1. Drag Reduction of MAV by Biplane Effect
Chinnapat THIPYOPAS
Graduate student, Department of Aerodynamics
and
Jean-Marc MOSCHETTA
Associate Professor of Aerodynamics, Department of Aerodynamics
Ecole Nationale Supérieure de l’Aéronautique et de l’Espace (SUPAERO)
10 Av. Ed. Belin, Toulouse, France
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2. Department of Aerodynamics SUPAERO
Contents
Introduction
Part 1 Optimization - (Experimental)
- (Numerical)
Part 2 Biplane Combinations
Part 3 Propeller Influence
Conclusions
Department of Aerodynamics SUPAERO
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3. Department of Aerodynamics SUPAERO
Contents
Introduction
Part 1 Optimization - (Experimental)
- (Numerical)
Part 2 Biplane Combinations
Part 3 Propeller Influence
Conclusions
Department of Aerodynamics SUPAERO
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4. Monoplane MAV concepts
Minus-Kiool 57g cm
Plaster 64g - 23 cm
Department of Aerodynamics SUPAERO
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5. Total Drag = Parasite Drag + Induced drag
Department of Aerodynamics SUPAERO
Monoplane-MAVs
Plaster, SUPAERO
Maxi-Kiool, SUPAERO
Induced Drag 76%*
Drenalyne, SUPAERO
Biplane Concept !!
Total Drag = Parasite Drag + Induced drag
100 %
20-30 %
70-80 %
* J.L’HENAFF, SUPAERO 2004
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6. Department of Aerodynamics SUPAERO
Monoplane vs. biplane
wing drag = Parasite Drag + Induced Drag
Parasite drag is a function of Skin-Friction which depends on Wing Chord
Induced Drag is very strongly effected by Aspect Ratio
Constant lift, speed & overall dimension
- Why interest biplane plane concept ?
- high parasite drag (skinfriction drag) due to boundary layer
- Low induced drag because of higher aspect ratio
Biplanes were most successfully marketed in the early days of aviation when the wing sections used were very thin and consequently the wing structure needed to be strengthened by external bracing wires. The biplane configuration allowed the two wings to be braced against one another, increasing the structural strength.
The big disadvantage of the biplane layout was that the two wings interfered with one another aerodynamically, each reducing the lift produced by the other.
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7. Department of Aerodynamics SUPAERO
Contents
Introduction
Part 1 Optimization - (Experimental)
- (Numerical)
Part 2 Biplane Combinations
Part 3 Propeller Influence
Conclusions
Department of Aerodynamics SUPAERO
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8. Department of Aerodynamics SUPAERO
Optimization process
Design Constraints
Maximum overall dimension : 20 cm
Lift at 10 m/s = Weight = 80 grams
Manoeuvrability :
20 grams min.
for payload
Cost function
Minimum Drag at cruise condition
Department of Aerodynamics SUPAERO
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9. Department of Aerodynamics SUPAERO
Experimental setup
Wind tunnel
Test Section 45cm x 45cm
Velocity 10 m/s
Measurement
3-component balance
Models
16 flat-plate wing models
Aspect ratio 1 – 4
Taper ratio 0.2 – 1.0
Sweep angle °
Reference surface/length
For comparison, every model is referenced by same area, length
AR1, Taper 1, No Swept
Strut
20cm.
AR2.5, Taper0.6, Swept25°
Department of Aerodynamics SUPAERO
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10. Model’s Drag Correction
Strut
Model is not attached to strut
Model
Strut
Department of Aerodynamics SUPAERO
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11. Department of Aerodynamics SUPAERO
Results
No.
Model Name
Area * * *
(cm.)
Disc
314.2
2.8223
0.0232
0.0147
1.997
0.3578
8.32
0.127
5.052
8.56
0.055
5.871
4.6 1
A1S0T0.2
144.0
2.1647
0.0146
0.0202
0.887
0.5127
6.176
0.293
2.209 23
0.085
3.803
12.3 2
A1S0T1
200.0
2.5556
0.0219
0.0214
1.449
0.3888
5.336
0.189
3.399
14.6
0.073
4.39
8.56 3
A1S25T0.6
224.8
2.4667
0.0112
0.01
1.621
0.3857
8.926
0.164
3.953
13.5
0.058
5.532
7.56 4
A1S50T0.2
144.0
2.4114
0.0163
0.0224
1.046
0.4178
9.967
0.256
2.530 21
0.078
4.128
11.3 5
A1S50T1
130.2
2.4902
0.0183
0.0281
0.944
0.3738
7.633
0.252
2.552
21.8
0.081
3.967
12.2 6
A2,5S0T0.6
146.7
3.7786
0.02
0.0273
0.627
0.2814
3.099 - - -
0.055
6.036
6.38 7
A2,5S0T1
137.9
3.556
0.0112
0.0162
0.572
0.2966
2.43 - - -
0.054
5.899
7.44 8
A2,5S25T0.6
146.7
3.6615
0.0172
0.0234
0.619
0.3032
4.904 - - -
0.052
6.288
6.38 9
A2,5S25T1
137.9
4.0961
0.02
0.029
0.601
0.2683
4.503 - - -
0.061
5.227
6.5 10
A2,5S50T1
102.9
3.0513
0.0067
0.0131
0.535
0.319
5.766 - - -
0.071
4.552
11.5
Only AR1 wings have lift enough for 80 grams.
Approximated 50% produced by each wing for biplane, some of AR2.5 wings have lift enough to fly.
Biplane has L/D more than monoplane (4 and 6)
All configuration that best in L/D have maximum wing area. 11
A4S0T0.2
99.3
4.3273
0.0166
0.0326
0.355
0.2413
2.453 - - -
0.060
5.404
8.46 12
A4S0T1
94.1
4.5539
0.0167
0.0345
0.381
0.2455
1.497 - - -
0.074
4.386
9.83 13
A4S25T0.6
96.6
4.9468
0.0133
0.0275
0.418
0.2363
3.261 - - -
0.058
5.613
7.6 14
A4S50T0.2
84.1
3.3926
0.0124
0.0295
0.481
0.2943
5.221 - - -
0.092
3.499
14.3 15
A4S50T0.6
79.5
3.4883
0.0095
0.0239
0.442
0.3056
5.95 - - -
0.091
3.533
14.9 16
A4S50T1
76.7
3.5983
0.0141
0.0368
0.424
0.2781
5.311 - - -
0.091
3.508
15.1
Red color is a value referenced by wing’s area
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12. Department of Aerodynamics SUPAERO
Numerical method
Vortex lattice method : code TORNADO v126b [T. Melin; KTH]
Drag evaluation
Parasite Drag = 1.5 of equivalent flat plate skin friction drag (Blasius Eq. + Thwaites formula) +
Induced drag (TORNADO)
Various models :
aspect ratio
taper ratio
sweep angle
Department of Aerodynamics SUPAERO
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13. Department of Aerodynamics SUPAERO
Results
Triplane
Biplane
Monoplane
An approximate
stall angle curve
L/D at cruise cond. increases with AR
Poor manoeuvrability of monoplane wings with AR 2 and higher
greater L/D for biplanes
L/D of Triplane AR4 is smaller than biplane because of high parasite drag.
Biplane AR2-3 is suitable for flight
Department of Aerodynamics SUPAERO
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14. Department of Aerodynamics SUPAERO
Biplane vs. monoplane
-50 50
100
150
200
250
0,05
0,1
0,15
0,2
0,25
0,3
0,35
0,4
Drag
Mass
Monoplane
Biplane
60 grams 80
Department of Aerodynamics SUPAERO
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15. Department of Aerodynamics SUPAERO
Contents
Introduction
Part 1 Optimization - (Experimental)
- (Numerical)
Part 2 Biplane Combinations
Part 3 Propeller Influence
Conclusions
Department of Aerodynamics SUPAERO
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16. Department of Aerodynamics SUPAERO
Other planforms
Zimmerman
Planform
Area (m2)
CL (max)
CD (min)
L/D (max)
Zim1
0.0264
1.251
0.0533
4.03
Zim2
0.0173
0.586
0.0419
5.21
Zim1Inv
0.986
0.0538
3.75
Zim2Inv
0.605
0.0344
4.96
Plaster1
0.0245
0.909
0.0411
4.92
Plaster2
0.0166
0.0354
5.47
Drenalyne1
0.0273
1.260
0.0528
4.46
Drenalyne2
0.585
0.0375
4.81
Plaster
Drenalyne
Department of Aerodynamics SUPAERO
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17. Inverse Zimmerman Torres et al., Univ. Florida, 1999
Calculation
Inverse Zimmerman Torres et al., Univ. Florida, 1999
Plaster wing Reyes et al., SUPAERO, 2001
Department of Aerodynamics SUPAERO
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18. Department of Aerodynamics SUPAERO
Scale 1 (SUPAERO)
Scale 3 (S4, ENSICA)
End-plates
Decalage
angle
Parameters
Gap
Stagger
Decalage angle
Upper Wing
Stagger
The difference in the angle of incidence of the two wings of a biplane is called the decalage
Gap U
Lower Wing
Side View
Department of Aerodynamics SUPAERO
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19. Department of Aerodynamics SUPAERO
Gap
Reduced an influence between both wings
Increase lift slope and maximum lift
Not change position of aerodynamics center
Increase drag from the structure  L/D not change
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20. Department of Aerodynamics SUPAERO
Stagger
Increase lift slope and maximum lift
Aerodynamics center is between two wing
No stagger has more L/D
Local AoA of fore-wing is bigger
Department of Aerodynamics SUPAERO
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21. Department of Aerodynamics SUPAERO
Decalage Angle
Done with positive stagger model
Strongly effect to stall angle and L/D
Negative decalage give highest wing performance
Department of Aerodynamics SUPAERO
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22. Department of Aerodynamics SUPAERO
Visualisation
S4, ENSICA
Department of Aerodynamics SUPAERO
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23. Department of Aerodynamics SUPAERO
Contents
Introduction
Part 1 Optimization - (Experimental)
- (Numerical)
Part 2 Biplane Combinations
Part 3 Propeller Influence
Conclusions
Department of Aerodynamics SUPAERO
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24. Department of Aerodynamics SUPAERO
Propeller Effect (S4)
Upper Wing
Lower Wing U
Motor
Side View 7 4 6 5 1 2 3
Front View
Half Span
Center line
Upper wing
7 motor positions
were observed.
Lower wing stall at 22°
Lower wing not stalled
The stall angle is delayed, lower wing is still not stall at AoA 22°
Upper wing stalls
At pre-stall regime, lift is increased due to propeller.
Lift increases
Motor & propeller
Test section
Power supply
Moveable
system
Tube
Lift, maximum lift and L/D are increased.
Department of Aerodynamics SUPAERO
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25. Propeller Effect (Scale 1)
Zim2 wing planform scale (20cm. Max dim.)
Monoplane Wing
Motor in front of wing gives highest performance.
The motor countering / encountering wingtip vortex effects are very small.
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26. Effect of induced flow to model Attach Motor to the model
Propeller Effect
Motor sting
Model struts
Effect of induced flow to model -2 -1 1 2 3 4 5 6 7
-10 -5 10 20 25
Incidence
B = mid position
R = upper wing
G = lower wing
L/D 15
Motor on upper and lower wing have the same effect
Middle position is poorest
Attach Motor to the model
Attached on upper and lower wing
Same efficiency
Delay stall phenomena, increase maximum lift
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27. Department of Aerodynamics SUPAERO
Contents
Introduction
Part 1 Optimization - (Experimental)
- (Numerical)
Part 2 Biplane Combinations
Part 3 Propeller Influence
Conclusions
Department of Aerodynamics SUPAERO
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28. Conclusions On-going developments
Department of Aerodynamics SUPAERO
Conclusions
Biplane is better than monoplane for this design criteria
Wind tunnel measurements and numerical calculations confirm the interest for biplane MAV wings.
AR 2.5 to 3 are appropriate for biplane MAV concepts.
On-going developments
More accuracy measurement
Further optimization of motor position (wingtip)
Optimizing biplane-connecting structure
Pototype of Biplane MAV
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29. Thank you for your attention
P29/29

30. Drag Reduction of MAV by Biplane Effect
Chinnapat THIPYOPAS
Graduate student, Department of Aerodynamics
and
Jean-Marc MOSCHETTA
Associate Professor of Aerodynamics, Department of Aerodynamics
Ecole Nationale Supérieure de l’Aéronautique et de l’Espace (SUPAERO)
10 Av. Ed. Belin, Toulouse, France

31. Parasite and Induced Drag
Department of Aerodynamics SUPAERO
Parasite and Induced Drag 55
- Why interest biplane plane concept ?
- high parasite drag (skinfriction drag) due to boundary layer
- Low induced drag because of higher aspect ratio
The zone which biplane has total drag less than monoplane configuration
(when Induced drag > 45% total drag)

32. Parasite and Induced Drag
Airplane drag = Parasite Drag + Induced Drag
Parasite drag is a function of Skin-Friction which depends on Wing Chord
Induced Drag is very strongly effected by Aspect Ratio
The zone which biplane has total drag less than monoplane configuration
(when Induced drag > 45% total drag)
case
a.)
AR1
b.)
AR2
c.) 2 x AR2
total
Surface S
S/2
Lift for each wing W
W/2
Max. Lift L
L/2
Lift coef. CL
2CL
Skin friction drag Df
Df/1.414
1.414Df
Induced drag coef.
CDi
2CDi
CDi/2
Induced drag Di
Di/4
Di/2
Total drag
1.5Df + Di
1.5Df / Di
1.5*1.414Df + Di/2 55
- Why interest biplane plane concept ?
- high parasite drag (skinfriction drag) due to boundary layer
- Low induced drag because of higher aspect ratio

33. Results Reynolds number effect on L/D
Winglet can improve wing performance
Gap increases the lift slope and maximum lift
L/D increased by positive stagger
Stall angle and maximum lift changed by decalage angle
Parasite drag from the strut between two wing is very important
The induced drag is independent of the stagger angle (Munk's stagger theorem). If the system is unstaggered then D_ij = D_ji.
which is Munk's reciprocity theorem. The induced drag of a multiplane system does not change if the elements are translated in a direction parallel to the direction of flight.

34. Propeller-induced lift
Increasing in lift

35. Why are these 16 models ?
The Taguchi method was used in the first experimental design table. But an interaction between each parameters is very strong.
To determine the optimizing model, some interpolation was formed to complete the experimental table.

36. Gap effect

37. Stagger effect

38. Decalage effect

39. Scale 1 Sweptm Plaster and Inv-Zim planeform Connected with strut
Biplane
parameters
Gap
Stagger
Decalage angle
The difference in the angle of incidence of the two wings of a biplane is called the decalage

40. Swept Planform

41. Inverse-Zimmerman

42. Visualisation
Smoke generation
Tuft method

43. Motor-Propeller Effect
Attached on upper and lower wing
Same efficiency
Delay stall phenomena, increase maximum lift

44. GEOBAT