Flow instabilities of liquid and mushy regions during alloy solidification and under high gravity environment induced by rotation

Abstract

Linear flow instabilities of the liquid and mushy regions during directional solidification of a binary alloy are studied under a high gravity environment where the rotation axis is inclined with respect to the high gravity vector. Stability analysis and numerical computation are carried out to determine the results for the stationary disturbances at several values of the rotation rates and for given values of the other parameters. The results provide information about the effects of Coriolis force on various flow features in the liquid and mushy layers. The preferred structure of the mush–liquid interface is found to be that of longitudinal rolls. The main mode of convection is found to be able to generate double-cell structure in the vertical direction and is strengthened in the mushy layer by the Coriolis force. The Coriolis force appears to be generally stabilizing in the sense that the motion in the liquid zone is significantly weakened, the tendency for the chimney formation in the mushy zone is reduced and the critical values of the liquid and mush Rayleigh numbers and the wave number increase with increasing the rotation rate.