Ricard González-Cinca

Polytechnic University of Catalonia, Barcino, Catalonia, Spain

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Publications (34)43.73 Total impact

  • Francesc Suñol · Ricard González-Cinca
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    ABSTRACT: We present an experimental study on the characteristics of liquid jets in different configurations. We consider jets injected perpendicular to gravity, jets injected parallel to gravity, and jets injected in a microgravity environment. We study the role played by gravity in the jet breakup length and in the dynamics of the droplets generated after breakup. We analyze droplets obtained in the dripping and jetting regimes, focusing the study on their size, trajectory, oscillation, and rotation. The particularities of the considered injection configurations are analyzed. In normal gravity conditions, in the dripping and jetting regimes, the breakup length increases with the Weber number. The transition between these regimes occurs at Wecr ≈ 3.2. Droplets are notably larger in the dripping regime than in the jetting one. In the latter case, droplet mean size decreases as the liquid flow rate is increased. In microgravity conditions, droplet trajectories form a conical shape due to droplet bouncing after collision. When a collision takes place, coalescence tends to occur at low modified Weber numbers (We m < 2) while bouncing is observed at higher values (We m > 2). The surface of a droplet oscillates after bouncing or coalescence events, following a damped oscillator behavior. The observed oscillation frequency agrees with theoretical predictions.
    No preview · Article · Jul 2015 · Physics of Fluids
  • Francesc Suñol · Ricard González-Cinca
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    ABSTRACT: We present an experimental analysis of the effects of gravity level on the formation and rise dynamics of bubbles. Experiments were carried out with millimeter-diameter bubbles in the hypergravity environment provided by the large-diameter centrifuge of the European Space Agency. Bubble detachment from a nozzle is determined by buoyancy and surface tension forces regardless of the gravity level. Immediately after detachment, bubble trajectory is deviated by the Coriolis force. Subsequent bubble rise is dominated by inertial forces and follows a zig-zag trajectory with amplitude and frequency dependent on the gravity level. Vorticity production is enhanced as gravity increases, which destabilizes the flow and therefore the bubble path.
    No preview · Article · May 2015 · Physical Review E
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    ABSTRACT: We perform a characterization of a recently reported microbubble injector in conditions relevant to microgravity. Injection of bubbles is based on the generation of a slug flow in a capillary T-junction, whose operation is robust to changes in the gravity level. We address questions regarding the performance under different working regimes. In particular, we focus on the regimes found within a large range of gas and liquid injection flow rates. The injection performance is characterized by measuring bubble generation frequency. We propose curves obtained empirically for the behavior of generation frequency and crossover between regimes.
    Full-text · Article · Sep 2014
  • Anna Garcia-Sabaté · Angélica Castro · Mauricio Hoyos · Ricard González-Cinca
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    ABSTRACT: A method for the experimental measurement of inter-particle forces (secondary Bjerknes force) generated by the action of an acoustic field in a resonator micro-channel is presented. The acoustic radiation force created by an ultrasonic standing wave moves suspended particles towards the pressure nodes and the acoustic pressure induces particle volume oscillations. Once particles are in the levitation plane, transverse and secondary Bjerknes forces become important. Experiments were carried out in a resonator filled with a suspension composed of water and latex particles of different size (5-15 [Formula: see text]) at different concentrations. Ultrasound was generated by means of a 2.5 MHz nominal frequency transducer. For the first time the acoustic force generated by oscillating particles acting on other particles has been measured, and the critical interaction distance in various cases has been determined. Inter-particle forces on the order of [Formula: see text] have been measured by using this method.
    No preview · Article · Mar 2014 · The Journal of the Acoustical Society of America
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    ABSTRACT: One of the biggest challenges of the exploration of the Moon is the survival of the crew and the lunar assets during the lunar night. The environmental conditions on the lunar surface and its cycle, with long periods of darkness, make any long mission in need of specific amounts of heat and electricity to be successful. We have analyzed two different systems to produce heat and electricity on the Moon's surface. The first system consists of Thermal Wadis, sources of thermal power that can be used to supply heat to protect the exploration systems from the extreme cold during periods of darkness. Previous results showed that Wadis can supply enough heat to keep lunar devices such as rovers above their minimum operating temperature (approximately 243 K). The second system studied here is the Thermal Energy Storage (TES), which is able to run a heat engine during the lunar night to produce electricity. When the Sun is shining on the Moon's surface, the system can run the engine directly using the solar power and simultaneously heat a thermal mass. This thermal mass is used as a high temperature source to run the heat engine during the night. We present analytical and numerical calculations for the determination of an appropriate thermal mass for the TES system.
    No preview · Article · Jan 2014 · Acta Astronautica
  • Francesc Suñol · Ricard González-Cinca
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    ABSTRACT: The characteristics of two impinging bubble jets have been experimentally studied in microgravity conditions. The experimental setup, designed to be used in a drop tower, allows to change the gas and liquid flow rates for the jet generation, and the separation distance between the jets. A slug flow with millimetric air bubbles is created in a T-junction and injected through a nozzle in a water tank. The formation and dynamics of the generated bubble jets have been recorded by means of a high-speed camera. The effects of the momentum flux and the separation distance on the two-phase flow have been investigated. When jets do not interact, they show a conical shape with an opening angle which decreases from Psi=63 degrees to Psi=12 degrees as the momentum flux is increased from J = 1 g cm/s(2) to = 88 g cm/s(2). Bubble velocities in the direction of injection decrease from v(x) = 361 cm/s to v(x) = 23 cm/s in the most extreme case, as the bubble center position reaches the impingement region. Interacting bubble jets form a cross-like shape as the jets evolve in time. Bubble mean diameter decreases from (d) over bar = 1.7 cm to (d) over bar =1.3 cm, as the momentum flux increases from J=8 g cm/s(2) to J=43 g cm/s(2). Coalescence events, occurring mainly near the nozzles and in the impingement region, are responsible for the widening of the tail in the bubble size distribution. The global jet behavior and the individual bubble dynamics present several differences in microgravity compared to previous observations carried out on ground.
    No preview · Article · Jun 2013 · Chemical Engineering Science
  • S. Arias · R. González-Cinca
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    ABSTRACT: We present an experimental study on the bubble–slug flow pattern transition which takes place in two-phase flows in microgravity related conditions. Two different sets of experiments were performed on ground with air/water and air/ethanol mixtures in a minichannel with an internal diameter of 1 mm. We address questions regarding the existence of a critical void fraction for the bubble–slug transition to occur. Experimental data are compared to the drift-flux and Suratman models predictions. We obtain results on the extension of applicability of these models for different boundary conditions.
    No preview · Article · Mar 2013 · Chemical Engineering Science
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    Santiago Arias · Dominique Legendre · R. González-Cinca
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    ABSTRACT: 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.
    Preview · Article · Mar 2012 · Computers & Fluids
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    N Méndez · R González-Cinca
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    ABSTRACT: A new Boundary Element Method software for simulating bubble dynamics is presented. This tool allows us to simulate a wide variety of scenarios, including external acoustic fields and multiple bubble interaction. We present results on the interaction between two oscillating bubbles in various configurations. Different sized bubbles under the effects of acoustic fields at different frequencies have been considered.
    Preview · Article · Dec 2011 · Journal of Physics Conference Series
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    Francesc Sunol · Ricard Gonzalez-Cinca
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    ABSTRACT: The droplet dynamics and collisions after a liquid jet breakup have been experimentally studied in low gravity conditions. An experimental setup was designed in order to be used at the I.N.T.A. Drop Tower, which allows for 2.1 seconds of microgravity. The dynamics of distilled water jets injected into a rectangular tank was recorded by means of a high-speed video camera. Observations of the droplet trajectories showed a conical shape of the liquid jet caused by droplet collisions just after detachment from the liquid jet. The detached droplets initially follow straight paths at constant velocity in the direction of injection. Deviation of these trajectories is a consequence of the collision between two droplets with an impact parameter slightly different from zero. The collision between two droplets can give rise to coalescence or bouncing between droplets depending on the droplet velocity difference and impact parameter. At low values of the relative velocity, the collision leads to coalescence between droplets, while at higher values the collision results in bouncing between droplets.
    Preview · Article · Dec 2011 · Journal of Physics Conference Series
  • Francesc Suñol · Ricard González-Cinca
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    ABSTRACT: The impingement of bubbly jets in distilled water and ethanol has been experimentally studied on ground. An experimental apparatus for the study of jet impingement on ground and in microgravity has been designed. The opposed-jet configuration with changeable orientation is used in order to study which is the better disposition to achieve an efficient mixing process. The impact angle between jets that can be changed from 0° (frontal collision) up to 90° (perpendicular collision). The impinging jets are introduced into a test tank full of liquid by means of two bubble injectors. The bubble generation method, insensitive to gravity level for low Bond numbers, is based on the creation of a slug flow inside a T-junction of capillary tubes of 0.7 mm of diameter. Bubble velocities at the injector outlet and generation frequencies can be controlled by changing gas and liquid flow rates. Individual bubble properties and coalescence events, as well as the whole jet structure are analyzed from the images recorded by a high speed camera. Bubble velocities are compared with the velocity field of a single-phase jet. Rate of coalescence between bubbles is found higher in ethanol than in water, creating a higher dispersion in bubble sizes. KeywordsJet impingement–Bubbly jet–Two-phase flow–Jet mixing
    No preview · Article · Feb 2011 · Microgravity - Science and Technology
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    S. Arias · R. González-Cinca · X. Ruiz · L. Ramírez-Piscina · J. Casademunt
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    ABSTRACT: We perform a characterization of a recently reported minibubbles (bubbles with a diameter of the order of 10−3 m) generator in microgravity related conditions. Generation of bubbles is based on the generation of a slug flow in a capillary T-junction, whose operation is robust to changes in the gravity level. We address questions regarding the performance under different working regimes. In particular, we focus on the regimes found within a large range of gas and liquid injection flow rates. The injection performance is characterized by measuring bubble generation frequency. We propose curves obtained empirically for the behaviour of generation frequency and crossover between regimes.
    Full-text · Article · Aug 2010 · Colloids and Surfaces A Physicochemical and Engineering Aspects
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    Francesc Suñol · Ricard González-Cinca
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    ABSTRACT: The structure of two colliding water jets containing small gas bubbles is studied experimentally. The effects of the separation distance between jets, as well as the orientation angle, on the spatial distribution of bubbles have been considered. Results on the global structure of the final jet and bubble properties have been obtained using a high-speed video camera, and measurements of the positions of coalescence events are presented. Jets are introduced through inclined pipes (with a diameter of 0.7 mm) into a large water tank to avoid wall effects. Inclination angle has been changed from 0° to 45° with respect to the horizontal, resulting in a 0° up to 90° impact angle between jets. Generation of bubbles is controlled by a T-junction device where a regular slug-flow is created prior to injection. Bubble sizes have been measured, and a mean diameter of around 1 mm has been obtained using high values of the liquid flow rate. In the studied range of separation distances between the bubbly jets, a more homogeneous dispersion of bubbles is created as the distance between jets is decreased and the momentum flux of each jet is increased. Higher numbers of coalescences are observed when using smaller distance between jets, and the obtained measurements revealed that the number of bubble coalescence events is reduced significantly using high values of liquid flow rates.
    Preview · Article · Aug 2010 · International Journal of Multiphase Flow
  • Francesc Suñol · Ricard González-Cinca
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    ABSTRACT: The rise, bouncing and coalescence processes of millimetric gas bubbles impacting at a free surface were studied experimentally. Single air bubbles were released from a syringe into a methacrylate tank filled with ethanol. The position and shape of the bubbles were measured from the images recorded by means of a high-speed camera. Bubbles with equivalent diameters de<0.47 mm rise until they touch the free surface and coalesce with it immediately. In contrast, bubbles with equivalent diameters de≥0.47 mm bounce repeatedly before the coalescence with the free surface occurs. We present results on the bubble terminal velocities, drag forces, and shape of the bubble during its steady rise before coalescence takes place. The oscillatory behavior of the bubble shape after the collision is described, and the position and velocities of bubbles during the bouncing process are analyzed. The motion of the bubble after the first bounce is found to be very similar to that of a damped oscillator. Bouncing time increases with bubble size, and so does the height of the bounce.
    No preview · Article · Aug 2010 · Colloids and Surfaces A Physicochemical and Engineering Aspects
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    ABSTRACT: Presentamos aquí una nueva metodología en la impartición de un curso de ciencias de la computación con énfasis particular en aspectos de dinámica de fluidos computacional (DFC) y las experiencias que se derivan de esta implementación. Las actividades principales que los estudiantes realizan en este curso son: el desarrollo de un proyecto inicial en la temática de ciencias de los materiales, la elaboración de un proyecto largo en DFC y una introducción al uso de un paquete de software específico de DFC. Los proyectos se realizan por grupos y consisten en la implementación (programación) de modelos matemáticos y una interfaz gráfica que permita la visualización de los resultados que se obtengan mediante la resolución numérica de los modelos considerados. La innovación en la asignatura se da en la utilización de técnicas de aprendizaje basado en proyectos o Project Based Learning y en el hecho que el curso es impartido de forma coordinada por varios profesores que provienen de áreas distintas. Otro aspecto novedoso lo constituye la oportunidad que presenta el curso para que los estudiantes redacten informes escritos, hagan presentaciones orales, utilicen el inglés y trabajen en un entorno Linux para el desarrollo de los proyectos. Postprint (published version)
    Full-text · Article · Dec 2009
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    F. Suñol · O. Maldonado · R. Pino · R. González-Cinca
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    ABSTRACT: A new experimental setup for the study of bubble coalescence and bubble jet interactions in microgravity conditions is presented. The section consists of a cavity full of liquid containing two bubble injectors whose separation distance and relative orientation angle can be controlled. Injection of bubbles is based on the generation of a slug flow in a capillary T-junction, which allows a control of bubble size and velocity by means of liquid and gas flow rates. Individual and collective behaviour of bubbles injected in the cavity has been studied. On ground results on the individual trajectories, maximum distance reached, and the delimitation between turbulence and buoyancy regions are presented. The influence on these results of the inclination angle of one injector with respect to gravity has also been considered. A good knowledge of bubble jets behaviour in microgravity will enhance the development of space technologies based on two-phase systems.
    Full-text · Article · Dec 2008 · Microgravity - Science and Technology
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    Ricard González-Cinca · Eduard Santamaria · J. Luis A. Yebra
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    ABSTRACT: This article describes an innovative methodology for teaching an undergraduate course on Computational Science, with a particular emphasis in Computational Fluid Dynamics (CFD), and the experiences derived from its implementation. The main activities taking place during this course are: development by students of a training project on a topic in materials science, development of a larger CFD project, and an introduction to a CFD commercial package. Projects are carried out by groups of students and are assigned from a set of different available possibilities. Project development consists in the implementation in code of the corresponding mathematical models and a graphical interface which permits the visualization of the results derived from the numerical resolution of the models. The main innovative aspects of the methodology are the use of Project Based Learning combined with the participation of lecturers from different areas of expertise. Other innovative issues include the opportunity for students to practice skills such as report writing, doing oral presentations, the use of English (a foreign language for them) and the use of Linux as the development environment.
    Full-text · Chapter · Jun 2008
  • Pere Bruna · Daniel Crespo · Ricard González-Cinca · Eloi Pineda
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    ABSTRACT: Calorimetric data of primary crystallization is usually interpreted in the framework of the Kolmogorov [Dokl. Akad. Nauk SSSR 1, 355 (1937)] , Johnson and Mehl [Trans. AIME 135, 416 (1939)] , and Avrami [J. Chem. Phys. 7, 1103 (1939) ; 8, 212 (1940) ; 9, 177 (1941)] (KJMA) theory. However, while the KJMA theory assumes random nucleation and exhaustion of space by direct impingement, primary crystallization is usually driven by diffusion-controlled growth with soft impingement between the growing crystallites. This results in a stop of the growth before the space is fully crystallized and induces nonrandom nucleation. In this work, phase-field simulations are used to check the validity of different kinetic models for describing primary crystallization kinetics. The results show that KJMA theory provides a good approximation to the soft-impingement and nonrandom nucleation effects. Moreover, these effects are not responsible of the slowing down of the kinetics found experimentally in the primary crystallization of glasses.
    No preview · Article · Sep 2006 · Journal of Applied Physics
  • P. Bruna · D. Crespo · R. González-Cinca · E. Pineda
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    ABSTRACT: A variety of nano-structured materials are obtained by primary crystallization of rapidly-quenched amorphous precursors, the new phase developing by nucleation and diffusion controlled growth [1,2]. In many cases slowly diffusing elements are added in order to control the crystallite growth and obtain refined grain size distributions [3]. Surface instability is not observed in such crystallizations due to the reduced grain size, but the concentration profiles around the growing crystallites affect both the nucleation and the growth of neighbor particles [4]. On the one hand, the stabilization in the crystalline grain surroundings inhibits the nucleation process, thus reducing the probability of nucleation of new particles. In this work this non-homogeneously distributed nucleation probability will be referred as Non-Random Nucleation (NRN). On the other hand, the overlapping of the slowest solute concentration profiles reduces the gradients and consequently the growth rate of the grain boundary region facing a neighbor crystallite. The grain growth of the grains is then stopped before direct impingement and, besides, it becomes non-isotropic because of its dependence on the local distribution of neighbor particles. This behavior is commonly referred as diffusion controlled Growth with Soft-Impingement (GSI).
    No preview · Article · Aug 2005
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    R González-Cinca · Yves Couder · A Hernández-Machado
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    ABSTRACT: The development of side-branching in solidifying dendrites in a regime of large values of the Peclet number is studied by means of a phase-field model. We have compared our numerical results with experiments of the preceding paper and we obtain good qualitative agreement. The growth rate of each side branch shows a power-law behavior from the early stages of its life. From their birth, branches which finally succeed in the competition process of side-branching development have a greater growth exponent than branches which are stopped. Coarsening of branches is entirely defined by their geometrical position relative to their dominant neighbors. The winner branches escape from the diffusive field of the main dendrite and become independent dendrites.
    Full-text · Article · Jun 2005 · Physical Review E

Publication Stats

255 Citations
43.73 Total Impact Points

Institutions

  • 1996-2015
    • Polytechnic University of Catalonia
      • Department of Applied Physics (FA)
      Barcino, Catalonia, Spain
    • Universitat Oberta de Catalunya
      • Department of Applied Physics
      Barcino, Catalonia, Spain
  • 2014
    • University of Alabama in Huntsville
      Huntsville, Alabama, United States
    • French National Centre for Scientific Research
      Lutetia Parisorum, Île-de-France, France
  • 2011
    • University of Barcelona
      Barcino, Catalonia, Spain