Microgravity interfacing

Stefanescu, D.M. Juretzko, F.R. Dhindaw, B.K. Catalina, A. Sen, S. Curreri, P.A. Particle engulf-ment and pushing by solidifying interfaces Part II. Microgravity experiments and theoretical analysis. Metall. Mater. Trans. A. 1998, 29A, 1697-1706. 

In the next paper Surfactants Effects on Mass Transfer in Liquid-Liquid Systems Dr Alcina Mendes (Imperial College, UK) reviews the work done by herself and co-workers on the effect of surfactants on mass transfer in binary and ternary liquid-liquid systems. The selected organic-aqueous interfaces has been visualised during the mass transfer process in the presence of ionic and non-ionic surfactants. Results obtained in laboratory and under microgravity conditions are reported. The most significant finding is that surfactants in some cases can induce or increase convection. The latter enhance the mass transfer rate as compared to the Pick s law. The latter means that surfactants can be used to manipulate interfacial stability and particularly in space applications. 

Jones, D.E.H. and Walter, U.J. (1998) The silicate garden reaction in microgravity a fluid interfacial instability. J. Colloid Interface Sci., 203, 286-293. 

If a system lacks an interface between different fluids, such a monomer/air interface, then only buoyancy-driven convection will occur. If a free interface exists, then we will see that gradients in the interfacial tension can cause fluid motion — a process called Surface-Tension Induced Convection or Marangoni convection. This will be especially important in "microgravity". (How the condition of apparently zero gravity is achieved is discussed in chapter 2.)... 

FIGURE 14.2 Comparison of Liquid/Vapor Interface in (a) 1-g Environment and (b) Microgravity Environment. 

As illustrated in Figure 14.2b, the velocity profile for Region 2 in microgravity is assumed to be a fully developed parabolic profile, similar to the profile for Region 2 in the 1-g case. However, in the microgravity model, the average velocity value is the interface velocity, and not the exit velocity ... 

FIGURE 14.4 Comparison of Microgravity Liquid/Vapor interface in (a) Case B and (b) Case C. 

As shown in Figure 14.5, the normalized interface velocity rapidly decays as the LAD is exposed to vapor. With an interface velocity profile, ullage bubble growth model, cryogenic bubble point model, and analytical flow model, the velocity and pressure fields inside the LAD can be determined in microgravity. The velocity can also be visualized as a function of time as the tank is drained. 

DreyerM, Delgado A, Rath H. (1994) Capillary rise of liquid between parallel plates under microgravity. J Colloid Interface Sci 163 158-168. 

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