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Experimental investigation of shock-induced separation and flow control in a transonic compressor cascade

Klinner, Joachim and Hergt, Alexander and Grund, Sebastian and Willert, Christian (2019) Experimental investigation of shock-induced separation and flow control in a transonic compressor cascade. Experiments in Fluids, 60 (96). Springer. DOI: 10.1007/s00348-019-2736-z ISSN 0723-4864

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Official URL: https://link.springer.com/article/10.1007%2Fs00348-019-2736-z

Abstract

The influence of transition control on shock-induced flow separation was investigated in a highly loaded transonic compressor cascade at an inlet Mach number of 1.21 and a chord based Reynolds number of 1.4×10^6. Transition was influenced by raising the free-stream turbulence from 0.5% to 2.5%. Two further cases employed either air jet vortex generators (AJVG) or a surface roughness patch as transition control devices. Velocity fields in the vicinity of the unsteady transonic separation were captured by particle image velocimetry (PIV). Blade flexure induced by the unsteady aerodynamic loading was tracked for each image and compensated individually prior to PIV processing. The captured flow fields indicate shape variations of the separation region while the shock foot moves within a range of up to 20% of chord. The frequency of separation for each investigated case was assessed on the number of vectors with negative velocity in each PIV sample. To further quantify the size of the separation region, the statistically independent PIV samples were conditionally averaged for various passage shock positions at a resolution of 1% chord length. Insight to the dynamics and frequency of the passage shock motion was further provided by high-speed shadowgraphy. Large bubble separation occurs if the turbulence of the incoming flow is low. The size of separation region decreases when AJVGs are applied but still exhibits bubble separation as the passage shock moves downstream. 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 flow conditions showing bubble separation in the mean flow also exhibit distinct spectral peaks indicating periodic shock oscillations.

Item URL in elib:https://elib.dlr.de/127546/
Document Type:Article
Title:Experimental investigation of shock-induced separation and flow control in a transonic compressor cascade
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Klinner, JoachimJoachim.Klinner (at) dlr.dehttps://orcid.org/0000-0003-2709-9664
Hergt, Alexanderalexander.hergt (at) dlr.deUNSPECIFIED
Grund, Sebastiansebastian.grund (at) dlr.deUNSPECIFIED
Willert, ChristianChris.Willert (at) dlr.dehttps://orcid.org/0000-0002-1668-0181
Date:20 May 2019
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:60
DOI :10.1007/s00348-019-2736-z
Publisher:Springer
ISSN:0723-4864
Status:Published
Keywords:Particle Image Velocimetry, PIV, transonic flow, shock-induced separation, SBLI, boundary layer separation, conditional average, transonic buffeting, transition control
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 - Fan and Compressor Technologies, L - Virtual Engine and Validation methods
Location: Köln-Porz
Institutes and Institutions:Institute of Propulsion Technology > Engine Measurement Systems
Institute of Propulsion Technology > Fan and Compressor
Deposited By: Klinner, Joachim
Deposited On:27 May 2019 09:39
Last Modified:21 May 2020 03:00

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