Effect of Marangoni Number on Thermocapillary Convection and Free-Surface Deformation in Liquid Bridges

• Published in: Journal of thermal science Vol. 25; no. 2; pp. 178 - 187
• Main Authors: Zhang, Yin, Huang, Hu-Lin, Zhou, Xiao-Ming, Zhu, Gui-Ping, Zou, Yong
• Format: Journal Article
• Language: English
• Published: Heidelberg Science Press 01.04.2016
• Subjects: Classical and Continuum Physics; Engineering Fluid Dynamics; Engineering Thermodynamics; Heat and Mass Transfer; Marangoni; Physics; Physics and Astronomy; 对流不稳定; 微重力条件; 流动结构; 液桥; 热毛细对流; 自由表面; 表面变形; microgravity; thermocapillary convection; Floating zone; VOF; liquid bridge; deformable free-surface
• ISSN: 1003-2169; 1993-033X
• DOI: 10.1007/s11630-016-0849-8

Floating zone technique is a crucible-free process for growth of high quality single crystals. Unstable thermocapillary convection is a typical phenomenon during the process under microgravity. Therefore, it is very important to investigate the instability of thermocapillary convection in liquid bridges with deformable free-surface under microgravity. In this works, the Volume of Fluid（VOF） method is employed to track the free-surface movement. The results are presented as the behavior of flow structure and temperature distribution of the molten zone. The impact of Marangoni number（Ma） is also investigated on free-surface deformation as well as the instability of thermocapillary convection. The free-surface exhibits a noticeable axisymmetric（but it is non-centrosymmetric） and elliptical shape along the circumferential direction. This specific surface shape presents a typical narrow ‘neck-shaped＇ structure with convex at two ends of the zone and concave at the mid-plane along the axial direction. At both θ = 0° and θ = 90°, the deformation ratio ξ increases rapidly with Ma at first, and then increases slowly. Moreover, the hydrothermal wave number m and the instability of thermocapillary convection increase with Ma.