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Search Results: 1 - 10 of 462458 matches for " Eloy; García-Sucre "
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A simple model to describe dimple dynamics
Acevedo-Malavé,Alejandro J; Sira,Eloy; García-Sucre,Máximo;
Interciencia , 2009,
Abstract: a model based on the hydrodynamics equations that allows to describe the dynamics of a dimple, once it has formed, is proposed. the navier-stokes equations are considered, and two fundamental approaches are used to simplify the mathematical treatment of the hydrodynamics equations. certain conditions are considered that must be fulfilled at the interface, which serve to close the system of differential equations and lead to an evolution equation that describes the interfacial film dynamics. with the intention of solving this equation, the method of finite differences has been used.
Film drainage between two drops: Vortex formation in thin liquid films
Acevedo-Malavé,Alejandro J; Sira,Eloy; García-Sucre,Máximo;
Interciencia , 2009,
Abstract: in this study, a mathematical formalism that takes into account the surfactant effect on the drainage of the interfacial film between two drops is considered. the effects of thermal perturbations and van der waals forces are neglected. in the mathematical formalism the navier-stokes equations within the lubrication approximation are coupled to a diffusion-convection equation leading to an evolution equation for the interfacial film. this last equation is solved by using the numerical method of lines coupled with an implicit runge-kutta method for the integration with respect to time. as a result of the inclusion of interfacial tension gradients a non oscillating dimple arises, even beginning with an initial condition corresponding to a plane interfacial film.
Coalescence collision of liquid drops I: Off-center collisions of equal-size drops
Alejandro Acevedo-Malavé,Máximo García-Sucre
AIP Advances , 2011, DOI: 10.1063/1.3624553
Abstract: The Smoothed Particle Hydrodynamics method (SPH) is used here to model off-center collisions of equal-size liquid drops in a three-dimensional space. In this study the Weber number is calculated for several conditions of the droplets dynamics and the velocity vector fields formed inside the drops during the collision process are shown. For the permanent coalescence the evolution of the kinetic and internal energy is shown and also the approaching to equilibrium of the resulting drop. Depending of the Weber number three possible outcomes for the collision of droplets is obtained: permanent coalescence, flocculation and fragmentation. The fragmentation phenomena are modeled and the formation of small satellite drops can be seen. The ligament that is formed follows the “end pinching” mechanism and it is transformed into a flat structure.
Coalescence collision of liquid drops II: Off-center collisions of unequal-size drops
Alejandro Acevedo-Malavé,Máximo García-Sucre
AIP Advances , 2011, DOI: 10.1063/1.3624554
Abstract: We applied the Smoothed Particle Hydrodynamics method to simulate for first time in the three-dimensional space the hydrodynamic off-center collisions of unequal-size liquid drops in a vacuum environment. The Weber number for several conditions of the droplets dynamics is determined. Also the velocity vector fields inside the drops are shown in the collision process. The evolution of the kinetic and internal energy is shown for the permanent coalescence case. The resulting drops tend to deform, and depending of the Weber number two possible outcomes for the collision of droplets arise: either permanent coalescence or flocculation. In the permanent coalescence of the drops a fragmentation case is modeled, yielding the formation of little satellite droplets.
Efecto de la interacción hidrodinámica en la velocidad de floculación de partículas brownianas
Toro-Mendoza, J;Urbina-Villalba, G;García-Sucre, M;
Revista mexicana de física , 2006,
Abstract: the effect of the fluid on the movement of suspended brownian particles is shown. in order to study the flocculation rate of a suspension, ermak and mccammon's algorithm [j. chem. phys. 69 (1978) 1352] is used to simulate systems containing a fixed initial number of particles but different volume fractions. commonly, brownian dynamics algorithms introduce hydrodynamic interactions (hi) through two-body diffusion tensors. these formulations are highly demanding in computer time and fail in dense systems due to an overestimation of hi. in this work, an effective diffusion constant is used. it is evaluated at each time from the local volume fraction of particles and an exact formulae valid at short inter particle distances [phys. rev. e 68 (2003) 061408]. for very dilute concentrations, our results are in good agreement with those for tensorial formulations, correcting the anomalous coalescence at higher concentrations. this procedure allows an adecuate evaluation of flocculation rates in dense systems.
Efecto de la interacción hidrodinámica en la velocidad de floculación de partículas brownianas
J. Toro-Mendoza,G. Urbina-Villalba,M. García-Sucre
Revista mexicana de física , 2006,
Abstract: The effect of the fluid on the movement of suspended Brownian particles is shown. In order to study the flocculation rate of a suspension, Ermak and McCammon's algorithm [J. Chem. Phys. 69 (1978) 1352] is used to simulate systems containing a fixed initial number of particles but different volume fractions. Commonly, Brownian dynamics algorithms introduce hydrodynamic interactions (HI) through twobody diffusion tensors. These formulations are highly demanding in computer time and fail in dense systems due to an overestimation of HI. In this work, an effective diffusion constant is used. It is evaluated at each time from the local volume fraction of particles and an exact formulae valid at short interparticle distances [Phys. Rev. E 68 (2003) 061408]. For very dilute concentrations, our results are in good agreement with those for tensorial formulations, correcting the anomalous coalescence at higher concentrations. This procedure allows an adecuate evaluation of flocculation rates in dense systems.
Efecto de la interacción hidrodinámica en la velocidad de floculación de partículas brownianas
J. Toro-Mendoza,G. Urbina-Villalba,M. García-Sucre
Revista mexicana de física , 2006,
Abstract: Se muestra el efecto del fluido sobre el movimiento de partículas Brownianas supendidas. Con el fin de estudiar la velocidad de floculación de una suspensión, se hace uso del algoritmo de Ermak y McCammon [J. Chem. Phys. 69 (1978) 1352] para simular sistemas a varias fracciones de volumen con el mismo número inicial de partículas. Normalmente, la interacción hidrodinámica (IH) se introduce en los algoritmos de dinámica Browniana por medio de tensores de difusión calculados mediante interacciones entre pares de partículas. Estas formulaciones, además de ser computacionalmente costosas, fallan en sistemas densos debido a la sobrestimación de la IH. En este trabajo se emplea una constante de difusión efectiva [Phys. Rev. E 68 (2003) 061408] que incorpora una corrección de la constante de difusión debida a la fracción de volumen local de partículas dispersas, conjuntamente con una formulación exacta de dicha constante para distancias cortas de aproximación. A concentraciones suficientemente diluidas, nuestros resultados reproducen aquellos de la formulación tensorial, corrigiendo las anomalías observadas a concentraciones mayores. Este procedimiento permite la evaluación adecuada de las constantes de floculación en sistemas densos.
Lifetime of oil drops pressed by buoyancy against a planar interface: Large drops
Clara Rojas,Máximo García-Sucre,Germán Urbina-Villalba
Physics , 2010, DOI: 10.1103/PhysRevE.82.056317
Abstract: In a previous report [10] it was shown that emulsion stability simulations are able to reproduce the lifetime of micrometer-size drops of hexadecane pressed by buoyancy against a planar water-hexadecane interface. It was confirmed that small drops (ri<10 {\mu}m) stabilized with {\beta}-casein behave as nondeformable particles, moving with a combination of Stokes and Taylor tensors as they approach the interface. Here, a similar methodology is used to parametrize the potential of interaction of drops of soybean oil stabilized with bovine serum albumin. The potential obtained is then employed to study the lifetime of deformable drops in the range 10 \leq ri \leq 1000 {\mu}m. It is established that the average lifetime of these drops can be adequately replicated using the model of truncated spheres. However, the results depend sensibly on the expressions of the initial distance of deformation and the maximum film radius used in the calculations. The set of equations adequate for large drops is not satisfactory for medium-size drops (10 \leq ri \leq 100 {\mu}m), and vice versa. In the case of large particles, the increase in the interfacial area as a consequence of the deformation of the drops generates a very large repulsive barrier which opposes coalescence. Nevertheless, the buoyancy force prevails. As a consequence, it is the hydrodynamic tensor of the drops which determine the characteristic behavior of the lifetime as a function of the particle size. While the average values of the coalescence time of the drops can be justified by the mechanism of film thinning, the scattering of the experimental data of large drops cannot be rationalized using the methodology previously described. A possible explanation of this phenomenon required elaborate simulations which combine deformable drops, capillary waves, repulsive interaction forces, and a time-dependent surfactant adsorption.
No-localidad, multiuniverso y principio cosmologico en un modelo simple de espacio-tiempo
Máximo García Sucre
Physics , 2015,
Abstract: Here we analyze the physical concepts of non-locality, multi-universe, and cosmological principle in the framework of a space-time discrete model previously developed. In previous developments of this model we have elucidated as derivative concepts those of time, space-time, reference frame, particle, interaction between systems of particles, field, interaction between fields, detector of particle, and wave function. We start from the primitive concept of preparticle and four postulates alluding simple concepts. The fundamental postulate says that space-time points can be represented by equivalent classes of points of crossing between particles having the same structure. In this way each point of space-time is represented by an equivalent class corresponding to a different structure from the one of any other equivalent class representing a space-time point. We have considered a new way to define system of observation and detector of particles, which leads to non- local properties of the space-time model considered. Finally we have speculated about dark matter and dark energy in the frame work of our model.
Tres soluciones en la restauración del Palacio de Toral de los Guzmanes. León-Espa a
Algorri García, Eloy
Informes de la Construccion , 1994,
Abstract: The Palacio de Toral de los Guzmanes is a building whose walls are mostly made of "tapia" (rammed earth). One of the basic objectives of the restoration which began in 1985 is acquiring new information in order to extend the knowledge of this type of masonry, commonly used in Spanish monumental architecture. After a few general considerations the author establishes an abbreviated decalogue of construction and strength behaviour of the "tapia". The example used as an illustration is that of the description and analysis for three solutions to specific problems which appeared during the restoration works. El Palacio de Toral de los Guzmanes es un edificio cuyos muros están predominantemente construidos con fábrica de tapia. Uno de los objetivos básicos de la restauración, que viene realizándose desde 1985, es el progreso en el conocimiento de esta fábrica tan común en la arquitectura monumental espa ola. Tras unas reflexiones de índole general, el autor establece un decálogo abreviado del comportamiento constructivo y resistente de la tapia y lo ejemplifica con la descripción y el análisis de tres soluciones a problemas específicos que se han experimentado en el curso de las obras.
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