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The University of Minnesota NASA
Validation of US3D for Capsule Aerodynamicsusing 05-CA Wind Tunnel Test Data
Alan Schwing
11/19/12
https://ntrs.nasa.gov/search.jsp?R=20120017946 2020-07-04T11:52:13+00:00Z
Outline of Presentation
Motivation
05-CA Overview
Numerical Inputs - Solver, Method, Grid
Sensitivity Analysis - Spacial, Temporal
Results‣Integrated Aerodynamic Loads‣Pressure Port Comparisons‣Possible improvements
Conclusions
Questions
Test 5-CA Final Report Crew Exploration Vehicle (CEV) Program
EG-CEV-06-19 Final Report Test 5-CA March 2006 James Bell Code AOX, MS 260-1 James.H.Bell@nasa.gov, (650)604-4142
National Aeronautics and Space Administration NASA Ames Research Center Moffett Field, California
Motivation
NASA is currently investigating and has a long history of employing capsule shapes for a variety of missions - manned and unmanned.
In order to design the most efficient system possible, correct characterization of the vehicle’s aerodynamics are imperative.‣Parachute Mass ‣Structural Loading ‣Downrange Concerns
Historically, a combination of wind tunnel testing and flight testing has been most useful. Computational Fluid Dynamics (CFD) are becoming an increasingly vital piece of this work, though.
Current models employed at NASA still allow for a large degree of uncertainty in aerodynamic prediction. There is room for new tools to assist in design decisions.
US3D continues to improve the state of the science and is beginning to see use in aerodynamic prediction for capsule shapes. This work is designed to:‣Help understand how applicable the code is to these shapes‣Provide suggestions on best practices‣Outline avenues for improvement and areas of greatest confidence
05-CA Overview
05-CA was a wind tunnel test performed in two NASA Ames test sections:‣9-foot x 7-foot supersonic test section : Mach 1.6 - Mach 2.5‣11-foot transonic test section : Mach 0.3 - Mach 1.4
This work will focus on the 11-foot section and a 7.66% model.‣Model was heavily instrumented and provides the largest wealth of validation data.
• 151 pressure ports with static measurements • 6-axis balance for integrated loads• 12 unsteady pressure transducers
‣Wide range of Mach number and Angle of Attack (α) available for comparison.
A supersonic, transonic, and subsonic case were considered at three angles of attack in order to provide an initial look at how US3D’s performance varied between these three regimes.
0.3 0.5 0.6 0.7 0.8 0.9 0.95 1.05 1.1 1.2 1.4140 x x x145150155 x x x160165170 x x x
α Mach
Flow Solver - US3D
US3D is an unstructured, finite-volume CFD code developed at the University of Minnesota. It is fully-parallel and implicit.‣Steiger-Warming flux vector splitting‣Differed-Correction approach to viscous fluxes‣Includes both RANS and LES turbulence modeling‣Detached Eddy Simulation (DES) also fully supported‣2nd-order implicit Euler time advancement‣Low dissipation numerics (CITE)
High-order and low dissipation allow for superior computations. Additionally, combined RANS/LES simulations (DES) provide much higher fidelity in the wake region - a major driver for this problem’s aerodynamics.
Going to compare three numerical methods in US3D:‣RANS turbulence model‣DES turbulence model with Steiger-Warming dissipative fluxes‣DES turbulence model with low-dissipation kinetic energy conserving fluxes
Grid Generation
All grid generation was performed with GridPro..
Some important notes and features:‣A portion of the sting was included to improve computational fidelity.‣Wind tunnel walls were not modeled.‣Extensive smoothing iterations were applied in order to drive the grid smoother to a
steady-state. This helped maintain similarity between grids of different resolutions.‣Wake refinement was aligned with the mid-α case in order to best capture the range of
the analysis. It extended 6 diameters downstream - a distance selected based on best practices used by NASA for similar computations using OVERFLOW (CITE).‣Similarly, the outer boundaries extended 30 diameters from the vehicle in order to
minimize their effect for the subsonic cases.‣Viscous wall-spacing selected to maintain y+ of less than 1 on entire geometry.
Grid Generation
Grid Generation
One of the first analysis performed was an investigation into the spacial refinement and its effect on the quantity of interest, aerodynamic loads.
Final grid of 18,217,949 points and 18,113,216 cells.
Grid Resolution Study
-1.4
-1.39
-1.38
-1.37
-1.36
-1.35
-1.34
-1.33
-1.32
1 10 100
CX
Cells (Millions)
Mach 1.4
0.048
0.05
0.052
0.054
0.056
0.058
0.06
0.062
0.064
0.066
0.068
1 10 100
CZ
Cells (Millions)
Mach 1.4
-0.02
-0.019
-0.018
-0.017
-0.016
-0.015
-0.014
-0.013
-0.012
-0.011
-0.01
-0.009
1 10 100
Cm
Cells (Millions)
Mach 1.4
Half-GridFull-Grid
Temporal Resolution Study
Just as significant to the validity of the results is the selection of the proper timestep to use for these simulations.‣One initial consideration was to maintain a CFL of less than 1 throughout the wake
region. Maximum CFL values varied for each Mach number.
-0.678
-0.676
-0.674
-0.672
-0.67
-0.668
-0.666
-0.664
-0.662
4.3 4.35 4.4 4.45
4.5 4.55 4.6 4.65
4.7
C A
Time (s)
/home/work-schwi262/projects/summer12/05-CA/runCase #1: coarse_155/m1.4a155_2oConfig = coarse_155, Mach = 1.4, α = 155, Order = 2, Vinf = 168.32, Rho = 1.43938, Tinf = 281.650
Diverge at 4.31 seconds
Iterations = 200000/200000CPU Time = 5226.2 hours
0.018
0.02
0.022
0.024
0.026
0.028
0.03
4.3 4.35 4.4 4.45
4.5 4.55 4.6 4.65
4.7
C N
Time (s)
/home/work-schwi262/projects/summer12/05-CA/runCase #1: coarse_155/m1.4a155_2oConfig = coarse_155, Mach = 1.4, α = 155, Order = 2, Vinf = 168.32, Rho = 1.43938, Tinf = 281.650
Diverge at 4.31 seconds
Iterations = 200000/200000CPU Time = 5226.2 hours
1000500250100
2000
-0.0048
-0.0046
-0.0044
-0.0042
-0.004
-0.0038
-0.0036
-0.0034
-0.0032
-0.003
-0.0028
4.3 4.35 4.4 4.45
4.5 4.55 4.6 4.65
4.7
C m
Time (s)
/home/work-schwi262/projects/summer12/05-CA/runCase #1: coarse_155/m1.4a155_2oConfig = coarse_155, Mach = 1.4, α = 155, Order = 2, Vinf = 168.32, Rho = 1.43938, Tinf = 281.650
Diverge at 4.31 seconds
Iterations = 200000/200000CPU Time = 5226.2 hours
Temporal Resolution Study
Also of concern was the effect on the integrated forces and moments.
Results
Mach 1.40
Results - Mach 1.40
Results - Mach 1.40
Instantaneous Averaged
Solutions are very unsteady and so the results were time-averaged in order to compare to similarly time-averaged wind tunnel data.
Effects of Numerical MethodKEC
SW
RANS
Instantaneous images show qualitative changes between the numerical methods.
Dissipation grows as we move from KEC → SW → RANS
There is also a noticeable difference in the flow features on the windward side.
Averaged KEC
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
140 145 150 155 160 165 170 175
CL
Alpha
Mach 1.4
1.05
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
1.5
1.55
140 145 150 155 160 165 170 175
CD
Alpha
Mach 1.4
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
140 145 150 155 160 165 170 175
Cm
CG
Alpha
Mach 1.4
0
0.05
0.1
0.15
0.2
0.25
140 145 150 155 160 165 170 175
CN
Alpha
Mach 1.4
-1.55
-1.5
-1.45
-1.4
-1.35
-1.3
-1.25
-1.2
140 145 150 155 160 165 170 175
CA
Alpha
XCG = 0.680 DZCG = -0.045 D
WTTRANS
SWKEC
Results - Mach 1.40
Comparisons are good‣RANS appears to perform the worst. SW appears to do a bit
better than KEC, but both are very close.‣It is not surprising that our comparisons are this strong for this
Mach number. The integrated loads are dominated by the forebody pressure and not as sensitive to the modeling in the wake.‣Largest error seen in α=170°, we’ll look at the pressure tap data
to investigate a bit more.
View From φ = 270 °
m1.40 a155
V∞
Page 3
M∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.13˚, ReD = 5.32 x106
RANS conditions: SW conditions:
KEC conditions: Run429 conditions:
View From Apex
m1.40 a155
Page 3
φ = 270 °
φ = 0 °
φ = 90 °
φ = 180 °
M∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.13˚, ReD = 5.32 x106
RANS conditions: SW conditions:
KEC conditions: Run429 conditions:
-0.5
0
0.5
1
1.5
2
60 90 120 150 186 150 120 90 60X (in)
m1.40 a155
Page 3
ConeShoulder
Heat ShieldShoulder
ConeCp
M∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.14˚, ReD = 5.32 x106, P = 30507.37 Pa, q = 41265.93 PaM∞ = 1.390, α = 155.22˚, β = 0.13˚, ReD = 5.32 x106
RANS conditions: SW conditions:
KEC conditions: Run429 conditions:
RANS - phi 0SW - phi 0
KEC - phi 0Run_429
RANS - phi 180SW - phi 180
KEC - phi 180
Results - Mach 1.40 α = 155°
Results
Mach 0.95
Results - Mach 0.95
Results - Mach 0.95
0.1
0.2
0.3
0.4
0.5
0.6
0.7
140 145 150 155 160 165 170 175
CL
Alpha
Mach 0.95
0.8
0.9
1
1.1
1.2
1.3
1.4
140 145 150 155 160 165 170 175
CD
Alpha
Mach 0.95
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
140 145 150 155 160 165 170 175
Cm
CG
Alpha
Mach 0.95
0
0.02
0.04
0.06
0.08
0.1
0.12
140 145 150 155 160 165 170 175
CN
Alpha
Mach 0.95
-1.4
-1.35
-1.3
-1.25
-1.2
-1.15
-1.1
-1.05
-1
-0.95
140 145 150 155 160 165 170 175
CA
Alpha
XCG = 0.680 DZCG = -0.045 D
WTTRANS
SWKEC
Comparisons are good‣RANS is clearly not as capable as the KEC DES for this regime.
SW was not run.‣Examination of the pressure ports for these cases reveals why
RANS has such trouble.
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
140 145 150 155 160 165 170 175
CL
Alpha
Mach 1.4
1.05
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
1.5
1.55
140 145 150 155 160 165 170 175C
D
Alpha
Mach 1.4
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
140 145 150 155 160 165 170 175
Cm
CG
Alpha
Mach 1.4
0
0.05
0.1
0.15
0.2
0.25
140 145 150 155 160 165 170 175
CN
Alpha
Mach 1.4
-1.55
-1.5
-1.45
-1.4
-1.35
-1.3
-1.25
-1.2
140 145 150 155 160 165 170 175
CA
Alpha
XCG = 0.680 DZCG = -0.045 D
WTTRANS
SWKEC
View From φ = 270 °
m0.95 a140
V∞
Page 3
M∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.09˚, ReD = 5.31 x106
RANS conditions: KEC conditions:
Run424 conditions:
View From Apex
m0.95 a140
Page 3
φ = 270 °
φ = 0 °
φ = 90 °
φ = 180 °
M∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.09˚, ReD = 5.31 x106
RANS conditions: KEC conditions:
Run424 conditions:
-1.5
-1
-0.5
0
0.5
1
1.5
60 90 120 150 186 150 120 90 60X (in)
m0.95 a140
Page 3
ConeShoulder
Heat ShieldShoulder
ConeCp
M∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.09˚, ReD = 5.31 x106
RANS conditions: KEC conditions:
Run424 conditions:
RANS - phi 0KEC - phi 0
Run_424RANS - phi 180
KEC - phi 180
Results - Mach 0.95 α = 140°
View From φ = 270 °
m0.95 a140
V∞
Page 3
M∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.09˚, ReD = 5.31 x106
RANS conditions: KEC conditions:
Run424 conditions:
View From Apex
m0.95 a140
Page 3
φ = 270 °
φ = 0 °
φ = 90 °
φ = 180 °
M∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.09˚, ReD = 5.31 x106
RANS conditions: KEC conditions:
Run424 conditions:
-1.5
-1
-0.5
0
0.5
1
1.5
60 90 120 150 186 150 120 90 60X (in)
m0.95 a140
Page 3
ConeShoulder
Heat ShieldShoulder
ConeCp
M∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.11˚, ReD = 5.31 x106, P = 54028.05 Pa, q = 34158.75 PaM∞ = 0.950, α = 142.32˚, β = 0.09˚, ReD = 5.31 x106
RANS conditions: KEC conditions:
Run424 conditions:
RANS - phi 0KEC - phi 0
Run_424RANS - phi 180
KEC - phi 180
Results - Mach 0.95
RANS Averaged KEC
α = 140°
Results - Mach 0.95 α = 140°
View From φ = 270 °
m0.95 a155
V∞
Page 3
M∞ = 0.946, α = 154.36˚, β = 0.13˚, ReD = 5.31 x106, P = 54219.28 Pa, q = 33995.35 PaM∞ = 0.946, α = 154.36˚, β = 0.13˚, ReD = 5.31 x106, P = 54219.28 Pa, q = 33995.35 PaM∞ = 0.946, α = 154.36˚, β = 0.12˚, ReD = 5.30 x106
RANS conditions: KEC conditions:
Run424 conditions:
View From Apex
m0.95 a155
Page 3
φ = 270 °
φ = 0 °
φ = 90 °
φ = 180 °
M∞ = 0.946, α = 154.36˚, β = 0.13˚, ReD = 5.31 x106, P = 54219.28 Pa, q = 33995.35 PaM∞ = 0.946, α = 154.36˚, β = 0.13˚, ReD = 5.31 x106, P = 54219.28 Pa, q = 33995.35 PaM∞ = 0.946, α = 154.36˚, β = 0.12˚, ReD = 5.30 x106
RANS conditions: KEC conditions:
Run424 conditions:
-1.5
-1
-0.5
0
0.5
1
1.5
60 90 120 150 186 150 120 90 60X (in)
m0.95 a155
Page 3
ConeShoulder
Heat ShieldShoulder
ConeCp
M∞ = 0.946, α = 154.36˚, β = 0.13˚, ReD = 5.31 x106, P = 54219.28 Pa, q = 33995.35 PaM∞ = 0.946, α = 154.36˚, β = 0.13˚, ReD = 5.31 x106, P = 54219.28 Pa, q = 33995.35 PaM∞ = 0.946, α = 154.36˚, β = 0.12˚, ReD = 5.30 x106
RANS conditions: KEC conditions:
Run424 conditions:
RANS - phi 0KEC - phi 0
Run_424RANS - phi 180
KEC - phi 180
Results - Mach 0.95 α = 140°
View From φ = 270 °
m0.95 a170
V∞
Page 3
M∞ = 0.944, α = 170.48˚, β = 0.08˚, ReD = 5.30 x106, P = 54479.16 Pa, q = 34005.19 PaM∞ = 0.944, α = 170.48˚, β = 0.08˚, ReD = 5.30 x106, P = 54479.16 Pa, q = 34005.19 PaM∞ = 0.944, α = 170.48˚, β = 0.07˚, ReD = 5.30 x106
RANS conditions: KEC conditions:
Run424 conditions:
View From Apex
m0.95 a170
Page 3
φ = 270 °
φ = 0 °
φ = 90 °
φ = 180 °
M∞ = 0.944, α = 170.48˚, β = 0.08˚, ReD = 5.30 x106, P = 54479.16 Pa, q = 34005.19 PaM∞ = 0.944, α = 170.48˚, β = 0.08˚, ReD = 5.30 x106, P = 54479.16 Pa, q = 34005.19 PaM∞ = 0.944, α = 170.48˚, β = 0.07˚, ReD = 5.30 x106
RANS conditions: KEC conditions:
Run424 conditions:
-1.5
-1
-0.5
0
0.5
1
1.5
60 90 120 150 186 150 120 90 60X (in)
m0.95 a170
Page 3
ConeShoulder
Heat ShieldShoulder
ConeCp
M∞ = 0.944, α = 170.48˚, β = 0.08˚, ReD = 5.30 x106, P = 54479.16 Pa, q = 34005.19 PaM∞ = 0.944, α = 170.48˚, β = 0.08˚, ReD = 5.30 x106, P = 54479.16 Pa, q = 34005.19 PaM∞ = 0.944, α = 170.48˚, β = 0.07˚, ReD = 5.30 x106
RANS conditions: KEC conditions:
Run424 conditions:
RANS - phi 0KEC - phi 0
Run_424RANS - phi 180
KEC - phi 180
Results
Mach 0.5
Results - Mach 0.50
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
140 145 150 155 160 165 170 175
CL
Alpha
Mach 0.5
0.55
0.6
0.65
0.7
0.75
0.8
0.85
0.9
0.95
1
140 145 150 155 160 165 170 175
CD
Alpha
Mach 0.5
-0.02
-0.01
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
140 145 150 155 160 165 170 175
Cm
CG
Alpha
Mach 0.5
-0.1
-0.08
-0.06
-0.04
-0.02
0
0.02
0.04
0.06
0.08
0.1
0.12
140 145 150 155 160 165 170 175
CN
Alpha
Mach 0.5
-1
-0.95
-0.9
-0.85
-0.8
-0.75
140 145 150 155 160 165 170 175
CA
Alpha
XCG = 0.680 DZCG = -0.045 D
WTTRANS
SWKEC
Results - Mach 0.50
Comparisons reveal greater errors in modeling‣Comparisons are definitely varied with no clear winner. RANS and
KEC appear to grab the trend across the forces/moment.‣For a flow this unsteady and with this low of a dynamic pressure,
there is a significant contribution from the base flow. Also of interest are large magnitude pressure near the shoulder.‣Pressure port measurements will help illustrate where each model
is having troubles.
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0.55
0.6
0.65
140 145 150 155 160 165 170 175
CL
Alpha
Mach 1.4
1.05
1.1
1.15
1.2
1.25
1.3
1.35
1.4
1.45
1.5
1.55
140 145 150 155 160 165 170 175C
D
Alpha
Mach 1.4
-0.05
-0.04
-0.03
-0.02
-0.01
0
0.01
0.02
140 145 150 155 160 165 170 175
Cm
CG
Alpha
Mach 1.4
0
0.05
0.1
0.15
0.2
0.25
140 145 150 155 160 165 170 175
CN
Alpha
Mach 1.4
-1.55
-1.5
-1.45
-1.4
-1.35
-1.3
-1.25
-1.2
140 145 150 155 160 165 170 175
CA
Alpha
XCG = 0.680 DZCG = -0.045 D
WTTRANS
SWKEC
Results - Mach 0.50
View From φ = 270 °
m0.50 a140
V∞
Page 3
M∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.500, α = 141.73˚, β = 0.11˚, ReD = 5.30 x106
RANS conditions: SW conditions:
KEC conditions: Run418 conditions:
View From Apex
m0.50 a140
Page 3
φ = 270 °
φ = 0 °
φ = 90 °
φ = 180 °
M∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.500, α = 141.73˚, β = 0.11˚, ReD = 5.30 x106
RANS conditions: SW conditions:
KEC conditions: Run418 conditions:
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
0.5
1
1.560 90 120 150 186 150 120 90 60
X (in)
m0.50 a140
Page 3
ConeShoulder
Heat ShieldShoulder
ConeCp
M∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.488, α = 141.73˚, β = 0.14˚, ReD = 5.11 x106, P = 122135.76 Pa, q = 20334.99 PaM∞ = 0.500, α = 141.73˚, β = 0.11˚, ReD = 5.30 x106
RANS conditions: SW conditions:
KEC conditions: Run418 conditions:
RANS - phi 0SW - phi 0
KEC - phi 0Run_418
RANS - phi 180SW - phi 180
KEC - phi 180
α = 140°
Results - Mach 0.50 α = 140°
RANS
Results - Mach 0.50 α = 140°α = 140°
SW
Results - Mach 0.50 α = 140°α = 140°
KEC
Unsteady Frequency Response
Wind tunnel model had 11 taps arranged on the surface of the backshell of the model. These probes recorded data at a rate of 6400 Hz for 6 seconds.‣All cases examined in this work included unsteady data.‣Comparisons revealed that the computational expense necessary to obtain results that
were ‘statically converged’ required significant wall time. For this reason, only one case was examined thoroughly.
The Mach 0.50 case at α = 140° was selected for comparison for two reasons:‣It was a massively separated case that had a strong response in the wind tunnel data.‣Integrated loads showed a large spread between the methods examined here and might
highlight differences between then.Data was sampled from the CFD at tap locations‣Downsampled to 6400 Hz using Welch’s Method with 50% overlap‣0.2 second intervals (wind tunnel test used 0.2s)‣Tukey Window used on each interval
Frequency response from integrated loads alsoconsidered 4 5 6
210
1 9 3
8117
Unsteady Frequency Response - TapsMonitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001Monitors - r0418s0001
4 5 6
210
1 9 38117
WTTRANSKECSW
Unsteady Frequency Response - CmCm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001Cm - r0418s0001
4 5 6
210
1 9 38117
WTTRANSKECSW
Varying DES Model
There is a sensitivity to the flavor of DES, but the differences are not substantial and in some cases are negligible.
0.08
0.09
0.1
0.11
0.12
0.13
0.14
0.15
0.16
Mach 0.5 Mach 1.4 0.215
0.22
0.225
0.23
0.235
0.24
0.245
0.25
0.255
0.26
0.265CL
DES Sensitivity
0.796 0.8
0.804 0.808 0.812 0.816 0.82
0.824 0.828 0.832 0.836 0.84
0.844 0.848 0.852 0.856 0.86
0.864 0.868
Mach 0.5 Mach 1.4 1.36
1.37
1.38
1.39
1.4
1.41
1.42
1.43
1.44
1.45CD
DES Sensitivity
-0.12
-0.08
-0.04
0
0.04
Mach 0.5 Mach 1.4-0.46
-0.45
-0.44
-0.43
-0.42
-0.41
-0.4
-0.3910*CmCG
DES Sensitivity
-0.008-0.004
0 0.004 0.008 0.012 0.016 0.02
0.024 0.028 0.032 0.036 0.04
0.044 0.048 0.052 0.056 0.06
0.064 0.068 0.072 0.076
Mach 0.5 Mach 1.4 0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045CN
DES Sensitivity
-0.876-0.872-0.868-0.864-0.86
-0.856-0.852-0.848-0.844-0.84
-0.836-0.832-0.828-0.824-0.82
-0.816-0.812-0.808
Mach 0.5 Mach 1.4-1.48
-1.47
-1.46
-1.45
-1.44
-1.43
-1.42
-1.41
-1.4
-1.39
-1.38CA
XCG = 0.680 DZCG = -0.045 D
DESIDES
DDES
Conclusions and Further Work
RANS is ill-suited for analysis of these problems. For transonic and supersonic cases, US3D shows fairly good agreement using DES across all cases.
Separation prediction and resulting backshell pressure are problems across all portions of this analysis. This becomes more of an issue at lower Mach numbers:‣Stagnation pressures not as large - wake and backshell are more significant‣Errors on shoulder act on a large area - small discrepancies manifest as large changes
Subsonic comparisons are mixed with regard to integrated loads and merit more attention. Dominant unsteady behavior (wake shedding) resolved well, though.
Further work:‣Evaluate the effect of other turbulence models on separation prediction‣Use more advanced tools to look into improvements that might be made with grid quality‣Investigate transition and its effect on separation
BACKUP
-0.765
-0.76
-0.755
-0.75
-0.745
-0.74
-0.735
-0.73
-0.725
-0.72
1 10 100
CX
Cells (Millions)
Mach 0.5
0.08
0.082
0.084
0.086
0.088
0.09
0.092
0.094
0.096
0.098
0.1
1 10 100
CZ
Cells (Millions)
Mach 0.5
0.03
0.031
0.032
0.033
0.034
0.035
0.036
0.037
1 10 100
Cm
Cells (Millions)
Mach 0.5
Half-Grid
-1.21
-1.205
-1.2
-1.195
-1.19
-1.185
-1.18
1 10 100
CX
Cells (Millions)
Mach 0.95
0.067
0.068
0.069
0.07
0.071
0.072
0.073
0.074
0.075
0.076
0.077
1 10 100
CZ
Cells (Millions)
Mach 0.95
-0.006
-0.005
-0.004
-0.003
-0.002
-0.001
0
1 10 100
Cm
Cells (Millions)
Mach 0.95
Half-Grid
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