Thermoelectric magnetohydrodynamic flows during various crystal growth processes with an externally applied magnetic field

The thermoelectric magnetohydrodynamic (TEMHD) effects occur when the applied magnetic field interacts with electric currents and when there is a temperature gradient along the liquid-solid interface with different absolute thermoelectric powers for the solid and liquid. This thesis presents the first models to investigate the TEMHD effects during various crystal growth processes, with an assumed temperature profile along the crystal-melt interface and an externally-applied uniform axial magnetic field.; The TEMHD flow exhibits different behavior under various magnetic field strengths. For strong magnetic fields, the flow becomes inertialess. For arbitrary strength magnetic fields, the inertial, viscous and electromagnetic damping effects are important. For weak magnetic fields, there is no electromagnetic damping in the melt motion, and the result is an ordinary hydrodynamic flow with a prescribed thermoelectric body force concentrated near the bottom of the melt domain.; All the models involve a radially outward flow near the crystal-melt interface which helps produce uniform and homogeneous crystals. Numerical results are presented for Bridgman and float zone processes with strong fields. The azimuthal motion dominates the melt motion. As the magnetic field strength is increased from zero to large values, the azimuthal and meridional motions first increase from zero to maxima and then decay back toward zero for very strong magnetic fields. Numerical results for traveling heater method are presented for arbitrary strength magnetic fields. The flow is inertialess at the beginning and the convective effects emerge as the Reynolds number Re is increased for a particular case. For relatively weak magnetic field strength, the convective effects dominate the EM damping effects for very large Re. For weak magnetic field case, the convective effects emerge as thermoelectric body force is increased, and they dominate the melt motion for strong body force. A similarity problem is considered to understand the insights for weak magnetic field case. The solutions reflect the numerical results for weak field cases. While strong magnetic field results are useful for terrestrial crystal growth processes, the arbitrary strength field and weak field results will be useful for future crystal growth experiments in space.