Convective Effects during Diffusivity Measurements in Liquids with an Externally Applied Magnetic Field

Dr. Yu Yu. Khine

Center for Microgravity and Materials Research
University of Alabama in Huntsville

September 28, 2001

Abstract

During liquid self-diffusion experiments, any radial non-uniformity in temperature within the melt drives buoyant convection in the presence of gravity (terrestrial experiments) or even in residual acceleration (microgravity experiments). This convection can result in erroneous values of the measured diffusivity which is very important in application in metallurgy and crystal growth. Recently, some researchers have applied magnetic fields to suppress the buoyant convection in the self-diffusion experiments since liquid metals and semiconductors have very large electrical conductivities. In this presentation, a 2-D numerical model is considered with an externally applied magnetic field to determine the convective contamination during self-diffusivity experiments. The diffusivity results for different heat transfer conditions are discussed for this model. Our results show that small uniform radial gradients have a much stronger influence than the periodic non-uniformities.