THE INFLUENCE OF OSCILLATORY AND STEADY SHEARS ON INTERFACIAL STABILITY DURING DIRECTIONAL SOLIDIFICATION

A linear stability analysis is performed on the interface formed during the directional solidification of a dilute binary alloy in the presence of a weak, time-dependent flow. In one case, the flow is generated by a simple harmonic, lateral oscillation of the crystal, resulting in solidification into a compressed Stokes boundary layer. In a second, more general, case, the crystal also has a mean horizontal velocity. The presence of the flow can either stabilize or destabilize the two-dimensional system relative to the case with no flow, with the result depending on the Schmidt number, segregation coefficient, and the frequency of the oscillations.