Studies of Magnetic Micro-Droplet Partition by Rosensweig Instability

• Main Authors: Zhi-Yuan Chang, 鄭智元
• Other Authors: none
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/22603978883239300658

碩士 === 雲林科技大學 === 機械工程系碩士班 === 96 === Experiments are carried to investigate the interfacial morphologies of a thin film of micro magnetic drops under a constant perpendicular field, or so-callde Rosensweig instability. Striking patterns of droplet breakup into numerous sub-scale droplets are observed. On a dry plate in which the surface tension dominates, the breaking patterns are characterized by a simensionless magnetic Bond number Bom. More pronounced instability, determined by a larger number of breaking sub-scale droplets N, occurs for a higher value of Bom in general. For a sufficient high value of magnetic Bond number, we identify a new mode of interfacial breakup pattern, which the central droplet is torn apart with major mass loss. In addition, the volume fractions of breaking sub-scale droplets are affected strongly by the height variation of the initial fluid surface and appear uneven partitions with domination by a center droplet. On the other hand, smaller contact angle on a prewetted plate leads to a nearly flat fluid surface. The breakups of sub-scale droplets are almost evenly distributed. A global size for all breaking sub-scale droplets is observed regardless their initial diameters. The number of breaking sub-scale droplets N and the diameter of initial droplet D can be approximated by a quadratic-proportionality of N~D2.