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Combination of Simultaneous Density and Velocity Measurements of Blade Tip Vortices under Cyclic Pitch Conditions

Braukmann, Johannes N. (2021) Combination of Simultaneous Density and Velocity Measurements of Blade Tip Vortices under Cyclic Pitch Conditions. DLR-Forschungsbericht. DLR-FB-2021-25. Dissertation. Leipniz-Universität Hannover. 123 S.

Full text not available from this repository.

Abstract

Blade tip vortices are a dominant phenomenon in rotor wakes. The interaction of vortices with rotor blades can cause noise emissions, vibrations and even flow separation. Particle Image Velocimetry (PIV) has become a standard tool in vortex investigations. A disadvantage of this method is its dependence on the tracking accuracy of the particles used, which often leads to erroneous or missing data in the vortex core. An alternative approach is the Background-Oriented Schlieren (BOS) method. Unlike PIV, BOS acquires data related to the density gradient of a transparent medium. BOS has been widely used to visualize the vortex system of a rotor and quantitative results have been obtained with respect to vortex positions. In the present work, BOS and PIV are used to measure blade tip vortices simultaneously. Velocity data from PIV are linked to density-related displacements from BOS. Using data from a numerical simulation by Goerttler, the assumption of isothermal rather than isentropic flow in the vortex is made, resulting in excellent agreement between the two measurement techniques. The BOS data are further used to quantify the vortex sizes, positions, and dynamics.

Item URL in elib:https://elib.dlr.de/145303/
Document Type:Monograph (DLR-Forschungsbericht, Dissertation)
Title:Combination of Simultaneous Density and Velocity Measurements of Blade Tip Vortices under Cyclic Pitch Conditions
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Braukmann, Johannes N.Johannes.Braukmann (at) dlr.dehttps://orcid.org/0000-0001-8046-9623
Date:November 2021
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Number of Pages:123
ISSN:1434-8454
Status:Published
Keywords:Blade Tip Vortices, Rotor, Background-Oriented Schlieren, Particle Image Velocimetry, BOS, PIV
Institution:Leipniz-Universität Hannover
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Efficient Vehicle
DLR - Research area:Aeronautics
DLR - Program:L EV - Efficient Vehicle
DLR - Research theme (Project):L - Virtual Rotorcraft and Validation
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Carter, Beatrice
Deposited On:08 Dec 2021 09:50
Last Modified:08 Dec 2021 09:50

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