Baerny, Jennifer

Dalle, Derek J.

Lee, Henry

Meeroff, Jamie G.

Rogers, Stuart E.

Roozeboom, Nettie

NASA Technical Reports Server

Comparison of SLS Sectional Loads from
Pressure-Sensitive Paint and CFD
AIAA SciTech Forum 2019
Jamie Meeroff, Henry Lee, Derek Dalle, Stuart Rogers,
Nettie Roozeboom, Jennifer Baerny
11 JAN 2019
https://ntrs.nasa.gov/search.jsp?R=20190002484 2019-08-30T21:28:25+00:00Z
Image Credit: NASA/MSFC
2
Image Credit: NASA
2
Image Credit: NASA/MSFC
2
Image Credit: NASA/MSFC
2
Image Credit: NASA/MSFC
2
Ascent Forces and Moments
0.5 1.0 1.5 2.0 2.5
Mach number
C
A
FUN3D w/ base correction
SLS-27-D-AFA-003
Power-on ascent FUN3D
Protuberance Air Loads
Surface Pressures
Line Loads
• Additional databases for other portions of flight (i.e. liftoff and transition)
• Most databases are a combination of wind tunnel data and CFD simulations
Introduction: Aerodynamic Databases
3
Sectional Loads
(Line Loads)
4
Sectional load slices for SLS Block 1B Crew configuration
Sectional load slices on forward portion of SLS Block 1B
• Line loads are a tool to evaluate the impact of aero loads on vehicle structures by
dividing vehicle into a number of fixed width slices
• Calculate the load on each slice, normalized by slice width
• Valid for long/skinny vehicles, like a rocket
Sectional Loads/Line Loads
5
Line loads for a section i typically take the form of:
CN,i =
∫ xˆi+1
xˆi
∫
CN (xˆ, s) ds dxˆ
Where xˆ is a non-dimensionalized axial coordinate and s is a parametric variable along the vehicle edge
In practice, these line loads are divided by slice length to provide a universal
value:
CˆN,i =
1
xˆi+1 − xˆi
∫ xˆi+1
xˆi
∫
CN (xˆ, s) ds dxˆ
discretized value for the derivative of CN with respect to xˆ, i.e. dCN/d(x/Lref )
The TRILOAD* routine from the CGT package (NASA
Ames) is used to calculated the final profiles
* Pandya, S. and Chan, W. M., Computation of Sectional Loads from Surface Triangulation and Flow Data, AIAA Paper 2011-3680
Sectional Load Calculation
6
• Deliver three force components (no
moments)
• Profiles are a function of axial distance
along the rocket
• For SLS, we use 200 slices and deliver line
loads on the core, left booster, and right
booster all separately
• Delivered database based on Flight CFD,
wind tunnel runs used as ”sanity check”
c A
(xˆ
)
m1.75a4.0r000.0
2 4 6 8 10 12 14
x/Lref
1
0
1
y
/L
re
f
Axial loads: cA(x/Lref ) = cA(xˆ)
c Y
(xˆ
)
m1.75a4.0r000.0
2 4 6 8 10 12 14
x/Lref
1
0
1
y
/L
re
f
Lateral loads: cY (xˆ)
c N
(xˆ
)
m1.75a4.0r000.0
2 4 6 8 10 12 14
x/Lref
1
0
1
z/
Lr
e
f
Normal loads: cN (xˆ)
Example of a Sectional Load
7
Experimental Setup
8
NASA Ames UPWT
• Tests completed in 11x11-foot and
9x7-foot test sections
• Three configurations tested: Block 1 Crew,
Block 1B Crew, Block 1B Cargo
• Tested at 1.3% scale
From: Baals, D. D. and Corliss, W., Wind Tunnels of NASA, Tech. Rep.
NASA-SP-440
Pressure-Sensitive Paint
• Steady PSP collected for all three
configurations in 11-foot test section
(Mach 0.2 to 1.4)
• No viscous contributions
• Light source: 40 x 400 nm LEDs
• Image collection: 8 cameras around plenum
Image Credit: NASA/ARC/Dominic Hart
Experimental Setup
9
• Format: Plot3D, multiple zone, no I-blanks
• Structured patches - user determined
• Resolution limited by image reduction process - coarse protuberances
PSP Surface Representation
10
• PSP requires clear optical path to produce accurate data
• Difficult to get optical access to regions under pressurization lines and
between booster and core (among others)
• These regions are considered to have CP = 0
Areas in red show regions with no optical access
PSP Optical Access
11
Post-processed
surface CP on
Plot3D mesh
Split Cells
→
Surface CP on
triangulated
mesh
TRILOAD
→
Sectional load
profile
⇒
PSP Sectional Load Extraction
12
CFD Setup
13
• Fun3D - 3D unstructured (mixed-element) flow solver developed at
NASA LaRC*
• Run in RANS or uRANS (whenever RANS solution was not steady) mode
using Spalart-Allmaras turbulence model
• 2 feature-based adaptations during every run
• 2250 Fun3D simulations run - only a subset is comparable to PSP
CFD Mesh
*Biedron, R. T., et al., FUN3D Manual: 13.1, Tech. Rep. TM-2017-219580
Flow Solver
14
Converged CFD Solution, Block 1B Crew, Mach 1.6 and αt = 4
◦
Flow field is colored by Mach number, surface is shaded by Cp
Sample CFD Solution
15
Converged CFD Solution, Block 1B Crew, Mach 1.6 and αt = 4
◦
500 1000 1500 2000 2500 3000
Iteration Number
10-2
10-1
100
101
102
L2
 r
e
si
d
u
a
l
1500 2000 2500 3000
Ite ration Number
C
A
CA = ##
CA = ##
(CA) = ##
L2 norm has converged a few magnitudes and bulk forces are stable
Sample CFD Solution
15
Sectional Load
Comparisons
16
• Comparisons made at three Mach numbers: 0.95, 1.10, and 1.30
• All at αt = 4.0
◦ and five different roll angles (missile axis CS)
Block 1B Crew STACK/CA at Mach 1.30
dC
A/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
A/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Sectional Load Comparisons
17
Block 1 Crew
18
STACK/CN at Mach 0.95
dC
N/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
N/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Good matching except at attach hardware and between booster and core
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1 Crew
19
STACK/CY at Mach 0.95
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Trends match, but more differences - larger projected area in Y
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1 Crew
19
STACK/CY at Mach 1.10
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Large differences between booster and core at φ = 90◦ due to shielding
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1 Crew
19
Block 1B Cargo
20
STACK/CY at Mach 0.95
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Divergence starts at FWD attach and continues downstream
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1B Cargo
21
STACK/CN at Mach 1.10
dC
N/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
N/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Very good agreement in normal force at this condition
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1B Cargo
21
STACK/CY at Mach 1.30
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
Y/
d(
x/
Lr
ef
)
4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Still poor agreement between booster and core, symmetry lacking
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1B Cargo
21
Block 1B Crew
22
STACK/CN at Mach 0.95
dC
N/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
N/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Good agreement except at attach points
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1B Crew
23
STACK/CY at Mach 1.10
dC
Y/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
Y/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Offset between booster and core seen for Block 1 Crew no longer present
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1B Crew
23
STACK/CY at Mach 1.30
dC
Y/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
dC
Y/
d(
x/
Lr
ef
)
2 4 6 8 10 12 14
x/Lref
1
0
1
y/
Lr
ef
• Trends match well, peaks at different magnitudes
Solid lines = PSP
Dashed lines = CFD
αt = 4°, φ = 180° (α = -4°, β =  0°)
αt = 4°, φ =   90° (α =  0°, β =  4°)
αt = 4°, φ = 360° (α = 4°, β = 0°)
αt = 4°, φ =   45° (α =  2.8°, β =   2.8°)
αt = 4°, φ = 225° (α = -2.8°, β =  -2.8°)
Block 1B Crew
23
Effects of Optical
Shielding
24
• Line loads calculated by zeroing out areas of no or little optical access
• These areas are sometimes regions of volatile loading (fwd/aft attach)
• Solution: remove cells from shielded areas in final CFD solution
PSP Surface with Shielded Regions in Red Masked CFD Surface Mesh
Accounting for Optical Shielding
25
• Line loads calculated by zeroing out areas of no or little optical access
• These areas are sometimes regions of volatile loading (fwd/aft attach)
• Solution: remove cells from shielded areas in final CFD solution
Cp on RSRB after Masking RSRB/CY Line Loads
Mach = 1.05, αt = 8
◦, φ = 0◦
Accounting for Optical Shielding
25
• Sectional loads for three different configurations of SLS were extracted
from PSP data and compared to those from CFD simulations
• Relatively good agreement can be seen between the two data sources
– CA and CN - good
– CY - worse, but still favorable [optical effects amplified]
• Areas of poor agreement often correspond to areas of poor optical access
(i.e. attach hardware)
• Favorable comparisons with PSP sectional loads gives more credence for
using CFD for database delivery
– Sectional load databases currently come from CFD at flight conditions
– CFD solutions from WT simulations used as sanity check for those at flight
conditions
Future Work
• Extend masking for all sectional loads
• Continue to improve PSP grid resolution and optical access
• Database buildup and uncertainty quantification
Summary
26
• SLS Program; this work is part of the SLS Aero Task Team
• Patrick Shea and team for organizing wind tunnel test efforts
• Other members of the NASA ARC/TNA SLS CFD Team:
– Jeff Onufer
– Tom Pulliam
– and many previous members
• NASA Advanced Supercomputing facilities
• NASA Ames UPWT
Acknowledgments
27
Backup Slides
28
Block 1B Crew, Mach 1.6 and αt = 4
◦
Wind Tunnel Flight
Flow field is colored by Mach number, surface is shaded by Cp
Salient differences: Reynolds number and plume-on effects
Wind Tunnel vs. Flight CFD
29


Comparison of SLS Sectional Loads from Pressure-Sensitive Paint and CFD

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