Applied Aerodynamics TC2nd Drag Prediction Workshop
Force and Moment Estimates for theDLR F6 Configuration Using NSU3D
Steve Klausmeyer
Cessna Aircraft Company
Applied Aerodynamics TC2nd Drag Prediction Workshop
Goals
• Further refine and quantify in-house drag prediction– Evaluate incremental drag capability
• Evaluate ICEM for unstructured viscous mesh generation– Flow solver compatibility
– Force and moment accuracy
Applied Aerodynamics TC2nd Drag Prediction Workshop
NSU3D
• Unstructured grid, mixed element, node based
• Thin-layer RANS with Spalart-Allmaras turbulence model
• Multigrid with automated coarse level generation viaagglomeration
• Implicit lines through boundary layer speed convergence
• Distributed memory parallel implementation
• Cache-based optimizations
Applied Aerodynamics TC2nd Drag Prediction Workshop
ICEM
• Features– CATIA interface
– Mesh sizes specified directly on patches
– Multi-Use --> structured, unstructured, mixed
• Issues– Memory requirements for large meshes
– Prism grid quality and robustness
– Octree mesh growth
Applied Aerodynamics TC2nd Drag Prediction Workshop
Mixed ElementUnstructured Meshes
• Self-generated using the Tetra & Prism modules withinICEM
• 25 prism layers
• Isotropic surface elements
• WB grid sizes: 1.2m 2.6m 6.2m
• WBNP grid sizes: 1.6m 4.0m 8.0m
• Generation times: ~ 8 hours for medium WB mesh
Applied Aerodynamics TC2nd Drag Prediction Workshop
Surface Meshes - Medium
Applied Aerodynamics TC2nd Drag Prediction Workshop
Computer Resources
• 48 node Linux cluster.– 1.7 GHz Athlon processors
– 48 Gbyte total memory
– 3 16 node banks
• 32 node Linux cluster– Alpha VP2000 motherboards
– 32 Gbyte total memory
• 8 node SGI ONYX– 600 MHz R14000 processors
– 6 Gbyte memory with 6 Gb swap
Applied Aerodynamics TC2nd Drag Prediction Workshop
Solution Statistics
• Each solution utilized 16 nodes
• For the medium WB mesh– 275 Mbytes per node (4.4 Gbytes total)
– 3.6 hrs for 500 multigrid cycles
– Drag polar or drag rise within a 24 hour window.
Applied Aerodynamics TC2nd Drag Prediction Workshop
Typical Solution Convergence
Applied Aerodynamics TC2nd Drag Prediction Workshop
Flow Features
Applied Aerodynamics TC2nd Drag Prediction Workshop
WB Surface PressureM=0.75 CL=0.5
Re=3M Fully Turbulent
2.6M nodes
Applied Aerodynamics TC2nd Drag Prediction Workshop WBNP Surface Pressure
M=0.75 CL=0.5Re=3M Fully Turbulent
4M nodes
Applied Aerodynamics TC2nd Drag Prediction Workshop Flow Features
Pressure
Skin Friction
Applied Aerodynamics TC2nd Drag Prediction Workshop Flow Features
Separation at wing/body junction
Flow around wing LE
Separation on tailcap
Applied Aerodynamics TC2nd Drag Prediction Workshop
Case 1 – Grid Convergence
Applied Aerodynamics TC2nd Drag Prediction Workshop Effect of Grid Size on
DragGrid Convergence - DragFully Turbulent
0.0290
0.0300
0.0310
0.0320
0.0330
0.0340
0.0350
0.0360
0.0370
0.0380
0.0390
Coarse Grid Medium Grid Fine Grid
CD
Computed
Wind Tunnel
Computed
Wind Tunnel
WBNP
WB
Applied Aerodynamics TC2nd Drag Prediction Workshop Effect of Grid Size on
Nacelle Installation DragNacelle Installation Drag
0.0000
0.0010
0.0020
0.0030
0.0040
0.0050
0.0060
Coarse Grid Medium Grid Fine Grid
DCD
Computed
Wind Tunnel
Applied Aerodynamics TC2nd Drag Prediction Workshop Effect of Grid Size on
Pitching MomentGrid Convergence - Pitching Moment
Fully Turbulent
-0.145
-0.140
-0.135
-0.130
-0.125
-0.120
-0.115
-0.110
-0.105
Coarse Medium Fine
CM
Computed
Wind Tunnel
WBNP WB
WB
WBNP
Applied Aerodynamics TC2nd Drag Prediction Workshop Effect of Grid Size on
Rolling MomentGrid Convergence - Rolling Moment
Fully Turbulent
0.775
0.780
0.785
0.790
0.795
0.800
0.805
0.810
0.815
0.820
0.825
0.830
Coarse Medium Fine
CRM
WB
WBNP
Applied Aerodynamics TC2nd Drag Prediction Workshop Effect of Grid Size on
WB Drag ComponentsGrid Convergence - Wing/Body
Fully Turbulent
0.0130
0.0140
0.0150
0.0160
0.0170
0.0180
0.0190
0.0200
Coarse Medium Fine
CD
Pressure
Friction
Applied Aerodynamics TC2nd Drag Prediction Workshop Effect of Grid Size on
WBNP Drag ComponentsWBNP Grid Convergence
Fully Turbulent
0.0150
0.0160
0.0170
0.0180
0.0190
0.0200
0.0210
0.0220
0.0230
Coarse Medium Fine
CD
Pressure
Friction
Applied Aerodynamics TC2nd Drag Prediction Workshop
Case 2 – Alpha Sweep
Applied Aerodynamics TC2nd Drag Prediction Workshop Drag Polar
CD
CL
0.0200 0.0240 0.0280 0.0320 0.0360 0.0400-0.10
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
DLR F6M=0.75 Re=3 million
Fully Turbulent
19 Jun 2003 21:37:41
/cfd/home3/steve/AIAA/DPW2/WindTunnel/DPW_forces_WBPN_175/cfd/home3/steve/AIAA/DPW2/WindTunnel/DPW_forces_WB_375/cfd/home3/steve/AIAA/DPW2/Analysis/Force/force.dat/cfd/home3/steve/AIAA/DPW2/Analysis/Force/dragpolar.lay
WB WBNP
10 cts
Applied Aerodynamics TC2nd Drag Prediction Workshop Lift
Angle-of-Attack (deg)
CL
-5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-0.10
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
WBNPWBWBWBNP
DLR F6M=0.75 Re=3 million
19 Jun 2003 21:39:57
/cfd/home3/steve/AIAA/DPW2/WindTunnel/DPW_forces_WBPN_175/cfd/home3/steve/AIAA/DPW2/WindTunnel/DPW_forces_WB_375/cfd/home3/steve/AIAA/DPW2/Analysis/Force/force.dat/cfd/home3/steve/AIAA/DPW2/Analysis/Force/lift.lay
Applied Aerodynamics TC2nd Drag Prediction Workshop Pitching Moment
Angle-of-Attack (deg)
CM
-5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0-0.18
-0.16
-0.14
-0.12
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
WBNPWBWBWBNP
DLR F6M=0.75 Re=3 million
19 Jun 2003 21:41:53
/cfd/home3/steve/AIAA/DPW2/WindTunnel/DPW_forces_WBPN_175/cfd/home3/steve/AIAA/DPW2/WindTunnel/DPW_forces_WB_375/cfd/home3/steve/AIAA/DPW2/Analysis/Force/force.dat/cfd/home3/steve/AIAA/DPW2/Analysis/Force/moment.lay
Applied Aerodynamics TC2nd Drag Prediction Workshop
Case 4 – Drag Rise
Applied Aerodynamics TC2nd Drag Prediction Workshop WB Drag Rise
Mach
CD
0.4 0.5 0.6 0.7 0.80.0260
0.0265
0.0270
0.0275
0.0280
0.0285
0.0290
0.0295
0.0300
0.0305
0.0310
Applied Aerodynamics TC2nd Drag Prediction Workshop WBNP Drag Rise
Mach
CD
0.4 0.5 0.6 0.7 0.80.0300
0.0305
0.0310
0.0315
0.0320
0.0325
0.0330
0.0335
0.0340
0.0345
0.0350
Applied Aerodynamics TC2nd Drag Prediction Workshop Conclusions
This was a lot of work.
Applied Aerodynamics TC2nd Drag Prediction Workshop More Conclusions
• Current methodology approaching adequacy for predictionof drag changes due to minor airframe modifications.
• There is enough variation in parasite, induced, and wavedrag characteristics to warrant further investigation beforeusing to develop a full drag basis.
• Flow solver performance– Robust - tolerant of meshes with isolated regions of poor grid
quality
– No startup trauma difficulties
– Fast convergence --> allows overnight drag polar runs
• Grid generation– Developed procedures for generating acceptable prism meshes.
– Prism mesh robustness and quality is an issue.
Applied Aerodynamics TC2nd Drag Prediction Workshop
Further Work
• Perform similar exercise on a business jet configurationwith fuselage mounted nacelles.
• Tripped boundary layer study with new version of code.
• Study induced drag prediction at lower Mach number (0.5)
• Investigate alpha shift– Grid resolution
– Comparisons with in-house configurations
• Investigate pitching moment discrepancy