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arXiv 2304.08009math.NAcs.NA
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采用自适应离散化提高涉及初始时间奇异性的非局部积分偏微分方程的精度

Enhancing accuracy with an adaptive discretization for the non-local integro-partial differential equations involving initial time singularities

Sudarshan Santra, Ratikanta Behera

AI总结:

本文提出一种高效高精度数值方法,利用 $L2$-$1_σ$ 格式与修改的复合梯形近似处理一维和二维时间分数阶抛物型积分偏微分方程的初始时间奇异性,并通过自适应网格实现高阶收敛。

摘要:

本文旨在构建一种高效且高精度的数值方法,以处理一维和二维中的一类时间分数阶抛物型积分偏微分方程在 $t=0$ 处涉及的时间奇异性。使用 $L2$-$1_σ$ 格式离散化时间分数阶算子,同时采用复合梯形近似的修改版本来离散化 Volterra 算子。随后,这有助于将所提出的模型转换为半离散形式的二阶 BVP。然后,使用多维 Haar 小波进行网格自适应和二维问题的高效计算,而对于一维情况,则采用标准的二阶近似来逼近空间导数。在时间自适应网格上进行了稳定性分析。基于 $L^\infty$ 范数,对于适当选择分级参数,收敛分析在具有时间奇异性的一维问题的时空域中给出了 $O(N^{-2}+M^{-2})$ 精度的解。此外,对于在 $t=0$ 处具有无界时间导数的二维问题,它提供了 $O(N^{-2}+M^{-3})$ 精度的解。分析还强调,即使网格是均匀离散的,对于位于 $C^3(\overlineΩ_t)$ 中的足够平滑的解,也具有更高阶的精度。给出了时间分数阶算子、积分算子和空间导数的截断误差估计。对几个例子进行了大量测试以支持理论分析。通过应用时间分数阶 Fokker-Planck 方程和具有弱奇异核的分数阶粘弹性动力学,展示了所提方法的进步性。它也证实了与文献中现有方法相比,所提方法的优越性。

英文摘要:

This work aims to construct an efficient and highly accurate numerical method to address the time singularity at $t=0$ involved in a class of time-fractional parabolic integro-partial differential equations in one and two dimensions. The $L2$-$1_σ$ scheme is used to discretize the time-fractional operator, whereas a modified version of the composite trapezoidal approximation is employed to discretize the Volterra operator. Subsequently, it helps to convert the proposed model into a second-order BVP in a semi-discrete form. The multi-dimensional Haar wavelets are then used for grid adaptation and efficient computations for the 2D problem, whereas the standard second-order approximations are employed to approximate the spatial derivatives for the 1D case. The stability analysis is carried out on an adaptive mesh in time. The convergence analysis leads to $O(N^{-2}+M^{-2})$ accurate solution in the space-time domain for the 1D problem having time singularity based on the $L^\infty$ norm for a suitable choice of the grading parameter. Furthermore, it provides $O(N^{-2}+M^{-3})$ accurate solution for the 2D problem having unbounded time derivative at $t=0$. The analysis also highlights a higher order accuracy for a sufficiently smooth solution resides in $C^3(\overlineΩ_t)$ even if the mesh is discretized uniformly. The truncation error estimates for the time-fractional operator, integral operator, and spatial derivatives are presented. Numerous tests are performed on several examples in support of the theoretical analysis. The advancement of the proposed methodology is demonstrated through the application of the time-fractional Fokker-Planck equation and the fractional-order viscoelastic dynamics having weakly singular kernels. It also confirms the superiority of the proposed method compared with existing approaches available in the literature.

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。

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