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arXiv 1702.03485math.NAcs.NA
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分数阶演化方程有限体积元方法的误差分析

Error analysis of a finite volume element method for fractional order evolution equations with nonsmooth initial data

Sultan Qaboos University(苏丹卡布斯大学);Indian Institute of Technology Bombay(孟买印度理工学院)

Samir Karaa, Amiya K. Pani

AI总结:

本文研究了分数阶扩散方程的有限体积元方法,针对非光滑初始数据建立了最优误差估计,并证明了超收敛结果,同时分析了两种全离散方案,通过数值实验验证了理论结果。

摘要:

本文考虑了用于时间分数阶扩散方程空间近似的一种有限体积元(FVE)方法,该方程包含时间Riemann-Liouville分数导数,阶数α∈(0,1)。在改进先前结果(Karaa等,IMA J. Numer. Anal. 2016)的基础上,建立了对于光滑和中等光滑初始数据(即v∈H²(Ω)∩H¹₀(Ω)和v∈H¹₀(Ω))的L²(Ω)-和H¹(Ω)-范数下的最优误差估计。对于非光滑数据(即v∈L²(Ω)),最优L²(Ω)-误差估计仅在三角剖分满足额外假设时成立,该假设在对称三角剖分中成立。还证明了超收敛结果,并由此在L^∞(Ω)-范数下建立了近优误差估计。进一步,分析了两种全离散方案,利用卷积求积在时间上由后向欧拉法和二阶后向差分法生成,推导了光滑和非光滑初始数据的误差估计。基于标准Galerkin有限元解与FVE解的比较,并利用Laplace变换与FVE解算子的半群性质,将分析以统一的方式扩展到几种时间分数阶演化问题。最后,进行了若干数值实验以验证理论结果。

英文摘要:

In this paper, a finite volume element (FVE) method is considered for spatial approximations of time-fractional diffusion equations involving a Riemann-Liouville fractional derivative of order $α\in (0,1)$ in time. Improving upon earlier results (Karaa {\it et al.}, IMA J. Numer. Anal. 2016), optimal error estimates in $L^2(Ω)$- and $H^1(Ω)$-norms for the semidiscrete problem with smooth and middly smooth initial data, i.e., $v\in H^2(Ω)\cap H^1_0(Ω)$ and $v\in H^1_0(Ω)$ are established. For nonsmooth data, that is, $v\in L^2(Ω)$, the optimal $L^2(Ω)$-error estimate is shown to hold only under an additional assumption on the triangulation, which is known to be satisfied for symmetric triangulations. Superconvergence result is also proved and as a consequence, a quasi-optimal error estimate is established in the $L^\infty(Ω)$-norm. Further, two fully discrete schemes using convolution quadrature in time generated by the backward Euler and the second-order backward difference methods are analyzed, and error estimates are derived for both smooth and nonsmooth initial data. Based on a comparison of the standard Galerkin finite element solution with the FVE solution and exploiting tools for Laplace transforms with semigroup type properties of the FVE solution operator, our analysis is then extended in a unified manner to several time-fractional order evolution problems. Finally, several numerical experiments are conducted to confirm our theoretical findings.

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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