Unsteadiness and related striation in directional solidification

2-D unsteady flow patterns in upward Bridgman solidification are numericall y investigated. The alloy under study is Pb-30%Tl. The purpose of the contr ibution is to characterise the striations induced by unsteadiness in the gr owing crystal. Unsteady solution branches are studied from onset threshold of unsteadiness to chaos. We report two examples for which time behaviour o f a given solution branch is studied versus Rayleigh number. We then estima te the magnitude of the time fluctuations in solute composition that the cr ystal incorporates. The period of the striations is also discussed.