Molecular Dynamics of Extreme Mass Segregation in a Rapidly Collapsing Bubble

Bass, Alexander; Ruuth, Steven J.; Camara, Carlos G.; Merriman, Barry; Putterman, Seth

doi:10.1103/physrevlett.101.234301

Cited by 35 publications

(31 citation statements)

References 24 publications

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“…It is well known that RP equation does not correctly describe the motion of the interface moving at speeds exceeding the speed of sound in the liquid. Nonetheless, this equation is frequently used to model the evolution of the radius R(t) of bubble during collapse [30,31]. Here we compare the evolution of the terms in the RP equation with the analogous terms recorded in our simulations.…”

Section: Comparison Of the Computer Simulations With The Solutionmentioning

confidence: 84%

Collapse of a nanoscopic void triggered by a spherically symmetric traveling sound wave

2012

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Molecular-dynamics simulations of the Lennard-Jones fluid (up to 10(7) atoms) are used to analyze the collapse of a nanoscopic bubble. The collapse is triggered by a traveling sound wave that forms a shock wave at the interface. The peak temperature T(max) in the focal point of the collapse is approximately ΣR(0)(a), where Σ is the surface density of energy injected at the boundary of the container of radius R(0) and α ≈ 0.4-0.45. For Σ = 1.6 J/m(2) and R(0) = 51 nm, the shock wave velocity, which is proportional to √Σ, reaches 3400 m/s (4 times the speed of sound in the liquid); the pressure at the interface, which is proportional to Σ, reaches 10 GPa; and T(max) reaches 40,000 K. The Rayleigh-Plesset equation together with the time of the collapse can be used to estimate the pressure at the front of the shock wave.

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Section: Comparison Of the Computer Simulations With The Solutionmentioning

confidence: 84%

Collapse of a nanoscopic void triggered by a spherically symmetric traveling sound wave

2012

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confidence: 99%

Inertially confined plasma in an imploding bubble

2010

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Models of spherical supersonic bubble implosion in cavitating liquids predict that it could generate temperatures and densities sufficient to drive thermonuclear fusion 1,2 . Convincing evidence for fusion is yet to be shown, but the transient conditions generated by acoustic cavitation are certainly extreme 3-5 . There is, however, a remarkable lack of observable data on the conditions created during bubble collapse. Only recently has strong evidence of plasma formation been obtained 6 . Here we determine the plasma electron density, ion-broadening parameter and degree of ionization during single-bubble sonoluminescence as a function of acoustic driving pressure. We find that the electron density can be controlled over four orders of magnitude and exceed 10 21 cm −3 -comparable to the densities produced in laser-driven fusion experiments 7 -with effective plasma temperatures ranging from 7,000 to more than 16,000 K. At the highest acoustic driving force, we find that neutral Ar emission lines no longer provide an accurate measure of the conditions in the plasma. By accounting for the temporal profile of the sonoluminescence pulse and the potential optical opacity of the plasma, our results suggest that the ultimate conditions generated inside a collapsing bubble may far exceed those determined from emission from the transparent outer region of the light-emitting volume.A bubble acoustically driven into nonlinear radial oscillation can focus the diffuse energy of the sound field by many orders of magnitude 8 . The energy focusing is such that broadband light emission is observed (sonoluminescence) 4 and molecular bonds are broken (sonochemistry) 9 . Measurement of the bubble dynamics of a single sonoluminescing bubble (single-bubble sonoluminescence (SBSL)) has shown the implosion velocity to be greater than the speed of sound with enormous acceleration near maximum collapse 10 . The bubble dynamics and the properties of the emitted light suggest the generation of extreme intracavity conditions. Indeed, recent molecular dynamics simulations predict temperatures approaching 10 8 K but lasting for only a few hundred femtoseconds 2 . The extreme conditions generated during SBSL arise from quasi-adiabatic compression of the bubble contents. One measure of the intensity of bubble implosion is the ratio of maximum to minimum bubble volume (that is, compression ratio). The value of the compression ratio, and hence the bubble kinetic energy, increases with increasing acoustic pressure (P a ; ref. 11). Thus, at high P a there is more energy available to be transferred to the bubble contents, which should ultimately produce more extreme intracavity conditions.Recently, Taleyarkhan and co-workers claimed to observe neutrons during acoustic cavitation in deuterated acetone 12,13 resulting from intracavity fusion reactions (that is, 'sonofusion'). These reports were met with immediate skepticism, and serious issues with the validity of the claims arose 14,15 . Indeed, subsequent studies in several independent laboratories ha...

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“…5,6 Numerous techniques have been developed to create cavitation in a laboratory setting, including boiling, 7 syringe injection, spark generation, 8 focused ultrasound, 9 neutron sources, 10 and focused lasers. 11,12 Compared with other methods, focused laser nucleation is attractive because it offers excellent spatial and temporal control and does not require any intrusive parts to contact the cavitating medium.…”

Section: Introductionmentioning

confidence: 99%

Optical nucleation of bubble clouds in a high pressure spherical resonator

Anderson

Sampathkumar

Murray

et al. 2011

The Journal of the Acoustical Society of America

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An experimental setup for nucleating clouds of bubbles in a high-pressure spherical resonator is described. Using nanosecond laser pulses and multiple phase gratings, bubble clouds are optically nucleated in an acoustic field. Dynamics of the clouds are captured using a high-speed CCD camera. The images reveal cloud nucleation, growth, and collapse and the resulting emission of radially expanding shockwaves. These shockwaves are reflected at the interior surface of the resonator and then reconverge to the center of the resonator. As the shocks reconverge upon the center of the resonator, they renucleate and grow the bubble cloud. This process is repeated over many acoustic cycles and with each successive shock reconvergence, the bubble cloud becomes more organized and centralized so that subsequent collapses give rise to stronger, better defined shockwaves. After many acoustic cycles individual bubbles cannot be distinguished and the cloud is then referred to as a cluster. Sustainability of the process is ultimately limited by the detuning of the acoustic field inside the resonator. The nucleation parameter space is studied in terms of laser firing phase, laser energy, and acoustic power used.

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Molecular Dynamics of Extreme Mass Segregation in a Rapidly Collapsing Bubble

Cited by 35 publications

References 24 publications

Collapse of a nanoscopic void triggered by a spherically symmetric traveling sound wave

Collapse of a nanoscopic void triggered by a spherically symmetric traveling sound wave

Inertially confined plasma in an imploding bubble

Optical nucleation of bubble clouds in a high pressure spherical resonator

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