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 B02: Shallow Bubble Collapse IFocus Recordings Available
|
Hide Abstracts |
Chair: Robin Williams, AWE Aldermaston Room: Anaheim Marriott Platinum 6 |
Monday, July 11, 2022 9:15AM - 9:45AM |
B02.00001: X-ray Imaging of Mg Cavitation Invited Speaker: Matthew T Beason The coupling of dynamic loading platforms with synchrotron light sources have enabled experiments examining void formation in optically opaque materials. Much like spallation in a solid, cavitation occurs when rarefaction waves collide within a liquid. The resulting deformation leads to a complex flow field with numerous voids. It has been suggested that compaction of such a structure may be a significant source of ejecta (i.e. shallow bubble collapse). Here, I will present recent experiments examining cavitation of shock melted Mg using synchrotron radiation. Experiments span shock states that release from just below the ambient melt boundary to into the liquid phase. These results show a complex structure following cavitation, which must be understood if ejecta generated from shallow bubble collapse is to be predicted. |
Monday, July 11, 2022 9:45AM - 10:00AM |
B02.00002: Shallow Bubble Collapse Mechanism: A demonstrated high-areal mass, high-temperature ejecta production mechanism with rapid atomization Garry R Maskaly, Fady M Najjar, W. Dale Turley, Gerald D Stevens, Brandon M LaLone, Thomas M Hartsfield, Matthew Staska, Ruben Valencia The Shallow Bubble Collapse (SBC) mechanism was proposed to explain anomalous 2nd shock ejecta measurements that the Richtmyer-Meshkov Instability growth model fails to capture. In the SBC regime, the first shock condition results in a melted state persisting after release. Release waves interact to result in subsurface cavitation shallow to the surface. A sufficiently strong 2nd shock then generates substantial entropy as the cavitated metal foam gets recompacted. When the 2nd shock breaks out at the free surface, the material rapidly expands resulting in a low-density cloud of liquid droplets. This results in temperatures that can be over 2-times higher than expected with a simple shock physics understanding of the two shocks. We observe areal masses over 1 g/cm2, temperatures over 5000 K, and estimate atomization fractions at over 15% of the ejected material. A modeling approach is developed enabling us to capture many of the salient aspects of SBC production. We have observed SBC in tin and cerium target samples on gun platforms. |
Monday, July 11, 2022 10:00AM - 10:15AM |
B02.00003: Computational & Experimental Study of Shallow Bubble Collapse Mechanism in Gas Cells at Various Pressure Conditions Georges Akiki, Garry R Maskaly, Fady M Najjar, Gerald D Stevens, W. Dale Turley, Brandon M LaLone, Matthew Staska Ejecta production and transport has been generally characterized by the Ricktmyer-Meshkov Instability (RMI). Under certain shock conditions, RMI falls short in predicting the large amount of ejecta observed in experiments. The mechanism responsible for this increase in production has been identified and referred to as Shallow Bubble Collapse (SBC) mechanism. Ejecta produced by SBC is characterized by large areal mass releases (~10X more than RMI), very high temperatures (more than twice that observed in RMI), and higher velocities (~20% to 40% faster than RMI). SBC has been investigated under vacuum conditions. The current study aims to understand the effects of gas on the sourcing, transport and evolution of SBC ejecta. We have performed computations using LLNL's hydrodynamic code, ARES, and fielded experiments on gas guns for tin and cerium samples in various gases at different pressures. |
Monday, July 11, 2022 10:15AM - 10:30AM |
B02.00004: On Evidence of Substantial Atomization in Shallow Bubble Collapse Mechanism Fady M Najjar, Garry R Maskaly, Gerald D Stevens, Brandon M LaLone, Matthew Staska, W. Dale Turley, Thomas M Hartsfield, Jeff A Paisner We have recently fielded an experimental campaign to study the Shallow Bubble Collapse (SBC) mechanism on gas gun platforms. The diagnostics included PDVs, Asay windows and foils, pyrometry and a new diagnostic for atomization measurement, Atomic Ejecta Source Optical Probe (AESOP). In both tin and cerium target materials, we have observed cooling thermal-radiance signatures that may suggest a significant amount of atomization, over 10%, in both materials. AESOP sees quantifiable vapor at the leading edge of the ejecta field. PDV records suggest that in some cases, enough vapor may have evolved in the cloud that the ejecta produced accelerate in vacuum. This talk will provide highlights from our diagnostic efforts in understanding the impact of atomization when the SBC mechanism is active. |
Monday, July 11, 2022 10:30AM - 10:45AM |
B02.00005: Shock-driven Metal Foams for Studying Shallow Bubble Collapse Eric Stallcup, Garry R Maskaly, Fady M Najjar, David B Bober, Gerald D Stevens, W. Dale Turley, Brandon M LaLone, Matthew Staska Study of shock-driven ejecta has historically focused on Richtmeyer-Meshkov instability (RMI) growth as the primary mechanism, but a fundamentally different method, termed Shallow Bubble Collapse (SBC), has recently been established. SBC describes the process by which a release after a shock forms cavitation bubbles directly beneath the surface, and a subsequent shock collapses these bubbles. This releases significantly more ejecta than the RMI mechanism. In this work, the cavitation bubble collapse and ejecta release process is isolated by shocking a porous aluminum foam with a strong single shock. This simplified problem allows for more control over the sample and shock conditions, while also enabling better diagnostic access. Results are compared for differences in pore size, morphology, and pore fraction in the foam. These experiments, supported by numerical simulation, have shown this method accurately reproduces the physical processes taking place in SBC, therefore enabling faster model development. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700