1,720,989 research outputs found
Onset of Faraday waves in a liquid layer covered with a surfactant with elastic and viscous properties
Full text linkIn this work, we analyze the formation of Faraday waves on the free surface of a liquid layer covered by an insoluble surfactant. The linear analysis that is conducted includes the effects of both surface elasticity and surface viscosity. The critical force needed to form the waves, as well as the critical wavenumber, are determined within a large range of values of the dimensionless parameters representing the physicochemical properties of the surfactant. The examination of carefully selected hydrodynamic variables provides further insight into the behavior of the system.Fil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Ubal, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Phoretic self-propulsion of microbubbles may contribute to surface cleaning
No full textSelf-propulsion of small bubbles and droplets through the action of surface-tension gradients is relevant to important processes in both nature and technology, ranging from Marangoni propulsion of microorganisms to transport in microfluidic devices. Here, we use high-fidelity simulations to characterize the fluid dynamical and interfacial phenomena underlying the spontaneous self-propulsion of a small bubble approaching a solid surface. The spreading of surface active contamination at the front of the bubble creates the surface-tension gradient which propels the bubble forward through the Marangoni effect. Results for finite Reynolds numbers and a deformable bubble show that the impact of the active bubble with the solid surface generates fluid stresses that may contribute to the cleaning of fouled surfaces. This effect, however, depends strongly on the initial separation between the bubble and the solid surface.Fil: Ubal, Sebastian. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; Argentina. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; Argentina. Purdue University; Estados Unidos. University of Massachusetts Amherst; Estados UnidosFil: Lu, Jiakai. University of Massachusetts Amherst; Estados UnidosFil: Corvalan, Carlos Maria. Purdue University; Estados Unido
The formation of Faraday waves on a liquid covered with an insoluble surfactant: Influence of the surface equation of state
Full text linkIn this work the effects of relatively large amounts of insoluble surfactants on the formation and evolution of two-dimensional Faraday waves is analyzed by means of numerical experiments. To describe the functional relationship between the surface tension and the local concentration of the absorbed solute, two equations of state are used: the Frumkin and the Langmuir expressions. A linear approximation is also employed for comparison. Results obtained show that the threshold conditions for the formation of the waves depend on the nature of the surfactant; nevertheless, the differences detected diminish as the amplitude of the external excitation is augmented.Fil: Ubal, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Saita, Fernando Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Influence of surface viscosity on two-dimensional Faraday waves
Full text linkThe onset for the formation of two-dimensional Faraday waves in a liquid with a viscous surface is numerically studied. The viscous behavior of the interface due to the presence of an insoluble surfactant, affects the surface traction and this, in turns, induces changes in the flow field. It is shown that the formation of waves of a given wavenumber in the absence of elastic effects requires a force that when plotted versus the Boussinesq number increases, producing a sigmoid curve. A detailed analysis of the interfacial variables and flow fields is carried out in order to understand this behavior.Fil: Ubal, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Saita, Fernando Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Active motion of contaminated microbubbles
No full textIn many natural and technological multi-phase systems, bubbles are exposed to surface-active contaminants (surfactants) that may cover the whole or part of the bubble interface. A partial coverage of the interface may result in a spontaneous self-propulsion mechanism, which is yet not fully characterized. Here, the self-propulsion dynamics of partially contaminated bubbles is examined using high-fidelity simulations. The simulations enable a detailed picture of the flow physics and interfacial mechanisms driving the transient active motion. Results also show that for the case of viscous surrounding and negligible surface diffusion the duration of the active motion is inversely proportional to the contaminated area fraction, and the corresponding bubble displacement is directly proportional to the clean fraction.Fil: Ubal, Sebastian. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Brown, N.. Purdue University; Estados UnidosFil: Lu, J.. University of Massachusetts; Estados UnidosFil: Corvalan, C. M.. Purdue University; Estados Unido
Elastic effects of an insoluble surfactant on the onset of two-dimensional Faraday waves. A numerical experiment
Full text linkThe elastic effects of an insoluble surfactant on the formation and evolution of twodimensional Faraday waves is investigated numerically. We analyse the influence of the elasticity of the surface-active agent on the amplitude of the vertical vibration needed to excite two-dimensional standing waves on the free surface. The numerical solutions show that the interface is always subharmonically excited at the onset and that the presence of the surfactant requires a higher external force to induce standing waves. They also show that the magnitude of the external amplitude is related to the temporal phase shift that exists between the evolution of the surfactant concentration and the free-surface shape. A detailed description of the time-varying velocity fields and interfacial distribution of surfactants helps to provide insight into the mechanisms ruling the phenomenon.Fil: Ubal, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Saita, Fernando Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
Coalescence preference in surfactant-laden bubbles of equal size
No full textCoalescence preference is the tendency of a bubble merged from two parent bubbles to be placed closer to one of the parents. Coalescence preference has been extensively studied for parent bubbles of different size, but mechanism of coalescence preference in bubbles of equal size have not yet been fully characterized. Here, we use high-fidelity simulations to investigate potential coalescence preference in contaminated bubbles of equal size. Results show that when a clean bubble merges with a surfactant-contaminated bubble of the same size, the merged bubble tends to be closer to the contaminated parent. By analyzing the coalescence events at different surfactant concentrations we also identify a novel preference mechanism characterized by spontaneous self-propulsion of the merged bubble. Elucidating mechanisms of coalescence in surfactant-contaminated bubbles has implications for technological processes involving bubble dispersions in the food and chemical industries where the presence of surfactants is ubiquitous.Fil: Ubal, Sebastian. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Lu, J.. University of Massachussets; Estados UnidosFil: Grifoni, R.. Università di Parma; ItaliaFil: Bozzoli, F.. Università di Parma; ItaliaFil: Corvalan, C. M.. Purdue University; Estados Unido
The Phan-Thien and Tanner Model Applied to the Lubrication of knee prosthesis
No full textThis work aims to provide a contribution to determine a proper model for the study of fluid film lubrication for the reduction of knee prostheses failure due to polyethylene wear. The Phan-Thien and Tanner (PTT) rheological law and the elastic deformation of the articular surfaces were considered in this modeling. The governing equations were solved numerically for different geometries and different Weissenberg numbers. The lubrication approximation applied to the PTT rheological law leads to an expression for the apparent viscosity similar to the Cross model. The results attest the importance of considering the non-Newtonian behavior of the synovial fluid, the elastic deformation, and the geometrical features of the prostheses to obtain quantitative information.Fil: Weiss, Brenda Anahí. Universidad Nacional de Entre Ríos. Facultad de Ingeniería. Departamento de Física Química. Laboratorio de Biomecánica Computacional; ArgentinaFil: Bou.Saïd, Benyebka. Universitè de Lyon; FranciaFil: Ubal, Sebastian. Universidad Nacional de Entre Ríos. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Investigación y Desarrollo en Bioingeniería y Bioinformática; ArgentinaFil: Di Paolo, José. Universidad Nacional de Entre Ríos. Facultad de Ingeniería. Departamento de Física Química. Laboratorio de Biomecánica Computacional; Argentin
Lubrication model of a knee prosthesis, with non newtonian fluid and porous rough material
Full text linkTibial component of knee prostheses, made of ultra high molecular weight polyethylene (UHMWPE), experiences a high degree of wear and may be expected to last twelve years on average. In this work, a steady state one-dimensional lubrication model of a knee prosthesis is solved through a nu-merical technique based on the Finite Element Method. The model takes into account a non Newto-nian synovial fluid, its ultra filtration mechanism and the surface roughness of a porous elastic layer on the tibial component. The benefits of a porous compliant material placed at the top of the metallic tibial component are shown taking into account the stiffness and exudation capacity of the material and hyaluronic acid concentration of synovial fluid.Fil: Berli, Marcelo Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentina. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; ArgentinaFil: Campana, Diego Martin. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; ArgentinaFil: Ubal, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Di Paolo, José. Universidad Nacional de Entre Ríos. Facultad de Ingeniería; Argentin
Influence of Surfactants on Dip Coating of Fibers: Numerical Analysis
Full text linkWe numerically analyze the process of dip coating on fibers when the liquid to be deposited contains soluble surfactants. The predictions obtained are in excellent agreement with experimental results reported by different authors. Our results show that the thickness of the film deposited, and particularly the so-called surfactant thickening effect, changes its behavior when the coating speed exceeds certain limits; therefore, the effects produced by inertia forces are scrutinized to uncover, for the first time, the mechanisms inducing those changes.Fil: Campana, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Ubal, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Giavedoni, Maria Delia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; ArgentinaFil: Saita, Fernando Adolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Desarrollo Tecnológico para la Industria Química. Universidad Nacional del Litoral. Instituto de Desarrollo Tecnológico para la Industria Química; Argentin
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