Taygoara Felamingo de Oliveira

Transferência de calor aplicada à prototipagem rápida por deposição de metal em camadas sucessivas utilizando soldagem 3D

This work presents a study on the heat transfer phenomena that occur during the process of Rapid Prototyping by layered arc welding metal deposition, also called, 3D Welding. The main goal is to understand the heat transfer process and its relations with the welding parameters, in order to enable a control of the thermal cycles that the deposited material shall be subjected to. A numerical model is developed using the finite difference method to analyze the heat transfer, in order to allow the simulation of certain situations. The numerical model was validated by means of simulating specific cases for which analytical solutions are available. From the theoretical model equations, some dimensionless numbers were defined, among which the so called π1 number, mainly related to the welding speed. Some numerical experiments were carried out in order to allow the observation of its influence on the average and peak temperatures and also on the amplitudes of the thermal cycles which the part is subject to.

Numerical Study of Wake Characteristics in a Horizontal-Axis Hydrokinetic Turbine

Over the years most studies on wake characteristics have been devoted to wind turbines, while few works are related to hydrokinetic turbines. Among studies applied to rivers, depth and width are important parameters for a suitable design. In this work, a numerical study of the wake in a horizontal-axis hydrokinetic turbine is performed, where the main objective is an investigation on the wake structure, which can be a constraining factor in rivers. The present paper uses the Reynolds Averaged Navier Stokes (RANS) flow simulation technique, in which the Shear-Stress Transport (SST) turbulent model is considered, in order to simulate a free hydrokinetic runner in a typical river flow. The NREL-PHASE VI wind turbine was used to validate the numerical approach. Simulations for a 3-bladed axial hydrokinetic turbine with 10 m diameter were carried out, depicting the expanded helical behavior of the wake. The axial velocity, in this case, is fully recovered at 12 diameters downstream in the wake. The results are compared with others available in the literature and also a study of the turbulence kinetic energy and mean axial velocity is presented so as to assess the influence of proximity of river surface from rotor in the wake geometry. Hence, even for a single turbine facility it is still necessary to consider the propagation of the wake over the spatial domain.

Heat transfer applied to rapid prototyping by metal deposition in successive layers using 3D welding

This article presents a study on heat transfer phenomena in the process of rapid prototyping by metal deposition in successive layers using arc welding, also called 3D welding. The main goal is to develop a simplified model and understand the heat transfer process and its relations with the welding parameters, in order to enable a control of the thermal cycles that the deposited material will be subjected to. The numerical model was validated by means of simulating specific cases for which analytical solutions are available. From the equations of the model, dimensionless parameters were defined, among which the so-called π1 dimensionless group can be cited, mainly related to welding speed. Some numerical experiments were carried out to observe the influence of this group on the maximum and mean temperatures, and on the amplitudes of the thermal cycles to which the piece is subjected.