Elucidation of the Shark Skin Phenomena Appeared in the Melting of an Ice Plate with a Temperature and Concentration Combined Effect

点击翻译按钮获取中文摘要

Experimental and numerical investigation were carried out of the melting of a horizontal ice plate from above into a calcium chloride aqueous solution inside the square cavity. A20 wt % calcium chloride mixture at the temperature of -5℃ poured into the cavity in which an ice plate in the temperature of -5℃ was located horizontally at the bottom. The ice plate melted with a driving force of the concentration gradient appeared near the melting front. A diffusion layer of the concentration soon appeared on the melting surface. The temperature of the melting surface decreased due to the absorption of the latent heat for melting. The thickness of the diffusion layer increased during the melting process along with the temperature depression of the melting front. After the diffusion thickness reached a critical value less than 1mm, many small plumes of low density liquid appeared from the diffusion layer due to the buoyancy of the low density melt water. The distance among the plumes was about 1mm. The appearance of the upward plumes caused the downward liquid flow of high concentration. Therefore, the downward flow caused the enhancement of the melting of ice. On the other hand, the ice melted more slowly at the locations of the upward flow (i.e., plumes) due to the low concentration of the liquid. These local differences of the melting rates caused the rough surface like a "mountain and valley" (i.e., a shark skin). The locations of the "mountain and valley" structure of a shark skin at the melting front basically did not vary during the melting process. However, a smaller valley soon disappeared eroded by the around larger valleys.