Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session F02: Particle TransportRecordings Available
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Chair: Alison Saunders, Lawrence Livermore Natl Lab Room: Anaheim Marriott Platinum 6 |
Monday, July 11, 2022 3:30PM - 3:45PM |
F02.00001: The importance of considering both DoP and VoP in forwards-ballistic penetrative experiments Daniel Powell, Gareth Appleby-Thomas, Jonathan Painter, Thiru Thirulogasingam The most common method of analysing armour performance is the Depth of Penetration (DoP). However, this 1-dimensional measurement does not provide insight into the method of penetration or energy absorbed by the target; the crater could be incredibly narrow or very wide and yield the same DoP. Analysis of the crater through Volume of Penetration (VoP) yields a more detailed metric to be used alongside DoP to visualise the crater, indicating whether energy was dispersed over a large area. VoP provides a wider insight into how the armour performed, giving evidence of potential defeat mechanisms. Digital reconstruction of the craters using x-ray radiographs or CT scanning can also provide a useful tool for computational models to be compared against. Success in utilising this analytical tool has been seen when comparing two layers of 5 mm alumina versus a single 10 mm monolithic block. A consistent difference in the ratio of DoP:VoP was seen between the layered and monolithic targets, indicating variation in the defeat mechanism between the two target configurations. |
Monday, July 11, 2022 3:45PM - 4:00PM |
F02.00002: A novel Doppler Monte Carlo code for modeling Photonic Doppler Velocimetry (PDV) spectrograms of ejecta from shock-loaded samples Zakaria Benameur, Jean-Bernard Maillet, Arnaud Sollier When a shock wave emerges at a metal free surface presenting geometrical defects such as pits, scratches, or grooves, "ejected matter" (ejecta) can be emitted from these defects in the form of thin jets expanding ahead of the main surface and breaking up into small particles. This process is referred to as microjetting. Photonic Doppler Velocimetry (PDV) is often used to track the velocity of the cloud of ejecta, due to its ability to record multiple velocities simultaneously. In recent years, various attemps have been undertaken in order to retrieve more information from the PDV spectrograms, especially the particle size and velocity distributions, using different methods to treat the radiative transfer within the cloud of ejecta. In this work, a novel Doppler Monte Carlo (MC) code, written in Python, has been developed for modeling optical radiation propagation in inhomogeneous polydisperse scattering ejecta clouds. A detailed convergence study, including the initial number of photons and the maximum number of scattering events, has first been performed in order to assess the accuracy of our MC algorithm. Then the code has been applied to the simulation of typical PDV ejecta spectrogams using a diversity of input distributions for their sizes and velocities, so as to build a representative database. This database is used to highligth how the PDV spectrograms are qualitatively and quantitatively influenced by the physical parameters of the cloud of ejecta. |
Monday, July 11, 2022 4:00PM - 4:15PM |
F02.00003: Obtaining the unsteady drag coefficient of micron-sized particles when the diameter is uncertain Adam A Martinez, Kyle Hughes, Dominique Fratantonio, Antonio B Martinez, John J Charonko The Los Alamos National Laboratory Horizontal Shock Tube (HST) studies response of shock-accelerated particles and droplets in a gas. When subjected to the highly unsteady flow of a shock, normal drag coefficients may not properly predict the motion of particles. The current experiments are done as a part of an ongoing campaign to improve drag laws in this regime, and are performed in conjunction with validation and computational efforts. Individual particle positions were obtained using a high speed eight-pulse particle tracking technique. Particles of several nominal diameters selected from the range of 1-10 μm were subjected to 1.2, 1.3, and 1.4 Mach number shocks in air. The nominal particle diameter was obtained from measurement of the size distribution before injection into the shock tube. While care is taken to narrow the width of the particle size distribution, averaging of the results is necessary to account for the polydispersity. We will describe the required averaging, and demonstrate how careful control of the uncertainty introduced by this diameter error was shown to reduce the bias in the resultant computed drag coefficients. |
Monday, July 11, 2022 4:15PM - 4:30PM |
F02.00004: Development of a Shell-Flaking Model for Hydriding Ejecta Particles Frederick Ouellet, Alan K Harrison, Jonathan D Regele Recent experiments performed at Los Alamos National Laboratory have shown that metal particles ejected from a shocked surface show vastly different behavior when the accepting medium is either inert or reactive. Particles which are ejected into an inert medium appear to breakup in a standard liquid droplet breakup mechanism. However, those ejected into the reactive, hydrogen-based media form a hydride shell and exhibit a non-monotonic velocity response in recorded LDV data. The physical processes which dictate this phenomenon are mostly unknown and are of interest for accurate modeling of the trajectories of the ejecta after formation. Point-particle simulations of the inert experiments are performed to validate the currently implemented ejecta sourcing and transport models of the hydrocode to be used for further model development and testing. Then, validation of a numerical solver for the inner and outer radii of the growing hydride shell around the ejecta due to chemical reactions with the ambient gas against experimental data is also shown for single particle cases. Finally, the ongoing development of a model meant to simulate shedding of small particles from the hydride shell formed around the reacting ejecta particles as they propagate through the gas is discussed. |
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