2013/06/24 by Nicholas K. Lowman, Mark A. Hoefer · 2 citations
Earth and Planetary Sciences · Engineering · Physics and Astronomy · #Boundary value problem #Buoyancy #Classical mechanics #Electrical conduit #Fluid Dynamics and Turbulent Flows #Fluid dynamics #Laminar flow #Mechanics #Nonlinear system #Ocean Waves and Remote Sensing #Oceanographic and Atmospheric Processes #Partial differential equation #Physics #Reynolds number #Turbulence #Viscous liquid #nlin.PS #physics.flu-dyn
paper · pdf · doi:10.1103/physreve.88.023016
10 pages, 1 figure
arxiv created 2013/06/24 · openalex publication_date 2013/08/19 · arxiv updated 2015/06/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The evolution of the interface separating a conduit of light, viscous fluid rising buoyantly through a heavy, more viscous, exterior fluid at small Reynolds numbers is governed by the interplay between nonlinearity and dispersion. Previous authors have proposed an approximate model equation based on physical arguments, but a precise theoretical treatment for this two-fluid system with a free boundary is lacking. Here, a derivation of the interfacial equation via a multiple scales, perturbation technique is presented. Perturbations about a state of vertically uniform, laminar conduit flow are considered in the context of the Navier-Stokes equations with appropriate boundary conditions. The ratio of interior to exterior viscosities is the small parameter used in the asymptotic analysis, which leads systematically to a maximal balance between buoyancy driven, nonlinear self-steepening and viscous, interfacial stress induced, nonlinear dispersion. This results in a scalar, nonlinear partial differential equation describing large amplitude dynamics of the cross-sectional area of the intrusive fluid conduit, in agreement with previous derivations. The leading order behavior of the two-fluid system is completely characterized in terms of the interfacial dynamics. The regime of model validity is characterized and shown to agree with previous experimental studies. Viscous fluid conduits provide a robust setting for the study of nonlinear, dispersive wave phenomena.