The Impact of Normal Magnetic Fields on Instability of Thermocapillary Convection in a Two-Layer Fluid System

Abstract

When a temperature gradient is imposed along a liquid-liquid interface, thermocapillary convection is driven by the surface tension gradient. Such flow occurs in many application processes, such as thin-film coating, metal casting, and crystal growth. In this paper, the effect of a normal magnetic field, which is perpendicular to the interface, on the instability of thermocapillary convection in a rectangular cavity with differentially heated sidewalls, filled with two viscous, immiscible, incompressible fluids, is studied under the absence of gravity. In the two-layer fluid system, the upper layer fluid is electrically nonconducting encapsulant B2O3, while the underlayer fluid is electrically conducting molten InP. The interface between the two fluids is assumed to be flat and nondeformable. The results show that the two-layer fluid system still experiences a wavelike state when the magnetic field strength Bz is less than 0.04 T. The wave period increases and the amplitude decreases with the increasing of magnetic field strength. However, the convective flow pattern becomes complicated with a variable period, while the perturbation begins to fall into oblivion as the magnetic field intensity is larger than 0.05 T. When Bz=0.1 T, the wavelike state does not occur, the thermocapillary convection instability is fully suppressed, and the unsteady convection is changed to a steady thermocapillary flow.