A numerical study of bubble and spike velocities in shock-driven liquid metals
We use detailed continuum hydrodynamics and molecular dynamics simulations to investigate the dynamics of ejecta that are initialized with large amplitude perturbations and non-sinusoidal shapes. Insights from the simulations are used to suggest a modified expression for the velocity associated with...
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Veröffentlicht in: | Journal of applied physics 2018-01, Vol.123 (2) |
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Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | We use detailed continuum hydrodynamics and molecular dynamics simulations to investigate the dynamics of ejecta that are initialized with large amplitude perturbations and non-sinusoidal shapes. Insights from the simulations are used to suggest a modified expression for the velocity associated with ejected spike structures, whereas a recently suggested model explains the observed bubble velocities. Specifically, we find the asymptotic bubble velocity prediction given by Mikaelian is in excellent agreement with the simulations, when a nonlinear correction for finite amplitudes is used in that model. In contrast, existing models can overpredict observed spike velocities if they do not include the modification of the initial spike growth rates due to nonlinearities. Instead, we find that when potential flow models are corrected with a suitable nonlinear prefactor, this leads to predictions in close agreement with our simulation data. We also propose a simple empirical expression for the nonlinear correction for spike velocities which is able to reproduce results from our simulations and published experimental and simulation data over a wide range of initial conditions and Mach numbers. We discuss extensions of these models to initial interfaces with arbitrary shapes. In particular, for non-sinusoidal shapes, the bubble and spike velocities are still predicted by these models provided we use an effective wavelength
λeff which is the wavelength of an equivalent sinusoid that has the same missing area. The issues of nonlinearity, non-standard shapes and shock Mach number addressed in this work are relevant to recent experimental campaigns involving twice-shocked targets. |
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ISSN: | 0021-8979 1089-7550 |
DOI: | 10.1063/1.5008495 |