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Experimental Analysis of Geometric, Pressure Gradient and Surface Temperature Effects on Boundary-Layer Transition in Compressible High Reynolds Number Flows

Costantini, Marco (2016) Experimental Analysis of Geometric, Pressure Gradient and Surface Temperature Effects on Boundary-Layer Transition in Compressible High Reynolds Number Flows. Dissertation. DLR-Forschungsbericht. DLR-FB-2016-62, 298 S.

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Abstract

The effect of sharp forward-facing steps on boundary-layer transition was systematically investigated in this experimental work in combination with the influence of changes in the following parameters: streamwise pressure gradient, Reynolds number, Mach number, and a non-adiabatic surface. The investigations were carried out in a quasi-two-dimensional flow at high Reynolds numbers and at both low and high subsonic Mach numbers in the Cryogenic Ludwieg-Tube Göttingen. The adopted experimental setup allowed an independent variation of the aforementioned parameters and enabled a decoupling of their respective effects on the boundary-layer transition. Transition, measured non-intrusively by means of temperature-sensitive paint, was found to move gradually upstream towards the step location with increasing step Reynolds number and relative step height. Stronger flow acceleration and lower wall temperature ratios led to an increase in the transition Reynolds number even in the presence of forward-facing steps; this favorable influence became, however, less pronounced at larger values of the non-dimensional step parameters. The representation of the results using the relative change in transition location with respect to the step location, plotted against the non-dimensional step parameters, gave good correlation and allowed the effect of the steps on boundary-layer transition to be isolated from the influence of variations in the other parameters. The present results were demonstrated to be applicable and transferable to the practical case of a natural laminar flow airfoil. Criteria for acceptable heights of forward-facing steps on unswept and moderately swept natural laminar flow surfaces can now be derived from the functional relations determined in this work.

Item URL in elib:https://elib.dlr.de/117965/
Document Type:Monograph (DLR-Forschungsbericht, Dissertation)
Additional Information:[D 82 (Diss. RWTH Aachen University, 2016)]
Title:Experimental Analysis of Geometric, Pressure Gradient and Surface Temperature Effects on Boundary-Layer Transition in Compressible High Reynolds Number Flows
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Costantini, MarcoMarco.Costantini (at) dlr.dehttps://orcid.org/0000-0003-0642-0199
Date:2016
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Number of Pages:298
ISSN:1434-8454
Status:Published
Keywords:boundary layer, transition, step, pressure gradient, non-adiabatic surface, temperature-sensitive paint
Institution:Rheinisch-Westfälische Technische Hochschule Aachen
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 for Aerodynamics and Flow Technology > Experimental Methods, GO
Deposited By: Bachmann, Barbara
Deposited On:09 Jan 2018 11:03
Last Modified:31 Jul 2019 20:15

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