V. V. Krotov

On the Theory of Heat Conductivity, Electrical Conductivity, and Hydraulic Conductivity of Polydisperse Polyhedral Foams and Highly Concentrated Emulsions

Rigorous formulas for the heat conductivity, electrical conductivity, and hydraulic conductivity of polydisperse polyhedral foams and highly concentrated emulsions are derived on the basis of the ideas recently formulated by one of the authors, with the structure of Plateau borders and films represented in the form of hierarchic series.

Optical Method of Studying Foam Structural Stability

A new method of studying the foam stability based on the determination of the evolution time of foam cell at a given level of foam column is developed. The method is based on optical measurements that allow one to determine the main structural parameters of a foam. Experimental results are reported for sodium dodecyl sulfate solutions.

On the Modulus of Transverse Elasticity of Thin Foam Films

The theory of transverse elasticity of thin foam films is formulated under the conditions when the action of Gibbs elasticity is excluded. The theory predicts the presence of maxima of the modulus of transverse elasticity and film thickness near the critical micellization concentration as functions of the content of surfactant at a given disjoining pressure. Theoretical conclusions are confirmed experimentally by measuring film thickness at various heights of equilibrium foam column.

Method of touching drops: a new method for measuring the surface and interfacial tension of liquids

A new technique for measuring the surface and interfacial tension of liquids, the method of touching drops, is elaborated. The method requires measuring only a single parameter, the height of one of the drops formed, and is suitable for studying surfactant solutions. The theoretical fundamentals of the method, the computer algorithm for the calculations, the apparatus construction, and the experimental procedure are described.

Four laws of energy and momentum losses during capillary jet disintegration

Very simple and strict equations thoroughly characterizing the effect of capillary self-retardation of a droplet in the process of its detachment from the continuous part of a disintegrating jet, this effect having been revealed earlier and then confirmed experimentally, are derived from Newton’s laws of momentum and energy variations. Equations describe four total (over the time of disintegration) losses of the momentum, translational energy, total energy, and internal energy per unit mass of a liquid. As the rate of an initial cylindrical jet rises, the loss of momentum and internal energy unlimitedly decreases, the loss of translational energy limitedly rises, and the loss of total energy remains unchanged.

On the theory of capillarity of three-phase disperse systems

The distribution of a liquid over the height of a vertical column (with the lower part immersed in a wetting liquid) of close-packed solid spherical particles is studied. For such a system, the equilibrium distribution of the liquid in the three-phase region with a high expansion ratio is shown to be described by the same formulas as for a two-phase disperse system (high-expansion monodisperse foam), but the radius of spherical particles is used in the three-phase case instead of the radius of polyhedral foam cells of equivalent volume. Linear, surface, and bulk capillary forces acting in model three-phase systems with liquid “collars” between close-packed spherical particles are considered. Specific forces of capillary adhesion are shown to be independent of the specific volume of the liquid if it is small enough, but they increase with decreasing size of the particles. In the two-dimensional case with hexagonal packing of particles, these forces are also independent of the particle size.