Linear stability analysis of capillary instabilities for concentric cylindrical shells
Motivated by complex multi-fluid geometries currently being explored in fibre-device manufacturing, we study capillary instabilities in concentric cylindrical flows of $N$ fluids with arbitrary viscosities, thicknesses, densities, and surface tensions in both the Stokes regime and for the full Navie...
| Main Authors: | , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
| Published: |
Cambridge University Press
2011
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| Online Access: | http://hdl.handle.net/1721.1/65905 https://orcid.org/0000-0001-7327-4967 |
| Summary: | Motivated by complex multi-fluid geometries currently being explored in fibre-device manufacturing, we study capillary instabilities in concentric cylindrical flows of $N$ fluids with arbitrary viscosities, thicknesses, densities, and surface tensions in both the Stokes regime and for the full Navier–Stokes problem. Generalizing previous work by Tomotika ($N= 2$), Stone & Brenner ($N= 3$, equal viscosities) and others, we present a full linear stability analysis of the growth modes and rates, reducing the system to a linear generalized eigenproblem in the Stokes case. Furthermore, we demonstrate by Plateau-style geometrical arguments that only axisymmetric instabilities need be considered. We show that the $N= 3$ case is already sufficient to obtain several interesting phenomena: limiting cases of thin shells or low shell viscosity that reduce to $N= 2$ problems, and a system with competing breakup processes at very different length scales. The latter is demonstrated with full three-dimensional Stokes-flow simulations. Many $N\gt 3$ cases remain to be explored, and as a first step we discuss two illustrative $N\ensuremath{\rightarrow} \infty $ cases, an alternating-layer structure and a geometry with a continuously varying viscosity. |
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