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CFD Methods for Predicting Aircraft Scaling Effects
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Aerodynamics.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis deals with the problems of scaling aerodynamic data from wind tunnel to free flight  conditions. The main challenges when this scaling should be performed is how the model support, wall interference and the potentially lower Reynolds number in the windtunnel should be corrected. Computational Fluid Dynamics (CFD) simulations have been performed on a modern transonic transport aircraft in order to reveal Reynolds number effects and how these should be scaled accurately. A methodology for scaling drag and identifying scaling effects in general is presented.  This investigation also examines how the European Transonic Wind tunnel twin sting model support influences the flow over the aircraft. When the Reynolds number is differing between the wind tunnel and free flight conditions, a change in boundary layer transition position can occur. In order to estimate first order boundary layer transition effects a correlation based transition prediction method, previously presented by Menter and Langtry, is implemented in the CFD solver Edge. The transition model is further developed and a novel set of equations for the production terms is found through a CFD/optimizer coupling. The transition data, used to calibrate the CFD transition model,  have been extracted from a low Mach number wind tunnel campaign. At these low Mach numbers many compressible CFD solvers suffer of poor convergence rates and a deficiency in robustness and accuracy might appear. The low Mach number effects are investigated, and an effort to prevent these is done by implementing different preconditioning techniques in the compressible CFD solver Edge. The preconditioners are mainly based on the general Turkel preconditioner, but a novel formulation is also presented in order to make the numerical technique less problem dependent.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , vi, 26 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2008:56
Keyword [en]
CFD, Scaling Effects, Boundary Layer Transition, Preconditioning
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-9209ISBN: 978-91-7415-134-3 (print)OAI: oai:DiVA.org:kth-9209DiVA: diva2:37506
Public defence
2008-10-24, D1, Lindstedtsvägen 17, KTH, 10:15 (English)
Opponent
Supervisors
Note
QC 20100903Available from: 2008-10-13 Created: 2008-10-06 Last updated: 2010-09-03Bibliographically approved
List of papers
1. Aerodynamic scaling to free flight conditions: past and present
Open this publication in new window or tab >>Aerodynamic scaling to free flight conditions: past and present
2008 (English)In: Progress in Aerospace Sciences, ISSN 0376-0421, E-ISSN 1873-1724, Vol. 44, no 4, 295-313 p.Article in journal (Refereed) Published
Abstract [en]

This report summarizes some of the problems when wind tunnel data should be scaled to free flight conditions. The main challenges in performing this extrapolation is how model support, wall interference, aeroelastic effects and a potentially lower Reynolds number in the wind tunnel should be corrected. A historical review of scale effects is presented showing wind tunnel to flight discrepancies of different types of aircraft configurations. An overview of scaling methodologies and Reynolds number effects are presented and discussed. Some modern approaches where computational fluid dynamics (CFD) are used, together with wind tunnel testing, in order to identify scaling phenomena are presented as well.

Keyword
Aerodynamics, Computational fluid dynamics, Mathematical models, Wind tunnels, Aerodynamic scaling, Free flight conditions, Wall interference
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9247 (URN)10.1016/j.paerosci.2008.03.002 (DOI)000257222200004 ()2-s2.0-44249120051 (Scopus ID)
Note
QC 20100903Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-12-11Bibliographically approved
2. Reynolds number effects identified with CFD methods compared to semi-empirical methods
Open this publication in new window or tab >>Reynolds number effects identified with CFD methods compared to semi-empirical methods
2006 (English)In: ICAS-Secretariat - 25th Congress of the International Council of the Aeronautical Sciences 2006, Curran Associates, Inc., 2006, Vol. 3, 1566-1579 p.Conference paper, Published paper (Refereed)
Abstract [en]

In order to estimate Reynolds number effects on a transonic transport aircraft CFD calculations have been performed. The CFD calculations have been done solving the RANS equations on an unstructured grid for varying Reynolds number at transonic conditions. Low Reynolds number data have been extrapolated to a higher Reynolds number condition with different scaling methodologies in order to evaluate each methods strengths and weaknesses.

Place, publisher, year, edition, pages
Curran Associates, Inc., 2006
Keyword
Aeronautics, CFD, Corrections, Reynolds number, Scaling
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-6183 (URN)2-s2.0-84896998317 (Scopus ID)
Conference
25th Congress of the International Council of the Aeronautical Sciences 2006, Hamburg, Germany, 3 September 2006 through 8 September 2006
Note

QC 20100903

Available from: 2006-10-03 Created: 2006-10-03 Last updated: 2015-04-14Bibliographically approved
3. Comparing different CFD methods accuracy in computing local boundary layer properties
Open this publication in new window or tab >>Comparing different CFD methods accuracy in computing local boundary layer properties
2009 (English)In: Engineering Applications of Computational Fluid Mechanics, ISSN 1994-2060, Vol. 3, no 1, 98-108 p.Article in journal (Refereed) Published
Abstract [en]

In aeronautical applications wind tunnels are often not capable of producing high Reynolds numbers which are achieved at free flight conditions. Today CFD methods are often used as a tool to estimate scale effects. CFD methods are commonly used to predict flow features at Reynolds numbers higher than what the aircraft model is subject to in the wind tunnel, and at higher Reynolds number than the turbulence model has been calibrated to. The investigation of local boundary layer properties could give useful information when the wind tunnel data is scaled to free flight conditions the question is whether the CFD methods compute these in a consistent manner when there is a large spread in Reynolds number. This work compares two different CFD solvers and two different turbulence models' accuracy in computing local boundary layer properties compared to wind tunnel measurements.

Keyword
CFD, wind tunnel measurements, Fluent, Edge
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9249 (URN)000276898200008 ()
Note
QC 20100903. Uppdaterad från accepted till published (20100903).Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2010-09-03Bibliographically approved
4. Implementation and Verification of a Correlation Based Transition Prediction Method
Open this publication in new window or tab >>Implementation and Verification of a Correlation Based Transition Prediction Method
2008 (English)In: 38th Fluid Dynamics Conference and Exhibit, American Institute of Aeronautics and Astronautics, 2008Conference paper, Published paper (Refereed)
Abstract [en]

In many applications such as turbine and aircraft design, boundary layer transition prediction is an important topic. This paper deals with the implementation and verification of a correlation based transition prediction method previously presented by Menter and Langtry. The two additional transport equations used for predicting transition and a novel set of equations for the production terms are implemented into the CFD code Edge. The results are compared to the well-known Ercoftac wind tunnel results.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2008
Keyword
Aircraft design, Boundary layer transitions, CFD codes, Transition prediction methods, Transport equation
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9250 (URN)2-s2.0-78049490178 (Scopus ID)
Conference
38th AIAA Fluid Dynamics Conference and Exhibit; Seattle, WA; United States; 23 June 2008 through 26 June 2008
Note

QC 20100903

Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2017-03-21Bibliographically approved
5. Implementation and Evaluation of Different Preconditioning Methods in the Compressible CFD Solver Edge
Open this publication in new window or tab >>Implementation and Evaluation of Different Preconditioning Methods in the Compressible CFD Solver Edge
2008 (English)In: 5th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2008), 2008Conference paper, Published paper (Refereed)
Keyword
Preconditioning, Convergence acceleration, Artificial viscosity, low Mach number, Robustness
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-9251 (URN)
Note
QC 20100903Available from: 2008-10-13 Created: 2008-10-13 Last updated: 2010-09-03Bibliographically approved

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Citation style
  • apa
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  • de-DE
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Output format
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