START: Smoothed particle hydrodynamics with tree-based accelerated radiative transfer
START: Smoothed particle hydrodynamics with tree-based accelerated radiative transfer
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开始：通过基于树的加速辐射传输平滑粒子流体动力学
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
M. Umemura
中科院分区：
文献类型：
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作者：
K. Hasegawa;M. Umemura
我们提出了一种新的辐射流体力学程序START，它是一种结合加速辐射传输的光滑粒子流体力学(SPH)格式。辐射传递加速的基本思想与迄今用于加速N体系统中引力计算的树形算法是平行的。计算结果表明，对于N个SPH粒子和N个S辐射源，计算时间为N p log N S，可以大大提高计算速度。这样的加速使我们不仅可以容易地包括许多源，而且还可以包括散射光子，即使辐射源的总数与SPH粒子的总数相当。这里，给出了一个多源问题的测试模拟，其中使用START的结果与没有基于树的加速的辐射SPH代码的结果进行了比较。我们发现，如果将公差参数设置为θCrit<；1.0时，计算结果吻合较好，这表明START可以在不降低精度的情况下更快地求解辐射传递问题。START的一个重要应用是解决漫射电离光子的传输问题，其中每个SPH粒子都被视为一个发射体。为了说明START的能力，我们模拟了在电离源周围密集聚集的阴影效应。结果发现，漫射复合光子对阴影的侵蚀是可以解决的。这种效应对揭示宇宙再电离过程具有重要意义。
We present a novel radiation hydrodynamics code, START, which is a smoothed particle hydrodynamics (SPH) scheme coupled with accelerated radiative transfer. The basic idea for the acceleration of radiative transfer is parallel to the tree algorithm that is hitherto used to speed up the gravitational force calculation in an N-body system. It is demonstrated that the radiative transfer calculations can be dramatically accelerated, where the computational time is scaled as N p log N s for N p SPH particles and N s radiation sources. Such acceleration allows us to readily include not only numerous sources but also scattering photons, even if the total number of radiation sources is comparable to that of SPH particles. Here, a test simulation is presented for a multiple source problem, where the results with START are compared to those with a radiation SPH code without tree-based acceleration. We find that the results agree well with each other if we set the tolerance parameter as θ crit < 1.0, and then it demonstrates that START can solve radiative transfer faster without reducing the accuracy. One of the important applications with START is to solve the transfer of diffuse ionizing photons, where each SPH particle is regarded as an emitter. To illustrate the competence of START, we simulate the shadowing effect by dense clumps around an ionizing source. As a result, it is found that the erosion of shadows by diffuse recombination photons can be solved. Such an effect is of great significance to reveal the cosmic reionization process.