Effects of gravity on pattern formation in directional growth of ice crystals

Abstract

Side-view images of interfacial patterns and solute concentration distribution during directional growth of ice crystals in a water-KCl solution were obtained by Moire phase shift interferometry. It was shown that the vertical distribution of solute concentration changed drastically due to the effect of gravity depending on the growth cell thickness h. In the case of h=900 μm, the concentrated solution near the growth interface subsided and flowed ahead much further than the diffusion length of solute. In thinner cells, the subsided dense solution extended the brine channel under the lower side of the interface instead of flowing ahead, and caused the formation of an asymmetrical wedged pattern. In the thinnest cell of h=135 μm, although the turbulence in the solution was quite small, the symmetry of the interfacial pattern was still broken. The results indicate that the three-dimensional analysis considering the effect of gravity is essential for the interfacial patterns even in the thin growth cell.