Model Experiment of Particle Engulfment into the Solidifying Shell under Fluid Flow

Abstract

A model experiment was performed to investigate movement of inclusions near the solid wall and engulfment into the solidifying front. Polystyrene particles (100 μm in diameter) were suspended in flowing melts (water, 20 mass% NaCl aqueous solution and succinonitrile). As the average flow velocity increased, number of the particles reaching the vicinity of the solid wall increased whereas the average stationary time of the particles near the wall decreased. Number of the particles engulfed into the solidifying shell deceased with increasing the flow velocity. Moreover, addition of 3 mass% acetone clearly reduced number of the engulfed particles. In this study, the stationary time and the capture time were introduced to consider the engulfment. The particle engulfment was qualitatively explained by considering changes of the stationary time and the capture time. According to the observation, probability of the engulfment for the particles reaching the solidifying front was 0.01 at most. Only the particles of which the stationary time was much longer than the average value were engulfed. The present study indicated that the particle engulfment under the melt flow should be considered as a probabilistic process.