INFLUENCE OF CONVECTION ON SOLIDIFICATION OF BINARY-SOLUTIONS COOLINGFROM BELOW

The directional solidification of aqueous ammonium chloride solutions has been considered by theoretical and experimental approaches to inve stigate the influence of convection on solidification. By comparing th e growth of crystal from experiments in which convective flows occur a nd that from theoretical analysis in which no convection is considered , the effect on solidification due to each individual convective flow, such as the double-diffusive salt-finger convection above the melt/mu sh interface, the buoyant flow in the mushy layer, the plume flow issu ed directly from the interior of the mush into the bulk melt, and the mushy-layer mode circulation induced by the subcritical instability an d so on, is identified. It is found, in general, that the salt-finger convection and mushy-layer mode circulation inhibit the growth of the dendritic mushy zone and the plume flow enhances the growth of eutecti c solid layer while suppresses the mushy layer. The buoyant flow effec t is virtually negligible.