We present the first detailed thermal and velocity field characterization of convection ina rotating cylindrical tank of liquid gallium, which has thermophysical properties similarto those of planetary core fluids. Our laboratory experiments, and a closely associateddirect numerical simulation, are all carried out in the regime prior to the onset of steadyconvective modes. This allows us to study the oscillatory convective modes, sidewallmodes and broadband turbulent flow that develop in liquid metals before the adventof steady columnar modes. Our thermo-velocimetric measurements show that stronglyinertial, thermal wind flows develop, with velocities reaching those of comparable non-rotating cases. Oscillatory bulk convection and wall modes coexist across a wide rangeof our experiments, along with strong zonal flows that peak in the Stewartson layer, butthat extend deep into the fluid bulk in the higher supercriticality cases. The flows containsignificant time-mean helicity that is anti-symmetric across the midplane, demonstratingthat oscillatory liquid metal convection contains the kinematic components to sustainsystem-scale dynamo generation.
|Journal||J. Fluid Mech.|
|Publication status||Accepted/In press - 21 Oct 2020|