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 • Postdocs • G. Caldwell (MP) • D. Chakraborty (MP) • A. Strachan (MP) • S. Sundaram* • Students • M. Arienti • C. Eckett* • P. Hung • Faculty • JE Shepherd • WG Knauss • P. Tang† • Staff • S. Dasgupta (MP) • R. Muller (MP) • E. Morano • J. Cummings † (CACR) • R. Samtaney (CT) *FY00 Alumni † FY00 additions

4. How subproject integrates into the VTF

5. 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

6. 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.

7. Research activities in FY’00 • 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

8. 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.

9. 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

10. 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

11. ILDM Reaction Mechanism Reduction • 2+2 dimensional ILDM for H2-air

12. Cellular Detonation Simulations • Self-propagating (not overdriven) cellular detonation in H2+O2+7Ar (Oran et al. 1998) • Finest grid level: 256 mesh cells across channel, 10 mesh cells per ZND induction length, AMR (Amrita)

13. Transparency Test

14. 2D Validation test of GFM • superseismic shock wave--elastic solid wave interaction

15. 2D AMR + GFM • 2D AMR HMX detonation simulation • FEM Copper simulation • GFM

16. Corner turning in HMX AMR (60x40) mesh refined twice with ratio 2, 10 processors

17. 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

18. 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

19. 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 toFY01 • Integrated simulation • Develop 3-D Eulerian AMR simulations of detonation with GFM IN PROGRESS

20. 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

21. 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 • Corner-turning experiments • Cylinder test experiments • Initiation experiments We need access to high-quality data on:

22. 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.

23. Plans for FY’01 • 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

24. 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.