Experimental study on transition to oscillatory thermocapillary flow in a low Prandtl number liquid bridge

Oscillatory Marangoni flow in half-zone liquid bridge of molten tin supported between two iron rods

“…We reported the first and second critical Reynolds numbers as functions of both aspect ratio and the Prandtl number. Our results indicate that the critical temperature difference (DT c ) to initiate oscillatory flow in a liquid bridge of low-Pr fluid increases as the aspect ratio decreases from 2.2 and shows a maximum value at about As ¼ 1:2: This trend was first reported by us but has not been confirmed experimentally, since very few experimental reports are available on the onset of flow oscillation in half-zone liquid bridges of low-Pr fluids, i.e., mercury [16], molten semiconductor materials [17][18][19][20][21][22][23][24][25][26][27][28][29] and molten tin [30,31]. These authors observed surface temperature oscillations, vibration of liquid bridge surface, and trajectories of tracer particles.…”

“…Thermal conductivities of these materials are smaller than those of the molten tin or silicon. The on-ground experimental apparatus at NAS-DA [31] used iron rods to support small liquid bridge of molten tin. They successfully detected onset of oscillation of local surface temperature.…”

Thermocapillary flows in liquid bridges of molten tin with small aspect ratios

“…Recently, JAXA (former NASDA) conducted a series of on-ground experimental studies (Takagi et al, 2001) on the liquid bridges of molten tin (Pr = 0.009) supported between iron rods. In these experimental studies, the free surface temperature oscillations were successfully observed by using radiation thermometers, however, the oscillations possess greater amplitudes and lower frequencies than those predicted by the numerical studies.…”

Suppression of thermocapillary oscillations in sodium nitrate floating half-zones by high-frequency end-wall vibrations

“…Further, depending on the zone properties, dimensions and the driving axial temperature gradients, the thermocapillary flow field can become nonsteady [3][4][5] with the radial inhomogeneities in dopant distribution being transformed into crystal striations [6,7]. In float zones of semiconductors and metals (low Prandtl number zones) the transition to oscillatory thermocapillary flow occurs readily at low Marangoni numbers [4,8]. The current experiments examine the possibility of suppression of thermocapillary oscillations, in sodium nitrate half zones, through high-frequency end-wall vibrations.…”