MELT PRODUCTIVITY AND RHEOLOGY: COMPLEMENTARY INFLUENCES ON THE PROGRESS OF MELTING

Abstract
The binary-eutectic model of phase change limits the application of continuum-mixture simulations to particular systems. We present a phase-change model that allows systems with more complex phase relations to be addressed. The model includes multiple invariant points, which yield a nonlinear production of melt as a function of temperature. A constitutive relation based on the hybrid model for viscosity and permeability is used to account for transport behavior as a function of the local melt fraction. Results are reported of two series of simulations, one utilizing the new two-invariant-point model and the other using a one-invariant-point model The comparison demonstrates that the efficiency of convective heat transport can be increased by over 200% in the two-invariant-point case. The total kinetic energy for the two-invariant-point system is typically 2 orders of magnitude greater. This comparison highlights the important link between melt productivity and the constitutive relations and illustrates the necessity of accurately modeling the variation of melt fraction with temperature in partially molten systems.

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