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Detonation Modeling

Detonation Modeling. Proposed detonation activities for Caltech Alliance beyond FY02. Group Leader: Joe Shepherd. Proposed changes. Merge existing Compressible Turbulence and HE groups into a single: “Compressible and Reactive Flow” group. Refocus efforts on gaseous explosives

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Detonation Modeling

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  1. Detonation Modeling Proposed detonation activities for Caltech Alliance beyond FY02 Group Leader: Joe Shepherd

  2. Proposed changes • Merge existing Compressible Turbulence and HE groups into a single: “Compressible and Reactive Flow” group. • Refocus efforts on gaseous explosives • More realistic scope of work • Equation of state, reaction mechanisms well characterized • Significant science and engineering topics: • Turbulent combustion in compressible flow • Integrated simulation (fluid and solid) with significant material properties issues • Plastic deformation and fracture can occur in confining structures • Current integrated simulation framework carries over completely ASCI-ASAP Research Review October 22-23, 2001

  3. Focus Areas • Detonation modeling in gases and interaction with structures • Development of realistic reduced reaction models for 2D and 3D simulations – follow on to current ILDM work • High resolution simulations resolving instability (transverse) wave • Analyse canonical problems such as diffraction to develop physical insight and theories for critical parameters • Development approximate methods to handle mixing and reaction in turbulent regions behind front • Fluid-structure interaction • Failure of structures by detonation waves • Failure of detonation waves due to yielding confinement ASCI-ASAP Research Review October 22-23, 2001

  4. Gaseous detonation • Nonlinear interaction of chemistry and fluid mechanics creates instabilities • Self-organizing microstructure “transverse waves” • Multiscale problems, reaction zone is 1 to 100 mm ASCI-ASAP Research Review October 22-23, 2001

  5. Reaction zone structure • Sharp rise in OH-concentration profile marks end of induction-zone • Induction zone length is stongly dependent on shock-velocity OH mole fraction Temperature, K Distance, cm 2H2-O2-60%N2 Induction Zone length, cm Normalized velocity, U/UCJ ASCI-ASAP Research Review October 22-23, 2001

  6. Detailed observations are possible ASCI-ASAP Research Review October 22-23, 2001

  7. Simulataneous [OH] and r visualization ASCI-ASAP Research Review October 22-23, 2001

  8. Gaseous detonation dynamics • Rich range of phenomena have been reported and studied • Some important critical issues • Role of turbulence in chemical reaction • Prediction of critical parameters • Initiation energy • Critical diffraction diameter • Minimum tube diameter • Key computational problems • Known but very large reaction mechanisms • Turbulent flow in portions of reaction zone ASCI-ASAP Research Review October 22-23, 2001

  9. Detonation Wave Diffraction • Detonation can fail, i.e., shock wave and reaction zone decouple during diffraction detonation shock flow d products shocked reactants ASCI-ASAP Research Review October 22-23, 2001

  10. Direct Initiation What is the critical E needed to start a detonation? ASCI-ASAP Research Review October 22-23, 2001

  11. Structural Response to Detonation ASCI-ASAP Research Review October 22-23, 2001

  12. 0.56 mm Surface Notch Wall Detonation propagation 41 mm Fracture due to Gaseous Detonations Detonation wave direction ASCI-ASAP Research Review October 22-23, 2001

  13. Summary • Eliminate condensed explosive continuum modeling • Combine HE and CT groups • Common numerical methods • Common issue – turbulent flow and mixing • Change scope of detonation problems • Gases only • Continue reaction mechanism reduction studies • Study critical processes, interaction between fluid dynamics and chemical reaction • Integration simulation is almost identical in scope • Focus more on fracture and plasticity than shock waves in solids ASCI-ASAP Research Review October 22-23, 2001

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