Effect of melt convection at various gravity levels and orientations on the forces acting on a large spherical particle in the vicinity of a solidification interface

Numerical modeling was undertaken to analyze the influence of both radial a nd axial thermal gradients on convection patterns and velocities during sol idification of pure Al and an Al-4 wt% Cu alloy. The objective of the numer ical task was to predict the influence of convective velocity on an insolub le particle near a solid/liquid (s/l) interface. These predictions were the n be used to define the minimum gravity level (g) required to investigate t he fundamental physics of interactions between a particle and a s/l interfa ce. This is an ongoing NASA funded flight experiment entitled "particle eng ulfment and pushing by solidifying interfaces (PEP)". Steady-state calculat ions were performed for different gravity levels and orientations with resp ect to the gravity vector. The furnace configuration used in this analysis is the quench module insert (QMI-1) proposed for the Material Science Resea rch Facility (MSRF) on board the international Space Station (ISS). The gen eral model of binary alloy solidification was based on the finite element c ode FIDAP. At a low g level of 10(-4)g(0) (g(0) = 9.8 m/s(2)) maximum melt convection was obtained for an orientation of 90 degrees. Calculations show ed that even for this worst case orientation the dominant forces acting on the particle are the fundamental drag and interfacial forces. (C) 2000 Else vier Science B.V. All rights reserved.