Turbulence, vortices, waves, jets and anomalous modes in hydrodynamic laboratory experiments in rotating systems

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• Otto Chkhetiani (A.M. Obukhov Institute of Atmospheric Physics of Russian Academy of Sciences)
• Tuesday 16 January 2024, 14:45-15:15
• Seminar Room 1, Newton Institute.

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Chkhetiani O.G., Gledzer E.B., Gledzer A.E., Khapaev A.A., Kalashnik M.V. The results of laboratory hydrodynamic experiments in circular resting and rotating vessels with thin layers of conducting fluid under MHD velocity generation using spatially distributed configurations of permanent magnets are presented. The magnet locations and the choice of rotation and motion excitation velocities were formulated, in particular, on the basis of numerical calculations with the shallow water model [1].             In regimes of fast rotation with a thin fluid layer, when the Rossby-Obukhov scale does not exceed the characteristic dimensions of the vessel, a system of disturbances with almost stationary blocked anticyclones in the outer part of the flow and rapidly moving cyclones in the main flow arises [2]. The diagram of modes in variables of relative angular velocities of the averaged zonal flow and vortex transport around the rotation axis of the system is constructed.             In the absence of rotation, the inverse cascade conditions are realized in a narrow range of parameters [3,4]. At the same time, large-scale almost circular vortices have been obtained for rotating configurations, arising as a result of energy transfer from a system of externally generated small-scale vortices to large-scale velocity fields under the influence of the Coriolis force in the case of rotation. Single large-scale vortices and jet streams appear in the subrotation and superrotation regimes with respect to the external rotation depending on its angular velocity [5].  The effects of cyclone-anticyclone asymmetry are clearly observed [6].   The conditions for realizing the existence of different modes of barotropic circulation in closed annular channels under identical external parameters that set the dynamics of flows have been studied [7]. Depending on the rotation period or magnet configurations, the following modes are possible; a) The initial and final modes differ quantitatively by the number of formed cyclonic or anti-cyclonic vortices. b). The number of vortex formations does not change, but their spatial localization differs, for example, the angular coordinates of the centers. c) After changing and restoring the value of the determining parameter, the flow returns to the regime, practically not differing from the initial one.             At the same time, a sectoral decrease in the intensity of the external forcing in some interval of values has an inhibitory effect on the velocity of the anticyclone passage through the channel, almost without affecting the dynamics of cyclones [8]. A significant part of the moving anticyclones can disappear or practically stop. New quasi-stationary anticyclones can also appear, although in the apparent pattern of vortex propagation in the channel there were no appreciable changes in the sector in which the external interference was carried out. The indicated anomalies can be interpreted as a decrease of the intensity of the subtropical Hadley cell, which is accompanied with weakening of the trade winds in some sector of the near-equatorial atmospheric circulation and a decrease of the westerly transport in the middle latitudes.  The state of the mixture of standing and moving vortices is considered on the basis of a simple analytical model of the resonant interaction of transient (with an intermediate velocity maximum) modes of Rossby waves in the shear flow. The amplitude of the stationary background state has the same dependence on the beta effect as for the known Sverdrup relation stream function for the surface flow in an ocean basin            in the study of the western boundary current intensification.                The research was supported by the Russian Science Foundation – project 23-17-00273.

Gledzer, A. E. (2016). Generation of large-scale structures and vortex systems in numerical experiments for rotating annular channels. Journal of Applied Mechanics and Technical Physics, 57, 1239-1253. Gledzer, A. E. E., Gledzer, E. B., Khapaev, A. A., & Chkhetiani, O. G. (2013). Experimental manifestation of vortices and Rossby wave blocking at the MHD excitation of quasi-two-dimensional flows in a rotating cylindrical vessel. JETP letters, 97, 316-321. Gledzer, A. E., Gledzer, E. B., Khapaev, A. A., & Chkhetiani, O. G. (2011). Structure functions of quasi-two-dimensional turbulence in a laboratory experiment. Journal of Experimental and Theoretical Physics, 113, 516-529.. Gledzer, A. E., Gledzer, E. B., Khapaev, A. A., & Chkhetiani, O. G. (2013). Effect of three-dimensional structures on the dynamics of turbulence in thin layers of fluid in a laboratory experiment. Izvestiya, Atmospheric and Oceanic Physics, 49, 187-200. Gledzer, A. E., Gledzer, E. B., Khapaev, A. A., & Chkhetiani, O. G. (2017). Emergence of sub (super)-rotation and jet streams from small-scale quasi-two-dimensional vortices in laboratory experiments. Izvestiya, Atmospheric and Oceanic Physics, 53, 579-591. Kalashnik, M. V., Khapaev, A. A., & Chkhetiani, O. G. (2016). On the cyclone-anticyclone asymmetry in the stability of rotating shear flows. Fluid Dynamics, 51, 167-179.Gledzer, A. E., Gledzer, E. B., Khapaev, A. A., & Chkhetiani, O. G. (2021). Multiplicity of Flow Regimes in Thin Fluid Layers in Rotating Annular Channels. Fluid Dynamics, 56, 587-599. Gledzer, A. E., Gledzer, E. B., Khapaev, A. A., & Chkhetiani, O. G. (2023). Rossby waves and zonal flux anomalies in the analogs of Hadley and Ferrell cells of the general atmospheric circulation: model and experiments. Izvestiya, Atmospheric and Oceanic Physics, 59(4), 321-336.

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