Profile Of Meniscus Research Articles

Modeling the effect of surface forces on the equilibrium liquid profile of a capillary meniscus.

The equilibrium profile of a capillary meniscus formed under combined action of disjoining/conjoining and capillarity pressures is investigated. Attention is focused on the shape of a transition zone between a spherical meniscus and a thin liquid film in front of the meniscus. The Poisson-Boltzmann equation is used for calculations of electrostatic contribution to the disjoining/conjoining pressure and the liquid shape inside the transition zone. Both complete and partial wetting conditions are investigated.

Analysis and experimental study on oil leakage from fluid bearing

The fundamental characteristics of the taper seal used to prevent oil leakage from fluid bearings were analysed theoretically and investigated experimentally. The three-dimensional flow field was theoretically analysed using numerical fluid dynamics, and the profile of the oil meniscus was calculated using the balance between the pressure field and surface tension. The oil meniscus was experimentally investigated using a micro-focus laser microscope. Three triggers for oil leakage were identified: the oil contact angle on the sleeve surface becoming excessive, the convex portion of the meniscus profile extending beyond the edge of the sleeve, and cavitation occurring in the oil.

Numerical Analysis of Flow Behavior in Meniscus Region of Viscoelastic Dip Coating Flows

Flow behavior in a meniscus region in viscoelastic dip coating flows was numerically analyzed using a finite element method. The Phan-Thien Tanner (PTT) model was used as a constitutive equation. The problem considered was a flow around a rod withdrawn from a viscoelastic liquid in a cylindrical reservoir. Both the velocity and stress fields were analyzed for three kinds of PTT fluids that were different in elongational properties. The profile of meniscus formed between the moving rod and the liquid level became thinner at higher withdrawal velocity and for a fluid having stronger stretch-thickening property of elongational viscosity.

Dislocation loops in overheated free-standing smectic films.

Static and dynamic phenomena in overheated free-standing smectic-A films are studied theoretically. The work is based on a generalization, introduced recently by the authors, of de Gennes' theory for a confined presmectic liquid. In this approach, smectic ordering in an overheated film is caused by an intrinsic surface contribution to the film free energy and vanishes at some temperature depending on the number of layers. Here the theory is further generalized to study the dynamics of films with planar inhomogeneities. A static application is to determine the profile of the film meniscus and the meniscus contact angle, the results being compared with those of a recent study employing de Gennes' original theory. The dynamical generalization of the theory is based on a time-dependent Ginzburg-Landau approach. This is used to compare two modes for layer-thinning transitions in overheated free-standing films, namely, "uniform thinning" versus nucleation of dislocation loops. It is concluded that the nucleation mechanism dominates provided there is a sufficiently large pressure difference arising from meniscus curvature. Properties such as the line tension and velocity of a moving dislocation line are evaluated self-consistently by the theory.

Surface tensiometer utilizing laser-beam reflection at cylindrical liquid menisci

A surface tensiometer has been devised which is based on the mathematical solution, as a function of the surface tension of a liquid, of the profile of a cylindrical meniscus formed against a flat plate brought into contact with the free surface of a quiescent pool of the liquid. Only the angles of inclination of the meniscus at two arbitrary points are to be actually measured; the angle at each point is known accurately by observing the angle of reflection of a laser beam vertically irradiated onto the point. No knowledge of the contact angle on the plate is required. The tensiometer is suitable for the study of surface adsorption or of insoluble monolayers just the same as in the Wilhelmy plate method, but it is still superior to the Wilhelmy plate tensiometers and other conventional surface balances in its applicability to the measurements in an atmosphere completely insulated from the laboratory air. An apparatus is demonstrated that has been constructed primarily for the measurements of surface tensions of aqueous lithium bromide (LiBr) solutions with higher alcohol additives, i.e., working fluids of absorption heat pumps, under reduced pressures and elevated temperatures.

Static menisci on the outside of cylinders

The Laplace equation for the pressure drop across curved liquid-gas interfaces is applied to the solution of the profile of a static liquid meniscus on the outside of a wire of circular cross-section. The resulting differential equation is integrated numerically, an operation complicated by the existence of boundary conditions at two points making a trial-and-error solution necessary. The accuracy of the solution is substantiated by comparison of computed profiles with experiments in which menisci of a blue dye in water are photographed clinging to the outside of brass wires, whose diameters lie within the range of technological interest.