BUOYANT-THERMOCAPILLARY FLOW WITH NONUNIFORM SUPRA-HEATING .1. LIQUID-PHASE BEHAVIOR

A computational study has been made of the transient heat transfer and fluid flow of a circular pool of liquid n-decane centrally heated from above by radiation. For the first time, volumetric absorption of the radiation incident on the pool surface is considered. Over the range of gravity levels investigated (0-1 g(n)), the flow is primarily thermocapillary-driven. However, buoyancy influences the number and recirculation rates of the subsurface vortices by stabilizing hot subsurface fluid above the colder core fluid. This affects the liquid surface temperature profile which, in turn, governs the velocity profile due to thermocapillarity. For a given heat flux profile from above, the surface temperature and velocity profiles are insensitive to: (a) liquid height for Re.A2 >> 1 (boundary layer flow) and (b) gravity level for Re.A2 << 1 (viscous flow), where A is the aspect ratio of the pool. Volumetric absorption of radiation in the liquid increases the thermal boundary layer thickness, decreases the liquid surface temperature by 20-35%, and increases the temperatures in the core region. However, the velocity field is only slightly changed by the volumetric absorption of radiation.