Abstract

Background: The heat transfer condition at the interface of two fluids is an important factor that affects the stability characteristics of a half floating zone with temperature driven Marangoni convection. Various relevant papers and patents report that under microgravity conditions the critical temperature difference beyond which the onset of oscillatory behavior occurs gets drastically affected by the volume ratio of the half-floating zone. Hence, the actual mechanism and influence of parameters that affect flow structure for different volume ratios is still an area of research interest.

Objective: To investigate the effect of viscous stresses exerted by the counter-directed ambient air flow on flow and thermal characteristics of a liquid bridge of a high Pr fluid with convex interface under microgravity conditions.

Methods: In the present study, thermo-capillary convection in half floating zone is simulated using an axisymmetric model. Computations are carried out using commercial software ANSYS Fluent 17.2 with dimensional variables in both liquid and air domains. As thermo-capillary flow is laminar and incompressible in nature, pressure based solver with SIMPLE algorithm has been used in present analysis.

Results: The study indicates that ambient air velocity has a significant influence on the variation of local surface velocity, local surface temperature and local Biot number at the convex interface. Flow and thermal fields inside liquid bridges are presented using isolines of stream function and temperature.

Conclusion: With the increase in ambient air velocity, the recirculating regions formed around the halffloating- zone are found to shrink in their size affecting the heat transfer conditions at the interface.

Keywords: Convex interface, counter-directed air flow, liquid bridge, Marangoni number, surface temperature and velocity, thermo-capillary convection.