Unconditionally Stable, Variable Step DLN Methods for the Allen-Cahn Active Fluid Model: A Divergence-free Preserving Approach

Fuente: arXiv
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Autori principali: Zheng, Nan, Pei, Wenlong, Guan, Qingguang, Zhao, Wenju
Natura: Preprint
Pubblicazione: 2025
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author Zheng, Nan
Pei, Wenlong
Guan, Qingguang
Zhao, Wenju
author_facet Zheng, Nan
Pei, Wenlong
Guan, Qingguang
Zhao, Wenju
contents This paper addresses the divergence-free mixed finite element method (FEM) for nonlinear fourth-order Allen-Cahn phase field coupled active fluid equations. By introducing an auxiliary variable $w = Δu$, the original fourth-order problem is converted into a system of second-order equations, thereby easing the regularity constraints imposed on standard $H^2$-comforming finite element spaces. To further refine the formulation, an additional auxiliary variable $ξ$, analogous to the pressure, is introduced, resulting in a mixed finite element scheme that preserves the divergence-free condition in $which = Δu$ inherited from the model. A fully discrete scheme is then established by combining the spatial approximation by the divergence-free mixed finite element method with the variable-step Dahlquist-Liniger-Nevanlinna (DLN) time integrator. The boundedness of the scheme is rigorously derived under suitable regularity assumptions. Additionally, an adaptive time-stepping strategy based on the minimum dissipation criterion is carried out to enhance computational efficiency. Several numerical experiments validate the theoretical findings and demonstrate the method's effectiveness and accuracy in simulating complex active fluid dynamics.
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id arxiv_https___arxiv_org_abs_2510_16860
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Unconditionally Stable, Variable Step DLN Methods for the Allen-Cahn Active Fluid Model: A Divergence-free Preserving Approach
Zheng, Nan
Pei, Wenlong
Guan, Qingguang
Zhao, Wenju
Numerical Analysis
This paper addresses the divergence-free mixed finite element method (FEM) for nonlinear fourth-order Allen-Cahn phase field coupled active fluid equations. By introducing an auxiliary variable $w = Δu$, the original fourth-order problem is converted into a system of second-order equations, thereby easing the regularity constraints imposed on standard $H^2$-comforming finite element spaces. To further refine the formulation, an additional auxiliary variable $ξ$, analogous to the pressure, is introduced, resulting in a mixed finite element scheme that preserves the divergence-free condition in $which = Δu$ inherited from the model. A fully discrete scheme is then established by combining the spatial approximation by the divergence-free mixed finite element method with the variable-step Dahlquist-Liniger-Nevanlinna (DLN) time integrator. The boundedness of the scheme is rigorously derived under suitable regularity assumptions. Additionally, an adaptive time-stepping strategy based on the minimum dissipation criterion is carried out to enhance computational efficiency. Several numerical experiments validate the theoretical findings and demonstrate the method's effectiveness and accuracy in simulating complex active fluid dynamics.
title Unconditionally Stable, Variable Step DLN Methods for the Allen-Cahn Active Fluid Model: A Divergence-free Preserving Approach
topic Numerical Analysis
url https://arxiv.org/abs/2510.16860