Analysis of the characteristic lengths in the bubble and slug flow regimes generated in a capillary T-junction

We present an analysis of the geometry of the continuous and disperse phases in the bubble and slug flow regimes in air–water mixtures generated in a capillary T-junction of 1 mm internal diameter. Bubble size dispersion is very low in the considered flow patterns. The concept of unit cell is used to identify two characteristic lengths of the two-phase flow, namely, the unit cell length and the bubble length. The relationship between these lengths and the gas and liquid superficial velocities, gas mean velocity, bubble generation frequency and volume average void fraction is analysed. We conclude that in the considered configuration the unit cell and bubble lengths can be predicted either by the ratio of the gas–liquid superficial velocities or the volume average void fraction.Peer ReviewedPreprin

Numerical simulation of bubble generation in a T-junction

We present a numerical study of the formation of mini-bubbles in a 2D T-junction by means of the fluid dynamics numerical code JADIM. Numerical simulations were carried out for different flow conditions, giving rise to results on the behavior of bubble velocity, void fraction, bubble generation frequency and length. Numerical results are compared with existing experimental data thanks to non-dimensional analysis

A 3D CFD numerical study of the bubble generation process into a bubble Tjunction generator and its comparison with experimental data: Part I

This work presents a 3D numerical study of the bubble generation process into a bubble generator obtained with the commercial Computational Fluid Dynamics solver ANSYS Fluent v15.0.7, and its comparison with experimental data reproducing the same conditions. The bubble generator is formed by two perpendicular capillaries in which liquid and gas are injected at perpendicular directions into a 1 mm internal diameter capillary T-junction with a total length of 10 mm. The fluids used in experiments and CFD simulations are air and water, both of them considered incompressible and isothermal, at a room temperature of 25º. A total of 23 different cases are studied for different injection conditions, and results between numerical simulations and experiments are compared. In this first part of the analysis, we focus on the flow pattern regimes and the dynamics of the bubble generation process. In addition to the new numerical simulations presented here, a new model has been used to predict the bubble generation frequency and tested with both experimental and numerical data. Results on bubble generation frequency are also presented by means of the non-dimensional Strouhal number. Same types of patterns, bubble and slug flow regimes, are obtained in simulations and experiments. In order to perform an exhaustive validation and comparison of numerical simulations with experimental data, several parameters have been selected: bubble velocity, volumetric void fraction, bubble generation frequency, Strouhal number and bubble equivalent diameter. Numerical simulations agree qualitatively, but not always quantitatively, with experimental results.Peer ReviewedPostprint (published version

Influence of contact angle boundary condition on CFD simulation of T-Junction

“This is a post-peer-review, pre-copyedit version of an article published in Microgravity Science and Technology. The final authenticated version is available online at: https://doi.org/10.1007/s12217-018-9605-x ”.In this work, we study the influence of the contact angle boundary condition on 3D CFD simulations of the bubble generation process occurring in a capillary T-junction. Numerical simulations have been performed with the commercial Computational Fluid Dynamics solver ANSYS Fluent v15.0.7. Experimental results serve as a reference to validate numerical results for four independent parameters: the bubble generation frequency, volume, velocity and length. CFD simulations accurately reproduce experimental results both from qualitative and quantitative points of view. Numerical results are very sensitive to the gas-liquid-wall contact angle boundary conditions, confirming that this is a fundamental parameter to obtain accurate CFD results for simulations of this kind of problems.Peer ReviewedPostprint (published version

Coupled CFD Shape Optimization for aerodynamic profiles

The present document deals with the optimization of shape of aerodynamic profiles -- The objective is to reduce the drag coefficient on a given profile without penalising the lift coefficient -- A set of control points defining the geometry are passed and parameterized as a B-Spline curve -- These points are modified automatically by means of CFD analysis -- A given shape is defined by an user and a valid volumetric CFD domain is constructed from this planar data and a set of user-defined parameters -- The construction process involves the usage of 2D and 3D meshing algorithms that were coupled into own- code -- The volume of air surrounding the airfoil and mesh quality are also parametrically defined -- Some standard NACA profiles were used by obtaining first its control points in order to test the algorithm -- Navier-Stokes equations were solved for turbulent, steady-state ow of compressible uids using the k-epsilon model and SIMPLE algorithm -- In order to obtain data for the optimization process an utility to extract drag and lift data from the CFD simulation was added -- After a simulation is run drag and lift data are passed to the optimization process -- A gradient-based method using the steepest descent was implemented in order to define the magnitude and direction of the displacement of each control point -- The control points and other parameters defined as the design variables are iteratively modified in order to achieve an optimum -- Preliminary results on conceptual examples show a decrease in drag and a change in geometry that obeys to aerodynamic behavior principle

Periodismo ciudadano, en los límites de la profesión periodística

Citizen journalism has become a concern for journalists, media industry and for communication theorists trying to decipher the apparently secret keys of this new way of communication. Among all the related texts, we miss a clear categorization of this communicative way. In this research environment we provided here some light regarding concepts on which we are daily talking about in newsrooms, classrooms and lectures, and in the own network that generates the citizen journalism. We find necessary to review this issue in all its terms and components, its actual sense, from birth to today’s situation, in order to definitely build a valid theory for this so modern and so widespread communication.El periodismo ciudadano se ha convertido en una preocupación para los profesionales, para las empresas periodísticas y para los teóricos de la comunicación que tratan de descifrar las claves de esta, al fin y al cabo, nueva forma de comunicación. Entre los textos dedicados a ello echamos en falta una categorización clara de esta forma comunicativa, y en el contexto de estas investigaciones hemos puesto aquí negro sobre blanco respecto a conceptos sobre los que estamos todos los días discutiendo en redacciones, en las aulas y en la propia red que lo genera. Es urgente un repaso a la cuestión en todos sus términos y elementos, desde su nacimiento hasta la situación actual, para que definitivamente podamos construir una teoría válida para esta comunicación tan actual y tan generalizada

An analysis of two-phase flows in conditions relevant to microgravity

Promising technological applications of two-phase flows in space have captured the increasing interest of the space sector, provoking a strong demand for more fundamental knowledge. Great efforts have been made in recent decades to study the behavior of two-phase flows in low-gravity environments, which is expected to be different than the behavior observed in the presence of gravitational forces. Nevertheless, many phenomena are still poorly understood. The development of any of these new technologies demands a better knowledge of two-phase flows. In this manuscript we address questions regarding the generation of gas-liquid flows and their behavior in conditions relevant for a microgravity environment. In particular, we focus on an air-water mixture formed in a capillary T-junction. To this end, an experimental setup has been designed to accurately control both gas and liquid flow rates. We performed a quantitative characterization on ground of the T-junction, whose operation is robust to changes in gravity level. Its main performance is the generation of bubbles at a regular frequency with small size dispersion. We obtained two working regimes of the T-junction and identified the crossover region between them. Bubble, slug, churn and annular flow regimes have been observed during the experiments and a flow pattern map has been plotted. We present an experimental study on the bubble-slug transition in microgravity-related conditions. In addition, we address questions regarding the existence of a critical void fraction in order for the bubble-slug transition to occur. The gas-liquid flow has been characterized by measuring the bubble generation frequency as well as the bubble and liquid slug sizes. Since bubble dynamics is also expected to be different in the absence of buoyancy, the bubble velocity has also been studied. The mean void fraction appears as one relevant parameter that allows for the prediction of frequency, bubble velocity, and lengths. We propose curves obtained empirically for the behavior of generation frequency, the bubble velocity and the lengths. The dependence of the frequency on the Strouhal dimensionless number has been analyzed. A numerical study of the formation of mini-bubbles in a 2D T-junction by means of the fluid dynamics numerical code JADIM is also presented. Simulations were carried out for different flow conditions, giving rise to results on the bubble generation frequency, bubble velocity, void fraction and characteristic lengths. Numerical results have been then compared with experimental data

Búsqueda de la desintegración B c + → η c μ + ν μ con datos del LHCb.

ilustracionesUsing pp collisions corresponding to 4fb −1 integrated luminosity, recorded by the LHCb experiment at centre-of-mass energies of 13TeV, the ratio of branching fractions B(B c + → η c μ + ν μ )/B(B c → J/ψ μ ν μ )= (3.49 ± 0.86 stat. ± 0.20 syst. ± 0.34 PDG ) × 10 −1 , is determined, where the first uncertainty is statistical, the second systematic and the third come from the experimental measurement of the branching fractions η c → pp̄ and J/ψ → pp̄. There has been found evidence of the existence of the B c + → η c μ + ν μ decay at 3.7σ, including statistical and systematic uncertainties. (Texto tomado de la fuente)Usando colisiones pp correspondientes a una luminosidad integrada de 4fb −1 , registrada por el experimento LHCb en energías de centro de masa de 13TeV, la relación B(B c + → η c μ + ν μ )/B(B c + → J/ψ μ + ν μ ) = (3.49 ± 0.86 stat. ± 0.20 syst. ± 0.34 PDG ) × 10 −1 , es determinada, donde la primera incertidumbre es estadística, la segunda sistemática y la tercera proviene de la medición experimental de las tasas de desintegración η c → pp̄ y J/ψ → pp̄. Se ha encontrado evidencia de la existencia de la desintegración B c + → η c μ + ν μ a 3.7σ, incluyendo incertidumbres estadísticas y sistemáticas.MaestríaFísica experimental de partículas

International Broadcasting Radio Evolution and Internet Concurrence. The Case of “Radio Exterior de España”

La introducción de los cibermedios en el panorama empresarial de la comunicación ha supuesto un vuelco completo en el quehacer habitual de los medios tradicionales, que han tenido que adaptarse con rapidez y con toda la eficacia posible a una nueva forma de hacer periodismo. Los nuevos medios han experimentado una rápida evolución que ha producido, con cinco generaciones de cibermedios. Se estudia aquí la incidencia de este nuevo escenario global de las comunicaciones en un sector concreto de los medios audiovisuales como es la radio. Y en concreto en uno de los canales de la radio pública, Radio Exterior de España, como caso a su vez particular debido a dos características principales: su carácter global y el carácter de servicio público.The new communication business landscape of the online media has supposed a complete break in the day by day of traditional media, which have had the necessity to adapt quickly and efficiently to a new journalism. The new media have undergone an evolution which has produced five generations of online media. We study here the impact of this new global status of communications, and in a particular related to the part of audiovisual media such as Radio media. Particularly in one of the public world radio channel, Radio Exterior de España, as a case in turn especially due to two main characteristics: its global nature and its character of public service

Opciones terapéuticas en el carcinoma hepatocelular. Revisión bibliográfica

El hepatocarcinoma es el principal tumor primario del hígado, representando aproximadamente el 85-90% de las neoplasias primarias hepáticas. Es considerado el 5º cáncer más frecuente en varones, y el 7º en mujeres, apareciendo en torno a las 50-60 años. Es considerado la tercera causa de muerte relacionada con cáncer en el mundo. El hepatocarcinoma normalmente se asocia a cirrosis, cuyas principales causas son el alcohol y la hepatitis vírica. En recientes estudios epidemiológicos, se ha observado también un importante papel de la obesidad, la diabetes y el síndrome metabólico en el desarrollo del hepatocarcinoma. El hepatocarcinoma es un tumor solido muy vascularizado que se caracteriza molecularmente por una alteración en la regulación del ciclo celular, angiogénesis aberrante y evasión de la apoptosis. La patogenia del hepatocarcinoma es muy compleja, e incluye múltiples alteraciones genéticas y epigenéticas.Grado en Medicin