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arXiv 2404.04737math.APphysics.flu-dyn
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三维Stokes流中浸没细丝的自由边界问题

A free boundary problem for an immersed filament in 3D Stokes flow

Laurel Ohm

AI总结:

本文研究三维Stokes流中浸没细丝的自由边界问题,通过角平均NtD算子分解证明简化演化方程为三阶抛物方程且局部适定,为细长体近似计算奠定数学基础。

摘要:

我们考虑一个半径为 $ε>0$ 的细丝浸没在三维Stokes流中的动态自由边界问题的简化可伸长版本。三维流体通过一种新型的Stokes方程的角平均Neumann-to-Dirichlet算子耦合到准一维细丝动力学上,分析中的大部分困难在于理解这个算子。在此我们证明,关于闭合弯曲细丝的角平均NtD映射的主要部分是关于直细丝的相应算子,对于后者我们可以推导出显式符号。由于曲率产生的余项在正则性或 $ε$ 的大小方面是低阶的。利用这种算子分解,可以证明简化的自由边界演化是一个三阶抛物方程,并且是局部适定的。这为基于细长体近似的薄浸没弹性结构的大量计算结果建立了更完整的数学基础。

英文摘要:

We consider a simplified extensible version of a dynamic free boundary problem for a thin filament with radius $ε>0$ immersed in 3D Stokes flow. The 3D fluid is coupled to the quasi-1D filament dynamics via a novel type of angle-averaged Neumann-to-Dirichlet operator for the Stokes equations, and much of the difficulty in the analysis lies in understanding this operator. Here we show that the main part of this angle-averaged NtD map about a closed, curved filament is the corresponding operator about a straight filament, for which we can derive an explicit symbol. Remainder terms due to curvature are lower order with respect to regularity or size in $ε$. Using this operator decomposition, it is then possible to show that the simplified free boundary evolution is a third-order parabolic equation and is locally well posed. This establishes a more complete mathematical foundation for the myriad computational results based on slender body approximations for thin immersed elastic structures.

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