https://repositorio.ufu.br/handle/123456789/5466 2026-04-21T22:33:48Z https://repositorio.ufu.br/handle/123456789/48633 Title: Modelling and analysis of fluid flow problems coupled with radiative heat transfer Abstract: Combustion plays a fundamental role in society, being one of the primary means of energy conversion and storage, with countless applications. As such, it is a key topic in engineering and industrial processes. In many cases, combustion and thermal radiation occur simultaneously: the high temperatures resulting from exothermic reactions, as well as the radiative interaction of the gases generated from these reactions, create an environment where complex radiative heat transfer takes place. Therefore, coupling CFD with radiative heat transfer models is essential for the accurate simulation of industrial reactive flows. Furthermore, literature shows that thermal radiation can significantly affect heat transfer in other situations, such as in thermal cavities at ambient temperature, a problem that is frequently studied without considering radiation effects. This work presents the development and benchmarking of a coupling between a CFD software (MFSim) and a radiative heat transfer solver for participating media (RTS), both internally developed by MFLab in the Federal University of Uberlândia. MFSim is a robust simulation package, capable of modelling turbulence, heat transfer, fluid–structure interactions, reacting flows, and Lagrangian particle transport. RTS is capable of modelling radiative transfer in gray and non-gray participating media containing gases like CO2 and H2O, as well as isotropic and anisotropic scattering phenomena. By integrating these codes, the extensive set of physical models available in MFSim, designed to simulate complex engineering problems, now includes radiative heat transfer, enabling more realistic and accurate modelling of combustion processes. The coupling employs distinct meshes for CFD and radiation, connected via interpolation, allowing for more computational efficiency, as radiative models do not usually require the same spatial resolution as CFD. Tests have shown that the interpolation layer between both algorithms has relatively low computational cost. Benchmarks performed on canonical cases show good agreement with the literature, verifying the approach and reinforcing the importance of radiation in heat transfer simulations. 2025-08-21T00:00:00Z https://repositorio.ufu.br/handle/123456789/48538 Title: ANDRADE, Rafael Moreira. Manufatura aditiva por deposição a arco para a recuperação de matrizes para injeção de alumínio sob pressão Abstract: Extending the service life of tooling in the high-pressure aluminum die-casting industry represents a technical and economic challenge, given the severity of the cycles to which these components are subjected. In this scenario, Wire Arc Additive Manufacturing (WAAM) emerges as a strategic alternative for the restoration of functional surfaces. The present study investigated the technical and metallurgical feasibility of applying WAAM for die repair, comparing the performance of three distinct alloys: Maraging 250 (solid wire), Martensitic Stainless Steel 420 (solid wire), and H13 Tool Steel (metal-cored wire). Initially, a decommissioned mold was characterized to identify the predominant failure mechanisms, thereby establishing the requirements to be met by additive manufacturing. The welding stability of the Maraging alloy was also investigated regarding three shielding atmospheres, while also varying two different deposition strategies. Maraging 250 steel stood out for its strength and structural integrity. The alloy benefited from the reheating thermal cycles intrinsic to the process, which promoted in-situ aging, resulting in a hardness gradient. In contrast, the martensitic alloys (Stainless Steel 420 and H13) showed high sensitivity to deposition strategies and cooling rates. It was observed that low heat input strategies resulted in the formation of untempered martensite, leading to brittle fracture. Implementing strategies aimed at heat accumulation enabled the processing of 420 Stainless Steel through the auto tempering mechanism, restoring the necessary ductility; however, this approach proved insufficient to mitigate cracking in H13 Tool Steel due to its high hardenability and segregation of brittle phases. Thus, thermal management is fundamental for the application of WAAM in tool steels, validating Maraging steel as the most robust solution for the remanufacturing of high-performance molds. 2026-02-26T00:00:00Z https://repositorio.ufu.br/handle/123456789/48527 Title: Desenvolvimento de equipamento e metodologia para avaliação do desempenho de rebolos aplicados na retificação tangencial em vidros Abstract: Glass grinding is an abrasive machining process widely employed in industry, in which grinding wheel performance and wear directly influence surface quality, dimensional stability, and production efficiency. In this context, the present study aimed at the development, instrumentation, and experimental validation of the TriboGlass test bench, designed to perform controlled accelerated wear tests of grinding wheels used in tangential glass grinding. The test bench was designed and built in partnership with Diamanfer and structured to enable continuous monitoring of the Material Removal Rate (MRR) as well as the main operational process variables. In parallel, a systematic methodology for grinding wheel wear assessment was developed, including mass loss measurements, three-dimensional geometric characterization through color map scanning, cross-sectional profile evaluation, and macroscopic surface inspection. Six experimental tests were conducted, in which initial transient regimes associated with the high aggressiveness of new grinding wheels were observed, followed by the progressive stabilization of the abrasive contact. Localized variations were also recorded due to operational events such as glass replacement, grinding wheel substitution, and mechanical interferences in the carriage displacement system. The monitoring system demonstrated high sensitivity in detecting such occurrences, confirming its reliability for continuous process evaluation. The results confirm the structural stability, repeatability, and operational robustness of the TriboGlass test bench, validating it as a reliable experimental platform for systematic test matrices and future investigations related to tribological mechanisms involved in glass grinding processes. 2026-02-27T00:00:00Z https://repositorio.ufu.br/handle/123456789/48467 Title: Identificação de desbalanceamento de máquinas rotativas usando metamodelagem cokriging Abstract: Along with misalignment, the leading cause of mechanical issues in rotating machinery is unbalance of the rotating assembly. Among the various balancing techniques available, the influence coefficient method is widely used. However, this technique demands test runs with trial masses, which is often inefficient, resulting in the need for new balancing attempts and prolonging service execution time. In the Oil and Gas industry, minimizing intervention time is paramount, directly translating to increased productivity and reduced lost profit, the financial loss due to the non-processing of oil derivatives. Specifically for refineries (downstream), where redundant (spare) machinery is often unavailable, any unscheduled intervention can lead to a complete unit shutdown. Therefore, exploring novel possibilities for unbalance detection without the need for trial mass runs is essential to significantly reduce the time required for these procedures. Thiswork addresses this context by implementing a balancing methodology without the use of test weights using a Cokriging Metamodel. This approach leverages two distinct data sources: experimental data, which consist of time-domain vibration signals collected directly from the machine (high-fidelity or expensive data), and numerical data, which are vibration signals generated from a numerical model (low-fidelity or cheap data). To validate the proposed methodology, two validation phases were conducted: a purely numerical validation and an experimental validation. For the numerical validation, vibration signals generated from a numerical model were utilized as high-fidelity samples and Monte Carlo uncertainty was added to stiffness and damping of the bearings and rotor modulus of elasticity in order to create the low-fidelity samples. For the experimental validation, tests were performed using a test rig (a rotor kit with two disks between bearings). Unbalance sets were applied in two planes (two disks) and vibration measurements in time domain were taken. Subsequently, this vibration data was divided into training and validation datasets and a cross-validation was performed. The experimental validation is a crucial factor in establishing the methodology, for instance, defining the optimal quantity of high-fidelity and low-fidelity samples to be included in the metamodel to maximize its performance. 2026-02-26T00:00:00Z