Abstract In a net heat gain condition via circumferential radiative heating, the effects of heating rate and aspect ratio (Ar) on the spatio-temporal evolution of thermocapillary convection in a full-zone liquid bridge, transverse and longitudinal velocities, and interfacial temperature variations were experimentally investigated by the particle image velocimetry (PIV) technique. Results showed that as the absolute Richardson number difference (|ΔRi|) between the upper and lower semi-floating zones increases, the penetration of the upper cellular flow into the lower zone intensifies, thereby compressing the lower cellular flow toward the free surface. As the surface flow heat transfer is enhanced, the surface flow is rapidly replenished with the cold fluid from the bulk return flow. Consequently, the interfacial temperature in the upper semi-floating zone exhibits an initial rise followed by a subsequent decline, accompanied by a progressive increase in temperature difference. This results in a pronounced “temperature downthrow” in the upper semi-floating zone and near the intermediate height region. Since the direction of surface flow coincides with that of radiative conduction in the lower semi-floating zone, the surface flow temperature gradually rises while the corresponding temperature difference decreases. Furthermore, the increasing of the Ar shifts upward the vortex core of cellular flow in the upper semi-floating zone, enhances the temperature difference in the lower semi-floating zone, promotes the surface flow velocity and the development of lower cellular flow. Further, the phenomenon of the “temperature downthrow” is effectively suppressed in the upper semi-floating zone.
Yang et al. (Sat,) studied this question.