DENDRITIC GROWTH AT VERY-LOW UNDERCOOLINGS

We have performed numerical simulations of dendritic growth at very lo w undercoolings in two spatial dimensions using a phase-field model. I n this regime of growth, the dendrites present sharp corners in the ti p region while the trailing region is parabolic, and the corresponding side-branching structures resemble the shape of the tip. The scaling upsilon rho(2) similar to constant, where rho is the tip radius of cur vature from the fitting to the parabolic trailing region, still holds approximately. We find that the values of upsilon rho(2) are consisten t with those given by microscopic solvability theory. The sharpness of the tip region of the dendrite can be characterized in terms of the d eviation lambda with respect to an Ivantsov parabola. We observe that this length scales as lambda similar to rho, consistent with experimen tal measurements.