LEANDRO GOULART DE ARAUJO

LEANDRO GOULART DE ARAUJO

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Three-dimensional transient numerical simulation of the solid volume fraction of a fluidized bed
2021 - OLIVO-ARIAS, L.P.; ARAUJO, L.G.
The FLUENT solver employed in the Computational Fluid Dynamics (CFD) has been extensively developed to extend its robustness and precision for a wide range of flow regimes. For that, the FLUENT solver has a numerical method in the pressure-based solver that has traditionally been used for incompressible and slightly compressible flows. The algorithm is based on the pressure that solves the equations in a segregated or decoupled mode. This algorithm has proven to be robust and versatile and has been used cooperatively with a wide range of physical models, including multiphase flows and conjugated heat transfer. However, there are applications in which the convergence rate of the segregated algorithm is not satisfactory, generally due to the need in these coupling scenarios between the continuity and momentum equations. The objective of this article is to validate the Eulerian model to determine the volumetric fractions of the solid phase fraction. For this, we used data from the literature and the PCSIMPLE algorithm (solver) at different orders of solution of the continuity, momentum, and turbulence equations. Also, we determined its efficiency in transient systems and how it would affect the results in the hydrodynamics of a three-phase fluidized bed reactor. The results were significant, thus representing the phenomenon of interaction between the liquid-solid and solid-gas phases.
The influence of the initial gas distribution on the dynamics of a three-phase fluidized bed reactor
2021 - OLIVO-ARIAS, L.P.; ARAUJO, L.G.
The hydrodynamic evolution of a three-dimensional (3D) liquid-gas-solid fluidized bed reactor was studied using computational fluid dynamics (CFD) simulations, and the results were compared with previous experimental data. The gas-solid and liquid-solid interactions were calculated using the Euler-Euler model, incorporating the kinetic theory for the solid phase. The momentum exchange coefficients for the fluid-solid interactions were calculated using the Gidaspow drag model, and the fluid-fluid interactions by using the Schiller-Naumann model. The predicted gas volume fraction agreed to the Kumar model and showed better performance with the use of higher-order discretization. Furthermore, the Peng Robinson thermodynamic correlation was used to determine the properties of the materials under high severity conditions. The results showed a consistent distribution of the phases, it was quite uniform and there was a reasonable expansion of the bed when gas injection was established as an initial condition.
Structural analysis of polydimethylsiloxane samples
2020 - OLIVO-ARIAS, L.P.; ARAUJO, L.G.
This work presents a structural analysis of polydimethylsiloxane (PDMS) samples through the study of the mechanical properties of a soft material. For this, the dimensions of the crosslinking samples were modified taking a cure ratio as a reference, to determine the stress-strain, applying the Prony model which the Ansys-Mechanical platform offers. Experimental data was collected from the literature and a force test was performed on three different cylindrical samples (10:1 ratio) of PDMS with a curing agent. Consistent results of the modulus of elasticity as a function of time were obtained. Finally, using the Neo Hookean model, with consideration of hyperelastic material, and employing longer relaxation times, the results showed interesting findings in the parameters of total and directional deformation and other viscoelastic properties for this type of material.
Computational fluid dynamic simulation of a gas-solid fluidized bed system
2019 - OLIVO-ARIAS, L.P.; ARAUJO, L.G. de; ROJAS-TRIGOS, J.B.
The study of the gas-solid system was performed through an analysis of computational fluid dynamics (CFD) in a fluidized bed reactor. This process begins with the interaction between the particles and the gas phase. The fluidization process analysis is achieved through the Eulerian approach represented in the behavior of the solid phase dynamics during the bed expansion process. Within the process, the formation of the dense phase was demonstrated and how it could affect the effects of temperature, pressure and surface velocity of the gas in the fluidized bed system. The purpose of this work is to establish hydrodynamic parameters by evaluating the volumetric fraction of the particles and the axial and radial velocity profile using the drag models of Syamlal O'Brien and Gibilaro. In addition, it should be considered the analysis of the computational dynamics of fluids, such as the generation of the mesh, the selection of the models, and the run time of the simulation. The results of the simulations showed that the solid phase concentration has had a uniform distribution, a dense phase formation, given the changes in operating conditions and a reasonable expansion of the bed in the final simulation time.