European Space Agency experiments on thermodiffusion of fluid mixtures in space

Abstract.: This paper describes the European Space Agency (ESA) experiments devoted to study thermodiffusion of fluid mixtures in microgravity environment, where sedimentation and convection do not affect the mass flow induced by the Soret effect. First, the experiments performed on binary mixtures in the IVIDIL and GRADFLEX experiments are described. Then, further experiments on ternary mixtures and complex fluids performed in DCMIX and planned to be performed in the context of the NEUF-DIX project are presented. Finally, multi-component mixtures studied in the SCCO project are detailed

A review of fluid instabilities and control strategies with applications in microgravity

We give a brief review of several prominent fluid instabilities representing transitions driven by gravity, surface tension, thermal energy, and applied motion/acceleration. Strategies for controlling these instabilities, including their pattern formation properties, are discussed. The importance of gravity for many common fluid instabilities is emphasized and used to understand the sometimes dramatically different behavior of fluids in microgravity environments. This is illustrated in greater detail, using recent results, for the case of the frozen wave instability, which leads to large columnar structures in the absence of gravity. The development of these highly nonlinear states is often complex, but can be manipulated through an appropriate choice of forcing amplitude, container length and height, initial inclination of the surface, and other parameters affecting the nonlinear and inhomogeneous growth process. The increased opportunity for controlling fluids and their instabilities via small forcing or parameter changes in microgravity is noted

Measurement of diffusion of atmospheric gases in a liquid perfluorocompound by means of optical technique

Diffusion of gas molecules dissolved in the liquid bulk is the problem that is rarely addressed experimentally, mainly due to a difficulty in sensing the presence of dissolved gas and quantifying its concentration. Approaches which are typically used to overcome the problem include either indirect methods (e.g. based on the gas dissolution kinetics [1]), or newly developed complicated sensing techniques [2]

Measurement of diffusion of atmospheric gases in a liquid perfluorocompound by means of optical technique

Diffusion of gas molecules dissolved in the liquid bulk is the problem that is rarely addressed experimentally, mainly due to a difficulty in sensing the presence of dissolved gas and quantifying its concentration. Approaches which are typically used to overcome the problem include either indirect methods (e.g. based on the gas dissolution kinetics [1]), or newly developed complicated sensing techniques [2]

Interfacial phenomena in immiscible liquids subjected to vibrations in microgravity

We consider the response to periodic forcing between 5 Hz and 50 Hz of an interface separating immiscible fluids under the microgravity conditions of a parabolic flight. Two pairs of liquids with viscosity ratios differing by one order of magnitude are investigated. By combining experimental data with numerical simulations, we describe a variety of dynamics including harmonic and subharmonic (Faraday) waves, frozen waves and drop ejection, determining their thresholds and scaling properties when possible. Interaction between these various modes is facilitated in microgravity by the relative ease with which the interface can move, altering its orientation with respect to the forcing axis. The effects of key factors controlling pattern selection are analysed, including vibrational forcing, viscosity ratio, finite-size effects and residual gravity. Complex behaviour often arises with features on several spatial scales, such as Faraday waves excited on the interface of a larger columnar structure that develops due to the frozen wave instability – this type of state was previously seen in miscible fluid experiments but is described for the first time here in the immiscible case

Investigation of diffusive and optical properties of vapour-air mixtures: The benefits of interferometry

info:eu-repo/semantics/publishe

Vibrational instabilities at the interface separating two immiscible liquids in microgravity

A wide variety of interfacial phenomena occurs in vibrated fluid systems, depending on frequency, amplitude and forcing orientation. On earth, there is a clear qualitative difference between vertical and horizontal vibrations. Vertical vibrations can be understood as a modulation of effective gravity and may be stabilizing, as with the Rayleigh-Taylor instability (Wolf 1970), or destabilizing, as with the phenomenon of Faraday waves (Faraday 1831). Horizontal forcing, on the other hand, immediately excites harmonic waves near the container boundaries. When a critical amplitude is reached, it also excites subharmonic cross-waves (Garret, 1970). If the interface separates immiscible layers of different viscosity, vibrations can lead to frozen waves (Lyubimov, Cherepanov 1986; Talib et al. 2007), which are generally bounded by the restoring effects of gravity and interfacial tension