Special issue on rotating turbulence

Rotating Turbulence has attracted extensive research efforts over the last decades due to its fundamental interests and relevance to a variety of natural and engineering processes. The present special issue on Rotating Turbulence collects five contributions from renowned researchers to showcase the variety of physical phenomena and recent advances in this exciting area. This Special Issue is opened by a review paper by L. Biferale, who presents an insightful discussion of Rotating Turbulence with varying degrees of complexity and provides a great introduction to the papers on the special issue. Besides, the paper gives thought-provoking future prospects in this area. The paper of G. Boffetta and coworkers reports a study of freely decaying rotating turbulent flows confined in domains with variable heights using laboratory experiments and numerical simulations. The authors show that vertical confinement has important effects on the formation of large-scale columnar vortices and in particular delays the development of the cyclone–anticyclone asymmetry. This effect is observed both in experiments and in numerical simulations which have structural differences in the boundary conditions, demonstrating the robustness of their findings. The paper by Z. Xia, S. Chen and coworker presents a numerical investigation of the hysteresis behaviour in a spanwise rotating plane Couette flow. By performing two groups of direct numerical simulations where Ro varies in steps along two opposite directions, they demonstrate the existence of hysteresis behaviour in the large-scale realisations at the highest Reynolds number considered, which is also manifested in the turbulent statistics. The paper of R. P. J. Kunnen presents an overview of our current knowledge of the geostrophic regime of turbulent rotating Rayleigh–Bénard convection. The phase diagram of the geostrophic regime of rotating convection is described in detail, with a discussion of the subranges characterised by different flow structures and heat transfer scaling. Complications in the laboratory studies of geostrophic convection are discussed, such as domain size, effects of centrifugal buoyancy, confinement and wall modes, non-Oberbeck–Boussinesq effects and inertial wave resonance. In the paper by S. Horn and J. M. Aurnou, the effects of centrifugal buoyancy on the formation of tornado-like vortices are studied computationally based on the Coriolis-centrifugal convection system. They show that centrifugal buoyancy is relevant for naturally occurring tornadoes and a rich variety of tornado morphologies are produced in the quasi-cyclostrophic regime of Coriolis-centrifugal convection. The Editorial Board thanks the authors for their contributions to the special issue and hopes that this special issue will stimulate further progress and interest in the area.