AFDM: An Advanced Fluid-Dynamics Model

This report gives the Advanced Fluid-Dynamics Model (AFDM) solution algorithm describing vaporization/condensation (V/C) and melting/freezing processes. The finite-difference equations used are derived from the general AFDM differential equations with convection ignored. In two-phase cells, V/C is determined by a simultaneous iterative solution. The objective is to retain stability and energy conservation with consistent interfacial and bulk conditions describing vapor/liquid densities and temperatures. Particular attention is given in the special cases required to obtain a solution. In single-phase cells, the heat transfer is determined first; then, a vapor composition is updated for the {alpha}{sub 0} volume based on the saturation pressures for the individual liquids. Melting/freezing rates are determined based on equilibrium considerations. Mass-transfer-induced velocity changes are calculated implicitly so as to conserve momentum. In addition to the treatment of the standard models, a description is provided on the energy transfers used for the simplified NOPHASE option.