1

Study of CFD Variation on TransportConfigurations from the Second Drag

Prediction Workshop

Christopher L. Rumsey

S. Melissa Rivers

Joseph H. Morrison

NASA Langley Research Center

2

Methods

• CFL3D – finite volume upwind Roe– using 1-to-1 ICEM grids (thin-layer in all 3 directions)

and overset grids (thin-layer in normal direction)

– 3 turbulence models (SA, SST, EASM-ko)

– EASM-ko is nonlinear explicit algebraic stress ink-omega formulation

• OVERFLOW – finite difference upwind Roe– using overset grids (thin-layer in normal direction)

– 2 turbulence models (SA, SST)

3

Case 1 – CL=0.5, fully turbulent

1.241.23SSTOVERFLOW,overset

1.221.211.201.191.181.17SAOVERFLOW,overset

1.161.151.141.131.121.11SACFL3D,overset

1.101.9EASMCFL3D, 1to1

1.81.7SSTCFL3D, 1to1

1.61.51.41.31.21.1SACFL3D, 1to1

wbnp(f)wbnp(m)wbnp(c)wb(f)wb(m)wb(c)Turbmodel

Code / Grid

(shaded = not done yet)

4

Case 2 – drag polar, transition specified

2.502.492.482.472.462.452.44wbnp(m)

SAOV, O

2.432.422.412.402.392.382.37wbnp(m)

SACF, O

2.362.352.342.332.322.312.30wbnp(m)

SACF, 1

2.292.282.272.262.252.242.23wb(m)SAOV, O

2.222.212.202.192.182.172.16wb(m)SACF, O

2.152.142.132.12wb(m)EASMCF, 1

2.112.102.92.8wb(m)SSTCF, 1

2.72.62.52.42.32.22.1wb(m)SACF, 1

1.510-1-1.5-2-3CaseTurbCode /Grid

5

Case 3 – CL=0.5, transition specified

3.63.5SAOV, O

3.43.3SACF, O

3.23.1SACF, 1

wbnp(m)wb(m)TurbCode / Grid

6

Grid issues

ICEM 1-to-1 grids: - less than factor 2 between successive grids - no uniform refinement, e.g., similar surface point distribution between successive grids

7

Grid issues, cont’d

8

Grid issues, cont’d

ICEM 1-to-1 WBNP grids: - non-smooth - non-orthogonal in places - sudden grid spacing changes

9

Grid effect, CL=0.5fully turbulent

N-2/3

CD

0 2E-05 4E-05 6E-05 8E-050.027

0.028

0.029

0.03

0.031

0.032

0.033

0.034

0.035

0.036

1-to-1 grids, CFL3Doverset grids, CFL3Doverset grids, OVERFLOW

WB 1-to-1 & overset grids, CL=0.5

finer

coarser

N-2/3

CD

0 2E-05 4E-05 6E-05 8E-050.027

0.028

0.029

0.03

0.031

0.032

0.033

0.034

0.035

0.036

1-to-1 grids, CFL3Doverset grids, CFL3Doverset grids, OVERFLOW

WBNP 1-to-1 & overset grids, CL=0.5

finer

coarser

10

Lift curve on medium gridstransition specified

alpha

CL

-5 -4 -3 -2 -1 0 1 2-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

CFL3D, 1-to-1 SACFL3D, overset SAOVERFLOW, overset SAexp

alpha

CL

-5 -4 -3 -2 -1 0 1 2-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

CFL3D SA, 1-to-1CFL3D SA, oversetOVERFLOW SA, oversetexp

WB WBNP

11

Drag polar on medium gridstransition specified

CD

CL

0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

CFL3D, 1-to-1 SACFL3D, overset SAOVERFLOW, overset SAexp

CD

CL

0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

CFL3D, 1-to-1 SACFL3D, overset SAOVERFLOW, overset SAexp

WB WBNP

12

CM on medium gridstransition specified

CM

CL

-0.2 -0.15 -0.1 -0.05 0-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

CFL3D SA, 1-to-1CFL3D SA, oversetOVERFLOW SA, oversetexp

CM

CL

-0.2 -0.15 -0.1 -0.05 0-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

CFL3D SA, 1-to-1CFL3D SA, oversetOVERFLOW SA, oversetexp

WB WBNP

13

Turbulence model effect on dragWB, CFL3D, medium 1-to-1 grid, transition specified

CD

CL

0.015 0.02 0.025 0.03 0.035 0.04 0.045 0.05-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

SASSTEASM-koexp

14 cts

7 cts

10 cts

14

Turbulence model effect on Cptypically significant only at root station

x/c-C

p0 0.2 0.4 0.6 0.8 1-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

CF, 1m, CL.5, SA(ft)CF, 1m, CL.5, SST(ft)CF, 1m, CL.5, EASM-ko(ft)exp, WBNP 183

2y/B=0.847

x/c

-Cp

0 0.2 0.4 0.6 0.8 1-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.62y/B=0.15

15

Overset grid density effect on Cplargest effects seen at root and tip stationsbiggest change between med & fine grids

x/c

-Cp

0 0.2 0.4 0.6 0.8 1-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.62y/B=0.15

x/c-C

p0 0.2 0.4 0.6 0.8 1-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

OV, Of, CL.5, SA(ft)OV, Om, CL.5, SA(ft)OV, Oc, CL.5, SA(ft)exp, WBNP 183

2y/B=0.847

16

Grid type effect on Cpdramatic difference at station inboard of nacelle

x/c

-Cp

0 0.2 0.4 0.6 0.8 1-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.62y/B=0.331

x/c-C

p0 0.2 0.4 0.6 0.8 1-1.2

-0.8

-0.4

0

0.4

0.8

1.2

1.6

CF, 1m, CL.5, SA(ft)CF, Om, CL.5, SA(ft)OV, Om, CL.5, SA(ft)exp, WBNP 183

2y/B=0.847

17

Grid type effect on nacelle Cpdifference at inboard location

X/C

-Cp

0 0.25 0.5 0.75 1-1.6

-1.2

-0.8

-0.4

0

0.4

0.8F = 60 (outboard nacelle)

X/C

-Cp

0 0.25 0.5 0.75 1-1.6

-1.2

-0.8

-0.4

0

0.4

0.8F = 300 (inboard nacelle)

X/C

-Cp

0 0.25 0.5 0.75 1-1.6

-1.2

-0.8

-0.4

0

0.4

0.8

CF, 1m, CL.5, SA(ft)CF, Om, CL.5, SA(ft)OV, Om, CL.5, SA(ft)exp, WBNP 183

F = 180 (lower nacelle)

18

Lower-wing pressure contoursoverset 1-to-1

19

Lower wing streamlinesoverset 1-to-1

20

Upper wing streamlinesoverset 1-to-1

21

T.E. wing-root bubble size

BLBUB (y-loc width)

FS

BU

B(x

-lo

cl e

ng

th)

80 85 90 95 100 105 110

140

150

160

170

180

190

200

210

open=wbfilled=wbnp

square=SA CFL3Dtriangle=SST CFL3Ddelta=EASM CFL3Ddiamond=SA OVERFLOW

small=1-to-1large=overset

Wing root separation bubble width and length

more separated

less separated

22

Summary of various effects on dragat CL=0.5

dr a

gco

un

t s( 1

ct=

0.0

00

1i n

CD)

0

2

4

6

8

10

12

14

16

18

20

Grid type Code Turb TransGrid type Code Turb Trans

WB WBNP

23

Summary• Grid has a big effect on physics (inboard of nacelle),

although this effect may be masked if only look atintegrated quantities

• Provided “b2b-icem” 1-to-1 grids not suitable for grid study(too little variation); WBNP grid of poor quality

• SA turbulence model tends to give the most wing rootseparation, EASM the least

• SST turbulence model drag generally lowest; by 7-15 cts

• Individual effects due to grid type, code, turb model, andtransition at CL=0.5: 5-10 cts for WB, 10-15 cts for WBNP

24

Typical CPU timingsfor the DPW-II cases

• Typically 2000-5000 cycles needed per case• CFL3D

– 60e-6 sec/gridpt/cycle/node PC cluster (1-to-1)– 30e-6 sec/gridpt/cycle/node PC cluster with Myrinet (1-to-1)– 60-110e-6 sec/gridpt/cycle/node Alpha cluster with Myrinet

(1-to-1 faster than overset for multi-processors)– 230e-6 sec/gridpt/cycle/node Origin 2000 cluster (1-to-1)– 17e-6 sec/gridpt/cycle Cray SV1 single processor

• OVERFLOW– 30e-6 sec/gridpt/cycle/node PC cluster– 75e-6 sec/gridpt/cycle/node Origin 3000 cluster (mlp version)