > C²A²S²E - Center for Computer Applications in AeroSpace Science and Engineering
Institute of Aerodynamics and Flow Technology > Experimental Methods
Deposited By: Micknaus, Ilka
Deposited On:03 Apr 2014 13:47
Last Modified:03 Apr 2014 13:47

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