A facility for simulating the dynamic response of materials

1
A facility for simulating the dynamic response of
materials

• High Explosives
• Joe Shepherd
• Caltech
• ASCI ASAP Site visit
• Oct. 10-11,2000

2
Description and goals of subproject

• Molecular properties and reaction rates
• chemistry of nitramine reactions
• molecular dynamics of shock initiation
• equation of state of unreacted nitramine
  explosives, polymers
• High explosive simulation capabilites
• AMR and GFM methods for VTF
• reaction mechanism reduction for detonation
  simulations
• Engineering models of High Explosives
• implement and test EoS and reaction models
• cylinder test
• corner turning

3
Personnel

• Faculty
• JE Shepherd
• WG Knauss
• P. Tang
• Staff
• S. Dasgupta (MP)
• R. Muller (MP)
• E. Morano
• J. Cummings (CACR)
• R. Samtaney (CT)

• Postdocs
• G. Caldwell (MP)
• D. Chakraborty (MP)
• A. Strachan (MP)
• S. Sundaram
• Students
• M. Arienti
• C. Eckett
• P. Hung

FY00 Alumni FY00 additions
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How subproject integrates into the VTF
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Interactions with other subprojects

• Develop engineering models of HE and provide to
  VTF team
• Equation of state
• Reaction rate
• Work with SD to couple to FEM solid simulations
• Develop and verify Eulerian-Lagrangian coupling
  schemes and provide to VTF team
• Use MP reaction rate model for nitramines as
  input to ILDM models
• Use MP Molecular Dynamics simulation for HE EoS
• Work jointly with MP on shock initiation of HE

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Response to FY99 review

• Caution is offered with respect to the use of the
  ILDM procedure for detonation reaction mechanism
  reduction . strategic planning with respect
  to alternatives for reaction mechanism reduction
  is recommended.
• Augmented ILDM method (induction manifold ILDM)
  was successful! Method was implemented,
  verified, and validated against 2D detailed
  chemistry simulation.
• Risk-taking was justified in this case -
  potential risk was more than offset by enormous
  benefits of success.

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Research activities in FY00

• Detailed reaction mechanisms for nitramines
• Condensed phase effects on reactions
• Molecular dynamics of shock initiation
• Reactive force field treatment of nitramines
• Reduced reaction mechanism via ILDM
• Engineering models of HE
• improved product EoS, initial temperature effects
• Parallel AMR-GFM method for HE simulation with
  realistic boundary response
• Evaluation of GFM implementation schemes
• transparency acceleration tests

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Computational Science interactions

• Use of GrACE C library for AMR
• Manish Parashar
• Use of Python to script FEM and EL test problems
• Michael Aivazis
• Use of POOMA solvers written as Python extensions
  as a PSE for EL computations
• Julian Cummings.

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Achievements in basic science/engineering

• Nitramine chemistry
• detailed gas phase reaction mechanism for HMX
  RDX
• reactive force field developed for nitramines
• molecular dynamic simulation of shock-initiated
  RDX
• EoS of shocked HE and polymers
• Reaction Mechanism Reduction
• 4D ILDM computed for H2-O2-Ar
• ILDM induction manifold implemented in 2D AMR
  gas detonation
• GFM validations
• AMR GFM implemented in 2D
• 2D AMR detonation in elastic tube simulation
  carried out
• Implemented JTF EoS model for PBX in 3D AMR
  solvers

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Accomplishment of MP group in HE

• Reaction mechanism for nitramines
• HONO elimination
• RDX HMX mechanism completed
• Reactive force field for nitramines
• shock simulations of initiation in DMNA,
  RDX
• Polymer EoS
• computation of Gruneisen coefficients, shock
  Hugoniots

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RDX mechanism

• Starting point
• GRI nitromethane mechanism (49 species, 300
  reactions)
• Melius nitromethane mechanism (27 species, 130
  reactions)
• Yetter RDX mechanism (48 species, 240 reactions)
• Extension
• DFT-B3LYP/6-31G theory structure for all
  reactants, intermediates (13), transition states
  (14) and products
• Analytical frequencies for all species
• Incorporation of detailed kinetics for early
  stage CHNO reactions
• Overall scheme
• 85 species, 461 reactions
• Thermochemical data for all new species
• Theoretical rate constants - RRKM/TST
  calculations
• J. Phy. Chem. A, 104, 2261-2272, 2000.

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Unimolecular Decomposition of RDX
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HMX mechanism summary

• NO2 elimination via NN bond dissociation leading
  to HMR (radical) subsequent decomposition to
  smaller products
• Successive 4 HONO elimination and further
  decomposition of both HONO and the mass 108
  intermediate
• O migration from NO2 to adjacent C forming open
  ring RDX structure and oxy-ring MN structure
  which undergo further decomposition
• NN homolysis pathway (1) connects HMX
  decomposition to RDX decomposition network

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Shock simulation of RDX using Reactive FF
Impact velocity
2km/sec
3km/sec
32 RDX molecules 672 atoms
Reaction above threshold up
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Reaction Products

• 2km/s - no reaction
• some conformational changes w.r.t. NO2
  orientation
• 3km/s - extensive reactions
• Major species formed
• HONO
• NO2, H2O
• O2, N2, NO, OH
• H2CNO2, H2CN, H2CN-NO

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ILDM Reaction Mechanism Reduction

• 22 dimensional ILDM for H2-air

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Cellular Detonation Simulations

• Self-propagating (not overdriven) cellular
  detonation in H2O27Ar (Oran et al. 1998)
• Finest grid level 256 mesh cells across channel,
  10 mesh cells per ZND induction length, AMR
  (Amrita)

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Transparency Test
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2D Validation test of GFM

• superseismic shock wave--elastic solid wave
  interaction

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2D AMR GFM

• 2D AMR HMX detonation simulation
• FEM Copper simulation
• GFM

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Corner turning in HMX
AMR (60x40) mesh refined twice with ratio 2, 10
processors
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Application of Model - T-effect in TATB

• Both the detonation velocity and the CJ pressure
  increase as the temperature goes down
• There is no performance degradation from cold in
  plane geometry
• Performance degradation comes from the slowing
  down of the propagation velocity in corner
  turning and divergence
• Performance degradation comes from larger
  unburned region
• Reaction model with kinetics is needed to address
  this issue

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Integrated 3D Parallel Simulation

• Adlib solid tantulum model, Cohen thermal EoS, J2
  plasticity
• RM3D fluid model with Morano MG HMX model 66 Gpa
  CJ pressure
• ASCI Blue Pacific 1024 processors

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Tasks for FY00

• Materials properties
• Complete reaction network for nitramines
  COMPLETED
• Investigate via MD early events in shocked high
  explosives IN PROGRESS
• Engineering model
• Reduced reaction network for nitramines and
  application to 1-D and 2-D detonation Developed
  ILDM method in FY00
• Integration of JTF models utilizing reduced
  reaction networks into 3-D Eulerian code Delayed
  to FY01
• Integrated simulation
• Develop 3-D Eulerian AMR simulations of
  detonation with GFM IN PROGRESS

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Status of Milestones for FY00

• 2-D parallel engineering model detonation
  calculations utilizing integrated VTF Q1 FY00 ?
• 3-D parallel engineering model detonation
  simulations using AMR Q3 FY00 ?- in place, 2D
  runs only so far
• Fully 3-D coupled Eulerian/Lagrangian simulation
  using ghost fluid method Q4 FY00 ?
• Simulation utilizing materials database Q1 FY01
• under development

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Validation

• AMR
• backward-facing step
• cylindrical shock
• GFM
• 1D piston tests
• 1D shock transparency tests ( EL, LE)
• 2D convergence and mass conservation tests
• 2D cylinder lift-off test
• 2D super-seismic shock wave propagation along
  elastic boundary
• ILDM
• ZND, CV,Oran et al 2D simulations

We need access to high-quality data on

• Corner-turning experiments
• Cylinder test experiments
• Initiation experiments

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Leveraging

• Navy MURI on Pulse Detonation Engines
• Using POOMA-based FEM methods to model transient
  response of structures loaded by shock and
  detonation waves. Experimental research on
  elastic waves and fracture used in code
  validation.

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Plans for FY01

• Reaction Rates and Early Events in Shocked HE
• joint work with MP group, effects of high density
• ILDM method for HE
• apply methods developed in FY00 to nitramines
• Engineering Models for HE
• next generation reaction model
• Integrated Simulations for HE
• transfer AMR-GFM methodology to VTF
• initiation, corner turning, cylinder test
• validation against experiments

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Milestone for FY01

• Performance of a large-scale parallel simulation
  of detonation propagation with an advanced model
  of the reaction zone. Q3 FY 01.
• Tasks
• 1. Develop revised, robust mixture equation of
  state
• 2. Implement AMR solution of multi-species
  reaction model
• 3. Develop ILDM reduced model of chemical
  reaction network
• 4. Verification and Validation testing
• 5. Large-scale demonstration simulation.

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Interactions with other ASAP centers

• Developing collaboration with Illinois center
  (Scott Stewart) on detonation models and EL
  coupling methods.

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Interactions with DP laboratories

• Transferred nitramine reaction mechanism to LLNL
• Nick Winter, Bill Pitz, Larry Fried
• POOMA (LANL)
• Julian Cummings (now at CIT)
• Engineering models of HE (LANL)
• Pier Tang (now at CIT)

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Publications

• Eckett, Quirk, Shepherd The role of unsteadiness
  in the direct intiation of gaseous detonation
  JFM 421, 147-183, 2000.
• Reduced reaction models for detonation
  simulation, in preparation.
• A simplified model of high explosive
  detonation, in preparation.
• Eulerian-Lagrangian Coupling Schemes, in
  preparation.