A numerical study of a liquid compound drop solidifying on a horizontal surface

Abstract

In this study, we present the three-phase numerical simulation results of an axisymmetric compound drop solidifying on a cold plate by the front-tracking method. The compound drop initially has a hemispherical shape with a concentric inner gas core (i.e. gas bubble). The temperature of the plate is lower than the fusion temperature of the shell liquid and thus causes the shell liquid to solidify from the plate surface. It is found that the solid-liquid interface propagates parallelly to the plate during the initial stage of solidification. Then, the region near the outer interface moves faster than that near the inner gas core does. The solidification process completes around the inner core first, and the drop top is the last region to be solidified. Accordingly, a break point is available on the temporal variation of the average height of the solid-liquid interface. Besides, in the presence of volume expansion, the solidified compound drop also has an apex at the top. The numerical results show that the presence of the inner gas bubble prolongs the solidification time. We also find that varying the Stefan number St (in the range of 0.032 – 1.0) or the Bond number Bo (in the range of 0.18 – 3.2) has a minor effect on the inner gas core after complete solidification even though the solidification time decreases with an increase in St or Bo. The effects of the Prandtl number and volume change on the final product of the solidification process are also considered.