摘要
使用Bridgman单向冷冻实验对毫米量级刚性颗粒与界面的相互作用进行可视化研究,观察到低速冷冻、中速冷冻、高速冷冻下三种不同现象.经典润滑理论指出,颗粒与界面之间总是存在极小的间隙.颗粒被推挤时,周围流体会流入到此间隙中,以供应相变过程中的界面成长.低速冷冻时界面首先要克服底面摩擦力才能推动颗粒;中速冷冻时颗粒周围的水有足够的时间补充到颗粒与界面的间隙中,颗粒可被界面持续推挤;高速冷冻时此间隙来不及补充液体,颗粒被界面包陷.低、中速冷冻时,界面呈直线;高速冷冻时,界面出现大量针状冰晶,界面表现出在液体底表和上表面不同步的斜面,差异宽度会随冷冻速度降低而减小.
A Bridgman unidirectional freezing method is employed to observe the interaction of interface and rigid particles having diameter of millimeter order. Three different phenomena according to the freezing rate are experimentally classified. The classical lubricating theory points out that there always exist small gaps between particles and interface. Fluid will flow into the gaps to replenish the growth of ice crystal. At low freezing rate, the interface should conquer the friction to move the particles away. At mediate freezing rate, the ice front is smooth. Liquid around the particle has enough time to flow into the gaps between the particle and the interface. At high freezing rate, the interface is easily to be dendrite like and engulf the particle. The interface inclined to show two edges at the top and bottom of liquid layer. The width of two edges decreases with the freezing rate.
出处
《应用基础与工程科学学报》
EI
CSCD
2004年第2期187-196,共10页
Journal of Basic Science and Engineering
基金
国家自然科学基金重点项目支持(No.50136020)
