Fluid flow into a dendritic array under forced convection

Abstract

The flow of liquid into the solid-liquid region of AISi, AlCu, and AlMg alloys, freezing upward, has been examined using radioactive tracers. With the liquid stirred by a rotating disc, it was found that the liquid penetrated a relatively short distance into the solid-liquid region, the penetration increasing a small amount with increasing flow velocity. The volume fraction liquid at maximum penetration was large, greater than 0.63. Flow into the solid-liquid region in AlMg was similar to that observed in AISi, but flow in AlCu was less. A water model containing solid dendrites, simulating the metal system, was used to observe directly fluid flow in a simplified solid-liquid region. The results showed that flow into the solid-liquid region increased appreciably when either the flow velocity was strongly increased or the temperature difference between the interdendritic liquid and free flowing liquid decreased. The penetration was not significantly changed with changes in dendrite morphology or the length of the solid-liquid region.