New results on MHD drag coefficients

Theoretical and experimental results of MHD drag coefficients are summarized. Special attention is paid to Stokes flow, where a typical error has been found in the literature. This situation is clarified here, and correct results are presented. Numerical calculations are performed for the MHD Stokes flow around a cylinder in a transverse magnetic field, yielding qualitative agreement for the drag with both measurement as well as a rough asymptotic analysis. The MHD drag coefficient of the cylinder in a transverse magnetic field increases proportionally to M . lnM if M >> 1 (where M is the Hartmann number). Finally, the deflection of a rising bubble in a liquid metal is determined if the direction of the magnetic field is inclined relative to the vertical line.