RANS Based Methodology for Predicting the Influence of Leading Edge Erosion on Airfoil ...

172 Pages·2017·4.31 MB·English

SANDIA REPORT
SAND2017-11289
Unlimited Release
Printed October 2017
RANS Based Methodology for Predicting

the Influence of Leading Edge Erosion on

Airfoil Performance

Christopher M Langel, Raymond Chow, C.P van Dam
David C. Maniaci, Sandia Technical Manager
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SAND2017-11289
Unlimited Release
Printed October 2017
RANS Based Methodology for Predicting the Influence
of Leading Edge Erosion on Airfoil Performance ∗
Christopher M. Langel, Raymond Chow, and C.P. van Dam
Department of Mechanical and Aerospace Engineering
University of California, Davis
Davis, CA 95616
Sandia Contract No. 1228734
Technical Manager:
David C. Maniaci
Wind Energy Technologies Department
Sandia National Laboratories
P.O. Box 5800
Albuquerque, NM 87185-1124
Abstract
The impact of surface roughness on flows over aerodynamically designed surfaces is o f interested in a
number of different fields. It has long been known the surface roughness will likely accelerate the laminar-
turbulent transition process by creating additional disturbances in the boundary layer. However, there are
very few tools available to predict the effects surface roughness will have on boundary layer flow. There are
numerous implications of the premature appearance of a turbulent boundary layer. Increases in local skin
friction, boundary layer thickness, and turbulent mixing can impact global flow properties compounding the
effects of surface roughness. With this motivation, an investigation into the effects of surface roughness on
boundary layer transition has been conducted. The effort involved both an extensive experimental campaign,
and the development of a high fidelity roughness model implemented i n a R ANS solver. Vast a mounts of
experimental data was generated at the Texas A&M Oran W. Nicks Low Speed Wind Tunnel for the calibra-
tion and validation of the roughness model described in this work, as well as future efforts. The present work
focuses on the development of the computational model including a description of the calibration process.
The primary methodology presented introduces a scalar field variable and associated transport equation that
interacts with a correlation based transition model. The additional equation allows for non-local effects of
∗TheworkdescribedinthisreportwasperformedforSandiaNationalLaboratoriesunderContractNo.1228734
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surfaceroughnesstobeaccountedfordownstreamofroughwallsectionswhilemaintaininga“local”formu-
lation. Thescalarfieldisdeterminedthroughaboundaryconditionfunctionthathasbeencalibratedtoflat
platecaseswithsandgrainroughness. ThemodelwasinitiallytestedonaNACA0012airfoilwithrough-
ness strips applied to the leading edge. Further calibration of the roughness model was performed using
results from the companion experimental study on a NACA 63 -418 airfoil. The refined model demon-
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strates favorable agreement predicting changes to the transition location, as well as drag, for a number of
different leading edge roughness configurations on the NACA 63 -418 airfoil. Additional tests were con-
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ductedonathickerS814airfoil, withsimilarroughnessconfigurationstotheNACA63 -418. Simulations
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runwiththeroughnessmodelcomparefavorablywiththeresultsobtainedintheexperimentalstudyforboth
airfoils.
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Acknowledgment
Numerous parties have contributed to the completion this report. The authors gratefully
acknowledge the support of the US Department of Energy’s Wind Energy Technologies
Office (WETO) and Sandia National Laboratories. Additionally the work was supported by
the National Science Foundation GK-12 RESOURCE program under grant No. DGE-0948021.
Significant contributions were provided by Professor Edward White, Dr. Robert
Ehrmann, and Dr. Benjamin Wilcox of Texas A&M University. In addition to conducting the
large wind tunnel campaigns described in the report, they supplied a large source of knowledge,
and shared valuable insights that helped push this work forward.
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Contents
Nomenclature 18
1 Introduction 21
2 LiteratureReview 25
TransitionOverview .............................................................. 25
TransitionPredictionModels ....................................................... 28
TransitionPredictionBasedonLinearStability .................................... 28
CorrelationBasedTransitionModels ............................................ 30
ParallelRANSCompatibleCFDModels ......................................... 33
LaminarKineticEnergyModel........................................... 33
N-factorTransportEquationModel ....................................... 33
Langtry-Menterγ−R˜e model .......................................... 34
θt
SA−γ−R˜e Model .................................................. 35
θt
OneEquationγ Model ................................................. 35
SummaryofTransitionModels ................................................. 35
RoughnessEffects................................................................ 36
Isolated2-DRoughness ....................................................... 36
Isolated3-DRoughness ....................................................... 37
DistributedRoughness........................................................ 38
RoughnessModels ............................................................... 41
AnalyticMethodsForRoughnessModeling ....................................... 41
TurbulentBoundaryLayerModificationsinRANSSimulations ....................... 43
ModificationstoTransitionCriteria.............................................. 45
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3 ExperimentalSetupandResults 47
WindTunnel .................................................................... 47
AirfoilModelDescriptions ......................................................... 48
RoughnessPatterns ............................................................... 50
RoughnessDistributionforNACA63 -418 ....................................... 52
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RoughnessDistributionforS814................................................ 52
WindTunnelEntriesandConfigurationsTested......................................... 53
MeasurementTechniques .......................................................... 55
RepresentativeResults-NACA63 -418 .............................................. 56
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RepresentativeResults-S814....................................................... 58
4 Methodology 61
NavierStokes ................................................................... 61
DNSandLargeEddySimulations ................................................... 63
DNS ...................................................................... 63
LargeEddySimulation ....................................................... 64
Reynolds-AveragedNavierStokes(RANS)Equations.................................... 65
Reynolds-stressTerm......................................................... 66
TurbulenceModeling ............................................................. 66
ZeroandFirstOrderModels ................................................... 67
k−ε andk−ω TwoEquationModels ........................................... 68
SSTTwoEquationModel ..................................................... 68
EddyViscosityAlternatives.................................................... 71
DetachedEddySimulation ......................................................... 71
OVERFLOW.................................................................... 72
GridGeneration.................................................................. 72
ParametricDefinitionofAirfoilSurface .......................................... 74
5 Langtry-Menterγ−R˜e TransitionModel 79
θt
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CorrelationBasedTransitionPrediction............................................... 79
LocalCorrelationTransitionModeling-γ−R˜e ....................................... 80
θt
LocalCorrelationModelSensitivities................................................. 84
FreestreamTurbulenceLevels ................................................. 85
GridQuality ................................................................ 86
TurbulenceModelSettings .................................................... 87
OVERFLOWSimulationswithTransitionModel ....................................... 91
NLF(1)-0414F .............................................................. 91
NACA63 -418 ............................................................. 93
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S814 ...................................................................... 94
6 SurfaceRoughnessModelDevelopment 97
RoughnessModelPreliminaries ..................................................... 97
RoughnessModelOutline.......................................................... 98
InputParameter.................................................................. 100
RoughnessCharacterization.................................................... 101
ModelCalibration ................................................................ 102
BoundaryConditionFunction .................................................. 102
ModifiedSourceTermFunction ................................................ 105
FinalFormoftheRoughnessModel.................................................. 109
ModificationofSSTBoundaryCondition......................................... 110
ImplementationinOVERFLOW ................................................ 111
ConvergenceandGridRecommendations......................................... 112
7 RoughnessModelResults 115
FlatPlateCases.................................................................. 115
NACA0012AirfoilCases ......................................................... 121
ComparisontoTexasA&MResults .................................................. 127
NACA63 -418 ............................................................. 127
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S814Airfoil ................................................................ 135
8 Conclusions 139
Appendix
A LowOrderMethod 143
A.1 Results-NACA63 -418 ...................................................... 146
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A.2 Results-S814 .............................................................. 149
B BezierPointsforAirfoils 151
C OptimizationAlgorithms 157
D SampleOVERFLOWInputFiles 161
References 163
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