The slender body free boundary problem
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866913023309905920 |
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| author | Ohm, Laurel |
| author_facet | Ohm, Laurel |
| contents | We consider the slender body free boundary problem describing the evolution of an inextensible, closed elastic filament immersed in a Stokes fluid in $\mathbb{R}^3$. The filament elasticity is governed by Euler-Bernoulli beam theory, and the coupling between this 1D elasticity law and the surrounding 3D fluid is governed by the slender body Neumann-to-Dirichlet (NtD) map, which treats the filament as a 3D object with constant cross-sectional radius $0<ε\ll1$. This map serves as a mathematical justification for slender body theories wherein such 3D-1D couplings play a central role. We develop a solution theory for the filament evolution under this coupling. Our analysis relies on two main ingredients: (1) an extraction of the principal symbol of the slender body NtD map, from the author's previous work, and (2) a detailed treatment of the tension determination problem for enforcing the inextensibility constraint. Our work provides a mathematical foundation for various computational models in which a slender filament evolves according to a 1D elasticity law in a 3D fluid. This forms a key development in our broader program to place slender body theories on firm theoretical footing. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_16800 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The slender body free boundary problem Ohm, Laurel Analysis of PDEs Fluid Dynamics We consider the slender body free boundary problem describing the evolution of an inextensible, closed elastic filament immersed in a Stokes fluid in $\mathbb{R}^3$. The filament elasticity is governed by Euler-Bernoulli beam theory, and the coupling between this 1D elasticity law and the surrounding 3D fluid is governed by the slender body Neumann-to-Dirichlet (NtD) map, which treats the filament as a 3D object with constant cross-sectional radius $0<ε\ll1$. This map serves as a mathematical justification for slender body theories wherein such 3D-1D couplings play a central role. We develop a solution theory for the filament evolution under this coupling. Our analysis relies on two main ingredients: (1) an extraction of the principal symbol of the slender body NtD map, from the author's previous work, and (2) a detailed treatment of the tension determination problem for enforcing the inextensibility constraint. Our work provides a mathematical foundation for various computational models in which a slender filament evolves according to a 1D elasticity law in a 3D fluid. This forms a key development in our broader program to place slender body theories on firm theoretical footing. |
| title | The slender body free boundary problem |
| topic | Analysis of PDEs Fluid Dynamics |
| url | https://arxiv.org/abs/2509.16800 |