Inertial oscillations in a confined monopolar vortex subjected to background rotation

• Published in: Physics of fluids (1994) 2009-11, Vol.21 (11)
• Main Authors: DURAN-MATUTE, M, KAMP, L. P. J, TRIELING, R. R, VAN HEIJST, G. J. F
• Format: Article
• Language: English
• Subjects: Earth, ocean, space; Exact sciences and technology; External geophysics; Geophysics. Techniques, methods, instrumentation and models
• ISSN: 1070-6631; 1089-7666
• DOI: 10.1063/1.3258670

We study the axisymmetric inertial oscillations in a confined monopolar vortex under the influence of background rotation. By first focusing on the inviscid linear dynamics, and later studying the effects of viscosity and of a no-slip bottom, we characterize the effects of rotation and confinement. It was found that background rotation allows for oscillations outside the vortex core even with frequencies larger than 2Ω, with Ω the background rotation rate. However, confinement is necessary for the system to sustain oscillations with frequencies smaller than 2Ω. Through the analytical solution for a small perturbation of a Rankine vortex, we obtain five regimes where the oscillations are qualitatively different, depending on their frequency. Numerical results for the linear inviscid waves sustained by a Lamb–Oseen vortex show a similar behavior. The effects of viscosity are twofold: the oscillations are damped and the vortex sustaining the oscillations is modified. When a no-slip bottom is considered, a boundary layer drives a secondary motion superimposed on the inertial oscillations. In this case, the vortex is quickly damped, but the oscillations persist due to the background rotation.