An asymptotic study of instability to Langmuir circulation in shallow layers
| Autor: | William R. Phillips, D. T. Hayes |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
010504 meteorology & atmospheric sciences Meteorology Computational Mechanics Perturbation (astronomy) Astronomy and Astrophysics Rayleigh number Mechanics 01 natural sciences Instability 010305 fluids & plasmas Physics::Fluid Dynamics Waves and shallow water Geophysics Geochemistry and Petrology Mechanics of Materials Free surface 0103 physical sciences Wavenumber Boundary value problem 0105 earth and related environmental sciences Langmuir circulation |
| Zdroj: | Geophysical & Astrophysical Fluid Dynamics. 110:295-316 |
| ISSN: | 1029-0419 0309-1929 |
| DOI: | 10.1080/03091929.2016.1173207 |
| Popis: | The role of boundary conditions applied to perturbation equations describing the instability of wavy shear flows to counter-rotating vortical structures aligned with the flow in shallow water layers is considered. In the ocean context the structures are described by the Craik-Leibovich equations and are known as Langmuir circulation (LC); they arise via an instability mechanism known as CL2, which requires the presence of shear U′ and differential drift D′ of the same sense and that a threshold Rayleigh number be exceeded. While Neumann or stress-free boundary conditions applied at the free surface in deep water act to yield a physically plausible spanwise wavenumber l at onset, that is not the case in shallow layers, where non-zero l at onset is ensured only when mixed boundary conditions are applied. This paper questions why that is so and goes on to determine how onset is affected by distributions of U′ and D′. In order to proceed analytically, results are computed by a small-l asymptotic approximation... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|