2016 Volume 56 Issue 2 Pages 195-204
In order to investigate the influence of static magnetic field on behavior of rising single bubble in conductive fluid, a series of axisymmetric numerical simulations are carried out. A uniform vertical magnetic field with intensities ranging from 0 to 0.4 T (Ha=0−16.97) is superposed and the bubble radii range from 2 mm to 6 mm (R*=0.2−0.6). The rising velocity, instantaneous bubble shape and terminal height are discussed and whether the magnetic field restrains bubble rising simply or transits from positive effect to negative one with the increasing of magnetic field intensities is analyzed clearly. Besides, the discrepancy of bubble motion under magnetic field with weak or strong surface tension is compared. Numerical results show that vertical magnetic field elongates the bubble shape along vertical direction and a stronger magnetic field intensity contributes to a longer bubble shape. The imposed magnetic field has an inhibitory effect on the rising velocity for bubbles with strong surface tension as well as bubbles with weak surface tension but small sizes. However, for bubbles with weak surface tension but large sizes, the rising velocity is promoted by weak magnetic field intensities whereas inhibited by strong magnetic field intensities. The peak Hartmann number reaching the strongest positive effect and the critical Hartmann number turning from positive effect to negative effect are determined respectively.