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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
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.
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
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
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
In cruise, trailing edge elements are adjusted at regular intervals to minimize dragSimplified actuation systemSmall angle variationsUp and down movements
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
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
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
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
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
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
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
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