Analysis of ray-effect mitigation techniques
Analysis of ray-effect mitigation techniques
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DOI：
10.13182/nse01-48
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发表时间：
2003-05-01
影响因子：
1.2
通讯作者：
Parsons, DK
中科院分区：
文献类型：
--
作者：
Morel, JE;Wareing, TA;Parsons, DK
我们分析了二维x-y几何中的三种射线效应缓解技术。特别地，分析了两种角有限元方法和调制p -1等效S-2方法。发现这些技术在某些传统测试问题上给出了不同程度的射线效应缓解，但所有这些技术都产生了空隙中线源的离散射线解。由于方向梯度算子实际上是双曲的，因此许多算子的离散化都保留了这一性质，这并不奇怪，任何导致方向梯度算子的双曲近似的输运角离散化技术都将产生空中线源的离散射线解。例如，我们的结果表明，连续和不连续的角有限元方法产生双曲逼近。我们的主要结论是，任何双曲射线效应缓解技术的有效性必然是高度依赖于问题的。特别是，这种技术在具有最严重的射线效应的问题上，即那些与空洞中的线源“相似”的问题上，一定会失败。
We analyze three ray-effect mitigation techniques in two-dimensional x-y geometry. In particular, two angular finite element methods, and the modulated P-1-equivalent S-2 method, are analyzed It is found that these techniques give varying levels of ray-effect mitigation on certain traditional test problems, but all of them yield discrete-ray solutions for a line source in a void In general, it is shown that any transport angular discretization technique that results in a hyperbolic approximation for the directional gradient operator will yield a discrete-ray solution for a line source in a void Since the directional gradient operator is in fact hyperbolic, it is not surprising that many discretizations of the operator retain this property. For instance, our results suggest that both continuous and discontinuous angular finite element methods produce hyperbolic approximations. Our main conclusion is that the effectiveness of any hyperbolic ray-effect mitigation technique will necessarily be highly problem dependent. In particular, such techniques must fail in problems that have the most severe ray effects, i.e., those that are "similar" to a line source in a void.