http://repositorio.ufc.br/handle/riufc/460 2026-04-16T04:31:00Z http://repositorio.ufc.br/handle/riufc/85750 Título: Proposta de metodologia para aplicação generalizada do método das soluções fundamentais Autor(es): Rodrigues Neto, Guilherme Costa Abstract: Numerical modeling of physical phenomena governed by the Laplace equation is a central topic in several engineering fields, including hydrogeological applications, in which limited data availability and geometric complexity of the domains impose additional challenges. Traditional mesh-based methods, such as Finite Difference and Finite Element methods, are highly robust but relieve an extensive set of physical parameters and mesh-related choices, which may restrict their applicability in exploratory studies and preliminary diagnostics. In this context, this thesis proposed and evaluated a generalized methodology for applying the Method of Fundamental Solutions (MFS) to two-dimensional problems governed by the Laplace operator, with subsequent application to groundwater flow simulation. The methodology is based on the adoption of a circular fictitious boundary with uniformly distributed points and on the systematic sweeping of its radius (dvalue), combined with objective criteria of stability, convergence, and accuracy. Numerical performance was assessed in an integrated manner using the root mean square error (RMSE), the inverse of the condition number of the main matrix (rcond), and pointwise evaluations inside the domain, complemented by a successiveerror convergence test. This approach transformed the selection of MFS operational parameters into a reproducible procedure, avoiding empirical decisions and numerical instabilities. The methodology was first applied to theoretical examples with known analytical solutions, involving rectangular and circular geometries, enabling validation under controlled conditions. The results evidenced the existence of well-defined operational ranges of dvalue, which depend on the number of boundary points (N) and the domain geometry. For the unit circular boundary, approximate practical limits of dvalue were identified as 1211.5 for N = 8, 25.1 for N = 16, and 3.58 for N = 32, while applications with N = 64 proved infeasible without additional numerical treatment due to severe degradation of matrix conditioning. Although increasing N improved solution accuracy, it significantly narrowed the operational window of the method, particularly for circular domains. Subsequently, the methodology was applied to a groundwater flow case study in an aquifer using observed piezometric data. In this application, the procedure proved capable of diagnosing operational limits of the MFS and guiding the interpretation of discrepancies between computed and observed values, suggesting the influence of uncertainties associated with boundary conditions and/or the presence of heterogeneities and anisotropies not explicitly represented. Comparison with traditional numerical procedures indicated that, under assumptions of homogeneous domains and steady-state conditions, the MFS produced numerically consistent and statistically comparable results, with reduced dependence on additional hydrogeological data. It was concluded that the proposed methodology enhances the reproducibility and applicability of the Method of Fundamental Solutions, positioning it as a robust tool for screening, diagnostics, and modeling support in generic Laplacian problems and in groundwater flow simulations under limited data availability. By establishing objective and quantifiable operational ranges for the method parameters, this thesis contributes to filling a gap identified in the literature and reinforces the potential of the MFS as an alternative or complementary approach to traditional numerical models in specific contexts. Tipo: Tese 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85449 Título: Propostas de modelos para dimensionamento de dispositivos de controle de percolação interna - abraços - em barragens de terra por meio de técnicas de apredizado de máquina Autor(es): Sousa, Ana Cinthya Mariano de Abstract: This research develops predictive models aimed at the optimized design of internal seepage control devices in earth dams, commonly referred to as wraparound, which play a key role in mitigating erosion processes along the soil–structure interface. To achieve this, an integrated approach was adopted, combining three-dimensional computational simulations based on the Finite Element Method (FEM) with machine learning techniques, enabling an in-depth analysis of hydraulic flow behavior across a wide range of geotechnical, hydraulic, and geometric conditions. The numerical modeling accounted for a series of parametric variations, including different values of hydraulic conductivity, degrees of saturation, foundation characteristics, and diverse geometries of the control devices. As a result, a robust and representative dataset was generated and used to train various machine learning algorithms, notably Artificial Neural Networks, Decision Trees, Random Forests, and the XGBoost model. Among the models evaluated, XGBoost exhibited the most satisfactory performance, achieving a coefficient of determination (R2) of 96.58% for the training dataset and 90.58% for the test dataset, along with low error metrics (Mean Absolute Error – MAE = 7.03; Root Mean Square Error – RMSE = 16.38; Mean Absolute Percentage Error – MAPE = 13.7%), demonstrating the model’s strong predictive capability in estimating the optimal device length. The use of these models enabled the identification of the most effective “abraço” configurations, leading to a reduction in critical hydraulic gradients and, consequently, the prevention of internal erosion mechanisms. Therefore, the findings provide valuable technical insights for improving earth dam design, particularly in contexts with limited experimental data, establishing a reliable, efficient, and cost-effective solution within geotechnical engineering applied to the safety of hydraulic structures. Tipo: Dissertação 2025-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85408 Título: Sistemas hidrológicos em transformação: impactos das mudanças antrópicas na dinâmica hidrológica da bacia hidrográfica do Rio São Francisco, Brasil Autor(es): Lima, Carlos Eduardo Sousa Abstract: In the Anthropocene, the increasing human influence on the hydrological cycle of watersheds has made their water availability and response patterns to climate extremes – both wet and dry – depend on both natural and anthropogenic factors. In this context, this thesis evaluated the impact of anthropogenic changes on the hydrological dynamics of watersheds. As a case study, the São Francisco River Watershed (BHSF) and the Grande River Basin (GRB), an important sub-basin of the BHSF, were used. Three different approaches were employed for this proposed assessment: the first applied more generally to the BHSF, while the second and third were applied more specifically to the GRB. In the first approach, the concept of climate elasticity of streamflow was applied to 10 sub-basins of the BHSF, enabling an evaluation of streamflow sensitivity to climate variations and the decomposition of total streamflow variation into climatic and anthropogenic components. In the second, a new methodology for assessing the impact of human activities on the development of hydrological droughts was proposed: the Drought Roulette Analysis (DRA). In the third, the watershed was interpreted as a complex hydrological system with multiple equilibrium states that switch between them in response to climatic and anthropogenic forcing. The results from these approaches led to the conclusion that anthropogenic activities have decreased water availability, increased the sensitivity of streamflow to climate variations, and slowed hydrological recovery after drought events, with streamflow deviations persisting even after precipitation levels are restored. Equally important, the results from the third approach showed that a watershed can naturally exhibit a non- stationary hydrological regime characterized by multiple hydrological states and a variable rainfall-runoff relationship; anthropogenic activities, in turn, modulate this non-stationarity, accentuating the asymmetry in transitions between these states. Additionally, incorporating information on hydrological states significantly improved the hydrological modeling process, providing a more dynamic representation of the variable rainfall-runoff relationship. Overall, these findings point to a dynamic risk to water availability and hydrological extremes in the BHSF, and more specifically in the Grande River watershed. This dynamic risk arises from the non-stationarity of the hydrological regime, which, although it can be caused by natural factors (climate variability), is strongly linked to human interventions induced in these watersheds. These interventions, in addition to potentially generating non-stationarity, modify transitions between hydrological states and the patterns of drought evolution. The aforementioned dynamic risk introduces significant uncertainty into the water resource management and planning process when not properly considered. The capacity of anthropogenic activities to modulate the non-stationarity of the hydrological regime, as well as the observed hydrological impacts of these activities, underscores the need for integrated management that considers both natural and human factors, along with their interactions and compensatory effects. Tipo: Tese 2026-01-01T00:00:00Z http://repositorio.ufc.br/handle/riufc/85371 Título: Avaliação da produção de biometano em biodigestores com sobras e restos de alimentos por meio de recirculação e inoculação de consórcio microbiológico Autor(es): Souza, Debora Nery de Abstract: The increasing energy demand, the growing volume of waste, the challenges in its proper management, and consequently its inadequate final disposal have necessitated the search for sustainable solutions. Accordingly, this study aimed to evaluate the generation of biogas and biomethane produced through anaerobic digestion of food waste in reactors with different recirculation configurations, varying organic loads, and utilizing a hydrolytic microbial consortium. In an initial phase, two 1.3 m3 reactors were operated semi-continuously: reactor 01 with recirculation at four bottom points and reactor 02 with a single bottom point. Subsequent phases assessed the effect of varying organic load (1% and 5% volatile solids – VS) and bioaugmentation with a hydrolytic microbial consortium (Bacillus subtilis [KJ870046.1] and Alcaligenes faecalis [CP013119.1]). Subsequently, the potential use of the digestate as biofertilizer was evaluated. Various physicochemical parameters were monitored over 90 days. Reactor 01 demonstrated higher efficiency in organic matter degradation, with lower solid concentrations and 60% volatile solids (VS) removal, compared to 8% in reactor 02, in addition to producing more biogas (35.80 Nm3) and biomethane (67.17%) than reactor 02 (26.73 Nm3 biogas and 64.57% biomethane). In the subsequent phases, the microbiological reactor with 1% VS (RM1) and the control reactor with 5% VS (RC5) showed higher efficiency in organic matter degradation with 71% VS removal, compared to 50% for RC1 and 49% for RM5. However, the microbiological reactors produced higher accumulated biogas volumes (22.74 Nm3 for RM5 and 21.22 Nm3 for RM1) relative to the control reactors (17.33 Nm3 for RC5 and 13.37 Nm3 for RC1). In evaluating the potential use of digestates as biofertilizers, the biodigesters with four-point bottom recirculation (R1 and RM1) exhibited greater stabilization than the digestate from the biodigester with single-point bottom recirculation (R2), displaying lower C/N ratios (0.79 and 1.25 for R1 and RM1, respectively, versus 1.63 for R2) and lower sodium concentrations (0.26 and 0.21 g/Kg for R1 and RM1, respectively, versus 0.30 g/Kg for R2). All evaluated digestates presented micronutrient concentrations below the maximum limits established for biofertilizers and macronutrient values below the reference values stipulated by Brazilian and European legislation. It is concluded that four-point bottom pumping recirculation proved more efficient than single- point recirculation, that the bioaugmentation strategy with the hydrolytic microbial consortium was effective for both biogas and biomethane production and organic matter degradation in the biodigesters, and that, generally, all digestates showed potential for use as complementary mineral fertilizer, contributing to the system's circular economy and aiding in environmental sustainability. Tipo: Tese 2025-01-01T00:00:00Z