argot: accelerated radiative transfer on grids using oct‐tree
argot: accelerated radiative transfer on grids using oct‐tree
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DOI：
10.1111/j.1365-2966.2011.19927.x
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发表时间：
2011-05
影响因子：
4.8
通讯作者：
T. Okamoto;K. Yoshikawa;M. Umemura
中科院分区：
文献类型：
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作者：
T. Okamoto;K. Yoshikawa;M. Umemura
我们提出了两种类型的数值处方，加速周围的点源的辐射传输计算在三维笛卡尔网格通过使用八叉树结构的辐射源的分布。在一个处方中，当远距离辐射源的角尺寸θs小于临界值θcrit时，远距离辐射源被分组为明亮的扩展源，并且辐射传递在角尺寸与源组的角尺寸相似的超网格上求解。超网格结构是通过对网格结构进行粗粒化来构造的。用这种方法，计算时间与Nm log（Nm）log（Ns）成比例，其中Nm和Ns分别是网格数和辐射源数。虽然这种方法是非常有效的，它不可避免地高估了光学厚度时，一组源作为一个扩展的强大的辐射源，并影响遥远的网格。在另一个处方中，一个遥远的源组被视为一个亮点源，忽略了组的空间范围和辐射传输的网格上，而不是超网格上解决。这个处方是一个简单的基于网格的版本的START由长谷川和Umemura和产生更好的结果，在一般略多的计算成本（/ N 4/3 m log（Ns））比supermesh处方。我们的方法可以很容易地实现任何基于网格的流体动力学代码，非常适合自适应网格加密方法。
We present two types of numerical prescriptions that accelerate the radiative transfer calculation around point sources within a three-dimensional Cartesian grid by using the oct-tree structure for the distribution of radiation sources. In one prescription, distant radiation sources are grouped as a bright extended source when the group’s angular size, θs, is smaller than a critical value, θcrit, and radiative transfer is solved on supermeshes whose angular sizes are similar to that of the group of sources. The supermesh structure is constructed by coarse-graining the mesh structure. With this method, the computational time scales with Nm log(Nm)log(Ns) where Nm and Ns are the number of meshes and that of radiation sources, respectively. While this method is very efficient, it inevitably overestimates the optical depth when agroup of sources acts as an extended powerful radiation source and affects distant meshes. In the other prescription, a distant group of sources is treated as a bright point source ignoring the spatial extent of the group and the radiative transfer is solved on the meshes rather than the supermeshes. This prescription is simply a grid-based version of START by Hasegawa & Umemura and yields better results in general with slightly more computational cost (/ N 4/3 m log(Ns)) than the supermesh prescription. Our methods can easily be implemented to any grid-based hydrodynamic codes and are well-suited to the adaptive mesh refinement methods.