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 J4: Turbulence and Mixing II |
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Chair: Allen Kuhl, Lawrence Livermore National Laboratory, H.S. Udaykumar, University of Iowa Room: Grand H |
Tuesday, June 16, 2015 11:15AM - 11:30AM |
J4.00001: Multiscale Modeling of Particles Embedded in High Speed Flows Sean Davis, Oishik Sen, Gustaaf Jacobs, H.S. Udaykumar Problems involving propagation of shock waves through a cloud of particles are inherently multiscale. The system scale is governed by macro-scale conservation equations, which average over solid and fluid phases. The averaging process results in source terms that represent the unresolved momentum exchange between the solid phase and the fluid phase. Typically, such source terms are modeled using empirical correlations derived from physical experiments conducted in a limited parameter space. The focus of the current research is to advance the multiscale modeling of shocked particle-laden gas flows; particle- (i.e. meso-)scale computations are performed to resolve the dynamics of ensembles of particles and closure laws are obtained from the meso-scale for use in the macro-scale equations. Closure models are constructed from meso-scale simulations using the Dynamic Kriging method. The presentation will demonstrate the multiscale approach by connecting meso-scale simulations to an Eulerian-Lagrangian macro-scale model of particle laden flows. The technique is applied to study shock interactions with particle curtains in shock tubes and the results are compared with experimental data in such systems. [Preview Abstract] |
Tuesday, June 16, 2015 11:30AM - 11:45AM |
J4.00002: Numerical Simulation of Shock/Detonation-Deformable-Particle Interaction with Constrained Interface Reinitialization Ju Zhang, Thomas Jackson, Sivaramakrishnan Balachandar We will develop a computational model built upon our verified and validated in-house SDT code to provide improved description of the multiphase blast wave dynamics where solid particles are considered deformable and can even undergo phase transitions. Our SDT computational framework includes a reactive compressible flow solver with sophisticated material interface tracking capability and realistic equation of state (EOS) such as Mie-Gruneisen EOS for multiphase flow modeling. The behavior of diffuse interface models by Shukla {\it et al.} (2010) and Tiwari {\it et al.} (2013) at different shock impedance ratio will be first examined and characterized. The recent constrained interface reinitialization by Shukla (2014) will then be developed to examine if conservation property can be improved. [Preview Abstract] |
Tuesday, June 16, 2015 11:45AM - 12:15PM |
J4.00003: Turbulent Mixing and Afterburn in Post-Detonation Flow with Dense Particle Clouds Invited Speaker: Suresh Menon Reactive metal particles are used as additives in most explosives to enhance afterburn and augment the impact of the explosive. The afterburn is highly dependent on the particle dispersal and mixing in the post-detonation flow. The post-detonation flow is generally characterized by hydrodynamic instabilities emanating from the interaction of the blast waves with the detonation product gases and the ambient air. Further, influenced by the particles, the flow evolves and develops turbulent structures, which play vital role in determining mixing and combustion. Past studies in the field in open literature are reviewed along with some recent studies conducted using three dimensional numerical simulations of particle dispersal and combustion in the post-detonation flow. Spherical nitromethane charges enveloped by particle shells of varying thickness are considered along with dense loading effects. In dense flows, the particles block the flow of the gases and therefore, the role of the inter-particle interactions on particle dispersal cannot be ignored. Thus, both dense and dilute effects must be modeled simultaneously to simulate the post-detonation flow. A hybrid equation of state is employed to study the evolution of flow from detonation initiation till the late time mixing and afterburn. The particle dispersal pattern in each case is compared with the available experimental results. The burn rate and the energy release in each case is quantified and the effect of total mass of the particles and the particle size is analyzed in detail. Strengths and limitations of the various methods used for such studies as well as the uncertainties in the modeling strategies are also highlighted. [Preview Abstract] |
Tuesday, June 16, 2015 12:15PM - 12:30PM |
J4.00004: Turbulent Combustion in Aluminum-air Clouds for Different Scale Explosion Fields Allen Kuhl, Kaushik Balakrishnan, John Bell, Vincent Beckner We have studied turbulent combustion effects in explosions, and proposed heterogeneous continuum models for the turbulent combustion fields. Also we have proposed an induction-time model for the ignition of Al particle clouds, based on Arrhenius fits to the shock tube data of Boiko. Here we explore scaling issues associated with Al particle combustion in such explosions. This is a non-premixed combustion system; the global burning rate is controlled by rate of turbulent mixing of fuel (Al particles) with air. For similitude reasons, the turbulent mixing rates should scale with the explosion length and time scales. However, the induction time for ignition of Al particles depends on an Arrhenius function, which is independent of such scales. To study this, we have performed numerical simulations of turbulent combustion in unconfined Al-SDF (shock-dispersed-fuel) explosion fields at different scales. Three different charge masses were assumed: 1-g, 1-kg and 1-T Al-powder charges. We found that there are two combustion regimes: an ignition regime---where the burning rate decays a power law function of time, and a turbulent combustion regime---where the burning rate decays exponentially with time. [Preview Abstract] |
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