MARCELO FABIAN PIVA - Academia.edu (original) (raw)

Papers by MARCELO FABIAN PIVA

En este trabajo se presenta un estudio experimental sobre el flujo producido por un rotor en el f... more En este trabajo se presenta un estudio experimental sobre el flujo producido por un rotor en el fondo de un cilindro vertical lleno parcialmente con un liquido. Esta configuracion geometrica genera un flujo rotante en el plano paralelo al eje de simetria y un flujo recirculante en planos meridionales. De entre los parametros que gobiernan el proceso el numero de Reynolds es, quizas, el mas importante por lo que el estudio abarca una extensa gama de valores de este parametro, cubriendo practicamente cinco decadas. Se ha dividido el campode estudio en tres regiones: Reynolds pequenos, medianos y grandes. Trabajando en el primer regimen se observo el fenomeno de ruptura del vortice (vortex breakdown)solo en la configuracion experimental en la que el disco cubre totalmente el fondo del recinto. Esta observacion motivo la realizacion de experiencias numericas que demuestran que la relacion entre el radio del disco y el radio del cilindro es un factor muy importante en el umbral de ruptur...

EPJ Web of Conferences, 2021

To gain an understanding of the factors affecting the interaction of one grain with its environme... more To gain an understanding of the factors affecting the interaction of one grain with its environment as it reaches equilibrium, we study a particle bouncing off a flat surface. The bouncing of the particle leads to dissipation that is usually characterized with t, the coefficient of restitution, defined as the ratio between the velocity component that is normal to the contact surface just before impact (Vn) and the same component, but immediately after the collision (Vn’), i.e. related to a kinetic energy corresponding to motion in the normal direction. We will show how d is affected by energy stored in other degrees of freedom and transferred to kinetic energy that leads to an increase in normal velocity after the impact Vn’, and therefore to, ɛ >1. For this purpose, the evolution of potential, translational kinetic energy and rotational kinetic energy is analysed during the whole relaxation process and just before and after each collision for two different types of particle, a d...

arXiv: Fluid Dynamics, 2018

We report on an experimental study of the Faraday instability for a uid layer situated over a per... more We report on an experimental study of the Faraday instability for a uid layer situated over a permeable rough substrate. A set of meshes and a at solid bottom are used to study different substrate permeabilities. We observe that, in comparison with a at solid bottom, the presence of a mesh leads to an increase of the critical acceleration of the instability. We interpret the results as a decrease of the effective thickness of the fluid layer, and we discuss its relation with the mesh properties.

Diego Barba Maggi, Alejandro Boschan, Roman Martino, Marcelo Piva and Jean-Christophe Géminard. G... more Diego Barba Maggi, Alejandro Boschan, Roman Martino, Marcelo Piva and Jean-Christophe Géminard. Grupo de Medios Porosos, Fac. de Ingenieŕıa, Universidad de Buenos Aires. Paseo Colón 850, (C1063ACV) Buenos Aires, Argentina. Université de Lyon, Laboratoire de Physique, Ecole Normale Supérieure de Lyon, CNRS, UMR 5672, 46 Allée d’Italie, 96007 Lyon, France. and Escuela Superior Politécnica de Chimborazo, ESPOCH, Panamericana Sur Km 1 1/2, Riobamba, Ecuador.

Physical Review E, 2020

The interaction between the oscillatory boundary-layer flow induced by Faraday waves and a sedime... more The interaction between the oscillatory boundary-layer flow induced by Faraday waves and a sedimentary granular layer was studied in a Hele-Shaw cell vertically vibrated. The experimental parameters were the vibration frequency f and acceleration a, and the particle diameter dp. At a critical value for the depth of the supernatant fluid layer, ∆hc, it was observed a transition between a flat motionless granular layer and a second regime in which the granular layer undulates and oscillates periodically. For the smallest value of dp (for which the Stokes number was St << 1) the reduced acceleration Γ = a/g (g is the acceleration of gravity) is independent on ∆hc, while for the larger ones, Γ depends linearly on ∆hc. Finally, it is shown that at the onset of grains motion, the wave velocity Vw = hwf /2 (hw is the wave amplitude) depends linearly on ∆hc and is independent of dp.

Journal of Engineering Mechanics, 2020

AbstractThe transport of spheres as a bed-load through a sparse network of immobile, bed-mounted ... more AbstractThe transport of spheres as a bed-load through a sparse network of immobile, bed-mounted submerged cylinders was experimentally studied to quantify how the mean velocity of the spheres in t...

Powder Technology, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Environmental Fluid Mechanics, 2017

Physical Review E, 2019

We report on an experimental study of the Faraday instability in a vibrated fluid layer situated ... more We report on an experimental study of the Faraday instability in a vibrated fluid layer situated over a permeable and rough substrate, consisting either of a flat solid plate or of woven meshes having different openings and wire diameters, open or closed (by a sealing paint). We measure the critical acceleration and the wavelength (on the images from top) at the onset of the instability for vibration frequencies between 28 and 42 Hz. We observe that, in comparison with the flat plate, a mesh leads to an increase of the critical acceleration, whereas the wavelength is not significantly altered in none of the explored cases. In order to rationalize the observations, we use the linear theory written for the case of a flat bottom and a viscous fluid to define an effective thickness of the fluid layer, which permits to define a slip length at the bottom. For the closed meshes the slip length is simply a linear function of the distance between wires constituting the mesh, whereas it exhibits a more complex behavior for the open meshes. We propose a qualitative understanding for the observed features.

European Journal of Mechanics - B/Fluids, 2019

The effect of lateral confinement due to very close side walls, on erosion caused by a water jet ... more The effect of lateral confinement due to very close side walls, on erosion caused by a water jet issuing from a rectangular sluice aperture, has been studied experimentally in a narrow laboratory flume. Velocimetry (PIV) in presence of a smooth, no erodible bottom, revealed self-similar velocity profiles with the structure of a wall jet, but upward-shifted with respect to the classical two-dimensional profile. The classical definition of the Shields number was modified, to include the influence of the relative roughness and the inlet aspect ratio. This last coefficient was also relevant in the definition of a suitable length scale to account for the effect of the lateral confinement. Scour patterns in the narrow flume have also shown differences with respect to erosion by two-dimensional wall jets: the downstream mound undergoes a morphological transition, from triangular to trapezoidal, at the early stage of the scour development, and grains move downhill driven by gravity inside the granular wedge, in a regime of steady recirculation (SR). Above this regime, a digging-refilling (DR) cycle, with periods of the order of seconds, triggers at a well-defined Shields number.

Physical Review E, 2018

We study the stability of granular systems constituted by particles with inhomogenous distributio... more We study the stability of granular systems constituted by particles with inhomogenous distribution of inner mass, which is a factor that has not been previously analyzed. In particular, we report experimental results concerning the stability of two-dimensional piles of hollow plexiglass cylinders containing an inserted smaller metal rod. These particles partially fill a rough-edged drum whose rotation produces successive avalanches. The distribution of the maximum angle of stability, angle of repose and avalanche sizes are analyzed for systems where the inserts are fixed or free to move.

Environmental Fluid Mechanics, 2011

ABSTRACT This contribution presents particle image velocimetry measurements for an open channel s... more ABSTRACT This contribution presents particle image velocimetry measurements for an open channel stationary uniform and fully developed flow of water over a horizontal flat bed of uniform glass beads in presence of a staggered array of vertical cylindrical stems. The main objective was to explore and quantify the influence of the stems-to-flow relative submergence, h v /h, over the mean flow and local turbulence intensities. A comparison with measurements for the non-vegetated flow over the same granular bed is presented. Results indicate a remarkable influence of h v /h over the whole flow field. The time-average mean flow presents a strong spatial variation in the layer of the flow occupied by the stems. The local velocity fluctuations are strongly affected by the presence of the stems, with regions in between the stems where they reach peaks that are several times larger than those encountered in the flow in absence of vegetation. The turbulence intensity profiles are noticeably different when compared to those measured in the non-vegetated flow conditions. From previous works it was possible to derive an equation for the mean velocity, U v , of the flow through the vegetated layer of height h v . The prediction of this equation is in good agreement with the uniform value for the double-average longitudinal velocity profile in this layer. A final brief discussion about the possible impact of these vegetated-flow features on the sediment transport is presented.

Journal de Physique III, 1997

$Research paper thumbnail of Caract�risation de la dispersion avec un mod�le fractionnaire$

Journal of Physics A-mathematical and General, 2003

The authors of this paper have noticed that they made a mistake concerning the stability of the f... more The authors of this paper have noticed that they made a mistake concerning the stability of the fixed points where the molecule is located horizontally, leading to figures 9 and 10 being incorrect. Please see pdf for full details.

$Research paper thumbnail of Caractérisation de la dispersion avec un modèle fractionnaire$

Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics-Physics-Chemistry-Astronomy, 1998

We use the fractional dispersion concept to analyse the anomalous diffusion regime shown in a tra... more We use the fractional dispersion concept to analyse the anomalous diffusion regime shown in a tracer dispersion in a hydrodynamical Taylor-Couette experiment. The anomalous diffusion is characterized with a parameter a (diffusion exponent), equal to two for the Gaussian diffusion. The results of the fractional advection-diffusion equa lion are compared to the concentration curves of the residence time distributions obtained

The Physics Teacher, 2009