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arXiv 2104.03096math.AP
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时间分数阶Cahn-Hilliard方程的适定性、退化性和数值解

Time-fractional Cahn-Hilliard equation: Well-posedness, degeneracy, and numerical solutions

Marvin Fritz, Mabel L. Rajendran, Barbara Wohlmuth

摘要:

本文从连续介质混合理论出发,通过对Fick扩散定律的修正,导出了时间分数阶的Cahn-Hilliard方程。该模型描述了具有非局部记忆效应的相分离过程。研究了时间分数阶Cahn-Hilliard方程弱解的存在性、唯一性和正则性.在这方面,我们考虑了Landau,Flory-Huggins和双障碍类型的简并迁移率函数和自由能。我们适用于系统的Faedo-Galerkin方法,推导出能量估计,并使用紧性定理传递到离散形式的极限。为了弥补分数阶导数的链式法则的缺失,我们证明了一个关于凸函数的分数阶链式不等式。工作的结论与数值模拟和灵敏度分析显示的分数功率的影响。在这里,我们考虑卷积求积方案的时间分数分量,并使用混合有限元法的空间离散。

英文摘要:

In this paper, we derive the time-fractional Cahn-Hilliard equation from continuum mixture theory with a modification of Fick's law of diffusion. This model describes the process of phase separation with nonlocal memory effects. We analyze the existence, uniqueness, and regularity of weak solutions of the time-fractional Cahn-Hilliard equation. In this regard, we consider degenerating mobility functions and free energies of Landau, Flory--Huggins and double-obstacle type. We apply the Faedo-Galerkin method to the system, derive energy estimates, and use compactness theorems to pass to the limit in the discrete form. In order to compensate for the missing chain rule of fractional derivatives, we prove a fractional chain inequality for semiconvex functions. The work concludes with numerical simulations and a sensitivity analysis showing the influence of the fractional power. Here, we consider a convolution quadrature scheme for the time-fractional component, and use a mixed finite element method for the space discretization.

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