The robust wall modes and their interplay with bulk turbulence in confined rotating Rayleigh-Bénard convection

In confined rotating convection, a strong zonal flow can develop close to the side wall with a modal structure that precesses along the wall counter to the applied rotation. It is surmised that this is a robust non-linear evolution of the wall modes observed before the onset of bulk convection. We perform direct numerical simulations of cylindrically confined rotating convection at high rotation rates and strong turbulent forcing. We find a fit-parameter-free relation that links the angular drift frequency of the robust wall mode observed far into the turbulent regime with the critical wall mode frequency at onset, firmly substantiating the connection between the observed boundary zonal flow and the wall modes. Deviations from this relation at stronger turbulent forcing suggest that the bulk turbulence hampers the development of the wall mode. By studying the interactive flow between wall mode and bulk turbulence, we identify radial jets penetrating from the wall mode into the bulk. These jets induce a large scale multipolar vortex structure in the bulk, dependent on the wavenumber of the wall mode. In a narrow cylinder the entire bulk flow is dominated by a quadrupolar vortex driven by the radial jets, whereas in a wider cylinder the jets are found to have a finite penetration length and the vortices do not cover the entire bulk.