Bulletin of the American Physical Society
17th Biennial International Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 56, Number 6
Sunday–Friday, June 26–July 1 2011; Chicago, Illinois
Session M4: Post Shock Turbulence II |
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Chair: D. Scott Stewart, University of Illinois at Urbana-Champaign Room: Renaissance Ballroom C |
Wednesday, June 29, 2011 11:00AM - 11:15AM |
M4.00001: Modelling of Unsteady Force in Compressible Multiphase Flows Manoj Parmar, Andreas Haselbacher, S. Balachandar Shock-particle interaction is a challenging problem because it is highly unsteady, inhomogeneous, nonlinear, and compressible in nature. The key to improved prediction of such flows depends on our understanding of the interaction of an individual particle in a compressible ambient flow. At present, due to lack of fundamental knowledge, no well-founded model exists for the evaluation of forces on a particle in an unsteady compressible flow. Current understanding is limited to the quasi-steady drag force. In compressible flows, unsteady contributions to the force can be very important but remain virtually unexplored. This work attempts to lay the foundation for improved understanding and prediction of compressible multiphase flows by obtaining a rigorous equation of motion for an isolated particle. Therefore, we first derive the compressible extension to the celebrated Basset-Boussinesq-Oseen equation. We then derive the compressible extension of the Maxey-Riley-Gatignol equation that accounts for the inhomogeneity of the ambient compressible flow. Through carefully constructed simulations, finite Mach- and Reynolds- number extensions for the quasi-steady and unsteady forces on the particle are developed. The improved formulation is tested for shock-particle interaction. [Preview Abstract] |
Wednesday, June 29, 2011 11:15AM - 11:30AM |
M4.00002: Importance of Unsteady Force and Heating to Particle Dispersal by Shock/Detonation Waves Yue Ling, Andreas Haselbacher, S. Balachandar Particle dispersal by shock/detonation waves is a challenging problem due to the complex interactions between the particles and the compressible flow features that must be captured rigorously in modeling and simulations. Previous experiments and direct numerical simulations have shown that the particle force and heating can be much larger than those predicted by the standard quasi-steady correlations, but little work has been done to improve the inter-phase interaction models. Based on recent research advances in our understanding of particle force and heating in compressible flows, this work proposes a rigorous inter-phase interaction model for unsteady compressible multiphase flows that includes all the unsteady contributions to the particle force and heating. The model is applied to investigate the particle dispersal in the classical explosion problems considered by Brode (J.\ Appl.\ Phys. 1955 and Phys.Fluids 1959) using the Eulerian-Lagrangian approach. The peak values and the overall effects are used to measure the importance of unsteady force and heating contributions. The simulation results show that ignoring compressibility and unsteady force and heating contributions in the inter-phase interaction model introduce significant errors. [Preview Abstract] |
Wednesday, June 29, 2011 11:30AM - 12:00PM |
M4.00003: A Lagrangian Framework for Analyzing the Fracture and Heating of PBXs under Impact Loading Invited Speaker: We have developed a Lagrangian framework for quantifying the thermomechanical response of polymer-bonded explosives (PBX) at the microstructural level. Based on the cohesive finite element method (CFEM), this framework accounts for large deformation, thermomechanical coupling, failure in the forms of microcracks in both bulk constituents and along grain/matrix interfaces, contact along crack surfaces and frictional heating. Implementations in 2D and 3D use both digitized micrographs of actual PBX materials and computationally generated microstructures with systematically varying attributes, allowing the effects of phase morphologies, packing and size to be considered. Constitutive responses considered include thermo-elasto-viscoelasticity for the polymeric binders, hyperelasticity for energetic grains, and thermo-elasto-viscoplasticity for metallic inclusions. In this presentation, I will discuss insights gained from analyses carried out using this Lagrangian framework, including quantitative relations between strength and microstructure, transition in heating mechanism from viscous dissipation to frictional dissipation, and distribution of hot spots. [Preview Abstract] |
Wednesday, June 29, 2011 12:00PM - 12:15PM |
M4.00004: Simulations of Heterogeneous Detonations and Post Detonation Turbulent Mixing and Afterburning Suresh Menon, Kalyana Gottiparthi Most metal-loaded explosives and thermobaric explosives exploit the afterburning of metals to maintain pressure and temperature conditions.The use of such explosives in complex environment can result in post detonation flow containing many scales of vortical motion, flow jetting and shear, as well as plume-surface interactions due to flow impingement and wall flows. In general, all these interactions can lead to highly turbulent flow fields even if the initial ambient conditions were quiescent. Thus, turbulent mixing can dominate initial mixing and impact the final afterburn. We conduct three-dimensional numerical simulations of the propagation of detonation resulting from metal-loaded (inert or reacting) explosives and analyze the afterburn process as well as the generation of multiple scales of mixing in the post detonation flow field. Impact of the detonation and post-detonation flow field on solid surface is also considered for a variety of initial conditions. Comparison with available data is carried out to demonstrate validity of the simulation method. [Preview Abstract] |
Wednesday, June 29, 2011 12:15PM - 12:30PM |
M4.00005: Particle-Turbulence Interaction Model for Aluminum Combustion Neeraj Sinha, William Calhoon, Jeremy Tomes Particle-turbulence interactions will have a substantial impact on the performance of thermobaric explosives that rely on the particle combustion for secondary heat release. Modeling these interactions from a fundamental perspective is very difficult and intractable for large-scale problems of practical interest. Alternatively, these interactions may be modeled from a macroscopic perspective that seeks to account for the probability distribution function (PDF) of variables within the modeled laminar burning rate for the particulates. Such a formulation would account for the first order effect of turbulent fluctuations on the burning rate within a computationally affordable model. This paper will describe the development of such a model for aluminum particle combustion in both the diffusion and kinetic burning regimes. This formulation is based on an assumed PDF method that may be parameterized into a database that may be deployed within a flow solver. As a result, the formulation is computational efficient and affordable for large-scale simulations. [Preview Abstract] |
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