arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1902.07934math.AP
收藏

关于分数阶导数算子用于非局部扩散过程建模的几点评论

Some comments on using fractional derivative operators in modeling non-local diffusion processes

Tokinaga Namba, Piotr Rybka, Vaughan Voller

摘要:

我们从一个一般的控制方程的扩散运输,写在一个保守的形式,其中的唯象通量定律可以构建在一些替代的方式。我们特别注意通量法,可以通过空间分数阶导数算子的非局部性。讨论了使用这种通量定律的控制方程的适定性的现有结果。一般守恒控制方程的离散控制体积数值解的开发和边界条件的一般离散处理,独立于特定的选择的通量法,提出。我们使用各种测试问题的数值解来比较分别基于Caputo(C)和Riemann-Liouville(RL)导数的两种离散分数阶扩散通量定律的操作和预测能力。当与C通量定律比较时,我们注意到RL通量定律包括一个附加项,在现象学意义上,它充当一种明显的平流输送。通过我们的测试解决方案,我们表明,当与C通量定律的性能相比,这个额外的长期可能会导致RL通量定律的预测,可能是物理和数学上不合理的。我们的结论是,通过提出一个简约的定义,分数阶导数为基础的通量法,消除了与RL和C分数阶导数的基础上的非本地通量法之间的选择相关联的模糊性。

英文摘要:

We start with a general governing equation for diffusion transport, written in a conserved form, in which the phenomenological flux laws can be constructed in a number of alternative ways. We pay particular attention to flux laws that can account for non-locality through space fractional derivative operators. The available results on the well posedness of the governing equations using such flux laws are discussed. A discrete control volume numerical solution of the general conserved governing equation is developed and a general discrete treatment of boundary conditions, independent of the particular choice of flux law, is presented. We use numerical solutions of various test problems to compare the operation and predictive ability of two discrete fractional diffusion flux laws based on the Caputo (C) and Riemann-Liouville (RL) derivatives respectively. When compared with the C flux-law we note that the RL flux law includes an additional term, that, in a phenomenological sense, acts as an apparent advection transport. Through our test solutions we show that, when compared to the performance of the C flux-law, this extra term can lead to RL-flux law predictions that may be physically and mathematically unsound. We conclude, by proposing a parsimonious definition for a fractional derivative based flux law that removes the ambiguities associated with the selection between non-local flux laws based on the RL and C fractional derivatives.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑