arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2104.01432math.NAcs.NA
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表面扩散问题的保结构参数有限元法

A structure-preserving parametric finite element method for surface diffusion

Weizhu Bao, Quan Zhao

摘要:

提出了一种结构保持参数有限元法(SP-PFEM),用于离散二维(2D)闭曲线或三维(3D)曲面的表面扩散问题。这里,“结构保持”是指保持表面扩散流的两个基本几何结构:(i)由闭曲线/表面包围的面积/体积的保持,以及(ii)曲线/表面的周长/总表面积的减小。为了简化符号,我们从二维闭曲线的表面扩散开始,并给出了控制方程的弱(变分)公式。然后在时间上采用向后欧拉法,在空间上采用分段线性参数有限元离散变分方程,并利用当前和下一时间步曲线的信息对单位法向量进行适当的逼近。所构造的数值方法保持了两种几何结构,并具有良好的渐近等网格分布特性。SP-PFEM是“弱”隐式(或几乎半隐式)的,并且在每个时间步上的非线性系统可以通过牛顿迭代法非常有效和精确地求解。然后将SP-PFEM扩展到离散三维闭曲面的表面扩散。广泛的数值结果,包括收敛性测试,结构保持性能和渐近相等的网格分布,证明了所提出的SP-PFEM模拟表面扩散在2D和3D的准确性和效率。

英文摘要:

We propose a structure-preserving parametric finite element method (SP-PFEM) for discretizing the surface diffusion of a closed curve in two dimensions (2D) or surface in three dimensions (3D). Here the "structure-preserving" refers to preserving the two fundamental geometric structures of the surface diffusion flow: (i) the conservation of the area/volume enclosed by the closed curve/surface, and (ii) the decrease of the perimeter/total surface area of the curve/surface. For simplicity of notations, we begin with the surface diffusion of a closed curve in 2D and present a weak (variational) formulation of the governing equation. Then we discretize the variational formulation by using the backward Euler method in time and piecewise linear parametric finite elements in space, with a proper approximation of the unit normal vector by using the information of the curves at the current and next time step. The constructed numerical method is shown to preserve the two geometric structures and also enjoys the good property of asymptotic equal mesh distribution. The proposed SP-PFEM is "weakly" implicit (or almost semi-implicit) and the nonlinear system at each time step can be solved very efficiently and accurately by the Newton's iterative method. The SP-PFEM is then extended to discretize the surface diffusion of a closed surface in 3D. Extensive numerical results, including convergence tests, structure-preserving property and asymptotic equal mesh distribution, are reported to demonstrate the accuracy and efficiency of the proposed SP-PFEM for simulating surface diffusion in 2D and 3D.

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