Development of a coating technology for highly vicous fluids

In cooperation with the institute for leather and synthetic materials (Forschungsinstitut für Leder und Kunststoffbahnen, FILK, Freiberg, Saxony) an innovative continuous technology to produce a laminate of a textile membrane using reactive and highly viscous silicone based adhesives has been successfully developed. The applied spraying technology is based on an especially developed rotary atomizer, which is capable to transform liquids of very high viscosities far higher than 30 Pas into droplets, see photography. The project was financially supported by the ministery of economy and technology (Bundesministerium für Wirtschaft und Technologie, BMWi).

Rotary Atomizer

Developed rotary head for the production of dropletsfrom highly viscous fluids

Thermocapillary Motion of Bubbles and Drops in a Space Shuttle Experiment

Bubbles and Drops will move in a liquid matrix despite of the absence of buoyancy in weightlessness, if the surface (separating area of the two phases) exhibits differences in surface tension. These can be caused by temperature differences at the bubble or drop periphery, since the surface tension depends on the temperature. In this situation the surface of the bubble or drop drives a flow, which is directed towards increasing surface tension. This phenomenon is termed thermocapillary convection and was confirmed and systematically investigated in space shuttle experiments under reduced gravity in a cooperation between the TU Bergakademie Freiberg (Germany), the Department of Chemical Engineering of the Clarkson University, Potsdam, New York, and the NASA Lewis Research Center.

An important motivation for this research is the through space flight generated possibility to produce novel materials with an improved quality. The reason for this is the absence of gravity dependent buoyant convection, which is believed to be the cause for a limited product quality in earth bound production processes. The investigations showed, that bubbles or drops in a liquid with temperature gradient move faster, the higher the applied temperature gradient and the larger the bubble or drop diameter is. Therefore, it is basically possible to move bubbles and drops in a liquid despite of the absence of gravity.

The first film sequence shows the injection of a bubble (air) and the following migra-tion through the liquid matrix (silicone oil) with temperature gradient under microgravity within the space shuttle. Bubble diameter: 8.2 mm; temperature gradient: 0.33 K/mm. The second sequence displays this experiment visualized by a laser interferometer. The fringe pattern gives indications on the temperature field of the flow.

The interested reader can find further details in the following publications:

  • Thermocapillary migration of bubbles and drops at moderate to large Marangoni number and moderate Reynolds number in reduced gravity.
    P. H. Hadland, R. Balasubramanian, G. Wozniak, R. S. Subramanian.
    Experiments in Fluids 26 (1999) 240 – 248
  • Temperature fields in a liquid due to the thermocapillary motion of bubbles and drops. G. Wozniak, R. Balasubramaniam, P. H. Hadland, R. S. Subramanian.
    Experiments in Fluids 31 (2001) 84 – 89

Suvis cooperates with the Chemnitz University of Technology regarding fundamental research

The Suvis GmbH is also active in fundamental research. For that, it closely cooperates with the chair of fluid mechanics of the Chemnitz University of Technology, faculty of mechanical engineering. Subject of research is the so-called Rayleigh-Benàrd convection, a flow configuration which results when a fluid layer is cooled from above and heated from below (unstable stratification). For that, joint experimental and numerical investigations have been performed, which already lead to two reviewed journal publications [1,2], see below. The investigated convective flow form plays a fundamental role in various technical applications like the heat transfer in solar collectors or double glazed windows, for example.

Velocity field of two convection vortices generated by flow simulation (CFD)

Velocity field of two convection vortices generated by flow simulation (CFD)

Temperature field of two convection vortices generated by flow simulation (CFD)

Temperature field of two convection vortices generated by flow simulation (CFD)


[1] H. G. Heiland, O. Sommer, G. Wozniak: Experimentelle Untersuchung der thermischen Konvektion in einem geneigten Spalt. Forschung im Ingenieurwesen 76, 87-95 (2012)

[2] O. Sommer, H. G. Heiland, G. Wozniak: Numerical and experimental investigation of thermal convection in an inclined narrow gap. Proc. Appl. Math. Mech. 12, 479-480 (2012)