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 P4: Post Shock Turbulence III |
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Chair: Fan Zhang, Defence Research and Development Canada Room: Renaissance Ballroom C |
Wednesday, June 29, 2011 2:00PM - 2:15PM |
P4.00001: Application of the Meshless Local Petrov-Galerkin (MLPG) Method to Rayleigh-Taylor Instability Bryan Susi, Beth Smith Legacy simulation techniques are inadequate for applications with complex boundary conditions and multi-material/multi-physics aspects. We applied the Meshless Local Petrov-Galerkin (MLPG) method to a transient, multi-fluid immiscible boundary problem to demonstrate the advantages of using meshless numerical methods for multi-material interactions. The MLPG method uses a domain characterized by a field of nodes where a local region influences the solution at each node. Meshless methods alleviate the burden of grid generation and manipulation. Node by node discretization and solution of the local weak formulation of the governing equations leads to a naturally coupled system of equations and the flexibility to properly handle multiple materials. To date this method has been primarily applied to solid mechanics benchmark problems. The modeling of transient multi-fluid interfaces in multiple dimensions is necessary to solve meaningful applications. We have demonstrated that the MLPG method can solve such problems confirming its potential as an effective method for simulating complex multi-physics/multi-material systems. [Preview Abstract] |
Wednesday, June 29, 2011 2:15PM - 2:30PM |
P4.00002: Physics Based Reaction Burn Model Prediction of Reaction Initiation and Growth in RDX for Thin and Thick Impactor Sunil Dwivedi, Yasuyuki Horie PBRB model for reactive composites simulates the reaction initiation and growth leading to detonation with built-in models for multiple individual as well as coupled phenomena: pre-existing statistical pore distribution, energy dissipation during shock loading and hot spot formations, surface temperature increase of the planar pore surfaces, surface reaction by sublimation, gas phase reaction, gas phase temperature rise and reverse heat flow to the pore surface aiding the surface reaction, solid phase heat conduction, etc. 1D idealized hot spot cell (1DHSC) version of the 3D PBRB model has been converted to a vectorized EOS form for the first time. Results validating the model with the pop plot of RDX in agreement with data through simulation of an assumed plate impact experiment will be presented. In addition, the effect of the surface sublimation model parameters on the rate of reaction, detonation shock pressure, and von-Neumann's peak for thin and thick inert impactor will be presented. We acknowledge Dr. Betsy Rice (ARL), Dr. Suhithi Peiris (DTRA) and Dr. John Brennan (ARL) for their support and discussion. This work is supported by Eglin AFB contract FA8651-08-0108/027 and in part by DTRA contract HDTRA-1-10-1-0035. [Preview Abstract] |
Wednesday, June 29, 2011 2:30PM - 2:45PM |
P4.00003: Shock-Driven Mixing: Experimental Design and Initial Conditions Gavin Friedman, Kathy Prestridge, Ricardo Mejia-Alvarez, Megan Leftwich A new Vertical Shock Tube (VST) has been designed to study shock-induced mixing due to the Richtmyer-Meshkov Instability (RMI) developing on a 3-D multi-mode interface between two gases. These studies characterize how interface contours, gas density difference, and Mach No. affect the ensuing mixing by using simultaneous measurements of velocity/density fields. The VST allows for the formation of a single stably-stratified interface, removing complexities of the dual interface used in prior RMI work. The VST also features a new diaphragmless driver, making feasible larger ensembles of data by reducing intra-shot time, and a larger viewing window allowing new observations of late-time mixing. The initial condition (IC) is formed by a co-flow system, chosen to minimize diffusion at the gas interface. To ensure statistically stationary ICs, a contoured nozzle has been manufactured to form repeatable co-flowing jets that are manipulated by a flapping splitter plate to generate perturbations that span the VST. This talk focuses on the design of the IC flow system and shows initial results characterizing the interface. [Preview Abstract] |
Wednesday, June 29, 2011 2:45PM - 3:00PM |
P4.00004: Vortex deposition and transition to turbulence in a shock-accelerated gas with particle/droplet seeding Peter Vorobieff, Joseph Conroy, Michael Anderson, Ross White, C. Randall Truman, Sanjay Kumar We present an experimental and numerical study of post-shock evolution of gas initially seeded with small droplets or particles. In two-phase media with gas being the embedding phase occupying most of the volume, shock acceleration can lead to vortex formation and eventually to turbulence. The physical mechanism responsible for the vorticity deposition in this case is different from that of Richtmyer-Meshkov instability that would emerge on a gas-gas density interface. After the shock passage, the particles or droplets lag behind the surrounding gas. Momentum exchange between the embedded phase and the embedding phase leads to non-uniform local equilibrium velocity distribution, and thus to shear and vortex formation. The cases we investigate include shock interaction with a cylindrical particle-seeded column (with and without reshock), as well as shock-driven advection of particles from a surface. [Preview Abstract] |
Wednesday, June 29, 2011 3:00PM - 3:15PM |
P4.00005: Experimental Study of the Interaction of a Planar Shock with a Dense Field of Particles Justin Wagner, Steven Beresh, Sean Kearney, Wayne Trott, Jaime Castaneda, Brian Pruett, Melvin Baer A novel multiphase shock tube has recently been developed to study particle dynamics in gas-solid flows having particle volume fractions that reside between the dilute and granular regimes. The particle field is generated by a gravity-fed method that results in a spanwise curtain of 100-micron spherical particles producing a volume fraction of about 15 percent. Interactions with incident shock Mach numbers of 1.67, 1.95, and 2.1 are reported. High-speed schlieren imaging simultaneous with high-speed wall pressure measurements are used to reveal the complex wave structure associated with the interaction. After the impingement of the incident shock, transmitted and reflected shocks are observed, which lead to differences in particle drag forces across the streamwise dimension of the curtain. Shortly thereafter, the particle field begins to propagate downstream and disperse. The trajectories of the upstream and downstream edges of the particle field at different Mach numbers are shown to be similar when normalized by the velocity of the flow induced by the incident shock. Furthermore, a control volume analysis is utilized to estimate the drag associated with the particles and is compared to drag estimates based on the schlieren imaging. [Preview Abstract] |
Wednesday, June 29, 2011 3:15PM - 3:30PM |
P4.00006: Laser-Accelerated Flyer System for Investigating Reactions in Ni-Al Mixtures Sean C. Kelly, Sara Baron, Naresh Thadhani, Timothy P. Weihs Experiments using a laser-accelerated flyer system were conducted on various forms of nickel-aluminum over a range of velocities in attempt to characterize the processes leading to complete reaction. The laser-accelerated flyer system consists of an Nd:YAG, 3-Joule, 1064-nm seeded laser, beam shaping optics, recovery experiment chamber, and velocity interferometry diagnostics. Using various flyer materials, impact velocities up to 1.5 km/sec have been measured using less than 50{\%} of the maximum laser energy. The laser-accelerated flyer system is used to conduct impact experiments on Ni-Al powder compacts, Ni-Al vapor-deposited foils, and single Ni-Al interface configurations. Subsequently, characterization using LOM, SEM, and XRD techniques is used to identify the reaction products and isolate the processes that lead to reaction initiation and products formed in the various Ni-Al configurations. [Preview Abstract] |
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