100 NotesonNumericalFluidMechanicsandMultidisciplinaryDesign(NNFM) Editors E.H. Hirschel/München W. Schröder/Aachen K. Fujii/Kanagawa W. Haase/München B. van Leer/Ann Arbor M.A. Leschziner/London M. Pandolfi/Torino J. Periaux/Paris A. Rizzi/Stockholm B. Roux/Marseille Y. Shokin/Novosibirsk 100 Volumes of ‘Notes on Numerical Fluid Mechanics’ 40 Years of Numerical Fluid Mechanics and Aerodynamics in Retrospect Ernst Heinrich Hirschel Egon Krause (Editors) ABC Prof.Dr.E.H.Hirschel Herzog-Heinrich-Weg 6 85604Zorneding Germany E-mail:[email protected] Prof.Dr.E.Krause RWTHAachen Aerodynamisches Institut Wüllnerstr. 5a 52062Aachen Germany E-mail:[email protected] ISBN 978-3-540-70804-9 e-ISBN 978-3-540-70805-6 DOI 10.1007/978-3-540-70805-6 Notes on Numerical Fluid Mechanics and Multidisciplinary Design ISSN 1612-2909 LibraryofCongressControlNumber:2009921827 (cid:2)c 2009Springer-VerlagBerlinHeidelberg Thisworkissubjecttocopyright. 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Printedinacid-freepaper 543210 springer.com NNFM Editor Addresses Prof.Dr.ErnstHeinrichHirschel Prof.Dr.MaurizioPandolfi (GeneralEditor) PolitecnicodiTorino Herzog-Heinrich-Weg6 DipartimentodiIngegneria D-85604Zorneding AeronauticaeSpaziale Germany CorsoDucadegliAbruzzi,24 E-mail:[email protected] I-10129Torino Italy Prof.Dr.WolfgangSchröder E-mail:pandolfi@polito.it (DesignatedGeneralEditor) RWTHAachen Prof.Dr.JacquesPeriaux LehrstuhlfürStrömungslehreund 38,BoulevarddeReuilly AerodynamischesInstitut F-75012Paris Wüllnerstr.zw.5u.7 France 52062Aachen E-mail:[email protected] Germany E-mail:offi[email protected] Prof.Dr.ArthurRizzi DepartmentofAeronautics Prof.Dr.KozoFujii KTHRoyalInstituteofTechnology SpaceTransportationResearchDivision Teknikringen8 TheInstituteofSpace S-10044Stockholm andAstronauticalScience Sweden 3-1-1,Yoshinodai,Sagamihara E-mail:[email protected] Kanagawa,229-8510 Japan Dr.BernardRoux E-mail:fujii@flab.eng.isas.jaxa.jp L3M–IMTLaJetée TechnopoledeChateau-Gombert Dr.WernerHaase F-13451MarseilleCedex20 HöhenkirchenerStr.19d France D-85662Hohenbrunn E-mail:[email protected] Germany E-mail:offi[email protected] Prof.Dr.YuriiI.Shokin SiberianBranchofthe Prof.Dr.BramvanLeer RussianAcademyofSciences DepartmentofAerospaceEngineering InstituteofComputational TheUniversityofMichigan Technologies AnnArbor,MI48109-2140 Ac.LavrentyevaAve.6 USA 630090Novosibirsk E-mail:[email protected] Russia E-mail:[email protected] Prof.Dr.MichaelA.Leschziner ImperialCollegeofScience TechnologyandMedicine AeronauticsDepartment PrinceConsortRoad LondonSW72BY U.K. E-mail:[email protected] Preface I Aircraft concepts are always driven by the requirements of the desired mis- sion. A different purpose for the use of the aircraft consequently results in a different design. Therefore, depending on the intended outcome, conflict- ing requirements need to be fulfilled, for example, efficient cruise speed and greatercargocapabilities,incombinationwithshorttake-offandlandingfield lengths, or high speed and agility combined with variable payload demands. Due to the highly complex, non-linearphysicalenvironmentin which aircraft operate, this task demands that the most advanced methods and tools are employed, to gain the necessary understanding of flow phenomena, and to exploit the flow physics to achieve maximum aircraft efficiency. Inthenaturalsciences,researcherstrytocreateandextendhumanknowl- edge by understanding and explaining the mechanisms of physical processes. In engineering, a designer is limited by certain requirements, and in order to fulfil these requirements the necessarytechnical tools need to be designed.In general,for a given problem the correspondingscientific or technical solution issought.Inordertosuccessfullyadvancefromaproblemtowardsasolution, three main methods may be used. The two classical methods include theory and experiment, which are now being complemented by a third method, de- scribedasnumericalsimulation.Theexperimentalapproachisbasedonphys- ical observation,measurementof relevantvalues, and methodical variationof the subject matter. For example, such experiments are used to gain a phys- ical understanding as well as to validate and investigate design alternatives. In aerodynamics, experimental research is carried out by wind tunnel and flight testing. However, in the theoretical approach, certain correlations be- tweenphysicalobservationandmathematicalprinciplesarehypothesized,and a corresponding mathematical formulation is developed, which describes the main mechanisms of the observedphenomena. A typical example of theoreti- cal design methods is the Lifting-Line-Theory, developed by Ludwig Prandtl in 1918, which is itself based on potential theory. With the progressive innovations in computer technology over the past decades,accompaniedby correspondingalgorithmic developments,numerical VIII Preface I simulationhasmaturedfromascientificpeculiaritytoatoolapplicabletothe broadspectrum,fromscientificinvestigationstoproduct-orientedengineering design. Numerical simulation emulates physical processes by solving systems of differential equations, and can be interpreted as a complementary element to experimentation and theoretical consideration. Furthermore, as it involves elements of both experimentation and theoretical consideration, it may be regarded as the bridge between experiment and theory. Numerical simulation is inherently interdisciplinary, as physics, mathe- matics, and informatics are all equally concerned. In 1755, Leonhard Euler proposed a set of non-linear partial differential equations, which describe the conservationofmassandmomentumforaninviscidfluid.Morethan50years later,ClaudeNavierin1822,andGeorgeStokesin1845,independently intro- ducedviscoustransportintotheseequations.Thiswassubsequentlyextended to include the energy equation. After being cast into the so-called conserva- tion form to capture flow discontinuities, the differential equations proposed now form the basis of numerical simulation in fluid dynamics today. A direct solution of these differential equations is not generally feasible, and analytical solutions can only be obtained in unique cases, which are of limited practical interest. Essentially, there are two major routes that are followed to solve these equations: Either the equations will be further sim- plified, so that solutions are easier to obtain, which for example, resulted in the establishment of the potential theory of aerodynamics. Or the original exactequationswillbe solvedonlyapproximatelyby establishingandsolving a corresponding set of discrete algebraic equations, which is numerical flow simulation. This process has been termed “Numerical Fluid Mechanics,” re- spectively “Computational Fluid Dynamics” (CFD), since the solution of the algebraicsystemofequationsrequirestheuseofhighperformancecomputers. For aerodynamics, the development of Computational Fluid Dynamics is particularlydrivenbyaninterestintransonicflows,whichevolvedintheearly days of commercialjet aviationwhen the transonic dragrise phenomenon re- ceived particular attention. The solution of the Euler equations was essential forCFDresearchinthe1980s.Thisiscomparabletothe1990s,whichwasthe decadeinstrumentaltosolvingthe Navier-Stokesequations.Aprojectforthe development and validation of a reliable and efficient numerical tool for the aerodynamic simulation of a complete aircraft was initiated under the lead- ership of the German Aerospace Center (DLR) which would meet industrial implementationrequirements.AsoftwaresystemtitledMEGAFLOWwasde- veloped, and incorporatedthe block-structured Navier-Stokescode FLOWer, and the unstructured Navier-Stokes code TAU. Both codes have reached a high level of maturity and in cooperation with the DLR are intensively used by the German Aerospace Industry and its European partners in the design processes of new aircraft. Numericalsimulationhas identifiedtwochallengesfor future researchand development. The first challenge is to extend the range of applicability of CFD methods. Furthermore, the second challenge is directly concerned with Preface I IX the cost of applying CFD methods in the design process within multidisci- plinarynumericalsimulationandoptimizationtools.Forinstance,inorderto determine the static and dynamic loads required for structural design, hun- dreds of thousands of aerodynamic load cases need to be evaluated. The tremendous progress achieved in numerical simulation over the past decades would not have been possible without the substantial increase in computational power. Therefore, in addition to the other notable theories of numerical simulation, the so-called Moore’s Law developed in the 1960s by Gordon Moore, describes the continuum of increasing computational power. More specifically the theory hypothesizes that within 30 years computational power would increase by a factor of 33,000; and a computational job, which today would require 30 years, will in the future take only 8 hours to process. To further meet the challenges of numerical simulations, as hypothesized by Moore,there will be opportunities to make use ofthe upcoming greatercom- putational capabilities. If efficiently implemented, this may open up the pos- sibility to “flight-test” a simulated aircraft with all of its multidisciplinary in- teractionsinavirtualenvironment.Thiswouldhelptoincreaseperformance, reduce risk and to promote cost effectiveness in aircraft design processes by notonlycompilingallthedatarequiredfordevelopmentandcertificationwith a guaranteed accuracy, but also in a significantly reduced time frame. Thus, within the framework of numerical simulation and the methods of aircraft conceptual design, development and detailed design, the capabilities will be revolutionized. There has been dramatic progress over more than 30 years in developing and applying numerical methods successfully in research and development. This success has been accompanied, stimulated and documented not only by appropriateworkinggroups,workshopsandinternationalconferencesbutalso by initiating in 1978 the book series “Notes on Numerical Fluid Mechanics.” This series,as wellasearlierthe GAMM Committee onNumericalFluid Me- chanics with its conferences and workshops, originated at the DLR (at that time DFVLR) in Cologne-Porz.The present volume, produced 30 years after the series’firstpublication,underlinesthe capabilitiesoftodaysmethods and tools and provides an impressive display of the expansive range of applica- tionsforscience,engineeringandparticularlyforaircraftresearch,designand development. Cologne Prof. Dr. Joachim Szodruch October 2008 Member of the Executive Board DLR German Aerospace Center Preface II Over the last three decades, Computational Science and Engineering evolved into a “third pillar” of scientific research alongside theory and experiment. The discipline ofComputationalScience,onthe onehand,enhancesscientific investigationby enabling theorists and practitionersto build and test models ofcomplexphenomena,yieldingnewinformation,innovationandfreshinsight into the research process that is not available through other means. On the other hand, it is a discipline sui generis that unlocks new areas of research, e. g., where experiments are impossible, too dangerous or forbidden. Essen- tial contributions from Computational Science can be expected in a variety of fields of interest. They will lead to major advances in scientific research, leading to importantindustrialinnovationand havinga highsocietalimpact. The interplay between mathematical modeling and algorithm develop- ment/implementation is the driving force for Computational Science and Engineering. The availability of sophisticated numerical methods like Com- putational Fluid Dynamics is crucial to enhance the usability of modern su- percomputers as for example the massively parallel IBM BlueGene systems. It’s one of the aims of the Jülich Supercomputing Centre to cooperate with all scientific communities to enable important new simulation software for supercomputing. The acceleration in the development of parallel supercomputers together with the advancing requirements of computational scientists and engineers with respect to application,memory,data storage,anddata transfer capabil- ities,makesitincreasinglydifficult forsingle institutions to providecontinual funding forlatesttop-rankedsystemsinevershorterperiods.Apossiblesolu- tionisthecreationofnetworksorallianceswhichagreeonclosecollaboration and internal innovation cycles. With the creation of the Gauß Centre for Su- percomputing in 2006,Germany createda new and powerful structure for its three national supercomputing centers, the Leibniz Supercomputing Centre atGarching/München,the Supercomputing CentreJülich,andthe HighPer- formance Computing Center Stuttgart, to take a leading role in Europe. The GaussCentreforSupercomputingrepresentsGermanyasasinglelegalentity XII Preface II in the European supercomputing infrastructure initiative PRACE (Partner- ship for Advanced Computing in Europe) which aims at the creation and sustainedoperationofapan-EuropeanTier-0supercomputingserviceandits fullintegrationintotheEuropeanHPCecosystemfrom2010on,asoneofthe list items of the European Strategy Forum on Research Infrastructures, ES- FRI.WithintheframeworkofPRACE,Germany’sForschungszentrumJülich aspires to host the first European supercomputing centre with Petaflop/s capability in 2009/2010. The potential of CFD applications on high-end HPC systems can be il- lustrated using a computation performed recently by CERFACS (Toulouse, France) on an IBM BlueGene/L machine as reported in the “Scientific Case for European Petascale Computing” by the HPC in Europe Taskforce. This simulation of the ignition of a helicopter gas turbine (about 20 millions nu- merical cells) is one of the most complex large eddy simulations in turbulent combustion and took 60,000 CPU hours on 1024 processors (about 2.5 days of wall clock time). In order to reach a steady state regime, 100 to 200,000 additional CPU hours are required which can only be achieved on Petaflop systems. The Notes on Numerical Fluid Mechanics and Multidisciplinary Design have been a most faithful companion of the field in the past. The Gauss Centre for Supercomputing is convinced that the NNFM will be a complete success in the forthcoming Petaflop Era as well. Jülich Prof. Dr. Achim Bachem October 2008 Gauß Centre for Supercomputing, Chairman of the Board of Directors of the Research Centre Jülich