Efficient Aerodynamic Optimization of Aircraft Wings Aerospace Engineering

118 Pages·2017·2.57 MB·English

by  Andre C. Marta

Efficient Aerodynamic Optimization of Aircraft Wings
Pedro Miguel Veríssimo Rodrigues
Thesis to obtain the Master of Science Degree in
Aerospace Engineering
Supervisor: Prof. André Calado Marta
Examination Committee
Chairperson: Prof. Filipe Szolnoky Ramos Pinto Cunha
Supervisor: Prof. André Calado Marta
Member of the Committee: Prof. João Orlando Marques Gameiro Folgado
April 2018
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Dedicatedtomyfamily.
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Acknowledgments
Firstly, I would like to express my profound gratitude to my supervisor, Professor Andre´ Calado
Marta, for introducing me to the fascinating subject of aerodynamic optimization and for giving me the
opportunity to developed this work. Also, I must thank him for his support and wise guidance since
withoutit,theconclusionofthisworkwithsuccesswouldbeimpossible.
Secondly, I would like to thank my parents and my brother for all their support during my stay in
InstitutoSuperiorTe´cnico,speciallytomymotherwhoalwaysbelievedinme.
Finally, I also express my gratitude to my friends for being a huge part of my life and for all their
supportduringthedevelopmentofthiswork.
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Resumo
A integrac¸a˜o disciplinar e´ um dos fatores-chave mais importantes para design eficiente. Multidisci-
plinaryDesignandOptimizatione´ umate´cnicapromissoraparaoefeito,umavezquecombinaana´lises
multidisciplinares com otimizac¸a˜o baseada em me´todos de gradiente. Assim, esta te´cnica requer a
avaliac¸a˜odasderivadasdasfunc¸o˜esdeinteresseemrelac¸a˜oa`svaria´veisdeprojeto,tarefaessaamais
pesada computacionalmente durante o processo de otimizac¸a˜o. Tradicionalmente, o ca´lculo destas e´
impreciso e pouco eficiente, uma vez que se recorrem a me´todos aproximados. Desta forma, o obje-
tivodestetrabalhoe´ odesenvolvimentodeumaferramentadeotimizac¸a˜oeficientecomopropo´sitode
resolver problemas de design aerodinaˆmico com recurso a informac¸a˜o do gradiente exata. Primeiro, e´
feito um levantamento dos va´rios me´todos de ana´lise de sensibilidade e assim entender as suas car-
acter´ısticas. Deseguida,ummodeloaerodinaˆmicobaseadonome´tododopainele´ adaptadoemcinco
mo´dulos, na qual os respetivos mo´dulos de ana´lise de sensibilidade sa˜o constru´ıdos recorrendo a:
diferenciac¸a˜oautoma´tica,diferenciac¸a˜osimbo´licaeme´todoadjunto. Tantoomodelocomoarespetiva
ana´lise de sensibilidade sa˜o verificados com uma ferramenta de design de asas e com o me´todo das
diferenc¸as finitas, respetivamente. Um estudo parame´trico e´ tambe´m conduzido para uma asa de re-
fereˆncia, analisando assim o impacto das varia´veis de projeto nos coeficientes aerodinaˆmicos. Por
u´ltimo, problemas de design aerodinaˆmico sa˜o resolvidos com sucesso recorrendo a` nova ferramenta
pois, quando comparado ao uso do me´todo das diferenc¸as finitas, o tempo de otimizac¸a˜o podera´ ser
reduzidoem90%.
Palavras-chave:
me´todosdegradiente,designaerodinaˆmico,ana´lisedesensibilidade,me´todo
dopainel,diferenciac¸a˜oautoma´tica,me´todoadjunto.
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Abstract
Oneofthemostimportantkeystothesuccessfuldesignofcomplexsystemsisdisciplinaryintegra-
tion. MultidisciplinaryDesignandOptimizationisnowapromisingmethodologyfortheefficientdesignof
suchsystems,sinceitcombinesmultidisciplinaryanalysiswithgradient-basedoptimizationtechniques.
Therefore, this methodology requires the derivatives evaluation of the functions of interest with respect
to the design variables, which is the most demanding computational task in the optimization process.
Traditionally, those derivatives are calculated inefficiently and inaccurately using approximate methods.
Therefore, the objective of this work is to develop an efficient optimization framework to solve aerody-
namicdesignproblemsusingexactgradientinformation. Firstly,asurveyonsensitivityanalysismethods
is conducted to identify which tools are available and understand their respective merits. Secondly, an
aerodynamic model based on the panel method is reformulated into five smaller modules, in which the
respective sensitivity analysis blocks are constructed using exact gradient estimation methods: auto-
matic differentiation, symbolic differentiation and the adjoint method. Both the aerodynamic tool and
respective sensitivity analysis are validated using a wing design tool and the finite-differences method,
respectively. Subsequently,aparametricstudyisalsopresentedforabaselinewingconfigurationtosur-
veytheimpactsofchangingthewing’sdesignvariablesontheaerodynamiccoefficientsandtherefore,
tounderstandthewing’saerodynamicbehavior. Finally,aerodynamicoptimizationproblemsaresolved
usingthenewtoolwithremarkablesuccesssince,whencomparedtothefinite-differencesmethod,the
optimizationtimecanbereducedby90%.
Keywords:
gradient-basedoptimization,aerodynamicdesign,sensitivityanalysis,panelmethod,
automaticdifferentiation,adjointmethod.
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