Abstract Monte Carlo ray-tracing method has become a promising technique for solving radiative transfer. However, large memory footprint or long CPU time hampers its further utilization. In this work, a Monte Carlo ray-tracing method radiation solver called mcrtFOAM is developed in the framework of open source CFD toolbox OpenFOAM. The radiative source term is calculated based on the radiation distribution factor to avoid repeated ray tracing. In addition, a mesh-agglomeration technique is used to overcome the problem of memory catastrophe for storing a huge radiation distribution factor matrix caused by a large number of mesh elements. The key principle is to agglomerate the refined mesh elements to the coarse ones, and the calculation of radiation distribution factor as well as radiative source term is carried out in the coarse mesh, while the procedure of ray tracing as well as solving the heat conduction is performed in the refined mesh. After validation of the algorithm code within a cubic enclosure, a coupled conductive–radiative heat transfer problem within a cylindrical enclosure filled with gray semitransparent solids is also tested. To test the present solver in realistic industrial systems, a coupled conductive–radiative heat transfer within a tomographic porous structure with gray surfaces is further investigated. All results are compared with previous studies and the solutions by the Finite Volume Discrete Ordinate Method (FVDOM) in OpenFOAM, and they all show great satisfaction. When the mcrtFOAM solver is used for solving the radiative transfer equation, it is found that the CPU time and the memory footprint consumed by the present mcrtFOAM solver with mesh-agglomeration technique are far less than that without this technique. Convincing first implementation exercises indicate that both significant memory and CPU benefits can be expected for configurations of industrial interest These findings will contribute greatly to achieve the calculation of coupled heat transfer involving radiation within large number of mesh elements.

中文翻译：

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mcrtFOAM：用于灰色半透明固体中辐射传递的网格聚集蒙特卡罗光线追踪求解器

摘要 蒙特卡罗光线追踪方法已成为解决辐射传递问题的一种很有前景的技术。但是，大量内存占用或较长的 CPU 时间阻碍了其进一步利用。在这项工作中，在开源 CFD 工具箱 OpenFOAM 的框架中开发了一种名为 mcrtFOAM 的蒙特卡罗射线追踪法辐射求解器。辐射源项是根据辐射分布因子计算的，以避免重复射线追踪。此外，采用网格聚合技术克服了因存储大量网格元素而导致的巨大辐射分布因子矩阵的内存灾难问题。其关键原理是将细化网格单元凝聚为粗网格单元，在粗网格中进行辐射分布因子和辐射源项的计算，而光线追踪和热传导求解过程则在细化网格中进行。在立方体外壳内验证算法代码后，还测试了填充有灰色半透明固体的圆柱形外壳内的耦合传导-辐射传热问题。为了在现实的工业系统中测试本求解器，进一步研究了具有灰色表面的断层扫描多孔结构内的耦合传导-辐射传热。所有结果与之前的研究和 OpenFOAM 中有限体积离散纵坐标法 (FVDOM) 的解决方案进行了比较，都表现出非常满意。当 mcrtFOAM 求解器用于求解辐射传递方程时，发现使用网格聚集技术的当前 mcrtFOAM 求解器所消耗的 CPU 时间和内存占用远远少于没有该技术的情况。令人信服的首次实施练习表明，对于具有工业意义的配置，可以预期显着的内存和 CPU 优势。这些发现将极大地有助于实现涉及大量网格元素内辐射的耦合热传递的计算。