Wobbling of a liquid column between unequal discs

Abstract

One of the most puzzling results of an experiment on the stability of long liquid columns under microgravity, performed aboard Spacelab-D2 in 1993 and named STACO, aiming at the analysis of deformations of nearly cylindrical liquid columns under several mechanical disturbances, is revisited here. It corresponds to the unexplained breakage of an 85 mm long liquid bridge of low viscosity silicone oil, established between unequal discs of 30 and 28 mm, intended to counterbalance the expected deformation by residual acceleration found in previous flights, and left idle because the vibrations and oscillations to be applied afterwards were not started, for fear of premature breakage. A detailed image analysis is performed to extract the maximum amount of data, to be able to check against available theories for axisymmetric and non-axisymmetric deformations of a liquid column.

Experimental analysis of the breakage of a liquid bridge under microgravity conditions

“…1), is also included. The formation of a satellite drop from the long neck, after breakage, is clearly seen in the video record (Martinez, 2010).…”

“…More difficult to explain is why the column maintains the same oscillation amplitude, without decaying, for such a long period, knowing that the natural dumping time, i.e. the period where the amplitude reduces to a half, is some 35 s (Martinez et al, 2005).…”

“…Gravity on ground prevents liquid bridges larger than a few millimetres (the capillary length l c = ^/a/(pg), with o surface tension, p density, and g gravity acceleration), but one may have liquid bridges of any size in weightlessness; we have built several liquid columns 85 mm long and 30 mm in diameter, lasting typically one hour in Spacelab (Martinez et al, 2005) and 6 min on Texus sounding rockets (Martinez et al, 2004).…”

“…This was already analysed when the flight results were reported in Martinez et al (1995), but at that time the tools available for image analysis were rather crude (we could just digitize full individual frames or series of video lines). Now we have performed a full video digitization (Martinez, 2010), and automated full-image analysis using Matlab®. Two such images, and corresponding binary edge contours, are presented in Fig.…”

Surface tension and microgravity

“…Since the value of the surface tension, σ, is hard to control on an Earth-based laboratory, in this environment small values of the Bond number can only be reached by decreasing the values of the parameters in the numerator of the Bond number expression. Thus, it could be reduced by using liquids of almost the same density, Δρ → 0, giving rise to the experimental technique known as neutral buoyancy or the Plateau tank technique [19][20][21][22][23], by decreasing the characteristic length l by working with samples of very small size, l → 0 [24][25][26][27][28], or by reducing the global acceleration acting on the sample, a → 0, as it happens in space platforms, in sounding rockets and in drop towers [29][30][31][32].…”