PERMEABILITY FOR CROSS-FLOW THROUGH COLUMNAR-DENDRITIC ALLOYS

Experiments for measuring permeability in columnar-dendritic microstru ctures have provided data only up to a volume fraction of liquid of 0. 66. Hence, the permeability for flow perpendicular to the primary dend rite arms in columnar-dendritic microstructures was calculated, extend ing our data base for permeability to volume fractions of liquid as hi gh as 0.98. Analyses of the dendritic microstructures were undertaken first by detecting the solid-liquid interfaces with a special computer program and then by generating a mesh for a finite-element fluid flow simulation. Using a Navier-Stokes solver, the velocity and pressure a t the nodes were calculated at the microstructural level. In turn, the average pressure gradient was used to calculate the Darcy permeabilit y. Permeabilities calculated by this versatile technique provided data at high volume fractions of liquid that merged with the empirical dat a at the lower volume fractions.