Experiment on the Self-Propagating Quasi-Monopolar Vortex

Abstract

The aim of this contribution is to present the results of laboratory experiments on the dynamics of basic self-propagating vortices generated in a large volume of fluid when a linear (P) and an angular (M) momentum are applied locally to a fluid. Using the method proposed, it is possible to generate a whole family of isolated (net vorticity is equal to zero) vortices with different values of the nondimensional parameter ε, which is proportional to the ratio of linear to angular momentum (ε ? RP/M, R is the eddy size). Typical examples include monopole (ε = 0), quasi monopole (ε = 0.1?0.3), quasi dipole (ε ≈ 1), and dipole (ε = ∞). One of the possible applications is the dynamics of oceanic eddies. Recently, Stern and Radko considered theoretically and numerically a symmetric barotropic eddy, which is subject to a relatively small amplitude disturbance of unit azimuthal wavenumber on an f plane. This case corresponds to a self-propagating quasi monopole. They analyzed the structure of the eddy and predicted that such an eddy remains stable and could propagate a significant distance away from its origin. This effect may be of importance for oceanographic applications and such an eddy was reproduced in laboratory experiments with the purpose of verifying these theoretical predictions. Another possible application may include large eddies behind maneuvering bodies. Recent experiments by Voropayev et al. show that, when a submerged self-propelled body accelerates, significant linear momentum is transported to the fluid and unusually large dipoles are formed in a late stratified wake. When such a body changes its direction of motion, an angular momentum is also transported to the fluid and the resulting structure will depend on the value of ε.