Thermocapillary convection in two-layer systems

• Published in: International journal of heat and mass transfer Vol. 41; no. 11; pp. 1499 - 1511
• Main Authors: Liu, Q.S., Roux, B., Velarde, M.G.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-06-1998; Elsevier
• Subjects: Boron compounds; Capillary flow; Convection and heat transfer; Cross-disciplinary physics: materials science; rheology; Crystal growth; Exact sciences and technology; Finite difference method; Fluid dynamics; Fundamental areas of phenomenology (including applications); Gallium compounds; Growth from melts; zone melting and refining; Materials science; Mathematical models; Methods of crystal growth; physics of crystal growth; Navier Stokes equations; Phase interfaces; Physics; Solidification; Theory and models of crystal growth; physics of crystal growth, crystal morphology and orientation; Turbulent flows, convection, and heat transfer; Gallium arsenides; Streamlines; Directional solidification; Digital simulation; Binary compounds; Weightlessness; Immiscible fluid; Marangoni effect; Convection; Thermocapillarity; Liquid liquid interface; Two layer medium; Liquid encapsulation; Heat transfer; Crystal growth from melts
• ISSN: 0017-9310; 1879-2189
• DOI: 10.1016/S0017-9310(97)00277-9

This paper concerns a numerical study of the flow characteristics of thermocapillary convection in a system composed of two immiscible liquid layers subject to a temperature gradient along their interface. We consider the two-layer system: B
2O
3 (encapsulant) and GaAs (melt), for its experimental relevance in crystal growth by the directional solidification method. Two cases have been studied: a system with only one liquid interface (melt/encapsulant) and a system where the outer surface of encapsulant is open to air (and so, subject to a second thermocapillary force). Both the liquid-liquid interface and the outer surface are assumed to be undeformable and flat, which is a valid assumption according to earlier theoretical and experimental results. A 2-D numerical simulation of convection is carried out in a rectangular cavity by solving the system of Navier-Stokes equations using a finite difference method with a staggered grid for the pressure. Having in perspective a Spacelab experimentation we disregarded gravity (
g = 0). We show that a strong damping of the melt flow can be obtained by using an encapsulant liquid layer having appropriate, viscosity, heat conductivity and/or thickness.