Shock front distortion and Richtmyer-Meshkov-type growth caused by a small preshock nonuniformity

The response of a shock front to small preshock nonuniformities of density, pressure, and velocity is studied theoretically and numerically. These preshock nonuniformities emulate imperfections of a laser target, due either to its manufacturing, like joints or feeding tubes, or to preshock perturbat...

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Veröffentlicht in:Physics of plasmas 2007-07, Vol.14 (7)
Hauptverfasser: Velikovich, A. L., Wouchuk, J. G., Huete Ruiz de Lira, C., Metzler, N., Zalesak, S., Schmitt, A. J.
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Sprache:eng
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Zusammenfassung:The response of a shock front to small preshock nonuniformities of density, pressure, and velocity is studied theoretically and numerically. These preshock nonuniformities emulate imperfections of a laser target, due either to its manufacturing, like joints or feeding tubes, or to preshock perturbation seeding/growth, as well as density fluctuations in foam targets, “thermal layers” near heated surfaces, etc. Similarly to the shock-wave interaction with a small nonuniformity localized at a material interface, which triggers a classical Richtmyer-Meshkov (RM) instability, interaction of a shock wave with periodic or localized preshock perturbations distributed in the volume distorts the shape of the shock front and can cause a RM-type instability growth. Explicit asymptotic formulas describing distortion of the shock front and the rate of RM-type growth are presented. These formulas are favorably compared both to the exact solutions of the corresponding initial-boundary-value problem and to numerical simulations. It is demonstrated that a small density modulation localized sufficiently close to a flat target surface produces the same perturbation growth as an “equivalent” ripple on the surface of a uniform target, characterized by the same initial areal mass modulation amplitude.
ISSN:1070-664X
1089-7674
DOI:10.1063/1.2745809