Force and Moment Estimates for the DLR F6 Configuration ...2nd Drag Prediction Workshop Effect of...

Applied Aerodynamics TC2nd Drag Prediction Workshop

Force and Moment Estimates for theDLR F6 Configuration Using NSU3D

Steve Klausmeyer

Cessna Aircraft Company


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


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


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


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


Surface Meshes - Medium


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


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.


Typical Solution Convergence


Flow Features


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


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


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


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


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


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


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


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


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


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


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.


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

Force and Moment Estimates for the DLR F6 Configuration ...2nd Drag Prediction Workshop Effect of...

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