Presented by : Simon TRAPIER Aerodynamics Department Airbus
19
June 2009 Drag Prediction Workshop 4 Airbus results Presented by : Simon TRAPIER Aerodynamics Department Airbus
Transcript of Presented by : Simon TRAPIER Aerodynamics Department Airbus
June 2009
Drag Prediction Workshop 4Airbus results
Presented by :
Simon TRAPIERAerodynamics DepartmentAirbus
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Method
• elsA solver:Developed by ONERACentred schemeDissipation : Jameson type scalar schemeImplicit time integration : LU-SSOR method
• Turbulence models used :Spalart-Allmaras (SA) 1-equation modelMenter k-ω Shear Stress Transport (SST) 2-equations model
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Grids characteristics
• Structured, multiblock grids
• In compliance with DPW commitee gridding guidelines
• C-topology around fuselage, wing and tail
• 7 grids generated :
- Coarse, Medium, Fine, Extra fine at iH=0°
- Medium at iH=-2°, +2°, No Tail
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Grids characteristics
Non-coincident junction between wing and tail
Grid level Nodes Zones y+ Cells across trailing edge
Coarse 4.6 millions 146 1 18
Medium (no tail) 8.9 millions 128 0.666 24
Medium (tail) 13.5 millions 167 0.666 24
Fine 37.2 millions 228 0.444 32
Extra fine 108.3 millions 334 0.296 48
• Grids dimensions :
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Grids characteristics : y+ at first cell
Coarse
Medium
Fine
Extra Fine
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t.Grids characteristics : number of cells in boundary layer
Coarse
Extra Fine
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Grid convergence at CL=0.5
• Total drag
Cd=f(1/N)
272,00
273,00
274,00
275,00
276,00
277,00
278,00
279,00
280,00
0,00E+00 5,00E-08 1,00E-07 1,50E-07 2,00E-07 2,50E-071/N
CD Cd=f(1/N^2/3)
272,00
273,00
274,00
275,00
276,00
277,00
278,00
279,00
280,00
0,0E+00 5,0E-06 1,0E-05 1,5E-05 2,0E-05 2,5E-05 3,0E-05 3,5E-05 4,0E-051/N^2/3
CD
N = number of grid nodesCL=0.5
M=0.85
k-ω SST model
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Grid convergence at CL=0.5
• Pressure and friction drag
Cdp
143,00
144,00
145,00
146,00
147,00
148,00
149,00
150,00
151,00
152,00
0,00E+00 5,00E-08 1,00E-07 1,50E-07 2,00E-07 2,50E-071/N
CD Cdf
128,40
128,50
128,60
128,70
128,80
128,90
129,00
129,10
129,20
129,30
0,0E+00 5,0E-08 1,0E-07 1,5E-07 2,0E-07 2,5E-071/N
CD
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Flow at CL=0.5
Small separated areas exist at wing and tail roots leading edgeand trailing edge
CL=0.5, fine grid
(red surfaces : u = -0.01m/s isosurface)
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Wing-fuselage separation bubble geometry
dividing streamline
EYE_W
EYE_B
BL_BUB
WL_BUB
dividing streamline
EYE_W
EYE_B
BL_BUB
WL_BUB
Small region (not more than 5 mm wide) of negative cfx starting at a quite upstream location : FS_BUB abscissa is low
CL=0.5, fine grid
(black lines : cfx= 0 contour)
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Wing-fuselage separation bubble geometry
No strong influence of mesh refinement on separation bubble geometry
Coarse Medium
Fine Extra-fine
CL=0.5
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LE separation bubble geometry
CL=0.5, fine grid
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Trailing edge separation
Small trailing edge separation in the outer part of the wing
CL=0.5, fine grid
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Polars
Cd
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,01000 0,02000 0,03000 0,04000 0,05000 0,06000Cd
CL
No TailiH=-2iH=0iH=+2Trimmed
iH Trim
-1,50
-1,00
-0,50
0,00
0,50
1,00
0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8CL
iHCM
-0,40
-0,30
-0,20
-0,10
0,00
0,10
0,20
0,30
0 0,5 1 1,5 2 2,5 3 3,5 4 4,5AoA
CM No TailiH=-2iH=0iH=+2
M=0.85
Medium grids
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Turbulence model effect
CL
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0 4,5 5,0AoA
Cl
kw-SST SA
CM
-0,12
-0,10
-0,08
-0,06
-0,04
-0,02
0,00
0,02
0,04
0,06
0,08
0,0 1,0 2,0 3,0 4,0 5,0AoA
CM
kw-SST SA
Cd
0,10
0,20
0,30
0,40
0,50
0,60
0,70
150,0 200,0 250,0 300,0 350,0 400,0 450,0 500,0 550,0 600,0Cd
Cl
kw-SST SA
SA and SST models diverge on CL, CD and CM for α > 3°
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Turbulence model effect
Cdp
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,00 50,00 100,00 150,00 200,00 250,00 300,00 350,00 400,00 450,00Cdp
Cl
kw-SST SA
Cdf
0,10
0,20
0,30
0,40
0,50
0,60
0,70
119,0 120,0 121,0 122,0 123,0 124,0 125,0 126,0 127,0 128,0 129,0 130,0 131,0 132,0Cdf
Cl
kw-SST SA
• Linear range (α=0 to 2.5°) :Good agreement for Cdp, drag difference between SA and SST is due to skin friction (1 to 1.5 drag counts)
• High angles of attack (α > 3°) :Divergence of pressure drag
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Turbulence model effect
• Spalart-Allmaras model overestimates the wing-fuselage separation at high angles of attack (>3°)
Spalart-Allmaras, α=4° kω-SST, α=4°
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Conclusions
• 4 grid levels used, from 4.6 to 108.3 millions nodes
• No clear grid convergence achieved for extra-fine grids
• Separated areas observed at wing root (leading edge and trailing edge), independent of grid level
• kω-SST model retained for submitted results because of better robustness at high angles of attack
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