Capillaiy forces

The fc mulation concept was one of the aims of a large-scale research effort to develop enhanced oil recovety methods after the 1973 oil embargo. The goal was to inject a surfactant solution in the oil reservoir in order to overwhelm the capillaiy forces that trap the almost 75% of the original oil in place remaining in the reservoir after waterflooding. 

This section presented a three-dimensional, two-phase model of the cathode and anode of a PEM Fuel Cell. The mathematical model accounts for the liquid water flux inside the gas diffusion layers by viscous and capillaiy forces and hence is capable of predicting the amount of liquid water inside the gas diffusion layers. The physics of phase change are included in this model by prescribing the local evaporation term as a function of the amount of liquid water present and the level of undersaturation, whereas the condensation has been simplified to be a function of the level of oversaturation only. 

The strongest attractive disj rsion interaction is anticijmted in vacuum or air. However, force-distance measurements in air are dominated by capillaiy forces (22) due to the presence of contaminant layers on the surfaces of probe and sample. For this reason, force-distance measurements with SPM techniques are often performed in vacuum or under liquids. 

Calculate the size of the contributing forces to the adhesion of a 10-Mm-diameter glass sphere to an aluminum oxide surface, considering van der Waals, electrostatic, and capillaiy forces are present. Assume the charge on the system has been approximated at 10 C. 

A high electrical field apphed to a solvent emerging from a capillaiy canses the solvent to break into fine threads which disintegrate into small droplets. This phenomenon, nowadays called electrospray, was first described by Zeleny [44] in 1917. Uniform droplets in the 1-pm-lD range are prodnced in a breakup process that results from autorepulsion of the electrostatically charged surface, which overcomes the cohesive forces of surface tension. ESI nebnlization is widely used in painting, nuclear sciences, and spacecraft tluusters. 

Sample introduction is often accomplished by pressure injection, in which one end of the capillary is inserted into a vessel containing the sample. The vessel is then raised briefly above the level of the capillaiy to force sample into the tube. Alternatively, a vacuum is applied to the detector end of the tubing. Introduction may also be canned out by electroosmotic flow, which is described in the next section. 

There have been a number of attempts to revise and elaborate Brown s description of the film formation process [11,30]. For an overview of these approaches the reader is refmed to Mazur s review [25]. Perhaps the most important insight is that in a strict thermodynamic sense, there is no distinction betweai the osmostic pressure, II, and the mean capillaiy pressure, pc, which develops when the meniscus intercepts the surface of the particles. As the system becomes more concentrated, there will be some contribution of capillary forces to 11 before the particles come into contact and before the particle-water meniscus develops. Ultimately, n must converge to pc once the particles are in contact This continuity of n and Pc is the main point of the theoretical analysis by Crowley et al. [31], and they showed that when the osmotic pressure rises to little as 1% of the equilibrium vapour pressure of water, the force should be sufficirait to densify the film. 

The analysis reveals that the unstable axisymmetric mode for electrically driven, highly conducting jets is not a capillaiy mode but is mainly driven by electrical forces due to the interaction of chaiges on the jet. Both experiments and stability analysis elucidated that the axisymmetric Instability with a high growth rate can be seen in practice when the electrical force is effectively coupled with viscoelastic forces. ... 

Already in the eighteenth century it was realized that the capillary effect of fluids must arise from attractive forces between the constituents of matter, the molecules. This realization led to the idea that examination of the capillaiy effects could tell something about the attractive forces and possibly also about the molecules. Also modem physicists are interested in the explanation of the capillaiy phenomena in terms of intermolecular forces. This chapter highlights some of the applications of the square gradient theory of van der Waals [1] in modeling the behaviour of fluids near interfaces. For a more extensive discussion of this theoiy we refer to Rowlinson and Widom [2]. 

Thus, the finer the capillaiy tube, the higher the water will rise. The vertical equilibrium between capDlaty forces and gravitational force determines the height of the capiUaiy fringe in an oil reservoir (or any other fluid reservoir). Equation (2.83) contains two types of properties ... 

I 7 Intetfacial Forces Between Fluid Inteijaces and Across Thin Films AP Capillaiy... 

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