Thermomagnetic convection induced in a temperature stratified state by a Halbach magnetic field

Abstract

Convection induced by the permanent magnets of the linear Halbach array is numerically investigated and validated experimentally. The working fluid is a paramagnetic fluid that is weakly attracted to the magnet with temperature dependency. The fluid is filled in a rectangular enclosure and heated from the top and cooled from the bottom. The external magnetic field is applied from the top wall. Two-dimensional computations show that the Halbach magnet array can induce a strong thermomagnetic force widely in the fluid layer compared with the conventional alternate magnetic pole array. The upward flow is induced below the edges of the center magnet and then separated left and right along the top heated wall. The local Nusselt number shows a higher value and wider area than those by the conventional pole array. An experiment using the Halbach array kit is conducted and the obtained local Nusselt number profile agrees well with the computational data both qualitatively and quantitatively.