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DPW-3 DLR F6/FX2B Results
O. BrodersenInstitute of Aerodynamics and Flow Technology
DLR38108 Braunschweig
Germany
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Slide 2 of 18, Brodersen
DPW-3, June 2006
Method
• RANS solver DLR TAU• Unstructured database, node based• State-of-the-Art algorithms• 1- and 2-eq. turbulence models• Fluid-Structure coupling• Overlapping grids• Grid adaptation• Hypersonic extensions• C code and Python scripting• High performance on parallel machines• Applied in European aircraft industryand research
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Slide 3 of 18, Brodersen
DPW-3, June 2006
Grids
• Unstructured hybrid grids generated with Centaur from Centaursoft• Prismatic elements for BL• 3 grid densities• Specification of sourcesfor wing surface
• Constant refinement factor
403121Prismatic layers
121588167434
85769112672
4506560423
Boundary nodes
8.5310.30
5.106.11
2.46 (f6wb)2.87 (fx2b)
Nodes
FineMediumCoarse
coarse medium fine
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Slide 4 of 18, Brodersen
DPW-3, June 2006
Results
• TAU sae, medium prismatic grids, CL=0.5• DPW-2:
- separations Wing/fuselage, pylon/wing found- no trailing edge flow separation
• Flow separation at fuselage wing junction• No separation for FX2B (all α)
F6wb
F6fx2b
Oil flow patternONERA S2 test
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Slide 5 of 18, Brodersen
DPW-3, June 2006
Results: Grid Influence
Convergence Study
Drag Delta Drag
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Slide 6 of 18, Brodersen
DPW-3, June 2006
Results: Grid Influence
Influence on Flow Separation F6wb for CL=0.5
coarse medium fine
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Slide 7 of 18, Brodersen
DPW-3, June 2006
Results: Grid Influence
Influence on Cp for CL=0.5
η=0.15 η=0.311
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Slide 8 of 18, Brodersen
DPW-3, June 2006
Results: F6 / F6FX2B
Medium Grid: lift and drag
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Slide 9 of 18, Brodersen
DPW-3, June 2006
Medium Grid: delta drag , moments
Results: F6 / F6FX2B
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Slide 10 of 18, Brodersen
DPW-3, June 2006
Medium Grid: influence on Cp for CL=0.5
Results: F6 / F6FX2B
η=0.15 η=0.331
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Slide 11 of 18, Brodersen
DPW-3, June 2006
Grids
• Well-known: grid quality and density is important• Different approach: hexahedrals and tetrahedrals• Hexahedral elements for BL resolution• Solar grid generator from Airbus, ARA, BAES• Grids generated by QinetiQ
4.244.11
Nodes
Medium
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Slide 12 of 18, Brodersen
DPW-3, June 2006
Results: Grid Influence
Convergence Study
Drag Delta Drag
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Slide 13 of 18, Brodersen
DPW-3, June 2006
Results: Grid Type
F6fx2b: Prismatic / Hexahedral hybrid grids
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Slide 14 of 18, Brodersen
DPW-3, June 2006
Results: Grid Type
F6wb: Prismatic / Hexahedral hybrid grids
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Slide 15 of 18, Brodersen
DPW-3, June 2006
Results: Grid Type
Influence of alpha on flow separation
α=-2.0 α=1.5CL=0.5
Prisms Prisms Prisms
HexahedralsHexahedralsHexahedrals
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Slide 16 of 18, Brodersen
DPW-3, June 2006
Results: Grid Type
Influence on flow separation F6wb for α=1.5
x=215y=80
x=188y=88
Triangles Hexahedrals
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Slide 17 of 18, Brodersen
DPW-3, June 2006
Results: Grid Type
F6wb / F6fx2b Delta Drag
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Slide 18 of 18, Brodersen
DPW-3, June 2006
Summary
• F6fx2b shows improved junction flow
• Delta drag at design point approx.:
- ≈ 1.5 dc for medium grid
- ≈ 9 dc for extrapolation
• Grid density in wing fuselage junction has major effect on sizeof separation bubble at high alpha (SAE model)
• Delta drag of F6wb-F6fx2b can switch its sign for high / low alpha
• Wing trailing edge separation can not be found with SAE (see also DPW-2)
• Hybrid hexahedral grids are very promising(improved convergence, less nodes)