Studies of the effects of gravitation on the behavior of fluids and the shapes of materials for the years 1977-1982 are reviewed, with a focus on ground-based research which complements and gives direction to experimentation in the reduced-gravity environment of space. Fluid-behavior topics discussed include crystal growth from melts and from vapor, dendritic solidification and casting, multiphase alloy solidification, electrophoresis, convection behavior, and special heat-flow considerations characteristic of the space environment. With regard to solids, such subjects as containerless positioning technology and its applications (in glass preparation, liquid drop and shell studies, nucleation experiments, and measurements of fundamental properties of molten reactants), liquid floating zones, solid self-deformation, and sedimentation and buoyancy effects are considered and illustrated.

Materials Processing in the Reduced-Gravity Environment of Space

The main effects on the dynamics of a liquid bridge due to the presence of an outer liquid, as occur in experiments using the Plateau-tank technique, are considered. The one-dimensional nonlinear model developed here allows us to perform the computation of both breaking processes and oscillatory motions of slender liquid bridges, although in this paper only the results concerning breaking processes are reported. Additionally, the oscillatory motions are studied both experimentally and by using a new linear model. Results from both sources show good agreement.

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The influence of the outer bath in the dynamics of axisymmetric liquid bridges

A one-dimensional inviscid slice model has been used to study numerically the influence of axial microgravity on the breaking of liquid bridges having a volume close to that of gravitationless minimum volume stability limit. Equilibrium shapes and stability limits have been obtained as well as the dependence of the volume of the two drops formed after breaking on both the length and the volume of the liquid bridge. The breaking process has also been studied experimentally. Good agreement has been found between theory and experiment for neutrally buoyant systems.

/pdf/numerical-and-experimental-study-of-the-dynamics-of-3d2v4lntxi.pdf

Numerical and experimental study of the dynamics of axisymmetric slender liquid bridges

In this paper the dynamics of axisymmetric liquid columns held by capillary forces between two circular, concentric, solid disks is considered. The problem has been solved by using a one‐dimensional model known in the literature as the Cosserat model, which includes viscosity effects, where the axial velocity is considered constant in each section of the liquid bridge. The dynamic response of the bridge to an excitation consisting of a small‐amplitude vibration of the supporting disks has been solved by linearizing the Cosserat model. It has been assumed that such excitation is harmonic so that the analysis has been performed in the frequency domain. The particular case of a cylindrical liquid bridge has been analytically studied and the transfer function has been calculated in the cases of oscillation of both disks (either in phase or in counterphase) or only of one of them. The resolution of the general formulation for a noncylindrical liquid bridge has been numerically made by using an implicit finite difference method. In this case, the influence of the volume of the liquid column and of the residual gravity level on the first resonance has been studied, and the results compared, for the inviscid case, with other potential models, both one and three dimensional. To demonstrate the usefulness of this theoretical model in predicting the vibrational behavior of axisymmetric viscous liquid bridges, some experiments have been performed by using the neutral buoyancy technique (also known as the Plateau technique) to simulate reduced gravity conditions, with good agreement between the results of the model and experiments.

/pdf/theoretical-and-experimental-study-of-the-vibration-of-2kuh21kvlr.pdf

Theoretical and experimental study of the vibration of axisymmetric viscous liquid bridges

We consider the problem of global stability of the rigid rotation of two fluids. The realized interfacial configurations minimize a potential. We derive the most general form of the potential in which the working of the contact line may be expressed as a potential. The resulting variational problem for the interfacial potential is solved when the contact-line conditions are prescribed and for coating flows in which the interface makes a tangent contact with the wetted rod. In the former case, good agreement with experiments is obtained except near lines of contact. This shows that a spinning rod interfacial tensiometer is viable. In the latter case of coating flow, we get good agreement with experiments when the effects of gravity are not too large. The problem of bifurcation of coating flow is discussed qualitatively and some experimental results are given. We show how bifurcating sequences fit well into our qualitative description of the solution which must minimize the interfacial potential as the angular velocity is increased. The last bifurcations lead to pendant drops on a rotating ‘ceiling’ under the influence of centripetal forces which replace gravity. The dynamics of rollers of oil in water, or part in water and part in air, are explained in terms of the wavelength dependence of rotating drops.

Stability of rigid motions and coating films in bicomponent flows of immiscible liquids

The dynamics of liquid drops rotating in another liquid were studied experimentally with an oil drop suspended in a neutral buoyancy tank. New stable shapes not predicted by the theory were observed.

/pdf/rotating-liquid-drops-plateaus-experiment-revisited-17k75d3vat.pdf

Rotating Liquid Drops: Plateaus Experiment Revisited

The nonaxisymmetric shapes of a rotating drop in an immiscible system were studied. Five basic families of shapes (axisymmetric, two-lobed, three-lobed, four-lobed, and toroidal) were observed. The sequence (axisymmetric to two-lobed to three-lobed to four-lobed to toroidal) seems to be linked to increasing spin-up velocity. For the axisymmetric case, direct comparisons of experiments with the theory of a free rotating drop were surprisingly good the equatorial area differs from theory by only 30%. Furthermore, the non-axisymmetric shapes are in good qualitative agreement with the theory, although the theory does not address the presence of an outer fluid.

https://ntrs.nasa.gov/api/citations/19820015571/downloads/19820015571.pdf

T. G. Wang

Papers

Rotating Liquid Drops: Plateaus Experiment Revisited

Non-axisymmetric shapes of a rotating drop in an immiscible system