The work was performed in 3 main steps:
Instability of rotating magnetic field driven flow in a counter-rotating cylinder.
The flows in small-scale (40 mm in diameter) cylindrical container with mercury melt was driven by rotating magnetic field and counter-rotation of the container. Weak axial DC field was applied on the melt with purpose to ensure the registration of the electric potential on the side-walls of the cavity.
Experimental and numerical results concerning the instability of a liquid metal flow driven by a rotating magnetic field in a finite rotating cylinder were obtained. We observed that counter-rotation of the container with respect to the direction of field rotation may have a pronounced stabilizing or destabilizing action depending on the relative rotation rate. The flow is stabilized if the mechanical counter-rotation is relatively strong. The rotating magnetic field then just slows slightly the core of the flow. As a result, the angular momentum increases with the radial position in a vertical side layer and the Rayleigh stability criterion is satisfied. The flow stays stable so far as it rotates in the direction of the container. A rapid transition takes place almost immediately after reversal of the azimuthal flow direction in a narrow region around the axis of the container. The flow is considerably destabilized at a relatively low counter-rotation of the container. This is observed as a linear instability island or a pronounced increase of fluctuating velocity at low or high control parameter values, respectively.
Results of this investigation were reported on the Joint 15th Riga and 6th Pamir International Conference (June 27 -July 1, 2005, Rigas Jurmala, Latvia) and published in Phys. Fluids 17, 104102 (2005).
Experimental study of suppression of Rayleigh-B'enard instability in cylinder by combined rotating and static magnetic fields
The study was done in collaboration with Forschungszentrum Rossendorf (Dresden, Germany).
The hydrodynamic flows in the scaled-up cylindrical container (60 mm in diameter) was driven by rotating field and thermogravitational convection. Either axial uniform or 'cusp' (axially-radial) steady magnetic fields were applied to the melt volume.
Results reported in I. Grants, A. Pedchenko and G. Gerbeth (2005)\\ Experimental study of suppression of Rayleigh-B'enard instability in cylinder by combined rotating and static magnetic fields. (Prepared for submission).
Scaled-up Gallium multi-purpose facility
To test how the effects scale up, a new experiment was set up with the multi-purpose laboratory facility. A series of experiments were performed with a large (15x15cm) rotating liquid metal cylinder heated from below and subject to various magnetic fields. The results showed that the mechanical rigid-body rotation has not that stabilizing power that the rotating magnetic field driven flow which induces also a meridional recirculation. The laboratory facility developed under WP10 is planned for use in further research as well as for laboratory works of students. More on this setup... (PDF version)