DENDRITIC GROWTH IN CONFINED SPACES

摘要

We simulate the growth of a single dendrite, starting from a spherical speed in a pure undercooled melt, in confined three dimensional space. In particular, we study the effect of the spacing between the top and bottom domain boundaries on tip selection, by quantifying the tip velocity and curvature, and the selection constant (σ~*), as a function of this spacing and dimensionless undercooling. We also examine dendrite evolution in the presence of a superimposed flow. We observe a three-dimensional to two-dimensional growth transition in the dendrite at a very small spacing, and conclude that there exists a critical spacing δ_c, for particular values of the free stream velocity and undercooling when this phenomenon occurs. We correlate the steady state diffusion field and δ_c.