Surface tension

About: Surface tension is a research topic. Over the lifetime, 25410 publications have been published within this topic receiving 695471 citations.

Method of centrifugally casting thin edged corneal contact lenses

Abstract: A CORNEAL CONTACT LENS IS MADE BY POLYMERIZING A CATALYZED MIXTURE OF ACRYLATES AND/OR METHACRYLATES OF POLYHYDRIC ALCOHOLS WITH A WATER MISCIBLE SOLVENT IN A MOLD CAVITY HAVING A SPHERICALLY CONCAVE BOTTOM SURFACE AND BEING ROTATED ABOUT AN AXIS PERPENDICUAR TO THAT SURFACE AT A SPEED TO PRODUCE AN EXPOSED CONCAVE SURFACE OF THE POLYMERIZATION MIXTURE, WHICH IS SUFFICIENTLY DIFFERENT FROM A PARABOLOID SHAPE BECAUSE OF SURFACE TENSION EFFECTS TO HAVE A CENTER EFFECTIVE AS A CORRECTIVE LENS.

Dilatational and Shear Elasticity of Gel-like Protein Layers on Air/Water Interface

Abstract: We propose a simple new method for measuring the surface shear elasticity modulus (μ) together with the dilatational modulus (K) of gel-like protein layers on an air/water boundary. The stress response to compression/expansion of the interface in a Langmuir trough is measured at two different orientations of a Wilhelmy plate, collateral and perpendicular to the movable barrier in the trough. The interfacial tension is a tensorial quantity, whence the measured values depend on the direction of the length along which the stress acts. The fact that the deformation in the trough is uniaxial, i.e., a combination of dilatation and shear, is used to determine the respective two elastic moduli (K, μ). The experiment demonstrates that adsorbed layers of β-lactoglobulin (BLG), when subjected to small deformations, exhibit a predominantly elastic rheological behavior. This proves the existence of the two-dimensional gel, as a result from partial denaturation and unfolding accompanied with entanglement of the protein...

Liquid drops and surface tension with smoothed particle applied mechanics

Abstract: Smoothed particle applied mechanics (SPAM), also referred to as smoothed particle hydrodynamics, is a Lagrangian particle method for the simulation of continuous flows. Here we apply it to the formation of a liquid drop, surrounded by its vapor, for a van der Waals (vdW) fluid in two dimensions. The cohesive pressure of the vdW equation of state gives rise to an attractive, central force between the particles with an interaction range which is assumed to exceed the interaction range of all the other smoothed forces in the SPAM equations of motion. With this assumption, stable drops are formed, and the vdW phase diagram is well reproduced by the simulations. Below the critical temperature, the surface tension for equilibrated drops may be computed from the pressure excess in their centers. It agrees very well with the surface tension independently determined from the vibrational frequency of weakly excited drops. We also study strongly deformed drops performing large-amplitude oscillations, which are reminiscent of the oscillations of a large ball of water under microgravity conditions. In an appendix we comment on the limitations of SPAM by studying the violation of angular momentum conservation, which is a consequence of noncentral forces contributed by the full Newtonian viscous stress tensor.

Three-dimensional lattice Boltzmann model for immiscible two-phase flow simulations.

Abstract: We present an improved three-dimensional 19-velocity lattice Boltzmann model for immisicible binary fluids with variable viscosity and density ratios. This model uses a perturbation step to generate the interfacial tension and a recoloring step to promote phase segregation and maintain surfaces. A generalized perturbation operator is derived using the concept of a continuum surface force together with the constraints of mass and momentum conservation. A theoretical expression for the interfacial tension is determined directly without any additional analysis and assumptions. The recoloring algorithm proposed by Latva-Kokko and Rothman is applied for phase segregation, which minimizes the spurious velocities and removes lattice pinning. This model is first validated against the Laplace law for a stationary bubble. It is found that the interfacial tension is predicted well for density ratios up to 1000. The model is then used to simulate droplet deformation and breakup in simple shear flow. We compute droplet deformation at small capillary numbers in the Stokes regime and find excellent agreement with the theoretical Taylor relation for the segregation parameter β=0.7. In the limit of creeping flow, droplet breakup occurs at a critical capillary number 0.35