research progress satellite drag in free-molecular and transition flow focus area viii october 26,...
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Research Progress
Satellite Drag in Free-Molecularand Transition Flow
Focus Area VIIIOctober 26, 2011
Marcin Pilinski, Craig Turansky, Brian ArgrowUniversity of Colorado, Boulder
Thanks to Scott Palo, Bruce Bowman, Ken Moe and Mildred Moe, Eric Sutton, and Eelco Doornbos
M. D. Pilinski, C. Turansky, B. M. Argrow 2
Focus Area VIII: Satellite Drag in the Re-Entry Region
10/28/2010
Objective: To significantly advance understanding of satellite drag in the transition and near-continuum regimes using state-of-the art numerical modeling, and to provide CD predictions under a broadened range of conditions
Yr Milestones Deliverables
1 Simulations of simple 3-D geometries with candidate GSI models.
DSMC/GSI with atmosphere model
2 Down-select/calibrate GSI models w/ satellite data
DSMC/GSI w/ calibrated GSI options
3 DSMC computation of transition-regime aerodynamic coefficients
Code to compute CD in slip/ transition flows for range of geometries
4 Create database of altitude-dependent CD for representative satellites in transition flow.
Integrated simulation environment code to produce CD database
5 Complete DSMC/GSI code for trajectory simulations w/ direct modeling of flow environment
Integrated simulation environment code to simulate real-time application
completed work ongoing work
Background: The Accommodation Coefficient
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[Doornbos. 2011]
M. D. Pilinski, C. Turansky, B. M. Argrow
Accommodation Coefficienta) α=1.00b) α=0.80c) Pilinski et al. 2010
Available Data: Fitted-Ballistic Measurements
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Rocket Body Orbits18:30:00, Jan 22, 1997
M. D. Pilinski, C. Turansky, B. M. Argrow
Data from 68 objects was provided by Bruce Bowman at AFSPC/A9A. Data spans 105 km to 520 km altitudes from 1969 to 2004.
Available Data: Tri-Axial Accelerometers
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Y
X
Z
β
φ
β
aligned with
boomtowards Earth
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SESAM Parameter Inversion
Fitted-Ballistic Coefficients t
t
t
t
B
B
, AtmosMod
obs,
, PhysMod
,obs
Results: SESAM model comparisons
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fuel margin: -0.05% to
0.05%
fuel margin:-3% to 0%
fuel margin:-0.05% to 5.0%
Results: Comparison with Paddlewheel Measurements
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CHAMP-GUVI Comparisons
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α = 0.78 (+0.10, -0.13)
Tri-Axial Accelerometer Analysis
Diffuse model with incomplete accommodation10/28/2010 M. D. Pilinski, C. Turansky, B. M. Argrow 10
α = 0.89 (+0.02, -0.03)
M. D. Pilinski, C. Turansky, B. M. Argrow 12
Spacecraft Simulation Goals
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Numerical Simulations(e.g. DSMC)
Rigid-body dynamics(modeling/approximation)
Full dynamic simulation
(beyond drag)
• Redefine the problem from satellite drag to spacecraft fluid dynamics
Treat spacecraft dynamics more like aircraft dynamics where possible
M. D. Pilinski, C. Turansky, B. M. Argrow 13
DSMC Development
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Bird’s “production” codes DS2V, DS3V Current, best available option for DSMC
DS2V User Interface
The Bad• Limited geometry, BCs• Requires a free-stream• Difficult batch processing• Only 2 GSI models
• Maxwellian diffuse• Pure specular
• Closed source• Can’t fix/extend it
The Good• Free, download at gab.com.au• Highly reliable• Verified by many people• Chemical reactions/internal modes present
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• DSMC is a tool for rarefied/transition gas flows that we need
• Current DSMC tools are “dull” (insufficient and/or unavailable)
• New code: Voldipar created to act as a sharper tool
• Current state of Voldipar verified with benchmark problems
• Supersonic Flat Plate• Hypersonic Cylinder• NACA0012
DSMC Development
M. D. Pilinski, C. Turansky, B. M. Argrow
1510/28/2010
Equations of Motion: 2D
�̇�=[𝑞𝑤+𝑋 (𝑢 ,𝑤 ,𝑞 , 𝑡)
𝑚
𝑞𝑢+𝑍 (𝑢 ,𝑤 ,𝑞 ,𝑡)
𝑚𝑀 (𝑢 ,𝑤 ,𝑞 ,𝑡)
𝐼 𝑦𝑦𝑞
]𝑋 (𝑢 ,𝑤 ,𝑞 ,𝑡)
𝒔 (𝑡)=[ 𝑢 (𝑡 )𝑤 (𝑡 )𝑞 (𝑡 )𝜃 (𝑡 ) ]
Source functions:
x
z
q
𝑽 ∞
𝛼
𝑍 (𝑢 ,𝑤 ,𝑞 ,𝑡)𝑀 (𝑢 ,𝑤 ,𝑞 ,𝑡)
Gas forces from some model or simulation
Take an example:• Panel method in Free-Molecular (FM) flow to get X,Z,M• What happens to an airfoil at Ma=10, Kn=100?
Rigid-Body Dynamics
M. D. Pilinski, C. Turansky, B. M. Argrow
1610/28/2010
separatrices
limitcycles
unstable trajectories
Aircraft-like Dynamics Results
NACA0012 in FM, Hypersonic flow: In-loop vs Sliding Taylor dynamic motion
Ma=10, Kn=100, Argon 1000K
𝛼0=15 ° 𝛼0=44 °
M. D. Pilinski, C. Turansky, B. M. Argrow
M. D. Pilinski, C. Turansky, B. M. Argrow 1710/28/2010
Conclusions
• Seeking to better understand spacecraft motion beyond drag• Want to make spacecraft as familiar as aircraft• Developing better numerical tools – DSMC (Voldipar code)• Starting to investigate how to apply this to rigid-body dynamics• Examples in 2D show this is possible
Future• Add more to Voldipar code (GSI, 3D upgrade, better BCs, generalized)• Examine new methods for approximation of dynamics• Look into possible LBM-DSMC coupling for transition region
Eventual Goal
Provide “single file”, full-dynamic description of spacecraft motion due to rarefied/transition flow