FULLY COUPLED SIMULATION OF COSMIC REIONIZATION. I. NUMERICAL METHODS AND TESTS
FULLY COUPLED SIMULATION OF COSMIC REIONIZATION. I. NUMERICAL METHODS AND TESTS
复制标题
宇宙再电离的全耦合模拟。
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
J. Wise
中科院分区：
文献类型：
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作者：
M. Norman;D. Reynolds;G. So;R. Harkness;J. Wise
我们描述了Enzo代码的扩展，以实现具有数千到数百万点源的大（100 Mpc）3宇宙体积中的非均匀再电离的完全耦合辐射流体动力学模拟。我们在同一网格上自一致地解决了所有动态，辐射传递，热和电离过程，而不是后处理方法，即粗粒度的辐射传递。然而，我们确实采用了一个简单的子网格模型来研究恒星的形成，并根据观测结果进行校准。所提出的数值方法是对Reynolds等人提出的较早方法的修改，主要区别在于我们用于推进方程组的算子分裂算法。辐射输运是在灰色通量限制扩散（FLD）近似下进行的，该近似是由气体能量和电离方程分离出来的隐式时间积分来求解的，这两个方程分别求解。与之前的方法相比，这将为宇宙学应用提供一个更快、更稳健的方案。利用LLNL的超最优可伸缩几何多网格求解器求解FLD方程。通过将电离辐射视为与射线相反的网格场，我们的方法可以根据电离源的数量进行扩展，仅受辐射求解器的平行缩放特性的限制。我们通过一些标准的验证和验证测试来测试我们方法的速度和准确性。我们通过与Enzo的自适应射线追踪方法Moray的直接比较表明，在再电离模拟验证测试中，FLD无法在不透明云后面投下阴影对电离体积和质量分数的演变影响很小。我们举例说明了我们的方法在用32003欧拉网格单元和暗物质粒子解决的80 Mpc移动盒中的非均匀再电离问题的应用。
We describe an extension of the Enzo code to enable fully coupled radiation hydrodynamical simulation of inhomogeneous reionization in large ∼(100 Mpc)3 cosmological volumes with thousands to millions of point sources. We solve all dynamical, radiative transfer, thermal, and ionization processes self-consistently on the same mesh, as opposed to a postprocessing approach which coarse-grains the radiative transfer. We do, however, employ a simple subgrid model for star formation which we calibrate to observations. The numerical method presented is a modification of an earlier method presented in Reynolds et al. differing principally in the operator splitting algorithm we use to advance the system of equations. Radiation transport is done in the gray flux-limited diffusion (FLD) approximation, which is solved by implicit time integration split off from the gas energy and ionization equations, which are solved separately. This results in a faster and more robust scheme for cosmological applications compared to the earlier method. The FLD equation is solved using the hypre optimally scalable geometric multigrid solver from LLNL. By treating the ionizing radiation as a grid field as opposed to rays, our method is scalable with respect to the number of ionizing sources, limited only by the parallel scaling properties of the radiation solver. We test the speed and accuracy of our approach on a number of standard verification and validation tests. We show by direct comparison with Enzo's adaptive ray tracing method Moray that the well-known inability of FLD to cast a shadow behind opaque clouds has a minor effect on the evolution of ionized volume and mass fractions in a reionization simulation validation test. We illustrate an application of our method to the problem of inhomogeneous reionization in a 80 Mpc comoving box resolved with 32003 Eulerian grid cells and dark matter particles.
影响因子：
8.7
作者：
Komatsu, E.;Smith, K. M.;Wright, E. L.
通讯作者：
Wright, E. L.