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

温度和浓度联合效应下冰板融化过程中出现的鲨鱼皮现象的解释

• 批准号: 15560166
• 负责人: SUGAWARA Masahiro
• 金额: $ 2.37万
• 依托单位: AKITA UNIVERSITY
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2003
• 资助国家: 日本
• 起止时间: 2003 至 2004
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-15560166/
• 关键词: Ice; Melting; Calcium Chloride Aqueous Solution; Concentration Diffusion; Double Diffusive Convection; Shark Skin; 水溶液

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.

对水平冰板在方腔内从上方融化到氯化钙水溶液中的过程进行了实验和数值研究。将温度为-5℃的20wt%氯化钙混合物倒入空腔中，其中温度为-5℃的冰板水平位于空腔底部。冰板融化的驱动力是在融化前沿附近出现的浓度梯度。在熔化表面上很快出现了浓度扩散层。熔化表面的温度由于吸收熔化潜热而降低。扩散层的厚度在熔化过程中沿着熔化前沿的温度降低而增加。当扩散层厚度小于1 mm时，由于低密度水的浮力作用，扩散层中出现了许多小的低密度液体羽流。羽状物之间的距离约为1毫米。上升羽流的出现引起了高浓度的向下液流。因此，向下流动导致了冰融化的增强。另一方面，冰在向上流动的位置（即，羽流）由于液体的低浓度。这些融化速率的局部差异导致粗糙的表面像“山谷”（即，鲨鱼皮）。鲨鱼皮的“山谷”结构在融化前沿的位置在融化过程中基本上没有变化。然而，一个较小的山谷很快就消失了周围较大的山谷侵蚀。