Computational Examination of Compaction Wave-Boundary Interaction in Granular Explosive

• Main Author: Mandal, Anirban
• Other Authors: Gonthier, Keith A.
• Format: Others
• Language: en
• Published: LSU 2010
• Subjects: Mechanical Engineering
• Online Access: http://etd.lsu.edu/docs/available/etd-08112010-163505/

Interactions between initially planar, piston supported compaction waves in heterogeneous energetic solids and macro-scale rigid boundaries were computationally examined for a wide range of piston impact speeds (20 ≤ U_p ≤ 500 m/s) and initial solid volume fractions of the material (0.73 ≤ ϕ₀ ≤ 0.90). The response of the material was described by a continuum theory that accounts for both elastic and inelastic compaction in a thermodynamically consistent manner. Initial conditions were imposed by interpolating the spatial structure of one-dimensional steady compaction waves onto two-dimensional domains considered in this study. For a planar wedge boundary, the peak solid pressure (P_s), dissipative heating rate (ė_c) and bulk temperature rise (ΔT) at the boundary increased when wedge angle θ was increased from 0º to a critical value (60º ≤ θ_c ≤ 65º) as the flow transitioned to a single Mach reflection (SMR) from a von Neumann reflection (vNR); these quantities decreased when θ was further increased due to flow transition to a regular reflection (RR) from a SMR for ϕ₀ = 0.85 and U_p = 500 m/s. Locations of the peak P_s, ė_c and ΔT were predicted to be removed from the wedge tip for a vNR and a SMR, but near the wedge tip for a RR. Qualitatively similar predictions were obtained for 0.73 ≤ ϕ₀ ≤ 0.90 and U_p ≥ 150 m/s. For a semi-circular boundary, the initial RR configuration transitioned to a SMR for all cases. For 0.73 ≤ ϕ₀ ≤ 0.90 and U_p ≥ 150 m/s, peak values of P_s, ė_c and ΔT were predicted at a location removed from the stagnation point. For both wedge and semi-circular boundaries, dissipative heating at the boundary was dominated by rate-dependent compaction. To aid in the development of a bulk-scale combustion sub-model, bulk-scale predictions were compared to locally averaged meso-scale predictions. Bulk-scale and averaged meso-scale predictions showed good agreement, provided that the averaging area size was suitably selected.