Optimized Off-Design Performance of Flexible Wings with Continuous Trailing Edge … · 2015. 2....
Transcript of Optimized Off-Design Performance of Flexible Wings with Continuous Trailing Edge … · 2015. 2....
-
Optimized Off-Design Performance of Flexible Wings with Continuous Trailing-Edge Flaps
!
!!!
David L. Rodriguez Michael Aftosmis Marian Nemec George Anderson
!Applied Modeling and Simulation Branch, NASA Ames Research Center
!!
AMS Seminar Series - February 17, 2015
-
3/2/15 DR
Modern Wing Structures Technology
• Many new concepts have high aspect ratio, light, very-flexible, composite wings
• Wing shape varies greatly throughout mission profile
• Boeing 787 wing tips deflect 10 feet at cruise!
2
-
3/2/15 DR
Wing Morphing Technology• Wing morphing has been used
since the beginning of human flight
• Basic concept is to actively reshape the wing in flight to improve performance and/or control
• One concept currently being researched is the VCCTEF
3
-
3/2/15 DR
Goal: Evaluate VCCTEF Concept• Variable Camber Continuous Trailing Edge Flaps
• Evaluate the maximum potential benefit of VCCTEF on a generic transport model (GTM) aircraft at cruise • aerodynamic evaluation sufficient
• other design features neglected or held constant (structural weight and layout, trim, actuator weight, viscous effects)
• for simplicity, work with wing and fuselage only
• Must include aeroelastic effects in analysis • conventionally stiff wing
• modern, highly flexible wing
• Develop methodology for designing (optimizing) transport wings while addressing aeroelastic effects
4
-
3/2/15 DR
VCCTEF Layout on GTM• Flaps over most of the span of the wing
• 1 large inboard flap, 14 smaller outboard flaps, 1 aileron
• 3 segments per flap (camber)
• Elastomer material between flaps to seal gaps
• Tailors spanwise lift distribution throughout mission
5
-
3/2/15 DR
Modeling the VCCTEF
6
-
3/2/15 DR
Modeling the VCCTEF
7
• Flap deflections controlled by Blender “armature,” which is analagous to a skeleton
• Surface triangulation is bound to “bones”
• Bones can only rotate about hinge lines
• Sequential flaps bones linked to each other
• Blended transition between flaps to mimic elastomer material
-
3/2/15 DR
Modeling the VCCTEF with Blender
8
-
3/2/15 DR
Goal: Evaluate VCCTEF Concept• Variable Camber Continuous Trailing Edge Flaps
• Evaluate the maximum potential benefit of VCCTEF on a generic transport model (GTM) aircraft at cruise • aerodynamic evaluation sufficient
• other design features neglected or held constant (structural weight and layout, trim, actuator weight, viscous effects)
• for simplicity, work with wing and fuselage only
• Must include aeroelastic effects in analysis • conventionally “stiff” wing
• modern, highly flexible, “soft” wing
• Develop methodology for designing (optimizing) transport wings while addressing aeroelastic effects
9
-
3/2/15 DR
Aerodynamic Analysis Load Transfer
Structural Analysis Deform Geometry
Deformed GeometryConverged?
Stop
Yes
No
Baseline Geometry
AeroelasticIteration
Deformer
AeroelasticAnalysis
Static Aeroelastic Analysis Architecture
10
Cart3D BEAM Blender
-
3/2/15 DR
Aerodynamic Shape Optimization Architecture
11
AeroelasticAnalysis
Aeroelastic Deformation Converged?
Stop
Optimized Undeformed Geometry
Aerodynamic Optimization
Baseline Undeformed Geometry
Yes
No
-
3/2/15 DR
Performance of Optimization Method• Alternating aeroelastic
analyses and aerodynamic optimizations • aeroelastic analysis required
5 iterations
• typical optimization required 60-80 design space samples
• Typical aeroelastic optimization • converges in 3-4 iterations
• one iteration ≈ 1 day of wall clock time on 64-cpus of endeavour
12
Optimization Iteration
Tip
Defle
ctio
n (fe
et)
Drag
Coe
ffici
ent
0 1 2 30
1
2
3
4
5
6
7
8
0.0146
0.0148
0.0150
0.0152
0.0154
0.0156
0.0158
0.0160
0.0162
AeroelasticAnalysis
Aeroelastic Deformation Converged?
Stop
Optimized Undeformed Geometry
Aerodynamic Optimization
Baseline Undeformed Geometry
Yes
No
-
3/2/15 DR
Problem Setup
1. Establish a new baseline for mid-cruise • aerodynamic optimization of GTM wing
with VCCTEF
• include aeroelastic effects
• disregard other disciplines
2. Re-design for off-design • repeat optimization at begin and end cruise
• determines best possible performance at off-design conditions
3. Adapt flap system on baseline for off-design • optimize only flaps while maintaining baseline twist
• compare results with best possible performance from step 2
13
Takeoff Landing
Climb Descent
Cruise @ 36,000 feet
Mach 0.797
Loiter
Mid-Cruise
50% fuel
-
3/2/15 DR
Problem Setup
1. Establish a new baseline for mid-cruise • aerodynamic optimization of GTM wing
with VCCTEF
• include aeroelastic effects
• disregard other disciplines
2. Re-design for off-design • repeat optimization at begin and end cruise
• determines best possible performance at off-design conditions
3. Adapt flap system on baseline for off-design • optimize only flaps while maintaining baseline twist
• compare results with best possible performance from step 2
14
Takeoff Landing
Climb Descent
Cruise @ 36,000 feet
Mach 0.797
Loiter
Mid-Cruise
50% fuelBegin-Cruise
80% fuelEnd-Cruise
20% Fuel
-
3/2/15 DR
Problem Setup
1. Establish a new baseline for mid-cruise • aerodynamic optimization of GTM wing
with VCCTEF
• include aeroelastic effects
• disregard other disciplines
2. Re-design for off-design • repeat optimization at begin and end cruise
• determines best possible performance at off-design conditions
3. Adapt flap system on baseline for off-design • optimize only flaps while maintaining baseline twist
• compare results with best possible performance from step 2
15
Takeoff Landing
Climb Descent
Cruise @ 36,000 feet
Mach 0.797
Loiter
Mid-Cruise
50% fuelBegin-Cruise
80% fuelEnd-Cruise
20% Fuel
-
3/2/15 DR
Load Distributions
16
Verti
cal L
oad
(pou
nds/
foot
)
-1500
-1000
-500
0
500
Distance Along Elastic Axis (feet)0 10 20 30 40 50 60 70
Stiff Wing StructureSoft Wing StructureFuel @ Begin-CruiseFuel @ Mid-CruiseFuel @ End-Cruise
Center Fuel Tank Outboard Fuel Tank
EngineElastic Axis
-
3/2/15 DR
Design Optimization Problem
17
• Minimize total drag (inviscid)
• Lift is held constant
• Design variables include wing twist and VCCTEF deflections
-
3/2/15 DR
Design Variables
18
• Angle of attack
• Wing twist distribution • modeled as perturbation to original
• Blender module
• VCCTEF deflections • circular deflection
• Bernstein polynomials
• inboard flap and aileron separate
-
3/2/15 DR
Design Variables• Angle of attack
• Wing twist distribution • modeled as perturbation to original
• Blender module
• VCCTEF deflections • circular deflection
• Bernstein polynomials
• inboard flap and aileron separate
19
fixed root section
twist perturbation stations
-
3/2/15 DR
• Angle of attack
• Wing twist distribution • modeled as perturbation to original
• Blender module
• VCCTEF deflections • link segments via “circular deflection”
• Bernstein polynomials for outboard flaps
• inboard flap and aileron separate
Design Variables
20
Inboard Flap
Aileron
Outboard Flaps
∆2 = 2∆1, ∆3 = 3∆1
∆3 = 15°∆2 = 10°∆1 = 5°
Flap
Defl
ectio
n /
Unit
Desig
n Va
riabl
e
0.0
0.2
0.4
0.6
0.8
1.0
Flap Number (Outboard)1 2 3 4 5 6 7 8 9 10 11 12 13 14
B1B2 B3
B4
-
3/2/15 DR
Stiff Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
21
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
) Original GTM 124.7
Optimize Twist & Flaps
-
3/2/15 DR
Stiff Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
22
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
) Original GTMOptimize
Twist
124.7123.8
Optimize Twist & Flaps
-
3/2/15 DR
Stiff Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
23
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
) Original GTM
120.4
Optimize Twist
124.7123.8
Optimize Flaps
Optimize Twist & Flaps
-
3/2/15 DR
Stiff Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
24
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
) Original GTM
120.4
Optimize Twist
124.7123.8
120.0
Optimize Flaps
Optimize Twist & Flaps
-
3/2/15 DR
Stiff Wing GTM - Mid-Cruise Optimized
25
Cha
nge
in T
wis
t (de
gree
s)
-5-4-3-2-1012345
Spanwise Location (feet)0 10 20 30 40 50 60 70
Flap
Defl
ectio
n (d
egre
es)
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
Inboard Flap Outboard Flaps Aileron
-
3/2/15 DR
Stiff Wing Off-Design Analysis and Optimization
• Analyze wing optimized for mid-cruise at off-design conditions • begin-cruise (80% max fuel)
• end-cruise (20% max fuel)
• Re-optimize wing for the off-design conditions
• Quantify penalty for flying mid-cruise optimized wing at off-design
26
50
100
150
200
Original GTM Mid-Cruise Opt. Begin-Cruise Opt.
148.7149.9156.2
Stiff Wing GTM CL = 0.565!80% fuel
Invi
scid
Dra
g C
ount
s
50
100
150
200
Original GTM Mid-Cruise Opt. End-Cruise Opt.
96.197.499.8
Stiff Wing GTM CL = 0.455!20% fuel
Invi
scid
Dra
g C
ount
s
-
3/2/15 DR
Stiff GTM Wing - VCCTEF Adaptation• Start with wing
designed for mid-cruise
27
Begin-Cruise
End-Cruise
Mid-Cruise Design
Invi
scid
Dra
g
(counts
)
149.9
Invi
scid
Dra
g
(co
unts
) Mid-Cruise Design 97.4
Best Possible
-
3/2/15 DR
Stiff GTM Wing - VCCTEF Adaptation• Start with wing
designed for mid-cruise
• Compare with wing optimized for off-design condition
28
Begin-Cruise
End-Cruise
Mid-Cruise Design
Invi
scid
Dra
g
(counts
)
148.7
149.9
Best Possible
Invi
scid
Dra
g
(co
unts
) Mid-Cruise Design 97.4
96.1Best Possible
-
3/2/15 DR
Stiff GTM Wing - VCCTEF Adaptation• Start with wing
designed for mid-cruise
• Compare with wing optimized for off-design condition
• Optimize VCCTEF deflections to recover lost performance
• Improvement in both cases
29
Begin-Cruise
End-Cruise
Mid-Cruise Design
Invi
scid
Dra
g
(counts
)
148.7
149.9
149.2Optimize Flaps
Best Possible
AdaptedVCCTEF
Invi
scid
Dra
g
(co
unts
)
Optimize Flaps
Mid-Cruise Design 97.4
96.1Best Possible96.2
AdaptedVCCTEF
-
3/2/15 DR
Soft Wing Definition• Stiff wing used structural model similar to that of actual
transport
• Soft wing is defined by halving the bending and torsional stiffness distribution of stiff wing
30
-
3/2/15 DR
Soft Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
31
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
)
Optimize Twist & Flaps
Original GTM123.4
-
3/2/15 DR
Soft Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
32
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
)
Optimize Twist & Flaps
Original GTM
Optimize Twist
123.4
118.2
-
3/2/15 DR
Soft Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
33
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
Invi
scid
Dra
g (co
unts
)
Optimize Twist & Flaps
Original GTM
114.9
Optimize Twist
123.4
118.2
Optimize Flaps
-
3/2/15 DR
Soft Wing Optimization and Analysis (Mid-Cruise)
• Start with original GTM
• Optimize twist
• Optimize flaps (fixed twist)
• Optimize twist and flaps
34
Invi
scid
Dra
g (co
unts
)
Optimize Twist & Flaps
Original GTM
114.9
Optimize Twist
123.4
118.2
114.5
Optimize Flaps
Spanwise Fraction
Sect
ion
Lift
0 0.2 0.4 0.6 0.8 10
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Elliptic DistributionOriginal GTMOptimized TwistOptimized FlapsOptimized Twist+Flaps
-
3/2/15 DR
Flap
Defl
ectio
n (d
egre
es)
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0
Inboard Flap Outboard Flaps Aileron
Cha
nge
in T
wis
t (de
gree
s)
-5-4-3-2-1012345
Spanwise Location (feet)0 10 20 30 40 50 60 70
Soft Wing GTM - Mid-Cruise Optimized
35
-
3/2/15 DR
Soft Wing Off-Design Analysis and Optimization
• Analyze wing optimized for mid-cruise at off-design conditions • begin-cruise (80% max fuel)
• end-cruise (20% max fuel)
• Re-optimize wing for the off-design conditions
• Quantify penalty for flying mid-cruise optimized wing at off-design
36
50
100
150
200
Original GTM Mid-Cruise Opt. Begin-Cruise Opt.
143.1143.5154.5
Soft Wing GTM CL = 0.552!80% fuel
Invi
scid
Dra
g C
ount
s
50
100
150
200
Original GTM Mid-Cruise Opt. End-Cruise Opt.
91.993.7100.6
Soft Wing GTM CL = 0.442!20% fuel
Invi
scid
Dra
g C
ount
s
-
3/2/15 DR
Soft GTM Wing - VCCTEF Adaptation• Start with wing
designed for mid-cruise
37
Invi
scid
Dra
g
(co
unts
) Mid-Cruise Design 143.5
Invi
scid
Dra
g
(counts
) Mid-Cruise Design 93.7
91.9
Begin-Cruise
End-Cruise
-
3/2/15 DR
Soft GTM Wing - VCCTEF Adaptation• Start with wing
designed for mid-cruise
• Compare with wing optimized for off-design condition
38
Invi
scid
Dra
g
(counts
) Mid-Cruise Design 93.7
91.9Best Possible
Invi
scid
Dra
g
(co
unts
) Mid-Cruise Design 143.5Best Possible
143.1
Begin-Cruise
End-Cruise
-
3/2/15 DR
Soft GTM Wing - VCCTEF Adaptation• Start with wing
designed for mid-cruise
• Compare with wing optimized for off-design condition
• Optimize VCCTEF deflections to recover lost performance
• Improvement in both cases
39
Begin-Cruise
Invi
scid
Dra
g
(co
unts
)
Optimize Flaps
Mid-Cruise Design 143.5Best Possible
143.1AdaptedVCCTEF
End-CruiseIn
visc
id D
rag
(counts
)
Optimize Flaps
Mid-Cruise Design 93.7
91.9Best Possible 92.1
AdaptedVCCTEF
-
3/2/15 DR
Conclusions• Fast iterative method developed to aerodynamically optimize
transport wings while addressing aeroelastic effects • VCCTEF system was evaluated on GTM wing (stiff and soft) as a
means to improve off-design cruise performance • achieved near optimal performance
• results suggest wave drag could be actively reduced
• flap system could reshape a wing with constant airfoil section (ease of manufacturing) to a more optimal design for any given flight condition
• Results similar on conventional (stiff) and highly flexible (soft) wings • Designer of an aircraft with VCCTEF could assume near-optimal
performance throughout cruise
40
-
3/2/15 DR
Future Work• Another off-design case - over-speed
• another common off-design case is flying faster (to keep a schedule)
• can the VCCTEF improve cruise performance at a higher Mach number?
• repeat evaluation at Mach 0.827 at mid-cruise
• Evaluate VCCTEF on other transport aircraft designs • Truss-Braced Wing
• Common Research Model (higher aspect ratio)
41