Three-Dimensional Simulations of Standing Accretion Shock Instability in Core-Collapse Supernovae
Three-Dimensional Simulations of Standing Accretion Shock Instability in Core-Collapse Supernovae
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DOI：
10.1086/533582
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发表时间：
2007-10
期刊：
影响因子：
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通讯作者：
W. Iwakami;K. Kotake;N. Ohnishi;S. Yamada;K. Sawada
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文献类型：
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作者：
W. Iwakami;K. Kotake;N. Ohnishi;S. Yamada;K. Sawada
我们已经研究了非轴对称的常设吸积激波不稳定性，或SASI，使用三维（3D）流体动力学模拟。这是我们以前研究的轴对称SASI的一个扩展。考虑到真实的状态方程和中微子的加热和冷却，我们制备了一个球对称的、稳定的吸积流，通过驻激波作用于原中子星星。这个未受扰动的模型是为了近似代表核心坍缩超新星的典型反弹后阶段。然后，我们添加了一个小扰动（~1%）的径向速度和计算随后的演变。轴对称和非轴对称扰动都已施加。我们已经应用模式分析的非球形变形的激波表面，使用球谐函数。我们发现：（1）SASI的增长率与球谐函数Ylm的方位角指数m有关，正如在球对称背景下所预期的那样：（2）非线性模耦合在轴对称扰动下只产生m = 0模，而在非轴对称扰动下，根据二次耦合的选择规则，也产生m = 0模;（3）在3D模式中，各模式的非线性饱和度一般低于2D模式，这是因为在3D模式中有更多的模式对湍流有贡献：（4）在非线性阶段，低l模式占主导地位：（5）在非线性阶段，不同m模式之间几乎建立了均分;（6）相对于l的光谱服从幂律，对于3D，斜率稍微更陡;（7）尽管这些特征对于模拟结束时有和没有激波复活的模型是共同的，在有激波复活的模式中，低- l模的优势更为显著。
We have studied nonaxisymmetric standing accretion shock instabilities, or SASI, using three-dimensional (3D) hydrodynamical simulations. This is an extension of our previous study of axisymmetric SASI. We have prepared a spherically symmetric and steady accretion flow through a standing shock wave onto a proto-neutron star, taking into account a realistic equation of state and neutrino heating and cooling. This unperturbed model is meant to represent approximately the typical postbounce phase of core-collapse supernovae. We then added a small perturbation (~1%) to the radial velocity and computed the ensuing evolutions. Both axisymmetric and nonaxisymmetric perturbations have been imposed. We have applied mode analysis to the nonspherical deformation of the shock surface, using spherical harmonics. We have found that (1) the growth rates of SASI are degenerate with respect to the azimuthal index m of the spherical harmonics Ylm, just as expected for a spherically symmetric background; (2) nonlinear mode couplings produce only m = 0 modes for axisymmetric perturbations, whereas m≠ 0 modes are also generated in the nonaxisymmetric cases, according to the selection rule for quadratic couplings; (3) the nonlinear saturation level of each mode is lower in general for 3D than for 2D, because a larger number of modes contribute to turbulence in 3D; (4) low-l modes are dominant in the nonlinear phase; (5) equipartition is nearly established among different m modes in the nonlinear phase; (6) spectra with respect to l obey power laws with a slope slightly steeper for 3D; and (7) although these features are common to the models with and without a shock revival at the end of the simulation, the dominance of low- l modes is more remarkable in the models with a shock revival.