Tuesday, August 6, 2013

1308.0829 (Wakana Iwakami et al.)

Parametric Study of Flow Patterns behind the Standing Accretion Shock Wave for Core-Collapse Supernovae    [PDF]

Wakana Iwakami, Hiroki Nagakura, Shoichi Yamada
The systematic research of flow patterns behind the accretion shock wave is conducted using three-dimensional hydrodynamics simulations for core-collapse supernovae in this study. Changing the accretion rate and neutrino luminosity, the steady solutions of the one-dimensional irrotational accretion flow passing through the spherical shock wave are evolved by imposing a random perturbation with 1% amplitude at the onset of the simulations. Depending on the accretion rate and neutrino luminosity, various flow patterns appear behind the shock wave. We classified them into the three fundamental flow patterns: (1) sloshing motion, (2) spiral motion, (3) multiple high-entropy bubbles, and the two anomalous flow patterns: (4) spiral motion with buoyant bubbles, and (5) spiral motion with pulsating rotational velocity. The sloshing and spiral motions tend to be dominant in the higher accretion rate and lower neutrino luminosity, and the generations of multiple buoyant bubbles tend to prevail in the lower accretion rate and higher neutrino luminosity. Near the critical neutrino luminosity, the dominant pattern does not always identical between the semi-nonlinear and nonlinear phases, and the anomalous pattern appear in the nonlinear phase. Moreover, we confirm the reproducibility of these flow patterns, imposing the various random perturbations with 1% amplitude on the initial flow. The different realizations reveal that most of flow patterns reappear while the direction of rotational axis of the flow behind the shock wave can change in various directions. However, there are some differences among realizations for specific cases: the spiral motion with pulsating rotational velocity, and the bistability of two flow patterns.
View original: http://arxiv.org/abs/1308.0829

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