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High Explosives

High Explosives. ASCI Academic Strategic Alliances Program Caltech Material Properties Meeting February 4-5, 1999. Overview. First Principles molecular models of explosives, binders and reactions reactive flow hydrodynamics with detailed chemistry and EoS Evolutionary

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High Explosives

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  1. High Explosives ASCI Academic Strategic Alliances Program Caltech Material Properties Meeting February 4-5, 1999

  2. Overview • First Principles • molecular models of explosives, binders and reactions • reactive flow hydrodynamics with detailed chemistry and EoS • Evolutionary • engineering models of explosives • high-resolution (AMR) computations with available models • Goals • Explosives: HMX, TATB , Binder: Kel-F • Equation of State, PVET surfaces, G, Cp, Hugoniots, isotherms, • corner-turning problem CIT ASCI Alliance Program

  3. Organization Thermodynamics Continuum Mechanics Quantum Mechanics Force Fields Molecular Dynamics Numerical Simulation High Explosive and Shock Data CIT ASCI Alliance Program

  4. 200 Isolated molecule 150 crystal 100 Heat Capacity (cal/mol-K) 50 0 0 1000 2000 3000 Temperature (K) HMX-b CIT ASCI Alliance Program

  5. 120 80 Specific Heat (cal/mol.K) 40 0 0 500 1000 1500 2000 2500 Temperature (K) 50 cold 300K 600K 40 900K 30 Pressure (GPa) 20 10 0 0.3 0.4 0.5 0.6 Specific Volume (cc/g) TATB CIT ASCI Alliance Program

  6. Cl F H F C C C C 70 0K F F H F 3 60 1 100K 50 200K 40 300K Pressure (GPa) 30 20 10 0 0.6 0.3 0.4 0.5 Volume (cm3/g) Kel-F CIT ASCI Alliance Program

  7. Thermodynamic Analysis • Purpose: Extract thermodynamic properties from molecular dynamics simulation results • Fit PVE surfaces: Birch-Murnaghan or Mie-Grüneisen • Compute: • Grüneisen coefficient • coefficient of thermal expansion • Hugoniots (shock adiabats) • compressibilities CIT ASCI Alliance Program

  8. Grüneisen coefficient CIT ASCI Alliance Program

  9. Thermal Expansion Coefficient Dobratz CIT ASCI Alliance Program

  10. Isotherms P(V) CIT ASCI Alliance Program

  11. Hugoniot (Shock Adiabat) P(V) CIT ASCI Alliance Program

  12. Hugoniot Temperatures CIT ASCI Alliance Program

  13. Reduced Reaction Models • Use partial equilibrium and steady-state assumptions • Reduce 19-reaction, 8-species model to 3-step, 5 species CIT ASCI Alliance Program

  14. Detailed Chemistry Solutions • Time-accurate integration of reacting flow • Adaptive Mesh Refinement (AMR) on spatial gradients • Resolved reaction zone • Example: shock wave in dissociating oxygen CIT ASCI Alliance Program

  15. Stable Detonation in H2-O2 • P = 1 atm, T = 300 K, stoichiometric, D = 1.2 DCJ CIT ASCI Alliance Program

  16. Numerical solution of Euler Equations • Amrita computational facility (Quirk) • Two-dimensional, unsteady compressible flow • Patch-based adaptive mesh refinement • Finite-volume discretization • Glaister version of Roe upwind scheme • minmod limiter • one-step reaction CIT ASCI Alliance Program

  17. HMX Corner Turning I CIT ASCI Alliance Program

  18. Adaptive Mesh Refinement CIT ASCI Alliance Program

  19. HMX Corner Turning - finite rate CIT ASCI Alliance Program

  20. Wave Propagation in Binders • S. Sundaram, W. Knauss • PBX is a mixture of HE and binder • binder is polymer with complex material response • at low pressure, binder is very compliant compared to HE • polymers become stiffer with increasing pressure • pressure-dependent viscoelastic constituitive model developed • finite-element simulations of wave propagation in rods and plates CIT ASCI Alliance Program

  21. Test Problem • Detonation inside of a tube (planar or axisymmetric) Plastic deformation Elastic deformation gas HE CIT ASCI Alliance Program

  22. Components & Algorithms • HE & Compressible Turbulence • Godunov solver, 2D, fixed mesh or AMR • engineering models for HE & gases • existing software (Amrita & legacy code) • needs to have boundary algorithm incorporated • Solid Mechanics • free Lagrange, continuous rezone FEM • multiphysics including plasticity, fracture • existing software (Adlib) • Boundary coupler algorithm(s) • level set tracks boundary in Euler code, intrinsic in Lagrange method • ghost fluid method to exchange forces, positions, velocity • time step coordination module CIT ASCI Alliance Program

  23. Proof-of-Principle • Single program (no splitting), various levels of refinement • compressible fluid dynamics • 1D • 2D • elastic solid • lumped mass structural model • thin-shell model • 2D elastic wave solution • 2D FEM model • boundary tracker • level set propagation, constrain to SM boundary • ghostfluid exchange of boundary values CIT ASCI Alliance Program

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