The Microgravity Research Experiments (MICREX) Database

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This TEXUS 8 experiment was the seventh in a series of investigations designed by BrŸckner et al. to study convective mass transfer driven by an interfacial tension gradient (see BrŸckner, TEXUS 1, TEXUS 2, TEXUS 3, TEXUS 3b, TEXUS 4, TEXUS 6). The specific objective of this experiment was to examine the fluid/fluid interface instabilities caused by interface concentration gradients.

The experiment was directly related to the earlier TEXUS 3b experiment by BrŸckner. During TEXUS 3b, two immiscible fluids ((1) acetone dissolved in toluene and (2) water)) were brought into contact during the coasting phase of the sounding rocket. Reportedly, acetone crossed the interface and was transported into the water.

This TEXUS 8 experiment was designed to investigate the reverse case of TEXUS 3b. According to theory, such a transport of acetone from a water-acetone mixture into toluol should result in different convective modes at the interface.

Prior to the initiation of the TEXUS 8 experiment, a shutter within the experiment cell separated (1) acetone dissolved in water and (2) toluol. "The same acetone concentration (water-acetone:1-2 in volume) as in the previous experiment was chosen in order to obtain quantitatively comparable results." (4, p. 44)

During the low-gravity coasting phase of the rocket, the shutter was withdrawn and the two fluids were brought into contact. Fluid flow patterns, observed using a schlieren-optical arrangement, were recorded by a cine camera.

Reportedly, acetone crossed the interface and was transported into the toluol "...about 40 seconds after starting to move the slide (which separated the two immiscible fluids), two eddys[sic] formed on each side of the interface, and they grew continually. After about 40 ...[seconds]... test time, one eddy on each side of the interface was consumed by the neighboring eddy, so that in each phase there was only one double eddy, which continued to grow at a constant rate, until the entire cell was filled by this double eddy and then, because of the occurring equalization of concentration, it collapsed." (2, translated)

Reportedly, the TEXUS 8 results were qualitatively in agreement with the theory of (1) Sternling and Scriven and (2) Sanfeld et al. Estimates of the magnitude of vortices, based on the theory of Sternling and Scriven, were also in good agreement with experimental values. It was further reported that this was a surprising result because while the theory was derived for low concentrations, large concentrations were used in the TEXUS 8 experiments.

No further information published in English was available.

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(2) BrŸckner, R. and Christ, H.: Diffusion-Induced Interface Convection. In TEXUS 11/12 Abschlussbericht 1985, DFVLR. (discusses TEXUS 8 as well as TEXUS 11; in German, post-flight)

(3) Input received from Principal Investigator R. BrŸckner, May 1988 and July 1993.

(4) Diffusion-induced Interfacial Convection. In Summary Review of Sounding Rocket Experiments in Fluid Science and Materials Sciences, ESA SP-1132, February 1991, p. 44. (post-flight)

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