Coalescence of lenticular anticyclones in a linearly stratified rotating fluid

Abstract

This study is devoted to laboratory experiments on the coalescence of two lenticular anticyclones in a linearly stratified rotating fluid. These anticyclones are generated by injecting small volumes of fluid at the centre of a rotating tank where a linearly stratified layer was previously prepared with salt. The characteristics of the interaction between the vortices are studied by visualisation and Particle Image Velocimetry (PIV) as a function of the initial separation distance between the vortices, the Coriolis parameter of the rotating table and the Brünt-Väisälä frequency of the density stratification. Our results show that the merging critical distance depends drastically on the Rossby radius of deformation of the vortices and are in complete agreement with previous numerical modelling of vortex coalescence. We have also observed that mergers involve three-dimensional processes as the vortices intertwine together possibly because of the presence of an elliptic instability that tilts the vortex cores. They are also accompanied by the emission of vorticity filaments and internal gravity waves radiation although we cannot prove that in our experiments these waves are solely due to the merging process.

Keywords:

• Lenticular vortices
• rotating stratified flows
• experimental fluid dynamics

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work has been carried out in the framework of the Labex MEC Project 410 (No. ANR-10-LABX-0092) and of the A*MIDEX Project (No. ANR-11-IDEX- 0001-02), funded by the “Investissements d'Avenir” French Government program managed by the French National Research Agency (ANR). The authors also acknowledge support from the American Physical Society's International Research Travel Award Program (IRTAP). We also thank for their financial supports, The Physics Department of the CUCEI (Centro Universitario de Ciencias Exacta e Ingenerias), University of Guadalajara and Aix Marseille Université for the fundings “Appel à Projets Actions Internationales” 2016. A.O.E. acknowledges CONACyT for his scholarship.