Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session K4: Turbulence and Mixing III |
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Chair: Justin Wagner, Sandia National Laboratories, David Frost, McGill University Room: Grand H |
Tuesday, June 16, 2015 2:15PM - 2:30PM |
K4.00001: Particle segregation during explosive dispersal of binary particle mixtures David Frost, Jason Loiseau, Bradley Marr, Sam Goroshin The explosive dispersal of a layer of solid particles surrounding a spherical high explosive charge generates a turbulent, multiphase flow. The shock-compacted particle layer typically fractures into discrete fragments which shed particles in their wakes forming jet-like structures. The tendency to form jets depends on the particle to explosive mass ratio and type of particles, with brittle particles (e.g., glass) as well as ductile metallic particles particularly susceptible to jet formation. In contrast, tough, dense (e.g., steel) particles are much less prone to forming jets. Experiments have been carried out to determine the degree of particle segregation that occurs during the explosive dispersal of a uniform binary mixture containing both ``jetting'' (silicon carbide) and ``non-jetting'' (steel) particles with various mass fractions of each particle type. During the dispersal of mixtures that contain predominantly non-jetting (steel) particles, the steel particles form a stable layer whereas the jetting (silicon carbide) particles rapidly segregate and form jets which lag behind the steel particles. As the fraction of silicon carbide particles increases, the jet structures dominate the particle motion and the steel particles are entrained into the jets. [Preview Abstract] |
Tuesday, June 16, 2015 2:30PM - 2:45PM |
K4.00002: Towards Time-Resolved Particle Image Velocimetry Measurements during Shock-Particle Curtain Interactions Justin Wagner, Steven Beresh, Edward DeMauro, Brian Pruett, Paul Farias Recent experiments in the Multiphase Shock Tube (MST) have provided rare data for the interaction of a planar shock wave with a dense curtain of particles having a volume fraction of about 20 percent. Through new models validated with MST data, it has been demonstrated that dense particle distributions lead to a significant increase in interphase momentum transfer and a prolonged flow unsteadiness. Increased knowledge of the particle dispersal necessitates measurements of the surrounding turbulent and unsteady gas phase. Towards this end, gas velocity measurements using particle image velocimetry (PIV) are presented using a conventional 10-Hz PIV system for an interaction of a Mach 1.4 shock wave with the dense curtain. Additionally, time-resolved PIV measurements in the MST using a pulse-burst laser are presented and progress made towards applying this diagnostic to shock-particle curtain interactions is discussed. [Preview Abstract] |
Tuesday, June 16, 2015 2:45PM - 3:00PM |
K4.00003: Microscale Simulations of Shock Interaction with Large Assembly of Particles for Developing Point-Particle Models Siddharth Thakur, Chris Neal, Yash Mehta, Prashanth Sridharan, Tom Jackson, S. Balachandar Micrsoscale simulations are being conducted for developing point-particle models that are needed for macroscale simulations of explosive dispersal of particles. These particle models are required to compute instantaneous force and heat transfer between particles and surroundings. A strategy for a sequence of microscale simulations has been devised for systematic development of hybrid surrogate models that are applicable at conditions representative of explosive dispersal. The microscale simulations examine particle force dependence on: Mach number, Reynolds number, and volume fraction (particle arrangements such as cubic, face-centered cubic, body-centered cubic and random). Future plans include investigation of sequences of fully-resolved microscale simulations consisting of an array of particles subjected to more realistic time-dependent flows that progressively better approximate the problem of explosive dispersal. Additionally, effects of particle shape, size, and number as well as the transient particle deformation dependence on parameters including: (a) particle material, (b) medium material, (c) multiple particles, (d) incoming shock pressure and speed, (e) medium to particle impedance ratio, (f) particle shape and orientation to shock, etc. are being investigated. [Preview Abstract] |
Tuesday, June 16, 2015 3:00PM - 3:15PM |
K4.00004: A Study of Interfacial-Instability-Induced Mixing in Explosive Dispersal of Particles Bertrand Rollin, Subramanian Annamalai, Frederick Ouellet Recent experiments have shown that when a bed of particles is explosively dispersed, a multiphase instability front may occur, and lead to the formation of aerodynamically stable jet-particle structures. It is believed that these coherent structures originates from the early phase of explosive dispersal, in particular, in the manner in which the initial layer of particles undergoes instability, as it rapidly expands in the radial direction. In this work we want to isolate and study the effect of gas-particle two-way interaction on the nature of Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities of an explosively driven particle layer. As a result we perform numerical experiments, where we limit the initial volume fraction of the particle layer. The focus of this investigation is on the RT and RM growth mechanisms in the linear and non-linear stages under the complexity of the cylindrical geometry, very high pressures and densities associated with the detonation process. Thus, in addition to the initial disturbance created by the random distribution of particles, we explicitly vary the initial density of the particle and gas distribution. Detailed analyses of single mode and two-mode RT/RM-induced mixing are presented. [Preview Abstract] |
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