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Oil is usually produced in the form of water-in-oil (w/o) stable emulsions due to the presence of natural stabilizing components in the oil phase. Oil and water phases need to be separated by coalescence of the dispersed drops. Different strategies are used to destabilize the produced emulsions and promote coalescence. In this work, we propose and qualitatively evaluate a new method to enhance water drop coalescence in stable water–oil emulsions. First, stable water-in-oil emulsions were prepared using a nonionic surfactant (Span 80) dissolved in mineral oil (Primol 352). Visualization experiments showed that the emulsion stability comes from the formation of small droplets along the water drop interface by spontaneous emulsification, leading to a droplet-rich rough interface. Water drops that are brought into contact after the formation of the rough interface do not coalesce, leading to very stable emulsions. Later, the water drops with a droplet-rich interface are passed through a capillary tube with a constriction smaller than the drop diameter. As the drop flows through the capillary throat, its surface area is increased and a strong shear stress is imposed along its surface, removing the droplets from the interface, which favors coalescence. A free water phase formed by water drop coalescence can be observed after flowing the stable water-in-oil emulsion through the constricted capillary. [ABSTRACT FROM AUTHOR]

We present a computational study of free surface flows with rheologically complex interfaces in the film formation region of a slot coater. The equations of motion for incompressible Newtonian liquids in the bulk flow are coupled with the Boussinesq–Scriven constitutive equation for viscous interfaces in the dynamic boundary condition at the liquid-air free surface and solved with a mixed finite element method. We show that the interfacial viscosity plays a major role in the flow dynamics and operating limits of slot coating. We find that the interfacial viscosity makes viscous interfaces generally stiffer than their simple counterparts, affecting both the normal and the tangential stress jumps across the free surface. As a result, the interfacial viscosity counteracts the meniscus retraction and slows down the film flow, increasing the development length over the substrate and changing the topology of the recirculation region in the coating bead. Remarkably, we also find that the interfacial viscosity can substantially broaden the operating boundaries of the coating window associated with the low-flow limit, suggesting that surface-active components can be suitably designed to allow for the stable production of thinner films at higher speeds by tuning interfacial material properties in slot coating applications. [ABSTRACT FROM AUTHOR]

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MUSE-based emission-line maps of the spiral galaxy NGC 4030 reveal the existence of unresolved sources with forbidden line emission enhanced with respect to those seen in its own H  ii regions. This study reports our efforts to detect and isolate these objects and identify their nature. Candidates are first detected as unresolved sources on an image of the second principal component of the H β, [O  iii ] 5007, H α, [N  ii ] 6584, [S  ii ] 6716, 6731 emission-line data cube, where they stand out clearly against both the dominant H  ii region population and the widespread diffuse emission. The intrinsic emission is then extracted accounting for the highly inhomogeneous emission-line 'background' throughout the field of view. Collisional to recombination line ratios like [S  ii ]/H α, [N  ii ]/H α, and [O  i ]/H α tend to increase when the background emission is corrected for. We find that many (but not all) sources detected with the principal component analysis have properties compatible with supernova remnants (SNRs). Applying a combined [S  ii ]/H α and [N  ii ]/H α classification criterion leads to a list of 59 sources with SNR-like emission lines. Many of them exhibit conspicuous spectral signatures of SNRs around 7300 Å, and a stacking analysis shows that these features are also present, except weaker, in other cases. At nearly 30 Mpc, these are the most distant SNRs detected by optical means to date. We further report the serendipitous discovery of a luminous (MV ∼ −12.5), blue, and variable source, possibly associated with a supernova impostor. [ABSTRACT FROM AUTHOR]

New species of insect‐specific viruses (ISV) have been reported worldwide. In the present study, the complete genome of Culex flavivirus (CxFV) and partial sequences of other ISVs in Culex quinquefasciatus Say 1823 females (n = 3425) sampled in 200 urban areas census tracts of Cuiaba, state of Mato Grosso, were identified via reverse transcriptase‐polymerase chain reaction for a NS5 region of flaviviruses, nucleotide and high‐throughput sequencing, and viral isolation in C6/36 cells. CxFV was detected in 16 of 403 mosquito pools; sequences found in the study presented a high similarity with isolates from São Paulo, Brazil and other countries in Latin American that belong to genotype II, supporting the geographical influence on CxFV evolution. The monthly maximum likelihood estimation for CxFV ranged from 1.81 to 9.94 per 1000 mosquitoes. In addition to the CxFV complete genome, one pool contained an ORF1 sequence (756 bp) that belongs to a novel Negevirus from the Sandewavirus supergroup most similar to the Santana virus (77.1%) and another pool presented an RNA‐dependent RNA polymerase sequence (1081 bp) of a novel Rhabdovirus most similar to Wuhan mosquito virus 9 (44%). After three passages in C6/36 cells, only CxFV was isolated from these co‐infected pools. The importance of ISVs relies on their possible ability to interfere with arbovirus replication in competent vectors. [ABSTRACT FROM AUTHOR]

Snap-off of bubbles and drops in constricted capillaries occurs in many different situations, from bio-fluid to multiphase flowin porous media. The breakup process has been extensively analyzed both by theory and experiments, but most work has been limited to pure interfaces, at which the surface stress is isotropic and fully defined by the interfacial tension and interface curvature. Complex interfaces may present viscous and elastic behavior leading to a complex stress state that may change the dynamics of the interface deformation and breakup. We extend the available asymptotic model based on lubrication approximation to include elastic interfacial stress. Drop breakup time is determined as a function of the capillary geometry and liquid properties, including the interfacial elastic modulus. Results show that the interfacial elasticity has a stabilizing effect by slowing down the growth of the liquid collar, leading to a larger break-up time. This stabilizing effect has been observed experimentally in different, but related flows [Alvarado et al., "Interfacial visco-elasticity of crude oil-brine: An alternative EOR mechanism in smart waterflooding," in SPE-169127 Improved Oil Recovery Symposium (Society of Petroleum Engineers, 2014)]. [ABSTRACT FROM AUTHOR]

The article presents a study which focuses on the creation of an asymptotic model of the three-dimensional (3D) flow of petroleum in a progressing cavity pump (PCP). It highlights the complexity of computing the flow inside a PCP which makes the use of computational fluid dynamics (CFD) an essential tool in petroleum engineering. It states that the model was developed for Newtonian fluid which utilized the lubrication theory to reduce the 3D Navier-Stokes equations.

The article reviews the viscocapillary model of slide coating flow and investigates the effect of different operating parameters on the flow and the limits of the process. It outlines the steps of the derivation of film profile equation of the flow down a slide. The parameters evaluated include domain length, mesh, matching conditions assignments and location. It compares the predictions made using the viscocapillary model of slide coating with the solution of the full two-dimensional Novier-Stokes equation in order to test the accuracy of the model.

This article deals with a study that examined the snap-off of large infinite liquid drops immersed in a continuous liquid as they flow through a cylindrical constriction. To determine the effect of the viscosity ratio of the two phases on the snap-off mechanism, different emulsions were used. Results of the study showed that the accumulation of the continuous phase can lead to the growth of a collar structure until the drop breaks up. It also found that surface tension driven forces are weaker than viscous forces in flows at high capillary number.

Flow in annular space occurs in drilling operation of oil and gas wells. The correct prediction of the flow of the drilling mud in the annular space between the well wall and the drill pipe is essential to determine the variation in the mud pressure within the wellbore, the frictional pressure drop, and the efficiency of the transport of the rock drill cuttings. A complete analysis of this situation is extremely complex: the inner cylinder is usually rotating, the wellbore wall will depart significantly from cylindrical, the drill pipe is eccentric, and the eccentricity varies along the well A complete analysis of this situation would require the solution of the three-dimensional momentum equation and would be computationally expensive and complex. Models available in the literature to study this situation do consider the rotation of the inner cylinder and the non-Newtonian behavior of the drilling fluids, but assume the relative position of the inner with respect to the outer cylinders fixed, i.e., they neglect the variation of the eccentricity along the length of the well and the flow is considered to be fully developed, This approximation leads to a two-dimensional model to determine the three components of the velocity field in a cross-section of the annulus. The model presented in this work takes into account the variation of the eccentricity along the well; a more appropriate description of the geometric configuration of directional wells. As a consequence, the velocity field varies along the well length and the resulting flow model is three-dimensional Lubrication theory is used to simplify the governing equations into a two-dimensional differential equation that describes the pressure field. The results show the effect of the variation of the eccentricity on the friction factor, maximum and minimum axial velocity in each cross section, and the presence of azimuthal flow even when the inner cylinder is not rotating. [ABSTRACT FROM AUTHOR]

We analyze the liquid-liquid displacement in capillary tubes. The goal is to determine the amount of displaced liquid that remains attached to the tube wall and the configuration of the liquid-liquid interface at different operating parameters. The study encompasses both numerical and experimental approaches. The finite element method is used to solve the governing equations and, in order to validate the predictions, visualization experiments are performed to capture images of the interface. The numerical results were obtained for the assumption of negligible inertia, and the effects of viscosity ratio and capillary number are investigated. The predictions and experimental observations are in good agreement. [ABSTRACT FROM AUTHOR]

Circular Couette flow of inelastic shear-thinning materials in annuli is examined. The curved streamlines of the circular Couette flow can cause a centrifugal instability leading to toroidal vortices, well known as Taylor vortices. The presence of these vortices changes the hydrodynamic and heat transfer characteristics of the processes at which this type of flow occurs. Therefore, it is quite important to be able to predict the onset of instability. Most of the available theoretical and experimental analyses are for Newtonian and viscoelastic (dilute polymeric solutions) liquids. In this work, the effect of the shear-thinning behavior of high concentration suspensions on the onset of the Taylor vortices is determined theoretically by solving the conservation equations, constructing the solution path as the inner cylinder speed rises and searching for the critical conditions. This procedure avoids the need for a stability analysis of the flow and the solution of an eigenproblem. The differential equations were solved by the Galerkin/finite-element method and the resulting set of nonlinear algebraic equations, by Newton's method. [ABSTRACT FROM AUTHOR]

Colloidal clay in water suspensions are known to exhibit a multitude of bulk phases depending on initial colloidal concentration and ionic strength, and examples of this include repulsive Wigner colloidal glasses at low ionic strength and attractive gels at higher ionic strength due to screened electrostatic forces by the electrolyte. From confocal Raman microscopy combined with elasticity measurements, we infer that clay trapped at quasi two-dimensional interfaces between oil and water also exhibit confined glass-like or gel-like states. The results can be important for the preparation of particles stabilized colloidal emulsions or colloidal capsules, and a better understanding of this phenomenon may lead to new emulsion or encapsulation technologies. [ABSTRACT FROM AUTHOR]

This work investigates the onset of wetting failure for displacement of Newtonian fluids in parallel channels. A hydrodynamic model is developed for planar geometries where an advancing fluid displaces a receding fluid along a moving substrate. The model is evaluated with three distinct approaches: (i) the low-speed asymptotic theory of Cox [J. Fluid Mech. 168, 169-194 (1986)], (ii) a one-dimensional (1D) lubrication approach, and (iii) a two-dimensional (2D) flow model solved with the Galerkin finite element method (FEM). Approaches (ii) and (iii) predict the onset of wetting failure at a critical capillary number Cacrit, which coincides with a turning point in the steady-state solution family for a given set of system parameters. The 1D model fails to accurately describe interface shapes near the three-phase contact line when air is the receding fluid, producing large errors in estimates of Cacrit for these systems. Analysis of the 2D flow solution reveals that strong pressure gradients are needed to pump the receding fluid away from the contact line. A mechanism is proposed in which wetting failure results when capillary forces can no longer support the pressure gradients necessary to steadily displace the receding fluid. The effects of viscosity ratio, substrate wettability, and fluid inertia are then investigated through comparisons of Cacrit values and characteristics of the interface shape. Surprisingly, the low-speed asymptotic theory (i) matches trends computed from (iii) throughout the entire investigated parameter space. Furthermore, predictions of Cacrit from the 2D flow model compare favorably to values measured in experimental air-entrainment studies, supporting the proposed wetting-failure mechanism. [ABSTRACT FROM AUTHOR]