Academic literature on the topic 'Fluids near interfaces'

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Journal articles on the topic "Fluids near interfaces"

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Daher, Ali, Amine Ammar, and Abbas Hijazi. "Nanoparticles migration near liquid-liquid interfaces using diffuse interface model." Engineering Computations 36, no. 3 (April 8, 2019): 1036–54. http://dx.doi.org/10.1108/ec-03-2018-0153.

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Purpose The purpose of this paper is to develop a numerical model for the simulation of the dynamics of nanoparticles (NPs) at liquid–liquid interfaces. Two cases have been studied, NPs smaller than the interfacial thickness, and NPs greater than the interfacial thickness. Design/methodology/approach The model is based on the molecular dynamics (MD) simulation in addition to phase field (PF) method, through which the discrete model of particles motion is superimposed on the continuum model of fluids which is a new ide a in numerical modeling. The liquid–liquid interface is modeled using the diffuse interface model. Findings For NPs smaller than the interfacial thickness, the results obtained show that the concentration gradient of one fluid in the other gives rise to a hydrodynamic drag force that drives the NPs to agglomerate at the interface. Whereas, for spherical NPs greater than the interfacial thickness, the results show that such NPs oscillate at the interface which agrees with some experimental studies. Practical implications The results are important in the field of numerical modeling, especially that the model is general and can be used to study different systems. This will be of great interest in the field of studying the behavior of NPs inside fluids and near interfaces, which enters in many industrial applications. Originality/value The idea of superimposing the molecular dynamic method on the PF method is a new idea in numerical modeling.
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Gouin, Henri, and Pierre Seppecher. "Temperature profile in a liquid–vapour interface near the critical point." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2204 (August 2017): 20170229. http://dx.doi.org/10.1098/rspa.2017.0229.

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Thanks to an expansion with respect to densities of energy, mass and entropy, we discuss the concept of thermocapillary fluid for inhomogeneous fluids. The non-convex state law valid for homogeneous fluids is modified by adding terms taking account of the gradients of these densities. This seems more realistic than Cahn and Hilliard’s model which uses a density expansion in mass-density gradient only. Indeed, through liquid–vapour interfaces, realistic potentials in molecular theories show that entropy density and temperature do not vary with the mass density as it would do in bulk phases. In this paper, we prove using a rescaling process near the critical point, that liquid–vapour interfaces behave essentially in the same way as in Cahn and Hilliard’s model.
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Daher, Ali, Amine Ammar, Abbas Hijazi, and Lazhar Benyahia. "Effect of Shear Flow on Nanoparticles Migration near Liquid Interfaces." Entropy 23, no. 9 (August 31, 2021): 1143. http://dx.doi.org/10.3390/e23091143.

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The effect of shear flow on spherical nanoparticles (NPs) migration near a liquid–liquid interface is studied by numerical simulation. We have implemented a compact model through which we use the diffuse interface method for modeling the two fluids and the molecular dynamics method for the simulation of the motion of NPs. Two different cases regarding the state of the two fluids when introducing the NPs are investigated. First, we introduce the NPs randomly into the medium of the two immiscible liquids that are already separated, and the interface is formed between them. For this case, it is shown that before applying any shear flow, 30% of NPs are driven to the interface under the effect of the drag force resulting from the composition gradient between the two fluids at the interface. However, this percentage is increased to reach 66% under the effect of shear defined by a Péclet number Pe = 0.316. In this study, different shear rates are investigated in addition to different shearing times, and we show that both factors have a crucial effect regarding the migration of the NPs toward the interfacial region. In particular, a small shear rate applied for a long time will have approximately the same effect as a greater shear rate applied for a shorter time. In the second studied case, we introduce the NPs into the mixture of two fluids that are already mixed and before phase separation so that the NPs are introduced into the homogenous medium of the two fluids. For this case, we show that in the absence of shear, almost all NPs migrate to the interface during phase separation, whereas shearing has a negative result, mainly because it affects the phase separation.
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Steytler, David C. "Microemulsions in near-critical fluids." Current Opinion in Colloid & Interface Science 1, no. 2 (April 1996): 236–40. http://dx.doi.org/10.1016/s1359-0294(96)80009-4.

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Scholz, Christian, Anton Ldov, Thorsten Pöschel, Michael Engel, and Hartmut Löwen. "Surfactants and rotelles in active chiral fluids." Science Advances 7, no. 16 (April 2021): eabf8998. http://dx.doi.org/10.1126/sciadv.abf8998.

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Surfactant molecules migrate to interfaces, reduce interfacial tension, and form micelles. All of these behaviors occur at or near equilibrium. Here, we describe active analogs of surfactants that operate far from equilibrium in active chiral fluids. Unlike molecular surfactants, the amphiphilic character of surfactants in active chiral fluids is a consequence of their activity. Our fluid of choice is a mixture of spinners that demixes into left-handed and right-handed chiral fluid domains. We realize spinners in experiment with three-dimensionally printed vibrots. Vibrot surfactants are chains of vibrots containing both types of handedness. Experiments demonstrate the affinity of double-stranded chains to interfaces, where they glide along and act as mixing agents. Simulations access larger systems in which single-stranded chains form spinning vesicles, termed rotelles. Rotelles are the chiral analogs of micelles. Rotelle formation is a ratchet mechanism catalyzed by the vorticity of the chiral fluid and only exist far from equilibrium.
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Braithwaite, Gavin J. C., and Gareth H. McKinley. "Microrheometry for Studying the Rheology and Dynamics of Polymers Near Interfaces." Applied Rheology 9, no. 1 (February 1, 1999): 27–33. http://dx.doi.org/10.1515/arh-2009-0003.

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Abstract The design of an instrument capable of opto-mechanical studies of the rheology of viscoelastic polymeric fluids near solid interfaces is described. The instrument probes the ‘meso’-scale (length scales of 0 (μm)) and bridges the gap between molecular-scale devices such as the Surface Force Apparatus (SFA) and conventional rheometers. The high viscosity materials and intermediate length scales probed with the current device are of direct relevance to industrial coating and thin film polymer processing operations, in addition to fundamental investigations of slip and interfacial instabilities. The device utilises small fluid samples (of the order of 1 μL), allows a wide range of viscosities (and thus molecular weights) to be investigated and can also be used with different substrate materials and surface coatings. Direct optical access to the sample also permits in-situ rheo-optical studies of material response under different loading conditions and flow histories.
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Schoen, M., and F. Porcheron. "Collective dynamics near a phase transition in confined fluids." European Physical Journal E 12, S1 (November 2003): 5–7. http://dx.doi.org/10.1140/epjed/e2003-01-002-8.

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HUNT, J. C. R., D. D. STRETCH, and S. E. BELCHER. "Viscous coupling of shear-free turbulence across nearly flat fluid interfaces." Journal of Fluid Mechanics 671 (February 24, 2011): 96–120. http://dx.doi.org/10.1017/s0022112010005525.

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The interactions between shear-free turbulence in two regions (denoted as + and − on either side of a nearly flat horizontal interface are shown here to be controlled by several mechanisms, which depend on the magnitudes of the ratios of the densities, ρ+/ρ−, and kinematic viscosities of the fluids, μ+/μ−, and the root mean square (r.m.s.) velocities of the turbulence, u0+/u0−, above and below the interface. This study focuses on gas–liquid interfaces so that ρ+/ρ− ≪ 1 and also on where turbulence is generated either above or below the interface so that u0+/u0− is either very large or very small. It is assumed that vertical buoyancy forces across the interface are much larger than internal forces so that the interface is nearly flat, and coupling between turbulence on either side of the interface is determined by viscous stresses. A formal linearized rapid-distortion analysis with viscous effects is developed by extending the previous study by Hunt & Graham (J. Fluid Mech., vol. 84, 1978, pp. 209–235) of shear-free turbulence near rigid plane boundaries. The physical processes accounted for in our model include both the blocking effect of the interface on normal components of the turbulence and the viscous coupling of the horizontal field across thin interfacial viscous boundary layers. The horizontal divergence in the perturbation velocity field in the viscous layer drives weak inviscid irrotational velocity fluctuations outside the viscous boundary layers in a mechanism analogous to Ekman pumping. The analysis shows the following. (i) The blocking effects are similar to those near rigid boundaries on each side of the interface, but through the action of the thin viscous layers above and below the interface, the horizontal and vertical velocity components differ from those near a rigid surface and are correlated or anti-correlated respectively. (ii) Because of the growth of the viscous layers on either side of the interface, the ratio uI/u0, where uI is the r.m.s. of the interfacial velocity fluctuations and u0 the r.m.s. of the homogeneous turbulence far from the interface, does not vary with time. If the turbulence is driven in the lower layer with ρ+/ρ− ≪ 1 and u0+/u0− ≪ 1, then uI/u0− ~ 1 when Re (=u0−L−/ν−) ≫ 1 and R = (ρ−/ρ+)(v−/v+)1/2 ≫ 1. If the turbulence is driven in the upper layer with ρ+/ρ− ≪ 1 and u0+/u0− ≫ 1, then uI/u0+ ~ 1/(1 + R). (iii) Nonlinear effects become significant over periods greater than Lagrangian time scales. When turbulence is generated in the lower layer, and the Reynolds number is high enough, motions in the upper viscous layer are turbulent. The horizontal vorticity tends to decrease, and the vertical vorticity of the eddies dominates their asymptotic structure. When turbulence is generated in the upper layer, and the Reynolds number is less than about 106–107, the fluctuations in the viscous layer do not become turbulent. Nonlinear processes at the interface increase the ratio uI/u0+ for sheared or shear-free turbulence in the gas above its linear value of uI/u0+ ~ 1/(1 + R) to (ρ+/ρ−)1/2 ~ 1/30 for air–water interfaces. This estimate agrees with the direct numerical simulation results from Lombardi, De Angelis & Bannerjee (Phys. Fluids, vol. 8, no. 6, 1996, pp. 1643–1665). Because the linear viscous–inertial coupling mechanism is still significant, the eddy motions on either side of the interface have a similar horizontal structure, although their vertical structure differs.
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Srivastava, S., P. Perlekar, L. Biferale, M. Sbragaglia, J. H. M. ten Thije Boonkkamp, and F. Toschi. "A Study of Fluid Interfaces and Moving Contact Lines Using the Lattice Boltzmann Method." Communications in Computational Physics 13, no. 3 (March 2013): 725–40. http://dx.doi.org/10.4208/cicp.411011.310112s.

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AbstractWe study the static and dynamical behavior of the contact line between two fluids and a solid plate by means of the Lattice Boltzmann method (LBM). The different fluid phases and their contact with the plate are simulated by means of standard Shan-Chen models. We investigate different regimes and compare the multicomponent vs. the multiphase LBM models near the contact line. A static interface profile is attained with the multiphase model just by balancing the hydrostatic pressure (due to gravity) with a pressure jump at the bottom. In order to study the same problem with the multicomponent case we propose and validate an idea of a body force acting only on one of the two fluid components. In order to reproduce results matching an infinite bath, boundary conditions at the bath side play a key role. We quantitatively compare open and wall boundary conditions and study their influence on the shape of the meniscus against static and lubrication theory solution.
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Castelo, Antonio, Alexandre M. Afonso, and Wesley De Souza Bezerra. "A Hierarchical Grid Solver for Simulation of Flows of Complex Fluids." Polymers 13, no. 18 (September 18, 2021): 3168. http://dx.doi.org/10.3390/polym13183168.

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Tree-based grids bring the advantage of using fast Cartesian discretizations, such as finite differences, and the flexibility and accuracy of local mesh refinement. The main challenge is how to adapt the discretization stencil near the interfaces between grid elements of different sizes, which is usually solved by local high-order geometrical interpolations. Most methods usually avoid this by limiting the mesh configuration (usually to graded quadtree/octree grids), reducing the number of cases to be treated locally. In this work, we employ a moving least squares meshless interpolation technique, allowing for more complex mesh configurations, still keeping the overall order of accuracy. This technique was implemented in the HiG-Flow code to simulate Newtonian, generalized Newtonian and viscoelastic fluids flows. Numerical tests and application to viscoelastic fluid flow simulations were performed to illustrate the flexibility and robustness of this new approach.
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Dissertations / Theses on the topic "Fluids near interfaces"

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Xiao, Cheng. "Computer simulation of fluid systems." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386636.

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Stoos, James Arthur Leal L. Gary Leal L. Gary Herbolzheimer Eric. "Particle dynamics near fluid interfaces in low-Reynolds number flows /." Diss., Pasadena, Calif. : California Institute of Technology, 1988. http://resolver.caltech.edu/CaltechETD:etd-02022007-110333.

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Yang, Seung-Man Leal L. Gary. "Hydrodynamics and Brownian motion of small particles near a fluid-fluid interface /." Diss., Pasadena, Calif. : California Institute of Technology, 1985. http://resolver.caltech.edu/CaltechETD:etd-06302005-124544.

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Moe, John Einar. "Near and far-field acoustic scattering through and from two dimensional fluid-fluid rough interfaces /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/6019.

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Curtiss, Geoffrey Aylwyn. "Non-linear, non-spherical bubble dynamics near a two fluid interface." Thesis, University of Birmingham, 2009. http://etheses.bham.ac.uk//id/eprint/411/.

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The interactions of bubbles with rigid and free boundaries have been well documented. Toroidal bubble formation has been observed, with jetting directed toward and away from the two types of interface respectively. This work generalises these interactions by studying the effect of a two fluid interface supporting a density discontinuity. Such interactions may provide significant new insight into the mechanisms present in bubble assisted mixing processes, and in biomedical procedures including laser ablation and sonoporation. A numerical investigation has been conducted to examine the essentially incompressible fluid dynamics of the exterior liquid layers, based on a boundary integral implementation coupled with the vortex ring toroidal bubble model [53]. The transition through the null impulse state has been investigated, demonstrating excellent agreement with the water/white spirit experiments of Chahine and Bovis [23]. Close standoff distance simulations have illustrated the retardation of surface spiking with increasing density ratios, and have shown how the toroidal phase can be beneficial to mixing processes. Multi-bubble simulations have demonstrated that the deformation to the interface is greatly affected by the configuration of the bubble column. The acoustic driving of ultrasound contrast agents near tissue layers has also been investigated, demonstrating a new mechanism for tissue damage due to the toroidal re-expansion, the membrane peeling phenomenon.
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Stoos, James Arthur. "Particle Dynamics near Fluid Interfaces in Low-Reynolds Number Flows." Thesis, 1988. https://thesis.library.caltech.edu/465/3/Stoos_js_1988.pdf.

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Numerical solutions for the creeping motion of a spherical particle in a linear axisymmetric straining flow normal to a deformable interface are presented for a range of viscosity ratios, capillary numbers and Bond numbers. The parameter ranges investigated have applications in areas of flotation (small interface deformation) and material processing (large interface deformation). The accuracy of previous solutions for flotation problems, which neglect interface deformation is considered, along with the magnitude and form of interface deformation "defects" that may appear in material processing applications involving fluids containing bubbles or small particles.

Numerical solutions for the equilibrium particle-interface configuration for a neutrally buoyant spherical particle contacting a deformable fluid/gas interface in a linear axisymmetric straining flow at low Reynolds number are presented for a range of contact angles and capillary numbers. These solutions may have applications both in flotation separation processes and in contact angle and surface tension measurement. In addition, the accuracy of simply combining previous results for particle detachment due to particle buoyancy with the results for particle detachment due to viscous forces is considered. The equilibrium configuration is especially sensitive to the inclusion of a small amount of flow for small contact angles and for capillary numbers near the critical capillary number.

Trajectories of small spherical particles around a spherical drop (bubble and solid) are calculated from an approximate solution employing a matched asymptotic expansion. Viscous interaction is seen to have a large effect on the trajectory around a solid collector and a small effect on the trajectory around a bubble. Previous solutions are found to be in error in their prediction of an increase in the capture efficiency because of viscous interactions; the capture efficiency decreases significantly in this case.

Finally, the trajectories of particles around bubbles and the capture of particles by bubbles is investigated experimentally.

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Yang, Seung-Man. "Hydrodynamics and Brownian Motion of Small Particles Near a Fluid-Fluid Interface." Thesis, 1985. https://thesis.library.caltech.edu/2786/1/Yang_s-m_1985.pdf.

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The general problems of particle motion in the vicinity of a flat, non-deforming fluid interface is studied. The approximate singularity method used by previous workers in this research group has been generalized to consider the motion of a sphere in any linear velocity field compatible with the existence of the undisturbed flat interface, and the motion of slender rod-like particles which undergo an arbitrary translation or rotation in either a quiescent fluid or in a linear flow. The theory yields the hydrodynamic mobility tensors which are necessary to describe Brownian movement near a phase boundary, as well as general trajectory equations for sedimenting particles near a fluid interface with an arbitrary viscosity ratio. These approximate solution results are in good agreement with both exact-solutions where they are available and experimental data for motion of a sphere near a rigid plane wall. Among the most interesting results for motion of slender bodies is the generalization of Jeffery orbit equations for linear simple shear flow.

The Brownian motion of a sphere in the presence of a deformable fluid interface is also examined. First, the fluctuation-dissipation theorem is derived for the random distortions of interface shape that are caused by spontaneous thermal impulses from the surrounding fluids. This analysis is carried out using the method of normal modes in conjunction with a Langevim type equation for the Brownian particle, and results in the prediction of autocorrelation functions for the location of the interface, for the random force acting on the particle (evaluated by a generalization of the Faxen's law), and for the particle velocity. The particle velocity correlation, in turn, yields the effective diffusion coefficient due to random fluctuations of the interface shape. Finally, we investigate the effects of interface deformation that are induced by the impulsive motion of a sphere that is undergoing Brownian motion. In this phase of our study, we consider both the spatially modified hydrodynamic mobility which occurs as a consequence of hydrodynamic interactions, and influence on the mean-square displacement of the Brownian particle of the interface relaxation back towards the flat equilibrium configuration after an initial deformation that is caused by the particle motion.

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Books on the topic "Fluids near interfaces"

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Kryukov, Alexei. Non-Equilibrium Phenomena near Vapor-Liquid Interfaces. Heidelberg: Springer International Publishing, 2013.

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Succi, Sauro. The Lattice Boltzmann Equation. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199592357.001.0001.

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Over the past near three decades, the Lattice Boltzmann method has gained a prominent role as an efficient computational method for the numerical simulation of a wide variety of complex states of flowing matter across a broad range of scales, from fully developed turbulence, to multiphase micro-flows, all the way down to nano-biofluidics and lately, even quantum-relativistic subnuclear fluids. After providing a self-contained introduction to the kinetic theory of fluids and a thorough account of its transcription to the lattice framework, this book presents a survey of the major developments which have led to the impressive growth of the Lattice Boltzmann across most walks of fluid dynamics and its interfaces with allied disciplines, such as statistical physics, material science, soft matter and biology. This includes recent developments of Lattice Boltzmann methods for non-ideal fluids, micro- and nanofluidic flows with suspended bodies of assorted nature and extensions to strong non-equilibrium flows beyond the realm of continuum fluid mechanics. In the final part, the book also presents the extension of the Lattice Boltzmann method to quantum and relativistic fluids, in an attempt to match the major surge of interest spurred by recent developments in the area of strongly interacting holographic fluids, such as quark-gluon plasmas and electron flows in graphene. It is hoped that this book may provide a source information and possibly inspiration to a broad audience of scientists dealing with the physics of classical and quantum flowing matter across many scales of motion.
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Kryukov, Alexei, Yulia Puzina, and Vladimir Levashov. Non-Equilibrium Phenomena near Vapor-Liquid Interfaces. Springer, 2013.

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United States. National Aeronautics and Space Administration., ed. A finite element model of conduction, convection, and phase change near a solid/melt interface. [Washington, DC]: National Aeronautics and Space Administration, 1991.

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United States. National Aeronautics and Space Administration., ed. A finite element model of conduction, convection, and phase change near a solid/melt interface. [Washington, DC]: National Aeronautics and Space Administration, 1991.

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Kraus, Eric B., and Joost A. Businger. Atmosphere-Ocean Interaction. Oxford University Press, 1995. http://dx.doi.org/10.1093/oso/9780195066180.001.0001.

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With both the growing importance of integrating studies of air-sea interaction and the interest in the general problem of global warming, the appearance of the second edition of this popular text is especially welcome. Thoroughly updated and revised, the authors have retained the accessible, comprehensive expository style that distinguished the earlier edition. Topics include the state of matter near the interface, radiation, surface wind waves, turbulent transfer near the interface, the planetary boundary layer, atmospherically-forced perturbations in the oceans, and large-scale forcing by sea surface buoyancy fluxes. This book will be welcomed by students and professionals in meteorology, physical oceanography, physics and ocean engineering.
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Book chapters on the topic "Fluids near interfaces"

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Ajaev, Vladimir S. "Flows and Interface Shapes Near Structured Surfaces." In Interfacial Fluid Mechanics, 125–40. Boston, MA: Springer US, 2011. http://dx.doi.org/10.1007/978-1-4614-1341-7_5.

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Hunt, J. C. R., T. Ishihara, D. Szubert, I. Asproulias, Y. Hoarau, and M. Braza. "Turbulence Near Interfaces—Modelling and Simulations." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 283–92. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-27386-0_17.

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Curtiss, G. A., D. M. Leppinen, Q. X. Wang, and J. R. Blake. "Bubble Behavior Near a Two Fluid Interface." In Integral Methods in Science and Engineering, 147–58. Boston: Birkhäuser Boston, 2011. http://dx.doi.org/10.1007/978-0-8176-8238-5_14.

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Koren, B., E. H. van Brummelen, P. W. Hemker, B. van Leer, and M. R. Lewis. "Fix for Solution Errors near Interfaces in Two-Fluid Flow Computations." In Computational Fluid Dynamics 2002, 523–28. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-642-59334-5_78.

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"Moderately Coupled Charged Fluids Near Dielectric Interfaces and in Confinement." In Electrostatics of Soft and Disordered Matter, 127–48. Jenny Stanford Publishing, 2014. http://dx.doi.org/10.1201/b15597-12.

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Kraus, Eric B., and Joost A. Businger. "Turbulent Transfer Near the Interface." In Atmosphere-Ocean Interaction. Oxford University Press, 1995. http://dx.doi.org/10.1093/oso/9780195066180.003.0009.

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The atmosphere and the ocean are in intimate contact at their interface, where momentum, water substance, heat, and trace constituents are exchanged. This exchange is often modest when a light breeze strokes the surface; sometimes the processes are violent, when gale force winds sweep up ocean spray into the atmosphere and when braking waves engulf air into the ocean. It may even appear that the transition between ocean and atmosphere becomes gradual and indistinct. The transition from ocean to atmosphere is usually an abrupt transition of one fluid to another. The interface may then be considered a continuous material surface. On both sides of the interface the fluids are usually in turbulent motion and properties are transported readily, but upon approaching the interface turbulence is largely suppressed so that on both sides of the interface a very thin layer exists where the molecular diffusion coefficients play a major role in the transport. The interface is consequently a significant barrier to the transport from ocean to atmosphere and vice versa, with little or no turbulent transport of scalar quantities across it. The quantitative determination of the thickness of the molecular sublayers and the strength of the gradients and shear layers within them are discussed in Section 5.1. We also examine the transition from the molecular sublayers to the well-mixed turbulent layers that exist beyond them, and the structure of these turbulent layers on either side of the interface. In Section 5.2 we discuss the effect of stratification on the structure of these surface layers. Some of the nonstationary interactions between the wind and the sea surface are described in Section 5.3. Sections 5.4 and 5.5 deal with practical applications: a formulation of gas transfer across the interface and of the sea surface temperature. Several observational techniques are discussed in Section 5.6.
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Amiroudine, Sakir. "Numerical Modelling of Hydrodynamic Instabilities in Supercritical Fluids." In Advanced Applications of Supercritical Fluids in Energy Systems, 33–54. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-2047-4.ch002.

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The case of a supercritical fluid heated from below (Rayleigh-Bénard) in a rectangular cavity is first presented. The stability of the two boundary layers (hot and cold) is analyzed by numerically solving the Navier-Stokes equations with a van der Waals gas and stability diagrams are derived. The very large compressibility and the very low heat diffusivity of near critical pure fluids induce very large density gradients which lead to a Rayleigh–Taylor-like gravitational instability of the heat diffusion layer and results in terms of growth rates and wave numbers are presented. Depending on the relative direction of the interface or the boundary layer with respect to vibration, vibrational forces can destabilize a thermal boundary layer, resulting in parametric / Rayleigh vibrational instabilities. This has recently been achieved by using a numerical model which does not require any equation of state and directly calculates properties from NIST data base (NIST, 2000) for instance.
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Amiroudine, Sakir. "Numerical Modelling of Hydrodynamic Instabilities in Supercritical Fluids." In Handbook of Research on Advancements in Supercritical Fluids Applications for Sustainable Energy Systems, 32–54. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-5796-9.ch002.

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The case of a supercritical fluid heated from below (Rayleigh-Bénard) in a rectangular cavity is first presented. The stability of the two boundary layers (hot and cold) is analyzed by numerically solving the Navier-Stokes equations with a van der Waals gas and stability diagrams are derived. The very large compressibility and the very low heat diffusivity of near critical pure fluids induce very large density gradients which lead to a Rayleigh–Taylor-like gravitational instability of the heat diffusion layer and results in terms of growth rates and wave numbers are presented. Depending on the relative direction of the interface or the boundary layer with respect to vibration, vibrational forces can destabilize a thermal boundary layer, resulting in parametric/Rayleigh vibrational instabilities. This has recently been achieved by using a numerical model which does not require any equation of state and directly calculates properties from NIST data base, for instance.
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Watanabe, Tomoaki, Koji Nagata, and Carlos B. da Silva. "Vorticity Evolution near the Turbulent/Non-Turbulent Interfaces in Free-Shear Flows." In Vortex Structures in Fluid Dynamic Problems. InTech, 2017. http://dx.doi.org/10.5772/64669.

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GAROFF, S., and E. RAMÉ. "EXPERIMENTAL STUDIES OF THE HYDRODYNAMICS NEAR MOVING CONTACT LINES." In Interfaces for the 21st Century: New Research Directions in Fluid Mechanics and Materials Science, 256. PUBLISHED BY IMPERIAL COLLEGE PRESS AND DISTRIBUTED BY WORLD SCIENTIFIC PUBLISHING CO., 2002. http://dx.doi.org/10.1142/9781860949609_0038.

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Conference papers on the topic "Fluids near interfaces"

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Mortezazadeh, Mohammad, and Kazem Hejranfar. "Simulation of Incompressible Multiphase Flows Using the Artificial Compressibility Method." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83013.

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The Eulerian methods are susceptible to generate the nonphysical spurious currents in the multiphase flow simulations near the interfaces. This paper presents a new Eulerian method to accurately simulate the velocity fields, especially near the multiphase flow interfaces and prevents the numerical results from generating the nonphysical currents. A Eulerian central difference finite-volume scheme equipped with the suitable numerical dissipation terms is used to simulate incompressible multiphase flows. The interface is captured by Flux Corrected Transport-Volume of Fluid method (FCT-VOF). Increasing the accuracy near the sharp gradients, such as interface, the conservative form of incompressible Navier-Stokes equations is solved to locally conserve the properties. The main feature of this algorithm is its ability to control the pressure gradient oscillation and also spurious currents near the interface; two common problems in multiphase flow simulations, and as a result improves the accuracy of the simulation by artificial numerical dissipations. The results show the FCT-VOF is able to precisely calculate the interface, and the numerical dissipation terms are the powerful device to prevent the spurious currents.
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2

Mitsui, Takashi, Shusaku Harada, and Kuniomi Asakura. "Sedimentation of a Stratified Suspension in a Quiescent Fluid." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37149.

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The sedimentation of fine particles in a stratified suspension, which has both the upper and lower interfaces, is studied experimentally. We measure the settling velocity of particles and observe the diffusion behavior near the interfaces. Especially we examine whether the macroscopic or the microscopic natures of suspension is dominant during sedimentation, i.e., the particles settle as an particle assembly relative to surrounding fluid or as a continuous suspension. The experimental observation shows that the gravity-induced instability of suspension-fluid interface, which has been already reported, governs the particle motion for high concentration and small particle size. However, the microscopic nature of suspension comes out in case of larger particles. In our study, the dependency of the sedimentation behavior on the particle size and the concentration is discussed quantitatively.
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Nourgaliev, Robert, Nam Dinh, and Theo Theofanous. "The ‘Characteristics-Based Matching’ (CBM) Method for Compressible Flow With Moving Boundaries and Interfaces." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45550.

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Recently, Eulerian methods for capturing interfaces in multi-fluid problems become increasingly popular. While these methods can effectively handle significant deformations of interface, they have been known to produce nonphysical oscillations near material interfaces due to the smeared out density profile and radical change in equation of state across a material interface. One promising recent development to overcome these problems is the ‘Ghost Fluid Method’ (GFM). While being able to produce excellent results for simulation of gas-gas flows, the GFM boundary treatment is unsatisfactory for the case of liquid-liquid or liquid-gas compressible flows. The present study devotes to a new methodology for boundary condition capturing in multi-fluid compressible flows. The method, named ‘Characteristics-Based Matching (CBM)’, capitalizes on the recent development of the level set method and related techniques, i.e., PDE-based re-initialization and extrapolation, and the ‘Ghost Fluid Method’ (GFM). Specifically, the CBM utilizes the level set function to ‘capture’ interface position and a GFM-like strategy to tag computational nodes. In difference to the GFM method, which employs a boundary condition capturing in primitive variables, the CBM method implements boundary conditions based on a characteristic decomposition in the direction normal to the boundary. Since the method allows to avoid over-specification of boundary conditions by respecting the information flow, we believe that the CBM is able to ‘cure’ above-mentioned problems of the GFM boundary condition capturing technique. In this paper, the method’s performance is examined on fluid dynamics problems with stationary and moving boundaries. Numerical results agree well with known analytical or computational solutions and experimental data. Robust and accurate solutions were obtained. In particular, spurious over/under-heating errors, typical for moving boundary treatment by other methods, are essentially eliminated in the CBM solutions.
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4

Grinstein, Fernando, Rick Rauenzahn, Juan Saenz, and Marianne Francois. "Coarse Grained Simulation of Shock-Driven Turbulent Mixing." In ASME 2017 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/fedsm2017-69057.

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We focus on the simulation of shock-driven material mixing powered by flow instabilities dependent on initial conditions (IC) at the material interfaces. Beyond complex multi-scale resolution issues of shocks and variable density turbulence, we must address the equally difficult problem of predicting flow transition promoted by energy deposited at the interfacial layers during the shock-interface interactions. Transition involves IC-dependent, large-scale coherent-structure dynamics capturable by a large eddy simulation (LES) strategy, but not by unsteady Reynolds-Averaged Navier-Stokes (URANS) approaches based on equilibrium developed turbulence assumptions and single-point-closure modeling. On the engineering end of computations, reduced-dimensionality (1D/2D) versions of such URANS tend to be preferred for faster turnaround in full-scale configurations. With suitable initialization around each transition, URANS can be used to simulate the subsequent near-equilibrium weakly turbulent flow. We demonstrate 3D state-of-the-art URANS performance around one such (reshock) transition — in the context of a sequential LES/URANS strategy.
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5

Hernandez, Joseph E., and Jeffrey S. Allen. "Optical Film Thickness Measurements Using a Reflectance Mode Swept-Field Confocal Microscope." In ASME-JSME-KSME 2011 Joint Fluids Engineering Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ajk2011-36037.

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Multiphase flow in microchannels is frequently encountered in microdevices. Predicting the behavior of the multiphase flow has been difficult. The dynamics of liquid films inside of capillaries is important to microfluidic flows. At high flow rates with gas-liquid flows, the dynamics of liquid films on the interior surfaces of the microchannels can have a global affect on device operation. Measurement via optical microscopy of velocities in these liquid films and interface dynamics has been hampered by the inability to correctly image near dyanamic interfaces due to optical reflection and very short time scales of the flow. A novel technique for optically measuring liquid film thicknesses within circular microchannels has been developed. A swept-field confocal microscopy unit has been modified to capture the reflected light by replacing the dichroic mirror, commonly used in fluorescence confocal microscopy, with a 50/50 beam splitter. “Optical slicing” in the x-y plane, coupled with precision z-axis stepping allows for the detection of the gas-liquid interface by blocking out-of-focus light.
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6

Fujita, Takao, and Keizo Watanabe. "Numerical Simulation of Fluid Slip at a Hydrophobic Surface." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56046.

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Laminar drag reduction is achieved by using a hydrophobic surface. In this method, fluid slip is applied at the hydrophobic surface. An initial experiment to clarify for a laminar skin friction reduction was conducted using ducts with a highly water-repellent surface. The surface has a fractal-type structure with many fine grooves. Fluid slip at a hydrophobic surface has been analyzed by applying a new wet boundary condition. In this simulation, an internal flow is assumed to be a two-dimensional laminar flow in a rectangular duct and an external flow is assumed to be a two-dimensional laminar flow past a circular cylinder. The VOF technique has been used as the method for tracking gas-liquid interfaces, and the CSF model has been used as the method for modeling surface tension effects. The wet boundary condition for the hydrophobic property on the surface has been determined from the volume ratio in contact with water near the surface. The model with a stable gas-liquid interface and the experimental results of flow past a circular cylinder at Re = 250 without growing the Karman vortex street are made, and these results show that laminar drag reduction occurring due to fluid slip can be explained in this model.
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7

Yang, Xiaofan, Zhongquan Charlie Zheng, and Ying Xu. "A Study on Flow Through a Periodic Array of Porous Medium Cylinders by Immersed-Boundary Methods." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30535.

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Numerical simulations with an immersed-boundary method are presented for the incompressible flow past a periodic array of porous-medium cylinders. Fluid/porous-medium interactions are greatly influenced by the accuracy on the interface between the surface of the porous cylinder and the flow around it, because of the sudden change in the governing equations for the fluid and for the porous material. In order to retain the smoothness on the interface, momentum fluxes near the interface are discretized using several schemes, including the 2nd- and 3rd-order upwind schemes and the 5th-order Weighted Essentially Non-Oscillatory (WENO) scheme. These schemes are combined with a direct-forcing immersed-boundary method to remove the discontinuity between the fluid and the porous material, and thus accuracy near the interface can be improved. Low and moderate Reynolds number flows, both outside and inside the porous cylinders, are computed simultaneously by solving a combined governing equation set for incompressible flow. The simulation is first validated using flow over an array of impermeable cylinders. The advantage of high-order schemes is then investigated by looking at the flow parameters near the interfaces between the porous cylinders and the outside flow. Species transport in flow with the porous-cylinder-array configuration is also studied.
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Lee, Jaewon, and Gihun Son. "Numerical Simulation of Transient Conjugate Heat Transfer in Liquid Jet Impingement." In ASME 2014 4th Joint US-European Fluids Engineering Division Summer Meeting collocated with the ASME 2014 12th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/fedsm2014-21419.

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Numerical simulation is performed for a quenching process in liquid jet impingement, which is applicable to thermal control in metal manufacturing and emergency cooling of nuclear reactors. The flow and cooling characteristics of jet impingement are investigated by solving the conservation equations of mass, momentum and energy in the liquid and gas phases. The liquid-vapor and liquid-air interfaces are tracked by a sharp-interface level-set method which is modified to include the effect of phase change at the liquid-vapor interface. The temporal and spatial variation of solid temperature is analyzed by solving a conjugate problem with the conduction in the solid as well as the convection in the liquid and gas phases. The numerical results demonstrate that the temporal variations of the temperature and heat flux near the fluid-solid interface are very steep compared to those inside the solid. The heat flux variations at the fluid-solid interface are observed to be much larger in the convection mode than in the film boiling mode. The solid temperatures and heat fluxes obtained from the present study are compared with the experimental data reported in the literature.
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9

Garafolo, Nicholas G., and Christopher C. Daniels. "An Empirical Investigation on Seal-Interface Leakage of an Elastomer Face Seal." In ASME 2012 Fluids Engineering Division Summer Meeting collocated with the ASME 2012 Heat Transfer Summer Conference and the ASME 2012 10th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/fedsm2012-72026.

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For the application of seals used in space, a common assumption is that all leakage is attributed to permeation, that is the gas flows through the porous seal material. In this case, leakage across any seal interfaces are assumed negligible. In fact, state-of-the-art gas leak rate prediction methods rely heavily on this assumption. A recent study into the quantification of the seal-interface leakage of elastomer face seals, however, has revealed that this is not the case. As the preliminary study previously presented, with moderate contact pressure the interface leakage components were found to be significant and distinct from zero. The objective of the research presented herein was to further quantify both the elastomer-metal and elastomer-elastomer interface leakages for various contact pressures. To this end, a series of leak rate experiments is presented on a square-ring seal, manufactured from silicone elastomer S0383-70. The unique experimental design affords the ability to quantify both the elastomer-metal interface, as well as an elastomer-elastomer interface. The experiments utilized matched sets of test specimens, each with a common width but different height. The test apparatus contained both a flow fixture capable of quantifying ultra-low leak rates and an electro-mechanical actuated load frame for precision contact pressure control. The leak rate apparatus consisted of stainless steel platens, near-hermetic plumbing, and the required instrumentation. The initial data reduction was accomplished by the mass point leak rate technique; whereas mass was calculated through measurements of gas pressure, temperature, and volume and a regression analysis yielded the leak rate of the seal. A secondary reduction of the leak rates in the unique experimental configuration further distinguished the total leakage into permeation and interface leak components, accomplished through the algebraic solution of the design of experiments guided matrix. Foremost, results confirmed that the interface leakage is non-negligible and distinct from zero, as with previous studies. Furthermore, results suggested that the interface leakage was drastically decreased with modest seal contact pressure.
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10

Kelly, Jesse. "GPU-Accelerated Simulation of Two-Phase Incompressible Fluid Flow Using a Level-Set Method for Interface Capturing." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-13330.

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Computational fluid dynamics has seen a surge of popularity as a tool for visual effects animators over the past decade since Stam’s seminal Stable Fluids paper [1]. Complex fluid dynamics simulations can often be prohibitive to run due to the time it takes to perform all of the necessary computations. This project proposes an accelerated two-phase incompressible fluid flow solver implemented on programmable graphics hardware. Modern graphics-processing units (GPUs) are highly parallel computing devices, and in problems with a large potential for parallel computation the GPU may vastly out-perform the CPU. This project will use the potential parallelism in the solution of the Navier-Stokes equations in writing a GPU-accelerated flow solver. NVIDIA’s Compute-Unified-Device-Architecture (CUDA) language will be used to program the parallel portions of the solver. CUDA is a C-like language introduced by the NVIDIA Corporation with the goal of simplifying general-purpose computing on the GPU. CUDA takes advantage of data-parallelism by executing the same or near-same code on different data streams simultaneously, so the algorithms used in the flow solver will be designed to be highly data-parallel. Most finite difference-based fluid solvers for computer graphics applications have used the traditional staggered marker-and-cell (MAC) grid, introduced by Harlow and Welsh [2]. The proposed approach improves upon the programmability of solvers such as these by using a non-staggered (collocated) grid. An efficient technique is implemented to smooth the pressure oscillations that often result from the use of a collocated grid in the simulation of incompressible flows. To be appropriate for visual effects use, a fluid solver must have some means of tracking fluid interfaces in order to have a renderable fluid surface. This project uses the level-set method [3] for interface tracking. The level set is treated as a scalar property, and so its propagation in time is computed using the same transport algorithm used in the main fluid flow solver.
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