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Wetting Phenomena and Contact Angles
Published in Van P. Carey, Liquid-Vapor Phase-Change Phenomena, 2020
If the pressure inside the bubble is Pb and the liquid-gas interface is flat, then at equilibrium, Pb must balance the liquid pressure across the interface in the liquid. If δ is large, then the pressure across the interface, Pf , will just equal the local ambient pressure in the liquid Pl = Patm + ρl gzh (note that zh is distance measured downward from the liquid-air interface). However, if the housing is brought very close to the solid surface, the pressure inside the bubble must not only balance the ambient liquid pressure Pl, but it must also counteract the attractive forces between the liquid molecules and the solid surface, which otherwise would maintain a thicker film of liquid on the surface. When the film is very thin, these attractive forces act to pull liquid into the layer as if the pressure in the layer were reduced below the ambient pressure Pl by an amount Pd, which is known as the disjoining pressure. By convention, if the affinity of the liquid for the solid draws liquid into the film, Pd is taken to be negative.
Wetting Phenomena and Contact Angles
Published in Van P. Carey, Liquid-Vapor Phase-Change Phenomena, 2018
The disjoining pressure is primarily a function of the film thickness and the nature of the liquid and solid surface. Because, for a given solid-liquid system, the disjoining pressure is only a function of film thickness δ, Eq. (3.45) can be written () dPddδ(dδdz) = –ρlg
Investigation of rock and fluid interactions during engineered water flooding in dolomite reservoir rocks
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Mir Saeid Safavi, Mohsen Masihi, Ali Akbar Safekordi, Shahab Ayatollahi, Saeid Sadeghnejad
where, Pc is the capillary pressure between two phases, defined as the non-wetting phase pressure minus the wetting phase pressure, is the interfacial tension of the two fluids, H is the mean curvature of the interface, and is the disjoining pressure. The disjoining pressure is a force that separates two interfaces and has a major role to the stability of the film fluid on the solid surface (Takahashi and Kovscek 2010). The disjoining pressure denoted by is defined as the sum of the intermolecular forces i.e. the London-vander Waals interaction (), the electrostatic double-layer interaction (), and the structural interaction () (Busireddy and Rao 2004);
Experimental investigation on the stability of foam using combination of anionic and zwitterionic surfactants: A screening scenario to obtain optimum compound
Published in Journal of Dispersion Science and Technology, 2023
Samiye Shahmarvand, Forough Ameli, Saber Mohammadi, Kazem Hossein Abad Fouladi
Foam stability is essential for efficient oil displacement and is influenced by factors such as surface tension, viscosity, and the disjoining pressure. The disjoining pressure is determined by the difference in pressure between the gas and liquid phases within a film and is affected by the thickness of the film. The DLVO theory explains that disjoining forces arise from electrostatic and van der Waals potentials, with the latter dominating in the absence of surfactant. Upon the introduction of surfactant, the repulsive force from the electrical double-layer stabilizes the lamellae. The ionic strength of the aqueous solution is one of many parameters that affect foam stabilization.[44]
Rheological characterization and prediction model of compressed air Class A foam
Published in Journal of Dispersion Science and Technology, 2022
Yuyan Fan, Yongkai Wang, Hong Gao, Quansheng Lin, Bo Song, Jianjun Xia
The compressed air Class A foams are non-Newtonian fluids with significant shear thinning. The relationship between foam apparent viscosity and structural damage coefficient at different shear rates is shown in Figure 9(a). The apparent viscosity of foams increased with the structural damage factor at the same shear rate. In other words, apparent viscosity of foams increased continuously during the drainage process. Moreover, the smaller the shear rate, the more pronounced the apparent viscosity change. Microscopically, the surge of disjoining pressure in the foam films is the main cause of apparent viscosity increasing. Disjoining pressure increases with the thickness of the liquid film when the thickness is between 5-10 nm but decreases with the further increase of the film thickness (above 10 nm).[43] In this experiment, the thickness of films is always above 10 nm. Thus, the thickness of films gradually became thinner during the drainage process, which causes apparent viscosity increases with structural damage coefficient at the same shear rate. In addition, the internal friction between the bubbles is small at high liquid volume fraction and thick liquid films at the early stage, leading to lower apparent viscosity. With the change of the foam structure, especially the appearance of polygonal foams, the elasticity and strength of the foam are enhanced during the drainage process, resulting in a higher internal friction between the bubbles, thus the apparent viscosity of foams increases. Moreover, it exists a difference in the distribution of liquid phase in the films and PBs, which makes the foam easier to deform and show smaller apparent viscosity under shear stress. The structure and size of bubbles are homogenized in the drainage process, which also increases the apparent viscosity of the foam.