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- ItemEstudo da adesão e incrustação de carbonato de cálcio no contexto da indústria do petróleo por técnica experimental e numérica(Universidade Federal do Espírito Santo, 2025-12-19) Rodrigo Simões Maciel; Pereira, Fabio de Assis Ressel ; https://orcid.org/0000-0002-1500-2952; http://lattes.cnpq.br/5476118728173549; Soares, Edson José ; https://orcid.org/0000-0003-4967-4957; http://lattes.cnpq.br/4485206584533650; https://orcid.org/0000-0001-7303-5958; http://lattes.cnpq.br/5898101623873773; Siqueira, Renato do Nascimento ; https://orcid.org/0000-0002-8397-8180; http://lattes.cnpq.br/9791817633014124; Martins, Andre Leibsohn ; https://orcid.org/0009-0008-4553-0503; Schluter, Helga Elisabeth Pinheiro ; https://orcid.org/0000-0002-7206-0606; Junqueira, Silvio Luiz de Mello; https://orcid.org/0000-0001-5935-4266; http://lattes.cnpq.br/2213804390733564Carbonate scaling in Brazilian pre-salt production systems represents a significant challenge for flow assurance, as these deposits can partially or completely restrict flow, increasing operational and maintenance costs. During production, pressure reduction promotes CO2 degassing, raises the pH, and consequently favors CaCO3 precipitation. Pre-salt reservoirs consist of carbonate rocks, naturally enhancing the supersaturation of formation water with cations such as Ca2+ and Mg2+, which combine with carbonate ions (CO2− 3 ) to form precipitates. Thus, variables such as pressure, temperature, brine composition, CO2 molar fraction, fluid properties, flow conditions, and surface characteristics are recognized in the literature as influential to the scaling process. Understanding the mechanisms of scale formation under well conditions is essential for developing prediction and mitigation technologies, as well as for defining production windows. Flow-induced scaling models require guidance and validation through experimental data and field observations. However, specific studies addressing the effect of flow on scale formation under well-like conditions remain limited, and no consolidated methodology exists for such investigations. Parameters such as pressure, temperature, flow intensity, and the presence of dissolved CO2 can substantially influence carbonate scaling and model accuracy but are still often neglected in laboratory studies. Recent works suggest that scaling rates increase with turbulence, but this phenomenon has not been thoroughly examined under conditions representative of production systems, and the combined effects of turbulence and temperature-dependent polymorphism remain unclear. Therefore, this study investigates the influence of flow on carbonate scaling under well-representative conditions. A batch reactor equipped with a rotating cage system (ASTM G184) was used to evaluate the effect of fluid dynamics on scaling at 60 °C and 80 °C, under different turbulence levels and considering CO2 degassing. Analyses included 3D profilometry, gravimetry, optical photomicroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and Rockwell C scratch tests. Single-phase numerical simulations of the reactor were performed to characterize flow behavior across rotation levels and to correlate hydrodynamic variables with the experimentally observed scaling features. These simulations also enabled comparison of the reactor flow with other geometries. The results demonstrate that, under conditions representative of oil wells (shear, temperature, and presence of CO2), fluid dynamics significantly influences carbonate scaling when compared to experiments performed at ambient temperature, atmospheric pressure, and without dissolved CO2. Unlike previous studies that do not consider these variables, a reversal point in the scaling rate was identified: beyond sufficiently high turbulence levels, scaling rates begin to decrease, even within the operational range of pre-salt wells. Analysis of the deposits adhered to the rotating cage coupons revealed that the calcium carbonate polymorphs play a critical role in this reversal behavior, as evidenced by experimental trials
- ItemEstudo analítico, numérico e experimental de um dispositivo atenuador tubular para escoamentos intermitentes(Universidade Federal do Espírito Santo, 2025-10-20) Santos, Michel de Oliveira dos; Ribeiro, Daniel da Cunha; https://orcid.org/0000-0003-3690-1938; http://lattes.cnpq.br/8563308324482367; Siqueira, Renato do Nascimento; https://orcid.org/0000-0002-8397-8180; http://lattes.cnpq.br/9791817633014124; https://orcid.org/0009-0009-2302-0091; http://lattes.cnpq.br/1279322328091122; Ramos, Rogério; https://orcid.org/0000-0003-4493-2435; http://lattes.cnpq.br/2975022316691139; Huebner, Rudolf; https://orcid.org/0000-0003-2613-304X; http://lattes.cnpq.br/9514309218273598; Santos, Fábio Pereira dos; https://orcid.org; http://lattes.cnpq.br/3266981988847625; Loureiro, Bruno Venturini; https://orcid.org/0000-0002-9792-8168; http://lattes.cnpq.br/4763904267889432Attenuators are widely employed in industrial pumping systems to reduce pressure and f low pulsations that cause excessive noise, mechanical vibrations, and process instabilities. Conventional devices use compressed gases (typically nitrogen or dry air) as the deformable medium; however, aiming at greater reliability, an attenuator may operate without gas compression provided that satisfactory attenuation is maintained within the desired frequency range. While three-dimensional numerical analyses capture behaviors beyond simplified models, lumped approaches remain useful for identifying global trends with low computational cost. In this work, a lumped-parameter model was developed to estimate the attenuation of intermittent-flow amplitude in a gas-free tubular attenuator. The device was also analyzed using a three-dimensional fluid–structure interaction (FSI) model under laminar flow. Experimentally, two tubular attenuators with different compliances were tested in laminar and turbulent regimes, at several pulsation frequencies and in two configurations: inline and side-branch. The analytical solution of the two-element Windkessel model showed that attenuation depends on the dimensionless frequency (ω′) and on the system parameter KRCL, remaining independent of the mean-flow Reynolds number (Reta). A modified Windkessel formulation was proposed to incorporate the dependence on Reta under turbulent conditions. FSI simulations performed for two values of KRCL (1.75 ×10−4 and 3.50×10−4), two values of Reta (750 and 1500), and six values of ω′ (20–160) confirmed qualitative agreement with the analytical model while revealing additional sensitivity to Reta associated with the mean internal pressure. In the turbulent experiments (17140 < Reta < 45700, 168 < ω′ < 450), attenuation increased with both parameters. The attenuator with Dd = 36 mm reached up to 85%, whereas the one with Dd =32 mm reached 75.6% but showed negative attenuation (down to–36%) under some operating conditions, attributed to its lower compliance and to geometric and constitutive nonlinearities. The relation between attenuation levels did not scale linearly with the ratio of compliances, underscoring the complexity of the phenomenon. In the laminar experiments (865 < Reta < 2212, 8.9 < ω′ < 24.5), attenuation ranged from 17.9% to 78.1%, with no negative cases, and similar results were obtained for both configurations. Across regimes, the trend of increasing attenuation with ω′ and Reta persisted, indicating that performance is governed primarily by the compliance response to pressure and flow f luctuations rather than by the flow regime itself.
- ItemEfeito de diferentes tratamentos térmicos na configuração microestrutural em aço TRIP (transformação induzida por deformação)(Universidade Federal do Espírito Santo, 2025-09-29) Martins, João Batista Ribeiro; Co-orientador1; https://orcid.org; https://lattes.cnpq.br; Orlando, Marcos Tadeu D’Azeredo; https://orcid.org/0000-0002-8387-6504; http://lattes.cnpq.br/3562894103432242; https://orcid.org/0000-0001-7305-0349; http://lattes.cnpq.br/3416041645368795 ; Passos, Carlos Augusto Cardoso; https://orcid.org/0000-0002-6303-3569; http://lattes.cnpq.br/2528679879816545; Rossi, Jesualdo Luiz; https://orcid.org/0000-0002-8304-9939; http://lattes.cnpq.br/0763948174052925 ; Oliveira, Marcelo Falcão de; https://orcid.org/0000-0003-4589-2463; http://lattes.cnpq.br/5681812218970006; Salustre, Mariane Gonçalves de Miranda; https://orcid.org/0009-0006-6362-5376; http://lattes.cnpq.br/2990952954091659This thesis investigated the development of advanced high-strength steels (AHSS), produced in a vacuum electric furnace, with controlled variations in chemical composition and thermal parameters. The resulting ingots showed satisfactory metallurgical quality and compositions aligned with the study's objectives. The phase transformation curves under continuous cooling conditions, also known as CCT (Continuous Cooling Transformation), were essential to define three kinetic ranges: (i) 0.5–1.0 °C/s with ferrite and pearlite; (ii) 3–9 °C/s with bainite and retained austenite; and (iii) 25–100 °C/s with lath martensite. The steel with the lowest carbon and manganese content (steel C) showed lower hardenability, expanding the bainitic field. Optical microscopy (OM) identified the main constituents (bainite, martensite, and retained austenite), while scanning electron microscopy (SEM) confirmed the refined morphology of the phases under rapid cooling. Characterization by electron backscatter diffraction (EBSD) revealed the progressive replacement of ferrite by bainite and martensite, and showed the predominance of displacive phases at high cooling rates. The novel application of the gamma distribution to misorientation data up to 5° of the substructures, also known as KAM (Kernel Average Map), enabled quantification of microstructural homogeneity (parameter α) and the average amplitude of misorientations (β), highlighting greater regularity in the steel with higher carbon and manganese content (steel A). The trend inversion (α↓/β↑) at 100 °C/s was interpreted as martensitic saturation, with reduced internal variability. Additionally, an in-situ diffraction experiment at the Brazilian Synchrotron Light Laboratory (LNLS), under 100 °C/s, confirmed the sequence austenite → epsilon martensite → body centered tetragonal martensite (γ → ε → α′), evidencing the transient formation of epsilon martensite, consistent with the double-step martensitic transformation theory. The results demonstrate that the compositions of steels with higher carbon and manganese (steel A) and lower carbon and manganese (steel C) have high potential as third-generation AHSS. Steel A, with greater sensitivity to cooling rate, allows microstructural adjustments for high strength, while steel C shows greater bainite stability. Thermal modulation proved to be an efficient strategy to balance strength and ductility without the need to alter the chemical composition.
- ItemEstudo de duas técnicas para a solução de problemas dinâmicos utilizando o método dos elementos de contorno: a superposição modal e a transformada de Laplace(Universidade Federal do Espírito Santo, 2024-12-20) Santos, Aquila de Jesus dos; Lara, Luciano de Oliveira Castro; Loeffler Neto, Carlos Friedrich; https://orcid.org/0000-0002-5754-6368; Saenz, Juan Sérgio Romero; Campos, Lucas Silveira; Bulcão, André; Albuquerque, Éder Lima deThe search for a reliable and accurate method to convert domain integrals involving non-self-adjoint operators into boundary integrals, in accordance with the philosophy of the Boundary Element Method, remains a significant challenge. One of the most recent proposals to achieve this goal is the Direct Interpolation Technique of the Boundary Element Method (DIBEM). Already successfully employed in solving scalar problems governed by the Poisson, Helmholtz, and Advection-Diffusion equations, this work presents the results of using DIBEM in the analysis of wave propagation problems in homogeneous media. The main objective is to evaluate the integration of DIBEM with two distinct techniques for handling the time-dependent term: Modal Superposition and the Laplace Transform, two well-established strategies. In the first formulation, a modified modal superposition, which uses a correlated eigenvalue problem associated with the transpose of the dynamic matrix, is applied to decouple the dynamic equations. Time advancement is performed using the Houbolt algorithm, whose fictitious damping eliminates spurious modal contents, producing greater stability. In the second formulation, the Laplace transform is used to eliminate time dependence; DIBEM is used to solve the resulting stationary problem in terms of the transformation variable, and an inversion method is used to return to the time domain. Several typical wave propagation problems were solved using linear boundary elements.
- ItemRedução de arrasto em escoamento monofásico e bifásico (líquido-líquido) com adição de polímeros solúveis em água e hidrocarbonetos(Universidade Federal do Espírito Santo, 2025-01-10) Barbosa, Kelvin Cristien de Oliveira; Soares, Edson José ; https://orcid.org/0000-0003-4967-4957; http://lattes.cnpq.br/4485206584533650; https://orcid.org/0000-0003-0752-1485; http://lattes.cnpq.br/6938448221920237; Siqueira, Renato do Nascimento ; https://orcid.org/0000-0002-8397-8180; http://lattes.cnpq.br/9791817633014124; Ramos, Rogério; https://orcid.org/0000-0003-4493-2435; http://lattes.cnpq.br/2975022316691139; Franco, Admilson Teixeira ; https://orcid.org/0000-0002-7977-6404; http://lattes.cnpq.br/3561428456009236; Oliveira, Márcia Cristina Khalil de ; https://orcid.org/0000-0001-8820-8567; http://lattes.cnpq.br/2392018269619309This work presents an experimental study on drag reduction (DR) in single-phase and liquid-liquid two-phase turbulent flows through the addition of polymers. The literature contains studies on drag reduction in two-phase flows; however, most investigations focus on gas-liquid flows or liquid-liquid flows with the polymer dissolved in the aqueous phase. In various industrial sectors, two-phase flow is a common occurrence, particularly in the oil and gas industry, where one of the main objectives is to enhance production flow rates. Consequently, there is growing interest in studying the effects of drag-reducing polymer additives in two-phase flows. The objective of this study is to evaluate the effect of polymers (soluble in both water and hydrocarbons) on pressure gradient reduction (drag reduction) and to analyze polymer degradation in single-phase and liquid-liquid two-phase flows. A water-soluble polymer (Diutan Gum 3 DG) and a hydrocarbon-soluble polymer (Polyisobutylene 3 PIB) with three different molecular weights are used. For the hydrocarbon-soluble polymer, rheological characterization, preliminary DR tests in single-phase flows, and degradation analysis for the three molecular weights are performed. As expected, drag reduction increases with higher polymer concentration and molecular weight. In two-phase flow experiments, the flow pattern is dispersed due to high flow rates. The effects of DG and PIB solutions are analyzed separately and in combination. It is concluded that drag-reducing additives are more effective in the dominant phase, meaning that the water-soluble additive is effective for water fractions greater than 0.5, while the hydrocarbon-soluble additive is effective for water fractions below 0.5. As expected, increasing DG concentration results in higher DR; however, an increase in flow rate when using only DG does not lead to further DR improvement. On the other hand, for PIB, an increase in flow rate results in greater DR. When both phases contain additives, a reduction in pressure is observed compared to the case without additives across the entire range of water fractions. Additionally, it is noted that at low concentrations (low water fractions), water droplets also contribute to drag reduction. PIB degradation increases as the total two-phase flow rate rises and is further intensified when the aqueous phase is also treated with additives