1. How CFD* and EFD complement each other in
development of the D8 aircra9
ASME Interna>onal Mechanical Engineering Congress and Exhibit
Phoenix, AZ. 15 November 2016
H. Doğuş Akaydın
Senior Research Scien>st/Engineer
Science and Technology Corpora>on
at NASA Ames Research Center
James C. Jensen
Research Scien>st/Engineer
Science and Technology Corpora>on
at NASA Ames Research Center
Shishir A. Pandya
Aerospace Engineer
NASA Ames Research Center
* CFD: Computa>onal Fluid Dynamics
EFD: Experimental Fluid Dynamics

2. /27 2
NASA is ac>vely sponsoring research and development of
cleaner, less noisy and more efficient transport aircra9
NASA Advanced Air Vehicles Program, AATT (Advanced Air Transport Technology) Project Briefing

3. /27 3
An overview of the state of the art:
plan
1960 1950 2010 t ?
Progress in commercial transport aircra9 has been driven mainly by
- Engines (became more efficient, more powerful and more reliable)
- Composite structures (became more reliable)
- Control surfaces and avionics (became more sophis>cated)
Airframe integra>on, however, lagged: Thin-tube fuselages and wing-mounted engines are
s>ll the state of the art.

4. /27 4
MIT’s vision: The D8 “Double Bubble” Aircra9
Aurora Flight Sciences, Inc. www.aurora.aero
MIT: Lead the research, design the aircra9, perform wind tunnel tests
Aurora Flight Sciences: Build wind tunnel models and flight demonstrators
Prae & Whitney: Develop the engines
NASA: Sponsor the project, provide wind tunnel and computer >me for advanced analysis

5. /27 5
40% reduc>on in fuel burn due to the synergis>c integra(on
of airframe components
Op>mized
engines
Newer
engines
D8 fuse.,
π-tail
Slow to
M=0.72
BLI*
Rela>ve Fuel Burn
Integrated
engines
Podded
engines
D8 variant:
*BLI: Boundary Layer Inges>on
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
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Greitzer et al., N+3 Aircra@ Concept Designs and Trade Studies. Volume 1, 2010, NASA CR-2010-216794/VOL1
B737-800

6. /27 6
How does BLI (boundary layer inges>on) work?
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
Drela, Development of the D8 Transport Configura(on, 2011, AIAA-2011-3970
Drela, Power Balance in Aerodynamic Flows, 2009, AIAA Journal 47(7)
Pk = Φjet+ Φwake+ Φfuse. + Φvortex + Ė = Φ
PK = p0∞−p0( )
!
V ⋅
!
n dS
propulsor
"∫∫ Φ = p0∞−p0( )
!
V ⋅
!
n dS
wake plane
− prop. reg.
"∫∫ + 1
2
V−V∞( )
2
ρ
!
V ⋅
!
n dS
wake plane
"∫∫
Consider two configura>ons at cruise (zero-net force):
⇥⇤⌅
⇥⇤⌅⇧
⌃⌥ ⌦
 ⇥
⇥⇤⌅
⇤ ⌅⇥
⌃⌥ ⌦
 ⇧
⇥⇤⌅
↵ ⇥⇤ ⇤✏
⇣⌥ ⌃⌥ ⌦
◆ ⇥⇤  ⌅⇧⌃⇥  ⌥ ⇥  ⌦↵ ⇤⇥  ⇥⇥⇤⌅
⌃⌥ ⌦
⌥⌘⇧ ⌥⌅ ✓◆
⌫ ⌘⌥
⌫ ⌘⌥ ⇠⇥ ⇡⌥⇢
⇠⇥ ⇡⌥⇢⇣⌅⌥
⇣⌅⌥
⌧⌥⇡
⌧⌥⇡
⇥⇤⌅⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
 ⌫⇠⇡ ⇢⇥⇤ ⌧ ⇤⌦ ⇡ ! "##
⌃⌥ ⌦↵ ✏⇣ ⌘✓⌘⌘ ◆ ↵ ⌫⇠⇡⇠⇢
Ė
Podded (non-BLI) configura>on

7. /27 7
How does BLI (boundary layer inges>on) work?
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
Drela, Development of the D8 Transport Configura(on, 2011, AIAA-2011-3970
Drela, Power Balance in Aerodynamic Flows, 2009, AIAA Journal 47(7)
Pk = Φjet+ Φwake+ Φfuse. + Φvortex + Ė = Φ
PK = p0∞−p0( )
!
V ⋅
!
n dS
propulsor
"∫∫ Φ = p0∞−p0( )
!
V ⋅
!
n dS
wake plane
− prop. reg.
"∫∫ + 1
2
V−V∞( )
2
ρ
!
V ⋅
!
n dS
wake plane
"∫∫
With BLI, the terms Φjet , Φwake and Ė become smaller.
Consider two configura>ons at cruise (zero-net force):
⇥⇤⌅
⇥⇤⌅⇧
⌃⌥ ⌦
 ⇥
⇥⇤⌅
⇤ ⌅⇥
⌃⌥ ⌦
 ⇧
⇥⇤⌅
↵ ⇥⇤ ⇤✏
⇣⌥ ⌃⌥ ⌦
◆ ⇥⇤  ⌅⇧⌃⇥  ⌥ ⇥  ⌦↵ ⇤⇥  ⇥⇥⇤⌅
⌃⌥ ⌦
⌥⌘⇧ ⌥⌅ ✓◆
⌫ ⌘⌥
⌫ ⌘⌥ ⇠⇥ ⇡⌥⇢
⇠⇥ ⇡⌥⇢⇣⌅⌥
⇣⌅⌥
⌧⌥⇡
⌧⌥⇡
⇥⇤⌅⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
 ⌫⇠⇡ ⇢⇥⇤ ⌧ ⇤⌦ ⇡ ! "##
⌃⌥ ⌦↵ ✏⇣ ⌘✓⌘⌘ ◆ ↵ ⌫⇠⇡⇠⇢
Ė
Ė
Podded (non-BLI) configura>on
Integrated (BLI) configura>on

8. /27 8
Experimental and Computa>onal Tools
Pandya, External Aerodynamics Simula(ons for the MIT D8 “Double-Bubble” Aircra@ Design, 2012, ICCFD7-4304
EFD: NASA Langley 14x229 Wind Tunnel. 3D-printed skin and modular components
Overflow 2.2, NASA’s workhorse flow solver for structured curvilinear overset grids.
Chimera Grid Tools (CGT) for to generate these CFD grids.
CFD:
Nichols and Buning, Users Manual for OVERFLOW 2.2, heps://overflow.larc.nasa.gov
Chan, Gomez, Rogers and Buning, Best Prac(ces in Overset Grid Genera(on, 2002, AIAA-2002-3191
M∞≈0.1

9. /27 9
EFD serves to validate and improve the CFD simula>ons
Pandya, External Aerodynamics Simula(ons for the MIT D8 “Double-Bubble” Aircra@ Design, 2012, ICCFD7-4304
80 million grid points. 35 near-body grids. Wall y+≈1
24 hours of wall-clock >me spent per solu>on on 380 Sandy Bridge cores on
Pleiades Supercomputer.
Unpowered (no-propulsor) D8 model.
SS-RANS (Steady-state Reynolds-Averaged Navier Stokes) solu>ons.
0 5 10 15
α
0.5
1
1.5
2
L
WT
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.5
1
1.5
2
L
WT
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.5
1
1.5
2
L
WT
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.05
0.1
0.15
0.2
0.25
CD
WT
Cart3D
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.05
0.1
0.15
0.2
0.25
CD
WT
Cart3D
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.05
0.1
0.15
0.2
0.25
CD
WT
Cart3D
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
0.5
1
1.5
2 WT
Overflow - Spalart-Allmaras
Overflow - SST
CL CD

10. /27 10
CFD provides further insights on the design
(and validates the design concepts)
0 0.5 1
π-Tail
Wing
Fuse.
Total
0 0.05 -0.1 0 0.1 0.2
CL CD CM α=4°
Pandya, External Aerodynamics Simula(ons for the MIT D8 “Double-Bubble” Aircra@ Design, 2012, ICCFD7-4304
• Tail of D8 creates posi>ve li9 or less nega>ve li9 than a comparable transport aircra9.
• Fuselage creates a fair amount of li9 and a substan>al amount of pitch-up moment…
• …which is balanced by the pitch-down moment from wing and tail.

11. /27 11
EFD and CFD complement each other.
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
Computa>on of propulsor power by experimental methods
Greitzer et al., Aircra@ and Technology Concepts for an N+3 Subsonic Transport – Phase 2. Year 3 Status Review, 2014
PK = p0∞−p0( )
!
V ⋅
!
n dS
propulsor
"∫∫
Integrated (BLI) configura>on:

12. /27 12
EFD and CFD complement each other.
Greitzer et al., Aircra@ and Technology Concepts for an N+3 Subsonic Transport – Phase 2. Year 3 Status Review, 2014
Stream tube into the propulsor is determined by CFD
PK = p0∞−p0( )
!
V ⋅
!
n dS
propulsor
"∫∫

13. /27 13
EFD and CFD complement each other.
⇥⇤⌅⇧⌃⇧⌃⌥ ⌦↵ ⌅ ✏⇣ ⌘ ✓ ◆ ⇤ ⌦ ⌫⇠
⇥⇤ ⌅⇧⌃⌥
⌦⇥↵
✏⇣⌘✓◆  ⌫✓⇣◆⇠⇡⇢ ⇡⇠⇡
⇥ ⇥⇤⇥ ⌅⇤⌅ ⇧ ⌃
⇡⇢⇢ ⇢✏⌧ ⇡◆⇠✓⇠✓
⇥ ⇥⇤⇥ ⌥⌅ ⇤⌅ ⇧ ⌃
⇡◆⇠✓⇠✓ ✏ ✓◆⇠⌫ ⇠
⇤ ⌦⌅ ↵
!⇧" ⌦#⇥⌥⌅" "⇥
"⇥"⌅⌥ ⌦⌅$ ⌃⌦!%
!⇧" ⌃⌦⌅"!⇥⇧
⌅⌦ ⌅
!⇧" ⌃⌦⌅"
⇠✏⇠⇡⇢ ⌫⇡&
⌫'( ⇡⇠⇡
⇥ ⇧ ⌃
⇠⇡⇠✓ ⌫⇡&
⌫'( ⇡⇠⇡
⇧ ⌃
⇠⇡⇠✓ )⌫✓⇠✏⇠⇡⇢ )⌫✓
*+ , + + ,
*+ ,
+
+ ,
⌅⌃
✏
*+ -
+
+ -
+ .
/ 0
/ ,
⇣⇤ ⌅⌃
⌘
⇧
✓
⇥⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆  ⌫⇠⇠
Pandya, External Aerodynamics Simula(ons for the MIT D8 “Double-Bubble” Aircra@ Design, 2012, ICCFD7-4304
Greitzer et al., Aircra@ and Technology Concepts for an N+3 Subsonic Transport – Phase 2. Year 3 Status Review, 2014
Local flow direc>ons on the rake survey
plane is determined by CFD
PK = p0∞−p0( )
!
V ⋅
!
n dS
propulsor
"∫∫

14. /27 14
EFD and CFD complement each other.
Pandya et al., Computa(onal Assessment of the Boundary Layer Inges(ng Nacelle Design of the D8 Aircra@, AIAA-2014-0907
⇤⌅⇧⌃⌥⇤⌅ ⌃⌦↵ ⌦⌃ ⇥⇧⌅ ⇤⌅ ✏ ⌦⇣
⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆  
⇥
⇤⌅⇧⌃ ⌥ ⌥⌦↵ ✏⇣⌃ ⌥ ⌥⌦↵ ⌘⇤ ⌥ ✓↵⌅
◆ ⌃↵ ⌥ ⌅ ⌦ ⌅ ⌅ ⌅⌫⌃ ⇥
⇥⇥ ⇥⇥
⇤
⇥⌘⌥⇥
⇤⌅⇥⌘⌥⇥
⇥⇤⌅ ⇥⇤⇧ ⇥⇤⌃ ⇥ ⇥⇤⌃ ⇥⇤⇧ ⇥⇤⌅
⇥
⇥⇤⌃
⇥⇤⇧
⇥⇤⌅
⇥⇤⌥
⇤⌃
⇥⇤ ⌦ ⇥⇤⌦ ⇥⇤⌃⌦ ⇥
⇥
⇥⇤⌃
⇥⇤⇧
⇥⇤⌅
⇥⇤⌥
⇤⌃
↵
✏⇣⌘✓
⇥⇤⌥
⇥⇤⌅
⇥⇤⇧
⇥⇤⌃
⇥
⇥⇤⌅ ⇥⇤⇧ ⇥⇤⌃ ⇥ ⇥⇤⌃ ⇥⇤⇧ ⇥⇤⌅
⇤⌅⇥⌘⌥⇥
⇥⌘⌥⇥
⇤⌅⇥⌘⌥⇥
⇥⇤⌅ ⇥⇤⇧ ⇥⇤⌃ ⇥ ⇥⇤⌃ ⇥⇤⇧ ⇥⇤⌅
⇥
⇥⇤⌃
⇥⇤⇧
⇥⇤⌅
⇥⇤⌥
⇤⌃
⇥⇤ ⌦ ⇥⇤⌦ ⇥⇤⌃⌦ ⇥
⇥
⇥⇤⌃
⇥⇤⇧
⇥⇤⌅
⇥⇤⌥
⇤⌃
⇥⇤⌥
⇥⇤⌅
⇥⇤⇧
⇥⇤⌃
⇥
⇥⇤⌅ ⇥⇤⇧ ⇥⇤⌃ ⇥ ⇥⇤⌃ ⇥⇤⇧ ⇥⇤⌅
⇤⌅⇥⌘⌥⇥
⌥⌅ ⇢⌅⌫⌃
⇤
⇢⌥⌦⌃⌃ ⌫
⇤
⇠⇡ ⌅↵↵⌅⌫⌃ ⇢⌥ ⌫⇥⇤⌅⇧⌃⌥⇤⌅ ⌃⌦↵ ⌦⌃ ✏⇣⌘⇤ ✓ ⌦◆
⇥⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆
⇥
⇤⌅⇧⌃ ⌥ ⌥⌦↵ ✏⇣⌃ ⌥ ⌥⌦↵
◆ ⌃↵ ⌥ ⌅ ⌦ ⌅ ⌅ ⌅⌫⌃ ⇥
⇥⇥
⇤
⌅ ⇧⌃ ⌅ ⇧⌥ ⌅ ⇧⇤ ⇧⇤ ⇧⌥ ⇧⌃⌅ ⇧⌃ ⌅ ⇧⌥ ⌅ ⇧⇤ ⇧⇤ ⇧⌥ ⇧⌃
⌅ ⇧⌃
⌅ ⇧⌥
⌅ ⇧⇤
⇧⇤
⇧⌥
⇧⌃
⇥⌥⇥
⇤⌅⇥⌥⇥ ⇤⌅⇥⌥⇥
⌅ ⇧⌥
⇧⌥
⇧⇣
⇥⇧⇤
⇥⇧⌃
⌅ ⇧⌃ ⌅ ⇧⌥ ⌅ ⇧⇤ ⇧⇤ ⇧⌥
⌅ ⇧⌃
⌅ ⇧⌥
⌅ ⇧⇤
⇧⇤
⇧⌥
⇧⌃
⇥⌥⇥
⇤⌅⇥⌥⇥
⌅ ⇧⌥
⇧⌥
⇧⇣
⇥⇧⇤
⇥⇧⌃
⌅ ⇧⌥ ⌅ ⇧⇤ ⇧⇤ ⇧⌥ ⇧⌃
⇤⌅⇥⌥⇥
⇧⌃ ⌅ ⇧⌃
⇠⇡⌥⌅ ⇢⌅⌫⌃
⌃ ⇤
⌧ ⇢⌥⌦⌃⌃ ⌫
⌃ ⇤
⌧ ⇧⌫ ⌅⇧⇧⌃⌅
Greitzer et al., Aircra@ and Technology Concepts for an N+3 Subsonic Transport – Phase 2. Year 3 Status Review, 2014
EFD:
CFD:
Inlet Outlet
L R
Total pressure coefficients. L: Le9 propulsor, R: Right propulsor. Views from rear of the model.
L R

15. /27 15
CFD and EFD reassures confidence in results: ⇧⌃⌥ ⇥ ⇥⌦ ↵ ✏ ⇣⌘⌅ ⌃⌥⇤ ⇧ ✓ ◆
⇥⇤ ⌅⇧⌃⇧⌥ ⌃ ⇧⌦↵ ⇥ ✏
⌘ ✓◆◆ ⌦ ⌃ ⇧ ⌫⇧⌦ ↵⇧⌃ ⇠↵⇧ ⇡  ⇢ ⌧ ⌘ ✓◆◆ ⌦ ⌃
⇥ ⇤ ⇥ ⌅ ⇥ ⇧ ⇥ ⌃ ⇥⌥ ⇥⌥⇤
⇥
⇥ ⌅
⇥ ⌦
⇥ ⇤
⇥ ⌥
⇥ ⌥
⇥ ⇤
⇥ ⌦
⇥ ⌅
⇥
↵
↵
✏⇣⌘⌘✓⌘◆
⌫✓⇠⇡⇢⌫✓⌘◆
✏⇣⌘⌘✓⌘◆↵ ⌧
⌫✓⇠⇡⇢⌫✓⌘◆↵ ⌧
⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆  ⌃ ⌫⌫
ΔCPk= -9%
ΔCPk= -8%
cruise
EFD predicts an 8% ± 0.7%
reduc>on in power to sustain cruise.
CFD predicts a 9% reduc>on.
A very good agreement between experimental and computa>onal
predic>ons of BLI benefit:
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
Greitzer et al., Aircra@ and Technology Concepts for an N+3 Subsonic Transport – Phase 2. Final Review, Dec. 2014
Pandya et al., Computa(onal Assessment of the Boundary Layer Inges(ng Nacelle Design of the D8 Aircra@, AIAA-2014-0907

16. /27 16
CFD facilitates in-depth and alternate analysis methods
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
Drela, Development of the D8 Transport Configura(on, 2011, AIAA-2011-3970
Drela, Power Balance in Aerodynamic Flows, 2009, AIAA Journal 47(7)
Pk = Φjet+ Φwake+ Φfuse. + Φvortex + Ė = Φ
PK = p0∞−p0( )
!
V ⋅
!
n dS
propulsor
"∫∫ Φ = p0∞−p0( )
!
V ⋅
!
n dS
wake plane
− prop. reg.
"∫∫ + 1
2
V−V∞( )
2
ρ
!
V ⋅
!
n dS
wake plane
"∫∫
Φ can be computed in separate zones in the wake planes
to analyze Φ in terms of Φjet, Φwake, Φfuse … etc.
⇥⇤⌅
⇥⇤⌅⇧
⌃⌥ ⌦
⇥⇤⌅
⇤ ⌅⇥
⌃⌥ ⌦
⇥⇤⌅
↵ ⇥⇤ ⇤✏
⇣⌥ ⌃⌥ ⌦
⇥⇤⌅
⌃⌥ ⌦
⌥⌘⇧ ⌥⌅ ✓◆
⌫ ⌘⌥
⌫ ⌘⌥ ⇠⇥ ⇡⌥⇢
⇠⇥ ⇡⌥⇢⇣⌅⌥
⇣⌅⌥
⌧⌥⇡
⌧⌥⇡
⇥⇤⌅⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
 ⌫⇠⇡ ⇢⇥⇤ ⌧ ⇤⌦ ⇡ ! "##
⌃⌥ ⌦↵ ✏⇣ ⌘✓⌘⌘ ◆ ↵ ⌫⇠⇡⇠⇢
Ė
Ė
Podded (non-BLI) configura>on
Integrated (BLI) configura>on
Understanding the losses:

17. /27 17
CFD facilitates in-depth and alternate analysis methods
Wake planes to compute Φ terms
Podded (non-BLI) configura>on Integrated (BLI) configura>on
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
⇥⇤⌅
⇥⇤⌅⇧
⌃⌥ ⌦
 ⇥
⇥⇤⌅
⇤ ⌅⇥
⌃⌥ ⌦
 ⇧
⇥⇤⌅
↵ ⇥⇤ ⇤✏
⇣⌥ ⌃⌥ ⌦
◆ ⇥⇤  ⌅⇧⌃⇥  ⌥ ⇥  ⌦↵ ⇤⇥  ⇥⇥⇤⌅
⌃⌥ ⌦
⌥⌘⇧ ⌥⌅ ✓◆
⌫ ⌘⌥
⌫ ⌘⌥ ⇠⇥ ⇡⌥⇢
⇠⇥ ⇡⌥⇢⇣⌅⌥
⇣⌅⌥
⌧⌥⇡
⌧⌥⇡
⇥⇤⌅⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
⇧⌃⌥ ⇥⇤ ⌦↵ ✏⇥⇤
 ⌫⇠⇡ ⇢⇥⇤ ⌧ ⇤⌦ ⇡ ! "##
⌃⌥ ⌦↵ ✏⇣ ⌘✓⌘⌘ ◆ ↵ ⌫⇠⇡⇠⇢
Ė
Ė
Podded (non-BLI) configura>on
Integrated (BLI) configura>on
Understanding the losses:

18. /27 18
CFD facilitates in-depth and alternate analysis methods
Podded Configura>on
Wing region
fuselage
region
Jet region
Wing region
Integrated Configura>on
Zoning of the wake plane to break-down Φjet, Φwake, Φfuse contribu>ons to Φ

19. /27 19
α=2°
Uranga et al., Preliminary Experimental Assessment of the Boundary Layer Inges(on Benefit for the D8 Aircra@, AIAA-2014-0906
Real and digital tu9s help iden>fy local flow direc>on into the propulsors.
CFD helps plan and improve the experiments

20. /27 20
CFD helps plan and improve the experiments
⇥ ⇤ ⌅⇧⌃⌥ ⌦⌅↵⇥ ⇥ ✏⇣⇧⌃ ✏⌅⌘ ⇣✓ ⇣⇧⌃ ✓⇥ ◆  ⌦↵ ⌦ ⌥✓ ↵
⌫ ◆◆ ◆ ⌦↵ ⌦ ⌥✓ ↵ ⇠⌅  ↵⌅⇣✓ ◆ ⇥ ⌅⇡ ⇣◆ ⇣⇧⇥ ↵⌅⇢⇥⇣ ⇧ ✏⇣⇥ ✏⇣⇧⌃ ✏⌅⌘
⇥⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆ 
⌧
⇤
Greitzer et al., Aircra@ and Technology Concepts for an N+3 Subsonic Transport – Phase 2. Year 3 Status Review, 2014
Wing wake would par>ally
ingested by podded propulsor
at α=6° but not at α=2°.
A suitable dihedral angle θ for the
pods were found by simula>ng
mul>ple models (not by building
and tes>ng mul>ple models).
θ=0° θ=30° … ( and other θ angles simulated)

21. /27 21
CFD helps plan and improve the experiments
Separa>on regions were iden>fied by CFD simula>ons.
Elimina>on of these regions will reduce dissipa>on losses of the next designs

22. /27 22
EFD and CFD complement each other.
Source Diagnos>c Test by NASA & GE
EFD enables development of advanced CFD models
Simple actuator disk model Advanced actuator zone model
Hall, Greitzer and Tan, Analysis of Fan Stage Design AZributes for Boundary
Layer Inges(on, ASME Turbo Expo 2016: GT2106-57808.
Akaydin and Pandya, An Advanced Actuator Zone Model for Propulsor
Simula(ons with OVERFLOW, (in review for AIAA Avia>on 2017)
Hughes, Aerodynamic Performance of Scale-Model Turbofan Outlet Guide
Vanes Designed for Low Noise, AIAA-2002-0374

23. /27 23
Summary & Discussion
0 5 10 15
α
0.5
1
1.5
2
CL
WT
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.5
1
1.5
2
CL
WT
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.5
1
1.5
2
CL
WT
Overflow - Spalart-Allmaras
Overflow - SST
0 5 10 15
α
0.5
1
1.5
2
CL
WT
Overflow - Spalart-Allmaras
Overflow - SST
⇥⇤⌅⇧⌃⌥ ⇥ ⇥⌦ ↵ ✏ ⇣⌘⌅ ⌃⌥⇤ ⇧ ✓ ◆
⇥⇤ ⌅⇧⌃⇧⌥ ⌃ ⇧⌦↵ ⇥ ✏
⇣⌘ ✓◆◆ ⌦ ⌃ ⇧ ⌫⇧⌦ ↵⇧⌃ ⇠↵⇧ ⇡  ⇢ ⌧ ⌘ ✓◆◆ ⌦ ⌃
⇥ ⇤ ⇥ ⌅ ⇥ ⇧ ⇥ ⌃ ⇥⌥ ⇥⌥⇤
⇥
⇥ ⌅
⇥ ⌦
⇥ ⇤
⇥ ⌥
⇥ ⌥
⇥ ⇤
⇥ ⌦
⇥ ⌅
⇥
↵
↵
✏⇣⌘⌘✓⌘◆
⌫✓⇠⇡⇢⌫✓⌘◆
✏⇣⌘⌘✓⌘◆↵ ⌧
⌫✓⇠⇡⇢⌫✓⌘◆↵ ⌧
⇥⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆ 
ΔCPk= -9%
ΔCPk= -8%
cruise
• In D8 project, u>liza>on of EFD and CFD methods goes beyond cross-check & valida>on.
CL

24. /27 24
Summary & Discussion
⇥⇤⌅⇧⌃⇧⌃⌥ ⌦↵ ⌅ ✏⇣ ⌘ ✓ ◆ ⇤ ⌦ ⌫⇠
⇥⇤ ⌅⇧⌃⌥
⌦⇥↵
✏⇣⌘✓◆  ⌫✓⇣◆⇠⇡⇢ ⇡⇠⇡
⇥ ⇥⇤⇥ ⌅⇤⌅ ⇧ ⌃
⇡⇢⇢ ⇢✏⌧ ⇡◆⇠✓⇠✓
⇥ ⇥⇤⇥ ⌥⌅ ⇤⌅ ⇧ ⌃
⇡◆⇠✓⇠✓ ✏ ✓◆⇠⌫ ⇠
⇤ ⌦⌅ ↵
!⇧" ⌦#⇥⌥⌅" "⇥
"⇥"⌅⌥ ⌦⌅$ ⌃⌦!%
!⇧" ⌃⌦⌅"!⇥⇧
⌅⌦ ⌅
!⇧" ⌃⌦⌅"
⇠✏⇠⇡⇢ ⌫⇡&
⌫'( ⇡⇠⇡
⇥ ⇧ ⌃
⇠⇡⇠✓ ⌫⇡&
⌫'( ⇡⇠⇡
⇧ ⌃
⇠⇡⇠✓ )⌫✓⇠✏⇠⇡⇢ )⌫✓
*+ , + + ,
*+ ,
+
+ ,
⌅⌃
✏
*+ -
+
+ -
+ .
/ 0
/ ,
⇣⇤ ⌅⌃
⌘
⇧
✓
⇥⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆  ⌫⇠⇠
• In D8 project, u>liza>on of EFD and CFD methods goes beyond cross-check & valida>on.
• The methods also complement each other: CFD facilitates the duty of EFD and vice versa.

25. /27 25
Summary & Discussion
• In D8 project, u>liza>on of EFD and CFD methods goes beyond cross-check & valida>on.
• The methods also complement each other: CFD facilitates the duty of EFD and vice versa.
↵ ⇥⌃ ⌃ ⌅✏ ⌅⇤ ⇣⌘⇥✓
⇥ ✏⇣⇧⌃ ✏⌅⌘ ⇣✓ ⇣⇧⌃ ✓⇥ ◆  ⌦↵ ⌦ ⌥✓ ↵
⇠⌅  ↵⌅⇣✓ ◆ ⇥ ⌅⇡ ⇣◆ ⇣⇧⇥ ↵⌅⇢⇥⇣ ⇧ ✏⇣⇥ ✏⇣⇧⌃ ✏⌅⌘
 ⌫⇠⇠

26. /27 26
Summary & Discussion
• In D8 project, u>liza>on of EFD and CFD methods goes beyond cross-check & valida>on.
• The methods also complement each other: CFD facilitates the duty of EFD and vice versa.

27. /27 27
Summary & Discussion
⇥⇤⌅⇧⌃⇧⌃⌥ ⌦↵ ⌅ ✏⇣ ⌘ ✓ ◆ ⇤ ⌦ ⌫⇠
⇥⇤ ⌅⇧⌃⌥
⌦⇥↵
✏⇣⌘✓◆  ⌫✓⇣◆⇠⇡⇢ ⇡⇠⇡
⇥ ⇥⇤⇥ ⌅⇤⌅ ⇧ ⌃
⇡⇢⇢ ⇢✏⌧ ⇡◆⇠✓⇠✓
⇥ ⇥⇤⇥ ⌥⌅ ⇤⌅ ⇧ ⌃
⇡◆⇠✓⇠✓ ✏ ✓◆⇠⌫ ⇠
⇤ ⌦⌅ ↵
!⇧" ⌦#⇥⌥⌅" "⇥
"⇥"⌅⌥ ⌦⌅$ ⌃⌦!%
!⇧" ⌃⌦⌅"!⇥⇧
⌅⌦ ⌅
!⇧" ⌃⌦⌅"
⇠✏⇠⇡⇢ ⌫⇡&
⌫'( ⇡⇠⇡
⇥ ⇧ ⌃
⇠⇡⇠✓ ⌫⇡&
⌫'( ⇡⇠⇡
⇧ ⌃
⇠⇡⇠✓ )⌫✓⇠✏⇠⇡⇢ )⌫✓
*+ , + + ,
*+ ,
+
+ ,
⌅⌃
✏
*+ -
+
+ -
+ .
/ 0
/ ,
⇣⇤ ⌅⌃
⌘
⇧
✓
⇥⇤ ⌅⇧⌃ ⌥ ⌦↵ ↵ ✏ ⌃ ⇣↵⌘✓↵◆  ⌫⇠⇠
• In D8 project, u>liza>on of EFD and CFD methods goes beyond cross-check & valida>on.
• The methods also complement each other: CFD facilitates the duty of EFD and vice versa.
• Ul>mately, this interplay between the CFD and EFD shortens the design cycle and reduces tes>ng costs.
↵ ⇥⌃ ⌃ ⌅✏ ⌅⇤ ⇣⌘⇥✓
⇥ ✏⇣⇧⌃ ✏⌅⌘ ⇣✓ ⇣⇧⌃ ✓⇥ ◆  ⌦↵ ⌦ ⌥✓ ↵
⇠⌅  ↵⌅⇣✓ ◆ ⇥ ⌅⇡ ⇣◆ ⇣⇧⇥ ↵⌅⇢⇥⇣ ⇧ ✏⇣⇥ ✏⇣⇧⌃ ✏⌅⌘
 ⌫⇠⇠
Acknowledgements: Thanks to MIT team (Edward Greitzer, Mark Drela, Alejandra Uranga, Arthur Huang and
David Hall) for technical discussions and many of the material presented here. Compu>ng resources for CFD
simula>ons were provided by NASA Advanced Supercompu>ng Division at NASA Ames Research Center.
This work is funded by NASA AATT (Advanced Air Transport Technologies) Project