Capillary deformable

Capillary Deformation. As water evaporates, curvature of the air-water interface causes a large negative capillary pressure in the water. Atmospheric pressure... 

Receding Waterfront. If significant deformation occurs by capillary deformation, but the voids remain in the film as water recedes, an inhomogeneous film is observed. The deformation is completed by either the dry or moist sintering mechanisms referred to above. This was first identified by Keddie and termed stage 11 ... 

When designing a film forming latex dispersion, the properties to consider are the final mechanical properties of the film, as well as the ease of film formation The mechanical properties required, as well as the environment of operation will dictate the polymers suitable for the coating and may well dictate the glass transition temperature of the polymer. The crack points alluded to earlier correspond to the transition from capillary deformation to the receding water front regime. Therefore, a value of X less than 100 will ensure a well-formed film. 

The main goal of this contribution is a review of the latest achievements in the theoretical investigation of the capillary force and the relevance of this work in the interpretation of some recent experiments. When possible we will dispense with the heavy mathematical apparatus involved in the calculations and provide instead a justification of the results based on the analogy of capillary deformation with 2D electrostatics and on rough estimates the detailed computations can be found in the bibliography. Additionally, we will be concerned only with static properties, that is, the interface and the particles are always assumed to be in equilibrium dynamical phenomena are out of the scope. 

An example of interaction stiffness and force curves for a Si surface with a native oxide at 60% relative humidity (RH) is shown in Fig. 12 [104]. The stiffness and force data show an adhesive interaction between the tip and substrate. The hysteresis on retraction is due to a real change in contact area from surface oxide deformation and is not an experimental artifact. The adhesive force observed during retraction was consistent with capillary condensation and the surface energy measured from the adhesive force was close to that of water. 

In filled thermometers the thermal expansion of a gas or a liquid is transmitted through a thin capillary tube to a bellows or helix, where the deformation indicates the temperature. The temperature range of filled thermometers is very wide, approximately -200 to +700 °C. They are extremely robust but are not very high in accuracy. The application is mainly for process instrumentation and as stand-alone control devices. 

H. G. J. Mol, H.-G. Janssen, C. A. Cramers and U. A. Th Brinkman, On-line sample enrichment-capillary gas clir omatography of aqueous samples using geometr ically deformed open-tubular extraction columns , 7. Microcolumn Sep. 7 247-257 (1995). 

To understand how the dispersed phase is deformed and how morphology is developed in a two-phase system, it is necessary to refer to studies performed specifically on the behavior of a dispersed phase in a liquid medium (the size of the dispersed phase, deformation rate, the viscosities of the matrix and dispersed phase, and their ratio). Many studies have been performed on both Newtonian and non-Newtonian droplet/medium systems [17-20]. These studies have shown that deformation and breakup of the droplet are functions of the viscosity ratio between the dispersity phase and the liquid medium, and the capillary number, which is defined as the ratio of the viscous stress in the fluid, tending to deform the droplet, to the interfacial stress between the phases, tending to prevent deformation ... 

The influence of the vi.scosity ratio 8 on the flow behavior in a capillary was discussed by Rumscheidt and Mason [lOj. They pointed out that when the viscosity ratio is small, the dispersed droplets are drawn out to great lengths but do not burst, and when the viscosity ratio is of the order of unity, the extended droplets break up into smaller droplets. At very high viscosity ratios, the droplets undergo only very limited deformations. This mechanism can explain our observations and supports our theoretical analysis assumptions, summarized previously as points 2, 3, and 4. 

For nonadhering bodies in contact in the presence of capillary condensation, the previous result for rigid solids is found to apply more generally to systems of small, hard, but deformable spheres in contact in vapor near saturation ... 

In contact mode, liquids are virtually impossible to image, because the mechanical contact of the tip deforms the surface. It is also possible for the liquid to wet the tip and form a capillary neck around it. 

Nanometric Solid Deformation of Soft Materials in Capillary Phenomena... 

In this chapter, we will review the consequences of solid deformation in the kinetics of the spreading of a liquid on a soft material, in both wetting and dewetting modes. The influence of solid deformation induced by the liquid surface tension will be shown in the case of a liquid drop placed on a soft elastomeric substrate and in the case of an unstable liquid layer dewetting on a soft rubber. The impact of solid deformation on the kinetics of the wetting or dewetting of a liquid will be analyzed theoretically and illustrated by a few concrete examples. The consequences of solid deformation in capillary flow will be also analyzed. 

Laplace s pressure produces the capillary rise inside a small tube. We propose to examine now the consequences of the solid deformation in capillary flow. 

The ratio of deforming viscous forces to resisting interfacial tension forces in the case of droplets is the capillary number, Ca. Similarly, the ratio of viscous to cohesive forces in agglomerates is the fragmentation number, Fa. 

The tensor L defines the character of the flow. The capillary number for the drop deformation and breakup problem is... 

The degree of deformation and whether or not a drop breaks is completely determined by Ca, p, the flow type, and the initial drop shape and orientation. If Ca is less than a critical value, Cacri the initially spherical drop is deformed into a stable ellipsoid. If Ca is greater than Cacrit, a stable drop shape does not exist, so the drop will be continually stretched until it breaks. For linear, steady flows, the critical capillary number, Cacrit, is a function of the flow type and p. Figure 14 shows the dependence of CaCTi, on p for flows between elongational flow and simple shear flow. Bentley and Leal (1986) have shown that for flows with vorticity between simple shear flow and planar elongational flow, Caen, lies between the two curves in Fig. 14. The important points to be noted from Fig. 14 are these ... 

Flow properties of macroemulsions are different from those of non-emulsified phases 19,44). When water droplets are dispersed in a non-wetting oil phase, the relative permeability of the formation to the non-wetting phase decreases. Viscous energy must be expended to deform the emulsified water droplets so that they will pass through pore throats. If viscous forces are insufficient to overcome the capillary forces which hold the water droplet within the pore body, flow channels will become blocked with persistent, non-draining water droplets. As a result, the flow of oil to the wellbore will also be blocked. 

Contributions to pressure drop have also been studied by lattice Boltzmann simulations. Zeiser et al. (2002) postulated that dissipation of energy was due to shear forces and deformational strain. The latter mechanism is usually missed by capillary-based models of pressure drop, such as the Ergun equation, but may be significant in packed beds at low Re. For a bed of spheres with N — 3, they found that the dissipation caused by deformation was about 50% of that... 

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