SPHRAY：一种用于辐射转移的光滑粒子流体动力学射线示踪器
SPHRAY: A Smoothed Particle Hydrodynamics Ray Tracer for Radiative Transfer
摘要：
我们介绍SPHRAY，一个光滑粒子流体动力学（SPH）射线示踪剂，旨在解决三维，时间相关的，辐射转移（RT）方程的任意密度场。SPHRAY的SPH特性使得单独的流体动力学和重力求解器的结合非常自然。SPHRAY依赖于蒙特卡罗（MC）射线追踪方案，该方案不将SPH粒子内插到网格上，而是直接通过SPH内核进行积分。给定初始条件和电离辐射源的描述，该代码将计算每个SPH粒子的非平衡电离态（HI，HII，HeI，HeII，HeIII，e）和温度（内能/熵）。辐射源可以包括点状物体、漫射复合辐射和来自计算体积外部的背景场。MC光线跟踪实现允许快速引入新的物理学，并且是并行化友好的。从计算机图形应用程序中获取的快速轴对齐边界框（AABB）测试允许加速光线跟踪组件。我们提出了SPHRAY中使用的算法，并通过执行Iliev等人最近的辐射转移比较项目中详细介绍的所有测试问题来验证代码。SPHRAY和示例SPH密度字段的Fortran 90源代码可在配套网站（www.sphray.org）上获得。
英文摘要：
We introduce SPHRAY, a Smoothed Particle Hydrodynamics (SPH) ray tracer designed to solve the 3D, time dependent, radiative transfer (RT) equations for arbitrary density fields. The SPH nature of SPHRAY makes the incorporation of separate hydrodynamics and gravity solvers very natural. SPHRAY relies on a Monte Carlo (MC) ray tracing scheme that does not interpolate the SPH particles onto a grid but instead integrates directly through the SPH kernels. Given initial conditions and a description of the sources of ionizing radiation, the code will calculate the non-equilibrium ionization state (HI, HII, HeI, HeII, HeIII, e) and temperature (internal energy/entropy) of each SPH particle. The sources of radiation can include point like objects, diffuse recombination radiation, and a background field from outside the computational volume. The MC ray tracing implementation allows for the quick introduction of new physics and is parallelization friendly. A quick Axis Aligned Bounding Box (AABB) test taken from computer graphics applications allows for the acceleration of the raytracing component. We present the algorithms used in SPHRAY and verify the code by performing all the test problems detailed in the recent Radiative Transfer Comparison Project of Iliev et. al. The Fortran 90 source code for SPHRAY and example SPH density fields are made available on a companion website (www.sphray.org).
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