Observation of a large stable anticyclone in rotating turbulence

A new turbulent regime in a rotating liquid system was discovered experimentally. A cubic aquarium with an edge of 1 m was filled with distilled water and mounted on a rotating platform. Turbulence was excited by vertically non-homogeneous mixers mounted in the corners of the cube. At a fixed intensity of turbulence forcing, a certain range of aquarium rotation frequency was found, within which a stable large-scale anticyclone was observed in the center of the aquarium, around which a peripheral cyclonic current was formed. The parameters of the turbulent regime obtained were measured for different cube rotation frequencies. A model was proposed, according to which the anticyclonic flow is supported by absorption of inertial waves that propagate toward the vortex axis from the peripheral region and carry an anticyclonic angular momentum. Such a wave with a fixed frequency, vertical wave number, and axial number is absorbed at a certain distance from the vortex axis in the critical layer. On the contrary, waves that carry a cyclonic momentum are reflected and, hence, eventually transfer their angular momentum to the peripheral cyclonic current. This separation of waves in an ensemble leads to the formation of the tangential Reynolds stress, which maintains the anticyclone. The separation process has a general nature, meaning that this mechanism of the stress formation should be relevant in all rotating turbulent flows with an axially symmetric mean current.