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arXiv 2103.07574math.NAcs.NA
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辐射传输方程的一种缩减基方法

A reduced basis method for radiative transfer equation

Zhichao Peng, Yanlai Chen, Yingda Cheng, Fengyan Li

摘要:

线性动力学输运方程在光学层析成像、辐射输运和中子输运中起着关键作用。阻碍其有效和准确的数值分辨率的根本困难在于物理和速度/角度变量的高维性,以及问题本质上是多尺度的事实。利用存在的隐藏的低秩结构暗示的扩散限制,在这项工作中,我们设计和测试的角度空间降阶模型的线性辐射传输方程,第一个这样的努力的基础上著名的减少基方法(RBM)。我们的方法是建立在一个高保真度求解器采用离散纵坐标方法在角空间,一个渐近保持迎风间断Galerkin方法的物理空间,和一个高效的合成加速源迭代所产生的线性系。为了解决通过积分算子耦合的参数值(或角度方向)的挑战,我们的方法的第一个新成分是一个迭代过程,其中宏观密度是从RBM快照构建的,明确对待并允许运输扫描,然后更新。然后,贪婪算法可以继续自适应地选择角度空间中的代表性样本并形成代理解空间。第二个新颖之处是最小二乘密度重建策略,在每个相关的物理位置,使强大的和准确的整合在一个任意的非结构化的角度样本集的宏观密度。数值实验表明,我们的方法是有效的计算成本减少在各种制度。

英文摘要:

Linear kinetic transport equations play a critical role in optical tomography, radiative transfer and neutron transport. The fundamental difficulty hampering their efficient and accurate numerical resolution lies in the high dimensionality of the physical and velocity/angular variables and the fact that the problem is multiscale in nature. Leveraging the existence of a hidden low-rank structure hinted by the diffusive limit, in this work, we design and test the angular-space reduced order model for the linear radiative transfer equation, the first such effort based on the celebrated reduced basis method (RBM). Our method is built upon a high-fidelity solver employing the discrete ordinates method in the angular space, an asymptotic preserving upwind discontinuous Galerkin method for the physical space, and an efficient synthetic accelerated source iteration for the resulting linear system. Addressing the challenge of the parameter values (or angular directions) being coupled through an integration operator, the first novel ingredient of our method is an iterative procedure where the macroscopic density is constructed from the RBM snapshots, treated explicitly and allowing a transport sweep, and then updated afterwards. A greedy algorithm can then proceed to adaptively select the representative samples in the angular space and form a surrogate solution space. The second novelty is a least-squares density reconstruction strategy, at each of the relevant physical locations, enabling the robust and accurate integration over an arbitrarily unstructured set of angular samples toward the macroscopic density. Numerical experiments indicate that our method is effective for computational cost reduction in a variety of regimes.

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