Natural convection of magnetic fluid in a rectangular Hele–Shaw cell of different aspect ratios

The nature convection of a magnetic fluid in a rectangular Hele-Shaw cell with an imposition of an even vertical magnetic field is studied experimentally. Heat transfer measurements with thermocouples and flow visualization with liquid crystal thermography are conducted in Hele-Shaw cells of aspect ratios 1.0, 1.5, and 2.0. Both results show that the vertically imposed magnetic field has destabilizing influence. The flow instability modes become different from that in two-dimensional cavity cases, with and without the magnetic field. A pair of symmetric counter-rotating vortices is observed for the first instability mode. Increasing the aspect ratio destabilizes the flow. Second instability mode is observed in the cases of aspect ratios 1.0 and 1.5, but not in 2.0.