katnet ii bremen presentation
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BOEING is a trademark of Boeing Management Company.Copyright © 2009 Boeing. All rights reserved.
The Next Decade in Commercial Aircraft Aerodynamics –
A Boeing Perspective
Mark GoldhammerPaul VijgenBoeing Commercial AirplanesSeattle, Washington, U.S.A.
KATnet II Conference on Key Aerodynamic TechnologiesBremen, Germany12 -
14 May 2009
ROI 2009-0501-1167
Copyright © 2009 Boeing. All rights reserved. KATnet II Bremen 2009 | 2
The next decade in commercial airplane aerodynamics – a Boeing perspective
Outline
Historical look at aerodynamic configuration design at Boeing
Driving factors for the future
Aerodynamic levers for the next decadeAerodynamic product technologiesAerodynamic tools, processes and capabilitiesAirplane configurations
Concluding remarks
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The next decade in commercial airplane aerodynamics – a Boeing perspective
The beginnings of the commercial jet age at Boeing
Boeing Stratocruiser (circa 1947)Straight wingPiston-powered propellersFowler flaps
Boeing 367-80 (circa 1954)Prototype for KC-135, B707 family Boeing’s first low-swept-wing transportConfiguration basis for the future:
Wing-mounted pod engines Double-slotted Fowler flaps with LE Krueger flaps
(B707)
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The next decade in commercial airplane aerodynamics – a Boeing perspective
B737
B747
Configuration evolution of the Boeing family
Swept-wing, pod-mounted engines (2 or 4)Continually increasing aerodynamic technologies:
CFD advancesAirfoil/wing technology advancesLE/TE high lift device advancesLessons learned from earlier productsHigher Reynolds number wind tunnel testingImproved structural conceptsMore integrated wing/engine/pylon configurationsRelaxed stabilityLoad alleviationMultidisciplinary optimization
B757
Wing-mounted pod engines became the configuration of choice
B787
B777
B767
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Other configurations
Wing-mounted pod engines were not always selectedAft-mount allows lower-to-the-ground configurationPerhaps more efficient with then-current technologyOdd number of engines (3)Cabin noise and vibration challenges
DC-10
DC-9
B727
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Driving factors for future improvement
Boeing commitment:Each new commercial airplane generation delivers at least 15% improvement in CO2
emissions and fuel efficiency
Relat
ive fu
el us
e
Early jet airplanes
New Generation jet airplanes
Noise dB
MORE FUEL
LESSFUEL
HIGHERdB
LOWERdB
70%
fuel improvement and reduced CO2
90%
reduction in noise footprint
EVENLOWEREVEN
LESS
Nose footprint based on 85 dBa.1950s 1990s 2010s
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Further drag reduction is required for future efficiency improvement
Systems
Materials
Aerodynamics
Engines
*Improvements are relative to 767-300ER
Core aircraft technologiesRelative contributors to
787 efficiency improvement*
For current aircraft configurations, remaining areas for significant fuel-burn improvement in next 10-20 years are:
Propulsion/propulsion integration Aerodynamic drag reductionMulti-disciplinary optimization
Alternate aircraft configurations may allow further integrated improvements from core technologies
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic levers
(3) Airplane Configurations
Aerodynamic product technologies
Aerodynamic tools, processes, and capabilities
Airplane configurations
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic levers
(3) Airplane Configurations
Aerodynamic product technologies
Aerodynamic tools, processes, and capabilities
Airplane configurations
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic product technologies
Laminar flow
Advanced variable camber concepts
Relaxed stabilityMulti-disciplinary optimization
Turbulent skin friction reduction
Active flow control
Advanced transonic wing concepts
Advanced trailing edge device concepts
Advanced leading edge device concepts
Integration of advanced engine concepts
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic drag breakdown and reduction potential
Viscous and lift-induced drag are dominant drag components for subsonic aircraft in cruise
Advances in materials, structures and aerodynamics enable significant lift-induced drag reduction
Maximize effective span extension using compositesIncorporate advanced wing-tip devices
Viscous drag is remaining area with largest potential for further drag reduction
Drag breakdown (typical)
Induced and trim drag
Viscous drag
Wave drag
Excrescence drag
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Laminar flow drag reduction benefits and issues
Natural Laminar Flow (NLF) and Hybrid Laminar Flow Control (HLFC) demonstrated in aerodynamic flight tests
Transition flow physics generally understoodScale and sweep affect laminar-flow application (NLF vs. HLFC)Continuous progress in analysis and design methods
Laminar flow reduces fuel burn, emissions and noise Benefit depends on scale of applicationImproved fuel burn allows smaller, lighter, quieter aircraftEstimated net potential fuel burn benefit for subsonic transports ~ 5 – 12 %
Laminar flow application issuesManufacturing, certification, and operational requirements and impactsDrag benefit needs to be traded against increased weight, maintenance, cost, reliability, etc.
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Some laminar flow activities1990 1995 2000 2005
757 HLFCflight test
Wing HLFCWT test
HLFCVLA studies
Wing HLFCWT test
787NLF
Nacelle
F-16XL SLFCflight test
SLFC Studies
Product Development trade studyWind-Tunnel (WT) or flight test
Steps WT Tests
757 NLFFlight test
1985
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The next decade in commercial airplane aerodynamics – a Boeing perspective
757 HLFC flight test program Leading edge suction panel
HLFCleading edge
suction panel
Hot-film sensors
Pressure belt
Infra-red cameras
Krueger/insect shield
Laminar-flow instrumentation
Equivalent to 6% airplane drag reduction on 757-
size airplane
Laminar flow achieved up to shock location
HLFCleading edgesuction panel
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Nacelles shaped for natural laminar flow (NLF) Committed to 787 in 2005
Nacelle contours optimized with laminar transition location as additional design parameterStructural design and manufacturing methods tailored for NLF benefit
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Airline operations
Applied aerodynamics
Fluid dynamics
Design integration and manufacturing
Flow physicsTransition prediction HLFC suction flow physics
Wind tunnel testing/scalingOff-design performanceHigh lift performance
CertificationOperational/environmental effectsGround handlingMaintenance
Simplified HLFC systemsHigh lift systemsIce protection systemsManufacturing techniques
Increasing technology readiness
Laminar flow integration and implementation challenges
Potentially large aerodynamic benefit needs to be integrated into practical design that meets requirements over lifeof aircraftSignificant integration and operational challenges need to be addressed Risk in net economic benefit of laminar flow remains
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Turbulent flow drag reduction benefits and issues
Riblet technology has been demonstrated to passively reduce local turbulent skin friction ~6 %
Tunnel and flight tests with riblet films conductedApplication constraints (shape, spacing, streamlining) are understood
Riblet application issues are not aerodynamic:Limited riblet shape and adhesive robustness over operational life (hydraulic liquids, hail, dirt and impact)Appearance relative to standard paint and liveryTime required to install, maintain, remove and re-apply
`
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Boeing drooped-spoiler flap Committed to 787 in 2005
787Single/single slotted
767Double/single slotted withFowler motion
Simple-hinged flap with drooping spoilersFewer parts (reduced maintenance)Lower weightSmaller fairingsFacilitates small flap adjustments in flight
6-bar linkage
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Inboard flapFlaperon
Outboard flapAileron
Boeing trailing edge variable camber Committed to 787 in 2005
Trailing edge variable camber allowsLoad optimizationCruise drag optimization
In cruise, trailing edge elements are adjusted at regular intervals to minimize dragSimplified actuation systemSmall angle variationsUp and down movements
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The next decade in commercial airplane aerodynamics – a Boeing perspective
High lift configurationwith AFC actuators
AFCAFC
Example: Application concept study with AFC augmented wing high lift system
(Reference NASA CR-1999-209338)
Active Flow Control (AFC)
Evaluating Active-Flow Control (AFC) actuator and integration concepts for simplified (lighter) systems with similar performance as traditional mechanical high-lift elements Robust, reliable and low-maintenance AFC actuation to be developed and demonstrated for commercial transportKey issues that affect application success for commercial aircraft are:
Actuator capability, robustness and noiseSystem power, complexity and costFailure modes and redundancy considerations
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic levers
(3) Airplane Configurations
Aerodynamic product technologies
Aerodynamic tools, processes, and capabilities
Airplane configurations
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic tools, processes and capabilities
Computational fluid dynamics
Wind tunnel testing
Flight testing
Future aerodynamics engineers
Wind tunnel
Flight testing
CFD
Aerodynamic design
and analysis
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Computational Fluid Dynamics (CFD)
Faster, more capable, and less costly computing hardwareFaster and better algorithms
Higher fidelity flow physics modeledExpanding simulations towards edges of flight envelopeIntegration with structural and systems modeling (MDO)Integration with wind tunnel and flight testing
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The next decade in commercial airplane aerodynamics – a Boeing perspective
CFD multipoint design/optimization
Transonic CFD for full configurationAdaptive grid technology for the design optimizationStructural model including aeroelasticsInclude weight effects in optimization Include manufacturing and structural constrainsFlight conditions from operating envelope
Drag accuracy is key to optimization
Tail-off
Lines Pre-test CFDSymbols Test data
Spar constraints
Spar constraints at side of body
Nacelle minimum keel height
Curvature constraints
Sample manufacturing and structural constraints
Tail-on and trimmed
Predictions of both drag
level and increment
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The next decade in commercial airplane aerodynamics – a Boeing perspective
CFD near edges of the flight envelope
Expanding calibrated CFD envelope to conditions with massively separated flows
Stability and controlBuffetWing deformations under extremer loadings
CFD challenges–
Large regions of separated flow–
Turbulence models–
RANS and URANS/DES–
Wind-tunnel test data needed for calibration–
Close to Mach one–
Model aeroelastics–
Wall effects
Separated flow
RANS four-engine transport
Cp comparison at approximately 2.5g at Mach dive
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The next decade in commercial airplane aerodynamics – a Boeing perspective
CFD near edges of the flight envelope
Asymmetric flight conditions for stability and control control-surface effectiveness
Full configurations in cruise and at low speedsComplex geometries (high-lift flaps, vortex generators)Shock boundary-layer interactionWing shape under loading
Lateral/Directional T&I and Wall Interference
Rudder effectiveness Yaw at high Mach number
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The next decade in commercial airplane aerodynamics – a Boeing perspective
CFD high lift aerodynamics
Pressure coefficients
Raw lofts
Positioned geometry Surface grid
Volume grid
Surface streamlines
Automated Navier-Stokes 3D process flow with one day turn around
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Determine jet/flap interaction/loads
Design for desired thermal environment of aft fairing
Initial design temperature
Improved design temperature
Optimize installed performance
Minimize cabin (shock-cell) noise
CFD propulsion aerodynamics
CFD has eliminated most powered wind tunnel model testing on conventional configurations
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The next decade in commercial airplane aerodynamics – a Boeing perspective
The future for wind tunnels
Wind tunnels will continue to play a significant role in commercial airplane aerodynamic development:
Design verificationDatabase collectionCFD validationNew technologiesNew configuration concepts
Reduction in testing time enabled by availability of mature and “calibrated” CFD
Boeing’s primary wind tunnel evaluation criteria:
767(1980)
777(1990)
787
(2005)
Occ
upan
cy h
ours
-25 %
-30 %
Technical viability – can do the required testing
Accuracy and Validation – results that can be trusted
Availability – ready and available when needed
Productivity – complete required testing in a timely manner
Reliability – keeps working without interruption
Security – privacy and confidentiality assured
Cost efficiency – good value for the money
Tunnel testing time
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Types of wind tunnel testing
Configuration development testingIncremental and absolute aerodynamic coefficient dataCruise, high-lift, and flight envelope limit dataAirframe noisePropulsion installationTare and interference testingFlow control conceptsAlternate configurations will require significant additional testing
Database development testingAirplane performanceStability and control including simulator databaseAerodynamic loads throughout envelope
Specialized testingFull scale Reynolds numberThrust reversersGround effectIce accretion/ice effects
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Primary wind tunnels used by Boeing Commercial Airplanes (2000 and on)
Mountain View, CA
Farnborough, UK
Cologne, Germany
Hampton, VA
Gifu, JapanSeattle, WA
Philadelphia, PA
Le Fauga, France
Minneapolis, MN
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Flight testing aerodynamic technologies
Flight testing for certificationFlight testing for development/evaluation of aerodynamic technologies
Certain technologies are difficult to simulate on scaled models in tunnelConcept to be flight tested must integrate with test vehicleFlight testing to provide operational experience
Natural laminar flow Quiet-Technology Demonstrator (QTD2)
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The next decade in commercial airplane aerodynamics – a Boeing perspective
COLLEGE
Future aerodynamics engineers
Industry/ academia collaboration
Nurture students through funded research, internships, scholarships, etc.
Encourage programs that teach teamwork, multi-disciplinary studies
Continuing education and on-the-job training
Retain knowledge from retiring senior engineers
Encourage youth into science, technology, engineering, math (STEM) careers
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic levers
(3) Airplane Configurations
Aerodynamic product technologies
Aerodynamic tools, processes, and capabilities
Airplane configurations
Copyright © 2009 Boeing. All rights reserved. KATnet II Bremen 2009 | 35
The next decade in commercial airplane aerodynamics – a Boeing perspective
Aerodynamic opportunities and challenges on alternate configurations
Geometries tailored to enhance laminar flow control
Advanced multi-
disciplinary optimization
Skin friction control
Aerodynamic surfaces designed for active flow control
Induced drag reduction with novel non-planar wing configurations
Boundary-layer ingestion for increased propulsion efficiency
Incorporation of novel propulsion systems (e.g., open fan)
Advanced integration of aerodynamics, structures and systems
Control configured empennage
Configuration optimized for noise
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Alternate configuration concepts New challenges for aerodynamic design
Aerodynamic tools and processes that have been refined for tube-and-wing configurations must be updated/calibrated for non-classical aircraft configurations
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Commercial airplane aerodynamics: What is next?
Readiness ofadvanced aerodynamic
technologies
Future configurations
Further significant reduction in fuel burn, noise, and emissions
Regulatory requirements
Market requirements
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The next decade in commercial airplane aerodynamics – a Boeing perspective
Summary
Aerodynamics will be key contributor to the future of aircraft designSafetyEfficiencyEnvironmental compatibility
The next decade of challenges will be multidisciplinaryNew aerodynamic technologies are on the horizonIntegration with structures, propulsion, and systems, enabled by further computational advancesManufacturability and maintainability to introduce flow control methods
Aerodynamic technologies, together with tools, processes, and people, will be keys to future advances
Copyright © 2007 Boeing. All rights reserved. 39