Post on 04-Jun-2018
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The “Flight Template”
A tool forOptimization of sailplane aerodynamics
at preliminary design stage
for cross country flight
Prepared and presented byMatthieu Scherrer
8/14/2019 Ostiv presentation V2
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Contents
IntroductionAerodynamic in sailplane optimization
Flight template TheoryFlight template concept & determination
Using Flight TemplatesFor airfoil selectionFor AR selectionFor airfoil optimization
Conclusion
8/14/2019 Ostiv presentation V2
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Introduction
8/14/2019 Ostiv presentation V2
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Optimizing according flight history
We should optimize the sailplane according toits use during a cross country flight :
h(t) V(t)
Climbing… … straight flight
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Sailplane optimization
Sailplane performance is not only aerodynamics :This is a mixing between mass (ballast capability) andaerodynamics aspects.A method is proposed, that put aerodynamics aspectof performance « in a nutshell ».
-5
-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
050 100 150 200 250
V (km/h)
V z
( m / s )
50kg/m²
30kg/m²
40kg/m²
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.025 0.05 0.075
CD
C L
Speed polars for differentwing loading …
… correspond to one single equivalent aerodynamic
polar…
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.5 1 1.5 2 2.5 3
1/sqrt(CL)
C D / C L ^ 1
. 5
… and one drag polar.
Performance for the pilot...
...performance for the designer.
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The aerodynamic designerdilemna 1/3
What would be great to do…
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.005 0.01 0.015 0.02
CD
C L
Decrease drag-> straight flight
Increase maximum lift-> climbing
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The aerodynamic designerdilemna 2/3
… and what is possible to do
You cannot win on all the aerodynamic topicsThere is always an “exchange rate”
-> what is best at the end ?
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.005 0.01 0.015 0.02CD
C L
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Given what is possible to do, what is the best between :
An aerodynamic behavior that favors climbing ?
An aerodynamic behavior that favors straight flight ?
This is a compromise : we have to quantify how manyof each aerodynamic component we should have(like a recipe)
There is a need for a «cost function», that gives a figurerepresentative for the global performance.
The aerodynamic designerdilemna 3/3
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Flight Template theory
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Flight template theory
Drag is the force that flies the sailplane down :-> we should try to minimize power absorbed by drag
Airspeed
Lift
Drag
Weight
No more explicit time dependencyTime depandancy embodied by the “Flight template”
L Lt L L D dC C f C V C C S
P rangeC
3
L
)()()(2
)(~1
)( L L
Lt C dC
t d T
C f
dt t V t C T S
T
dE P DFlight
3 )()(2
dt C SV Vdt DdE D32/1
Time dependant
M a t h e m a
t i c a l
t r a n s f o r m a
t i o n
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Flight template interpretation
Building & interpreting flight templateSpeed history
0
50
100
150
200
250
0 20 40 60 80 100t (s)
V a
( k m / h )
CL history
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 20 40 60 80 100t (s)
C L
CL history
Re-ordered CL history
dCL
dt
Flight tem plate
00.20.4
0.60.8
11.21.41.61.8
2
0 0.2 0.4 0.6 0.8 1 1.2 1.4CL
f t ( C L )
ft(CL=1)= 1/T*dt/dCL(CL=1) = 1/100*9/.1 = 0.9
Speed history
CL history ft(C L)= density of each CL
during the flight
)(1
)( L L
Lt C dC dt
T C f
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Performance cost function
For a reasonnably calm flight :
With a function of wing loading
At the end, power dissipated by drag is expressed as :
LC
V V 1
S m
h g
hS m
V )(
2, 1
2/3
31
2 L
D
C
C SV P
L Lt L
L D
L
D dC C f C
C C
C
C
rangeC 2/32/3
L
)()(
Aerodynamically relevant cost function =Weighted C D /C L
3/2
Aerodynamics aspects
Wing loading aspects
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How to get a Flight Template ?
GPS recording is widely used : we can easily get the history ofa flight.CL is extracted from :
2
21
)(
,)()(
W t V
hS m
V t Nz t C L
S m
h g
hS m
V )(
2, 1
2
1cos
1
g
V Nz
Speed history
Sailplane mass
(from path)
Wind estimation
)(1
)( L L
Lt C dC dt
T C f
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Selected flight template examples
Path color Wing loading Scoring Starting airfield
Pink 41kg/m² 464km Nogaro LFCN
Blue 33kg/m² 227km Moissac LFCX
Brown 31kg/m² 167km Bourg Saint Bernard LFIT
50 75 100 125 150 175 200
V
F T ( V )
Denis (454km) Mat thieu (227km) Adrien (167km)
3 Pegasus glider
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Selected flight template examples
50 75 100 125 150 175 200
V
F T ( V )
Denis (454km) Matthieu (227km) Adrien (167km)
0 0.2 0.4 0.6 0.8 1 1.2 1.4
CL
F T ( C L )
Denis (454km) Mat thieu (227km) Adrien (167km)
Transcriptionfrom speed to C
Lreduces dispersion betweenflights, pilots, flying days,sailplanes, etc…
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« Envelope Flight template » strategy
0 0.5 1 1.5CL
F T ( C L )
Enveloppe Flight Template
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Using Flight TemplatesFor airfoil selection
For AR selectionFor airfoil optimization
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Xfoil calculations (GNU licence)2D calculation, from airfoil geometryBoundary layer & transition modelingDirect & indirect design capabilities
Airfoil computation
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Calculated airfoils
Airfoil Sailplane
E603 (public) Astir, Twin Astir
FX S 02-196 (public) LS1c/d,standard cirrus
HQ300 (public) (DG --- ?)
OAP-1 (from photo) Pegase
HX83N80 (from photo) Discus BDuo Discus
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Calculated drag polars
Computed drag polar for various airfoils
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.005 0.01 0.015 0.02
CD
C L
Eppler E603 (public)FX S 02-196 (public)HQ-300GD-mod2 (public)OAP1 (from photo)Discus (from photo)
Xfoil Re*CL^(1/2)=1 250 000
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Sorting airfoilswith Flight template
Computed CD/CL^1.5 polar for various airfoils
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.01 0.02 0.03 0.04 0.05CD/CL^1.5
C L
Eppler E603 (public)FX S 02-196 (public)HQ-300GD-mod2 (public)OAP1 (from photo)Discus (from photo)
Xfoil Re*CL (̂1/2)=1 250 000
Weighted CD/CL^1.5 polar for various airfoils
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.01 0.02 0.03 0.04 0.05
CD
C L
Eppler E603 (pub lic)FX S 02-196 (public)HQ-300GD-mod2 (public)OAP1 (from photo)Discus (from photo)
Xfoil Re*CL^(1/2)=1 250 000
Envelope FlyingTemplate
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.5 1
FT
C LX
=
S i i f il
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Sorting airfoilswith Flight template
Weighted CD/CL^1.5 polar for various airfoils
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.01 0.02 0.03 0.04 0.05
CD
C L
Eppler E603 (public)FX S 02-196 (public)HQ-300GD-mod2 (public)OAP1 (from photo)Discus (from photo)
Xfoil Re*CL (̂1/2)=1 250 000
Detail of weightedpolaras function of C L
Final cost function value
-> Discus airfoil is the bestairfoil according to this criteria
L Lt L
L D
L
D dC C f C
C C
C
C
rangeC 2/32/3
L
)()(
0.0100 0.0110 0.0120 0.0130 0.0140 0.0150 0.0160 0.0170 0.0180
HQ-300GD-mod2 (public)
FX S 02-196 (public)
OAP1 (from photo)
Eppler E603 (public)
Discus (from photo)
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Using Flight TemplatesFor airfoil selectionFor AR selection
For airfoil optimization
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MIAReXNon linear extended lifting lineCoupled with Xfoil
Quick and accurate computation
Wing computation
Local “2,5D” characteristics Alpha polars
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If AR is augmented with fixed span :Induced drag is reducedAirfoil drag is increased
Global result as integrated overpolar needed.
AR effect 1/2
CDi(CL) & CDairfoil(CL)Discus case
-0.25
0
0.25
0.5
0.75
1
1.25
1.5
0 0.005 0.01 0.015 0.02 0.025 0.03
CD
C L
CDi for Discus AR=28.5
CDi for Discus AR=21.6 (Baseline)
CDi for Discus AR=17.3
CDairfoil for Discus AR=28.5
CDairfoil for Discus AR=21.6 (Baseline)
CDairfoil for Discus AR=17.3
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Cost function values as function of AR
AR effect 2/2
From Thomas F,“Fundamental of Sailplane Design”
Cost function as function of AR(modified Discus wing)
0.95
0.975
1
1.025
1.05
1.075
15 20 25 30 35
AR
R e l a t i v e c o s t f u n c t i o n v a l u
Baseline (Discus)
Quasi optimum geometry
0,5%
“Aerodynamic only” optimum
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Using Flight TemplatesFor airfoil selection
For AR selection
For airfoil optimization
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Numerical optimisation
Drag Polar
Aerodyn. Calc.- Xfoil (2D)- MIAReX(2.5D)
Geometryparametrization
Weightingbyflighttemplate
0.0145
OptimizedGeometry
Optimizer
Optimizationcriteria
Cost functionvalue
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Airfoil geometry
Relative thickness fixedRelative camber, position of thickness& position of camber to be optimized together (warping)
Max thicknessshifted backward
Max thicknessshifted forward
Camberincreased
Max cambershifted backward
Max cambershifted forward
Original airfoil
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A new geometry was found by the optimizer
Result of the optimization 1/2
OriginalAirfoil
ModifiedAirfoil
Relativethickness 15.80% 15.80%
Position ofmaximumthickness
41.00% 33.60%
Relativecamber 3.71% 3.29%
Position ofmaximumcamber
45.30% 43.80%
Cost functionvalue 0.01467457 0.01452589 - Decambered
- Camber moved forward- Thickness moved forward
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Result of the optimization 2/2
Computed drag polar
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.005 0.01 0.015 0.02
CD
C L
Discus Airfoil
Modified Discus airfoil
Xfoil Re*CL^(1/2)=1 250 000
Weighted CD/CL^1.5 polar
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.005 0.01 0.015 0.02 0.025 0.03 0.035
CD/CL^1.5
C L
Discus A irfoil
Modified Discus airfoil
Xfoil Re*CL^(1/2)=1 250 000
Aerodynamic characteristicsof the optimized airfoil
0.01467457
0.01452589
- Narrower laminar range- Higher C Lmax- Lower Cm 0
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Conclusion
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Sailplane Optimization
Using science…
… to make pilots happy
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Conclusion 1/3
A new tool is proposed : the “Flight template”
0 0.5 1 1.5CL
F T ( C L )
Enveloppe Flight Template Treatment of many flight recordinghad led to the definition of an
“Envelope Flight template”.
This represents a statistically relevantprogram of a typical cross country flight
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Aerodynamic optimization can be easily performedwith this new tools
Airfoil selection and sorting
Multipoint wing optimization
Airfoil numerical optimization
Aerodynamic only optimization
Conclusion 2/3
Computed drag polar for various airfoils
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 0.005 0.01 0.015 0.02
CD
C L
EpplerE603 (public)FXS 02-196(public)HQ-300GD-mod2(public)OAP1(from photo)Discus (from photo)
Xfoil Re*CL^(1/2)=1250000
Cost functionas functionof AR(modifiedDiscus wing)
0.95
0.975
1
1.025
1.05
1.075
15 20 25 30 35
AR
R e l a t i v e c o s t f u n c t i o n v a l u e
Baseline(Discus)
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Conclusion 3/3
Way forward :
Using the Flight template for computingaerodynamic performance, coupled with otherdisciplines for a multidisciplinary optimizationprocess.
Objective : optimizing the sailplane as a wholething, and not only its aerodynamic.
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Questions ?
Have nice flights !
Matthieu.scherrer@free.fr