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Investigation of shock-induced flow separation over a transonic compressor blade by conditionally averaged PIV and high-speed shadowgraphs

Klinner, Joachim and Hergt, Alexander and Grund, Sebastian and Willert, Christian (2018) Investigation of shock-induced flow separation over a transonic compressor blade by conditionally averaged PIV and high-speed shadowgraphs. In: 17th International Symposium on Applications of Laser Techniques to Fluid Mechanics. 19th International Symposium on Applications of Laser Techniques to Fluid Mechanics, 16.-19. July 2016, Lissabon. ISBN ISBN 978-989-98777-9-5

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Official URL: http://www.lisbon-lasersymposium.org/lxlaser2018

Abstract

The impact of separation control has been investigated in a highly loaded transonic compressor cascade at an inlet Mach number of 1.21 and a chord based Reynolds number of 1.4 × 106. Applied control devices are air jet vortex generators (AJVG) and a surface roughness patch. Comparative flows without transition control imply a variation of the upstream turbulence level from 0.5% to 2.5%. Above the suction side, velocities of the unsteady separation region have been captured by particle image velocimetry (PIV). The aerodynamic load alternation due to shock motion results in flexure of the blade surface which has been measured and compensated prior to PIV processing. Single PIV shots indicate shape variations of both the lambda shock system and the associated separation region while the shock foot position is fluctuating within a range of up to 23% of chord. Large sets of statistically independent PIV samples are conditionally averaged upon instantaneous passage shock positions at a resolution of 1% of chord length to quantify the size of flow separation. Large bubble separation occurs if the turbulence of the incoming flow is low. The separation region becomes smaller when AJVGs are applied but still exhibits bubble separation at rear shock positions. The size of the separation region is significantly reduced either if a roughness patch is applied or if the turbulence level of the incoming flow is high. The frequency range of shock motion is analyzed by shock tracking on the basis of high speed shadowgraphs. A Fourier analysis of shock motion in the low frequency range (<1khz) indicates the highest spectral densities for the turbulent case and the lowest densities if roughness patch are applied. Joined probability density distributions of blade displacements and amplitudes of shock movement revealed that upward transverse blade deflections are more frequent at shock positions downstream of the mean shock position while downward deflections are more frequent at frontal shock positions

Item URL in elib:https://elib.dlr.de/120895/
Document Type:Conference or Workshop Item (Speech)
Title:Investigation of shock-induced flow separation over a transonic compressor blade by conditionally averaged PIV and high-speed shadowgraphs
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Klinner, JoachimJoachim.Klinner (at) dlr.dehttps://orcid.org/0000-0003-2709-9664
Hergt, Alexanderalexander.hergt (at) dlr.deUNSPECIFIED
Grund, SebastianUNSPECIFIEDUNSPECIFIED
Willert, ChristianChris.Willert (at) dlr.dehttps://orcid.org/0000-0002-1668-0181
Date:16 July 2018
Journal or Publication Title:17th International Symposium on Applications of Laser Techniques to Fluid Mechanics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
ISBN:ISBN 978-989-98777-9-5
Status:Accepted
Keywords:shock-induced separation, bubble separation, conditional average, PIV, transonic buffeting, transition control, SBLI
Event Title:19th International Symposium on Applications of Laser Techniques to Fluid Mechanics
Event Location:Lissabon
Event Type:international Conference
Event Dates:16.-19. July 2016
Organizer:International Center for Innovation, Technology and Policy Research
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:propulsion systems
DLR - Research area:Aeronautics
DLR - Program:L ER - Engine Research
DLR - Research theme (Project):L - Virtual Engine and Validation methods
Location: Köln-Porz
Institutes and Institutions:Institute of Propulsion Technology > Engine Measurement Systems
Deposited By: Klinner, Joachim
Deposited On:11 Jul 2018 09:08
Last Modified:31 Jul 2019 20:18

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