Doutorado em Engenharia Ambiental
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Navegando Doutorado em Engenharia Ambiental por Autor "Aquije Chacaltana, Julio Tomás"
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- ItemAnálise das deformações viscosas e da segregação de fases em floculadores tubulares helicoidais e suas relações com a razão de curvatura(Universidade Federal do Espírito Santo, 2015-12-02) Sartori, Maurício; Teixeira, Edmilson Costa; Pires, Eduardo Cleto; Rauen, William Bonino; Aquije Chacaltana, Julio Tomás; Rigo, DanielHelical tubular flocculators (FTHs) when compared with the currently employed hydraulic flocculato s in water and wastewater treatment plants have demonstrated high efficiency in the floc formation with low hydraulic retention time (Tdh) and high power dissipation levels, challenging the current flocculation paradigm (high Tdh and low energy dissipation levels). However, the mechanisms that enable these flocculators operating satisfactorily in these operational conditions have not yet been elucidated. It is known that the fluid viscous deformations present a great influence on the collision opportunity and, consequently, on the flocculation. Another factor that also has relevance in the flocculation is the particles’ concentration which, in the current models, it is assumed uniform throughout the reactor. In this context, aiming at enhance the understanding of the flocculation in those flocculators, this work presents an evaluation of the influence of the FTHs’ curvature ratio (d/D, where d is the tube diameter and D is the coil diameter) on the fluid elements strain rate, which has been assumed to be the main collision mechanism between particles. It is also shown that d/D influences the phase segregation, a characteristic of two-phase flows in curved pipes. For this purpose, we evaluated 5 FTHs configurations with curvature ratio of 0.0091, 0.0182, 0.0364, 0.0729 and 0.1458, with the support of computational fluid dynamic simulations (monophasic and biphasic), with and without considering the gravitational field, by adopting horizontal and vertical coil axes, respectively. The results demonstrate the importance of taking into account the linear strains, neglected in some collision models, besides the direct relationship of the curvature ratio with both angular and linear strains, and, consequently, with the shear strain rate. Regarding the phases segregation, there was an inverse relationship with the curvature ratio. However, this segregation is influenced by the reactor's position relative to the gravitational field. In horizontal coil axis reactors, at each turn, there is a cycle of segregation and mixing. In vertical axis FTHs, there is a significant increase of particles’ concentration in the reactor region close to the inner wall, due to the combined effect of the secondary flow drag and gravitational attraction.
- ItemEstudo da fase gravitacional-inercial do espalhamento de óleo em mar calmo empregando o método lagrangiano de partículas smoothed particle hidrodynamics(Universidade Federal do Espírito Santo, 2014-12-15) Fraga Filho, Carlos Alberto Dutra; Aquije Chacaltana, Julio Tomás; Rigo, Daniel; Mendonça, Antônio Sérgio Ferreira; Maciel, Geraldo de Freitas; Morales, Rigoberto Eleazar MelgarejoOil spill on the sea is considered a serious environmental problem. It can occur during oil well drilling, repair and transport operations. The spreading of oil is due to the tendency of the pollutant to flow over itself. Knowledgement of oil physical properties during the spreading, like velocities and positions allows the adoption of environmental protection actions. The modelling of the physical process, due to a balance between gravitational, inertial, viscous and interfacial tension forces, started during the mid-twentieth century, when Fay adjusted curves to experimental data, considering a calm sea condition. These adjusted curves, defined for idealized theoretical conditions are still used, with some modifications. This Thesis presents the development and implementation of a purely Lagrangian meshless model, considering the fundamentals of the Smoothed Particle Hydrodynamics (SPH) method for the study of the spreading of oil. A model for the collisions between the particles and boundary was implemented, with the definition of a coefficient of restitution of kinetic energy. The model was validated by using results, from the literature, for classical problems: heat diffusion on a flat plate, static tank containing an incompressible fluid and dam breaking. After model validation, it was performed the numerical simulation of the spreading of oil on calm sea conditions, in its first phase (gravitational-inertial). There was agreement between the numerical results obtained with the use of an appropriate coefficient of restitution of kinetic energy and those provided by the adjusted curve proposed by Fay, for the diameter of the oil slick at the end of the studied phase.
- ItemEstudo numérico do sloshing utilizando o método smoothed particle hydrodynamics(Universidade Federal do Espírito Santo, 2018-03-12) Barbosa, Danilo de Almeida; Piccoli, Fábio Pavan; Aquije Chacaltana, Julio Tomás; Buarque, Diogo Costa; Teixeira, Edmilson Costa; Morales, Rigoberto Eleazar Melagarejo; Moreira, Roger MatsumotoThe increasing exploitation of offshore oil and consequent increase in the number of FPSO platforms and vessels to transport this fluid requires increasing attention to the effects produced by the free surface oscillation in transport tanks and storage of liquid petroleum and liquefied gas. In this thesis, a study on the impacts on the sidewalls of rectangular containers provoked by sloshing is proposed. The lagrangian free-particle method known as SMOOTHED PARTICLE HYDRODYNAMICS-SPH, which in its genuine form makes use of the force from the Lennard-Jones potential to keep the particles inside the domain was applied. Contributions to the method were also performed, such as the alteration in the search system of neighboring particles; proposal of a relation between the number of virtual particles and smoothing length; and pointing to an "optimal number" of contour particles. Besides the control of the correction parameters that allowed to reduce the processing time. However, the most relevant contribution was the creation of a new contour treatment technique using the COULOMB FORCE, which proved to be more robust than the classical technique (Lennard-Jones). The mathematical modeling passed through the equations of mass conservation and conservation of linear momentum. With this, two-dimensional simulations with different geometries were made and after identification of the causes and effects produced by sloshing, suppression mechanisms were installed inside the tanks. For validation of the models, three experimental tests were carried out by different authors, two of whom simulated the behavior of tanks under the action of horizontal forces on a reduced scale, and a third the movement of pitch with the tank on an inverted pendulum platform. The quantitative data of the hydrodynamic pressure were collected by transducers installed on the walls of the containers. The tests followed with baffles of two different heights and with arrow-shaped deflectors acting as fins. All baffles were effective in reducing normal stresses, however, those in the arrow shape presented higher than standard vertical baffles, indicating that adequate morphology may reduce sloshing damage.
- ItemModelo de escoamento multifásico para estudo da interação onda/sedimento(Universidade Federal do Espírito Santo, 2014-04-29) Piccoli, Fábio Pavan; Aquije Chacaltana, Julio Tomás; Rigo, Daniel; Reis, José Antonio Tosta dos; Maciel, Geraldo de Freitas; Rosman, Paulo Cesar ColonnaMultiphase flow models are widely used in many fields of environmental research, such as fluidized beds, gas dispersion in liquids, dam breaks, oil spill and others physical and chemical processes that use more than one property. Thus, a multiphase model to study the dynamics of two distinct properties represented on reference Eulerian-Lagrangian was developed. In order to study the dynamics of sediment transport due to wave’s action, a non-linear wave Boussinesq model in Eulerianframe, in which the numerical formulation based on Wei et al. (1995), and a Lagrangian particle model, whose formulation is given by the Newtonian principle of motion, has beendeveloped. In the Lagrangian particle model was added the scheme of hard-spheres particle collision. The coupling between the two models has been doing withthe wave transferring momentum to sedimentparticles, which is carried by the flow. For the wave’s model, the wave maker, defined by a Gaussian function, piston-paddle and flap-paddle, and the effects due to the depth of the waves were tested. The Gaussian wave maker showed better consistency in the generation of waves, getting errors about 0.11% compared tothe linear theory forkh . The wave’s nonlinearity simulated by the 2 nd order dispersion Boussinesq-wave model showed satisfactory results when compared withexperiment of wave propagation over a trapezoidal obstacle, where the deformation of the wave on the underwater structure is in agreement with literature data. In addition to the granular model was also tested in two experiments: the first, which simulates a dam break in a tank containing water-air; and the second experiment, the dam break interact withan obstacle in the center of the tank. In both experiments, the collision model was effective in the treatment of the interaction between the particles and the wall, and allowed the evidence of physical processes that are complicated to be simulated bymodels that use regular grids. For the coupling of wavesediment model, the algorithm has been tested with data obtained from the literature as the morphology of the bed. The results were compared with analytical data and numerical models, and it showed a certain agreement on points of erosion, sedimentation and change in shape of the sand bar.