bluuebunny/crossref_metadata_2025 huggingface dataset:
Translational joint in a Finite Element Analysis program of 2D frames with straight and curved elements
Authors: David dos Santos Coimbra  , Fernanda Gabriella Batista Santos Oliveira  , Luis Fernando Sampaio Soares
Published: January 2025

This paper describes the development of an algorithm for the structural analysis of bidimensional frames with straight and curved elements that include a translational joint which can be set to any specified angle. The code was written in Fortran following a Finite Element Method-based structure. Three elements were considered: a circumferential arc-shaped; a straight bar with cross-sectional height varying according to a linear polynomial function; and the traditional straight element with constant inertia. All Stiffness matrices and load vectors were derived from the inversion of their corresponding Flexibility matrices obtained using the Force Method. In a few cases, a Gaussian Quadrature was needed in order to calculate the integral. The resulting program was validated against solutions found in the scientific literature in addition to structures created and solved by the authors using the Virtual Work Method, and it is shown to give very accurate predictions for displacements and rotations as well as reactions and internal forces (axial, shear and bending).
An information-theoretic Machine Learning for upscaling and downscaling of uncertainty stochastic reservoir
Authors: Ianyqui Falcão Costa  , Liliane de Allan Fonseca  , Ramiro Willmersdorf  , Ézio da Rocha Araújo
Published: January 2025

This work brings together theoretical formulation and computational strategies for upscaling random heterogeneous media. In this context, heterogeneous means multiphysics models at different scales and correlated random parameters at different locations in the physical domain, such as Stokes-Brinkman flow and fractures at the microscale and heterogeneous Darcy flows at the macroscale when the target problem is hydrocarbon reservoir simulation, or a matrix with random inclusions on the rich scale and a homogeneous matrix on the poor scale when the target problem is solid mechanics. The approach uses information-theoretic machine learning methods to extract relevant probabilistic information from the rich scale and adaptively control the stochastic distance between the responses of the two scales. A goal-oriented upscaling procedure is defined to ensure equivalence between poor targets and rich scales for specific outcomes and its generalization to a multi-goal-oriented mathematically sound response, where users control distinct accuracies of specific target responses. Preliminary applications for elliptic and transient equations are presented with their respective results comparisons. Applications use a series of realizations of rich-scale parameter distributions, producing a reduced number of equivalent poor-scale realizations as required by the user's desired accuracy. The full formulation requires solving a difficult optimization problem for an extended Lagrangian formulation which is solved with a new Parallel Deterministic Annealing. The mathematical formulation is such that parallelization is done over realizations, so the overall cost of calculating stochastic upscaling is of the same order as deterministic. Furthermore, a regression with Tikhonov regularization in linear Machine Learning was used to interpolate and extrapolate data from Parallel Deterministic Annealing in order to find an optimal rich scale.
Physics-informed neural networks approach for one-dimensional beams
Authors: Felipe Pereira dos Santos  , Lapo Gori
Published: January 2025

Physics-informed neural network (PINN) is a machine learning technique where the physics of the problem is embedded into the loss function. The straightforward approach is to define the loss function using the problem governing differential equations and its boundary/initial conditions in a sort of collocation method. In general, the hyperparameters of neural networks for each problem at hands are defined via a grid search-like procedure, or simply by trial and error. In this paper, the application of PINNs is illustrated for one-dimensional beam problems, and the influence that the network weights initialization procedure has on the training is investigated. The code was built using SciANN, a Python package that uses TensorFlow and Keras for scientific computing and physics-informed deep learning employing artificial neural networks.
Piecewise Dynamic Mode Decomposition of Fluid Flow Simulations
Authors: Matheus Borges Seidel  , Alvaro Luiz Gayoso De Azeredo Coutinho  , Michèle Schubert Pfeil  , Renato Nascimento Elias  , Gabriel Freguglia Barros
Published: January 2025

The computational simulation of fluid flows over structures still is a major research area in fluid mechanics. Because of the multiscale nature of many of the application models and consequent large amount of data, these simulations are computationally expensive, but can benefit from modern Reduced Order Models and data-driven methods. In this work, Dynamic Mode Decomposition (DMD) and its recent variation, Piecewise DMD (pDMD), are presented and compared in terms of dynamic modes extracted from the data, accuracy in reconstructing an approximation for the original dataset as a reduced order model and, most importantly, computational cost. The pDMD method is shown to be a variation of the traditional DMD that aims to improve and overcome some of the caveats of the standard version. This variation consists in decomposing the entire data into smaller datasets and applying a linear mapping independently on each one of these subsets instead of calculating a global linear fitting. Basically, it is an application of multiple DMD on small subsets instead one DMD over the whole data. Piecewise DMD is a simple and elegant idea that is based on the "divide and conquer" approach well known in the numerical analysis literature. Even though pDMD is new and should be carefully and extensively tested, it can be considered as a promising improvement over the standard DMD. The preliminary results presented in this work show how DMD can capture the dynamics and accurately reconstruct the simulation data and how pDMD can provide more accurate results when traditional DMD reaches its limitations, capture the specific dynamics of different stages of transient flows, and reduce the computational cost by 90% for a two-dimensional flow over a cylinder when compared to standard DMD. Future applications of Reduced Order Models using both DMD and pDMD include future state predictions, computationally cheap parametric simulations, and qualitative dynamic analysis of fluid flows.
A proposal for a unified high-order quasi-3D kinematic model coupled with zigzag function to model laminated composite beams
Authors: Maria do Socorro Martins Sampaio  , Jéssica Simões Rodrigues  , Leonardo Fellipe Prado Leite  , Fabio Carlos da Rocha  , Leslie Darien Pérez Fernández  , Julián Bravo Castillero
Published: January 2025

Laminated composite materials have become increasingly prevalent in various engineering applications due to their remarkable stiffness/mass ratio and ease of manufacture. However, the classical theory fails to address certain limitations in modeling laminated composite beams, such as the absence of shear stress at the top and bottom edges, the non-uniform distribution of the shear stress field, and the zigzag effect in the field axial displacement. This study presents a newly proposed unified high-order quasi-3D kinematic model, which is coupled with a novel zigzag function to overcome the limitations encountered when it uses classical beam theory. This approach eliminates the need for correction factors required in Timoshenko beam theory and accurately captures the cross-section warping and transverse normal deformation resulting from the incorporated quasi-3D effect. Finally, the results were validated by comparing the displacement fields, normal stresses, transverse normal stress, and shear stress with reference values in the literature.
A Simple Geometrically Exact Displacement Based Shell Finite Element
Authors: Gustavo Canário Gomes  , Matheus Lucci Sanchez  , Paulo de Mattos Pimenta  , Adnan Ibrahimbegovic
Published: January 2025

This paper presents a modification of the T6-3iKL element based solely on displacements. It is a nonconforming triangular element with 6 nodes and a quadratic displacement field enhanced by a bubble function. Its coefficients are eliminated with three scalar rotation parameters at the mid-side nodes. The element approximates the Kirchhoff-Love shell model in the large displacement domain with only 21 DoFs . The rotation-continuity between adjacent elements is enforced at mid-side nodes, allowing for multiple branch connections in the mesh. The element allows the adoption of different material constitutive equations. The model is numerically implemented, and the results are compared to varying references in multiple examples, showing the capabilities of the formulation. The original desirable properties of the T6-i3KL element are preserved, which are the lack of penalties or Lagrange multipliers, a simple exact nonlinear kinematics, a relatively small number of DoFs, the possibility of using 3D material models, and is easily connected with multiple branched shells and beams.
Numerical investigation of an orthotropic finite elasticity problem using a constrained minimization theory to prevent material overlapping
Authors: Lucas Almeida Rocha  , Adair Roberto Aguiar
Published: January 2025

We consider the problem of an elastic annular disk with uniform thickness in equilibrium in the absence of body force. The disk is fixed on its inner surface and compressed by a uniform pressure on its outer surface. The disk is made of a cylindrically orthotropic material that has a constitutive response that is stiffer in the radial direction than in the tangential direction. Material properties of this type are found in carbon fibers with radial microstructure and some kinds of wood.In the context of the classical linear elasticity theory, the solution of this problem predicts material overlapping for a large enough pressure, which is not physically acceptable. An approach to prevent this anomalous behavior consists of minimizing the total potential energy functional subject to the constraint that the determinant of the deformation gradient, J, be positive. We have used this approach to eliminate material overlapping, yielding solutions with J not close to one, which contradicts the basic assumption of infinitesimal strains upon which the classical linear theory is founded.In this work, we extend our investigation to the nonlinear elasticity theory. Necessary conditions for a deformation field to be a minimizer were found elsewhere. It includes a nonzero Lagrange multiplier that represents a reaction pressure to prevent material overlapping. We use a finite element formulation to find that, differently from its linearly elastic counterpart, the Lagrange multiplier field associated with the local injectivity constraint remains bounded. In addition, we obtain convergent sequences of approximate solutions of the disk problem formulated with both this constrained minimization theory and a compressible and orthotropic Mooney-Rivlin material. This material has certain growth conditions on the deformation field that prevents material overlapping in classical problems of mechanics. Both sequences yield convergent solutions that are in very good agreement with each other.
Modeling Operational Parameters to Support Evaluation of Subsea-to-Shore Production System Implementation
Authors: Patrícia da Silva Figueirêdo Ferreira  , Juliana Souza Baioco  , Breno Pinheiro Jacob
Published: January 2025

The subsea-to-shore system represents an alternative approach to traditional offshore oil production, emphasizing environmental improvements by reducing carbon emissions through alternative energy sources like hydroelectric power. This system incorporates an onshore processing unit, eliminating the need for a Stationary Production Unit (SPU), thereby reducing costs, offshore personnel exposure, and its associated occupational risks. Additionally, terrestrial processing units offer greater flexibility for expansion and installation of new modules compared to SPUs, which are constrained by limited space. This paper aims to establish critical parameter limits essential for implementing the subsea-to-shore system based on a representative production field. Key parameters include distance to the coastline and various export pipeline diameters suitable for specific water depths, ensuring optimal operational performance. These studies utilized multiphase flow simulation software, leveraging data approximations from Norway's Ormen Lange Field, one of the largest gas fields, as a foundational basis. Results derived from the applied model and variables provide preliminary insights into the feasibility of implementing such systems, prompting further discussion within the scientific community regarding advancements in oil and gas production systems.
Three-dimensional finite element analysis of vortex-induced vibrations in deepwater steel catenary risers with large deformation
Authors: Zhenhua Li  , Carlos Eduardo da Silva Leandro Gazoni  , José Luis Drummond Alves  , Leandro Gazoni  , Yangye He  , Jian Su
Published: January 2025

Vortex-induced vibration (VIV) is an important phenomenon in fluid-structure interaction and one of the main challenges faced by slender offshore structures. Under the influence of ocean currents, long steel catenary risers (SCR) may exhibit nonlinear VIV dynamic response with various modes and frequencies, which occur simultaneously in three-dimensional space. These nonlinear dynamic response can lead to critical bending and longitudinal stresses, ultimately resulting in significant fatigue damage to offshore risers over time. This paper presents a large-deformation three-dimensional dynamic model for the SCR, which accounts for VIV and actual ocean loads, offering significant advantages over traditional small deformation beam or catenary theories. The model thoroughly considered the bending stiffness of the riser and the nonlinear effects of large deflections on the loads. It uses two Van der Pol wake oscillator equations to model the fluid dynamic impact of vortex shedding in both crossflow (CF) and in-line (IL) directions. Moreover, the model addresses the pipeline-soil interaction at the touchdown zone (TDZ). Employing the finite element method (FEM), each node was endowed with six degrees of freedom, enabling descriptions of vibrations in lateral, axial, and torsional directions for the riser. The structural dynamics and wake oscillator equations were solved using the Newmark-β and Runge-Kutta methods, respectively. The numerical model has been validated with published results and further simulations have been conducted to determine the dynamic behavior of the SCR. Subsequent comprehensive parameter analysis examined the effects of motion amplitude, current flow loads and the touchdown zone on the three-dimensional VIV responses of the SCR, which are crucial for understanding the dynamic behavior of the riser.
Dynamic amplification analysis in acoustic wave propagation problems subject to time-variable loads
Authors: Gyslane Aparecida Romano Dos Santos  , Carlos Friedrich Loeffler  , Luciano de Oliveira Castro Lara
Published: January 2025

In this work, the formulation of the direct interpolation boundary element method is applied to evaluate the dynamic behavior of continuous acoustic systems subject to the excitation of time variable loads. In such a condition, the temporal variation of the load may be close to some of the system's natural frequencies, and the evaluation of dynamic amplification and damping effects is very important. Physically, the analysis undertaken in this work provides an excellent indication of the dynamic behavior of a continuous system subject to pressure waves, which can be an aqueous medium or any seismic medium. In numerical terms, the simulations carried out show the robustness of the chosen technique in solving acoustic wave propagation problems compared to other methods.
Possibilities of node location optimization and the quest isoparametric versus isogeometric in the collocation boundary element method
Authors: Ney Augusto Dumont
Published: January 2025

We have recently laid down the theoretical basis for the consistent formulation of the collocation boundary element method, as it should have been conceived from the beginning. We proved a convergence theorem for two- and three-dimensional problems of elasticity and potential, which applies to arbitrarily curved elements in the frame of an isoparametric analysis. We also showed that arbitrarily high precision and accuracy may be achieved  limited only by the machines capacity to represent numbers. On the other hand, there still is the cost-benefit question  considering that the physical phenomenon is mathematically adequately idealized  of how to improve a real problems simulation without refining too much a discretization mesh. The first possibility of doing this is optimizing the geometric location of the primary parameters (as for displacements and tractions, in elasticity) for the problem's mechanical description. This primarily consists in locally refining a mesh. We may also attach the problems parameters to optimal locations inside the boundary element. A second issue is that an isoparametric formulation (generally in terms of polynomial interpolations along the boundary segment) may fail to reproduce the exact geometry of the idealized physical problem  as the isogeometric approach does. Since, for two-dimensional problems, we have the boundary element formulation under control regarding all numerical evaluations, we assess how an isoparametric analysis  with the introduced elegancy of a convergence theorem  compares to a formulation that preserves the problems idealized geometry, but to which the theorem no longer applies. We present the conceptual formulation, code implementation, and numerical illustrations.
Defining the Best Strain Gauge Placement through Numerical Simulations of the Mechanical Behavior of the Modified-WOL Specimen
Authors: Emerson da Trindade Marcelino  , Jorge Antonio Palma Carrasco  , José Maria Andrade Barbosa  , Nadège Sophie Bouchonneau da Silva
Published: January 2025

In structural steels, cracks are an inevitable occurrence, demanding an examination of their ability to resist crack propagation under expected loads and various environmental conditions. The process of experimentally determining fracture toughness comes at a significant expense, involving the use of multiple specimens and extended testing periods, which hinders the swift acquisition of crucial parameters. An alternative approach entails the execution of a constant displacement test using the Modified-WOL specimen, which is equipped with an instrumented bolt for self loading. The primary objective of this method is to provide the Threshold Stress Intensity Factor for Environment-Assisted Cracking, utilizing only a single specimen. The incorporation of electronic instrumentation is essential for obtaining reliable, real-time data. Despite its importance, a consensus is lacking in the literature regarding the best location for sensor installation on the Modified-WOL specimen, potentially influencing its mechanical response. This study aims to explore the mechanical behavior of the three components constituting the Modified-WOL specimen test in accordance with the guidelines outlined by ISO 7539-6. Employing the Finite Element Method with two- and three-dimensional models, this investigation utilizes the Augmented Lagrangian method for formulating the contact regions. Additionally, quarter-point singular elements are employed to accurately represent stress singularity behavior at the crack tip. The numerical computation of fracture parameter (KI) is conducted using the Displacement Correlation Technique. Comparative analyses are then carried out between the numerical and the analytical values of KI determined based on the ISO 7539-6 standard. The findings demonstrate alignment with empirical literature values, ultimately contributing to the identification of the best location for strain gauge installation among the highlighted regions of considerable interest.
Probabilistic Analysis of Slope Stability Considering Random Fields
Authors: André Luis Meier  , Fernando Weber  , Artur Machado Scheidt  , Tamires dos Santos  , Gracieli Dienstmann
Published: January 2025

The study of slope stability is of paramount importance for society, as it enables the evaluation of slope security and the establishment of alert parameters to mitigate financial losses and, in severe cases, prevent human casualties. Improving alert criteria necessitates a comprehensive assessment not only of the slope's safety factor but also its probability of failure. Therefore, the use of probabilistic techniques becomes imperative, with the Monte Carlo Method (MCM) emerging as a prevalent choice in geotechnical investigations. Employing MCM for slope stability involves modeling the target profile while varying crucial material parameterssuch as friction angle, cohesion, and specific weightin each iteration. As a result, the outcome yields a distribution of safety factors, aiding in the assessment of both average safety levels and failure probabilities. Failure probability is determined by counting simulations with safety factors below unity. Conventional approaches identified in the literature often employ uniform profiles in successive rounds, overlooking the spatial distribution of parameters. Hence, this study introduces a case analysis where failure probability is quantified through MCM, integrating random fields in each iteration. For assessing variability, the PLAXIS software was utilized, employing classical limit equilibrium methods alongside the LAS technique (Local Average Subdivision). This facilitates a comparative analysis of probabilities derived from distinct equilibrium methodologies. The case study will focus on a slope within Brazilian territory, where a comprehensive geotechnical survey encompassing field and laboratory assessments has been conducted.
Utilization of Random Fields for Prediction of Displacements in Laterally Loaded Piles
Authors: Rafael Marcus Schwabe  , André Luis Meier  , Gracieli Dienstmann
Published: January 2025

Soil is composed of materials that have organized over the ages, following the natural flow in the formation and development of the planet. Thus, we can infer that soil possesses characteristics of a random nature. Recent studies have been assisting geotechnical engineering in understanding this randomness, providing parameters for a more consistent mathematical representation of soil mass, aligned with probabilistic mathematics. Within this context, this work employs the theory of random variables coupled with the finite element method to estimate the behavior of laterally loaded piles. The study modeled the behavior of two piles using deterministic and stochastic methods, comparing the results with real load tests. These results showed good correspondence between predicted behavior and real tests.
Evaluation of Tolerance Selection Strategies and Multifidelity Techniques in ABC Methods
Authors: Graziele Daiana Sena de Sousa  , Renato Simões Silva  , Regina Célia Cerqueira de Almeida
Published: January 2025

Approximate Bayesian Computation (ABC) methods provides a flexible and robust framework for solve model fitting problems, particularly pertinent to complex models with intractable likelihood functions. This methodology is based on approximating a simulated parameter values through auxiliary data and evaluating the distance of this data with the true dataset. Effective implementation of these methods require reasonable decisions to be made about the selection of ABC techniques and how to implement the algorithm to ensure computational efficiency. A comprehensive understanding of these factors facilitates a more accurate inference about the model. This study aims to explore the impact of the tolerance selection and the integration of Multifidelity techniques to the convergence and cost of the method. In the initial approach, three methods of choosing tolerances are employed: a predefined vector, a percentile calculation, and a percentage calculation based on the distance vector obtained from model simulations, in order to verify the most effective strategy for the improvement of the inference process. Subsequently, the optimal approach of tolerances selection is combined with Multifidelity techniques to reduce the computational cost. This methodology is applied in the examination of infectious disease models of differential equations. This study aims to highlight the importance of careful decision-making when using ABC methods, through the evaluation of some approaches for choosing tolerance in combination with techniques that aim to reduce the computational cost in constructing samples in ABC methods. Through this analysis, we focus our efforts on trying to demonstrate insights about gains in computational efficiency and accuracy in results.
Multi-objective optimization of unconventional airfoils at low Reynolds numbers
Authors: Luciana Paixão Motta  , Heder Soares Bernardino  , Patrícia Habib Hallak
Published: January 2025

The widespread exploration of drones has generated increasing interest in Micro Aerial Vehicles (MAVs). Furthermore, an application that has gained notoriety is the use of aerial vehicles for exploration on Mars. Thus, the quest for efficient aerodynamic profiles for these applications has been intensified. These types of applications operate in a Reynolds number range from 10^4 to 10^5, which is significantly smaller than those commonly found in conventional low Reynolds regimes, such as when commercial drones are adopted. The main objective here is to identify more efficient shapes for airfoils, optimizing them through a multi-objective process aiming to maximize the lift coefficient and minimize the drag coefficient. To achieve this goal, two models of unconventional airfoils were optimized using the Generalized Differential Evolution 3 (GDE3) algorithm. The acquisition of aerodynamic coefficients, essential for evaluating the performance of the evolutionary algorithm, was carried out through simulations using Computational Fluid Dynamics (CFD). The method applied to describe the aerodynamic behavior of the structures proved to be consistent with experimental data. We used two base structures: a cubic Bézier-profile plate and a planar model with two inflections. Employing the aircraft's range or autonomy as decision criteria, it was observed that the cubic Bézier-profile plate presented superior results. Analyzing the graphs of the aerodynamic coefficients in relation to the angle of attack, the considerable increase in the stall point and lift provided by this model is notable. Such improvements, however, were accompanied by a slight disadvantage in the drag coefficient for small or negative angles of attack. It was also found that the evolutionary algorithm resulted in aerodynamic profiles with interesting characteristics for these applications when compared to existing models in the literature. In conclusion, the proposed cubic Bézier-profile plate model proved to be an interesting alternative for applications with a significantly small Reynolds number.
Sensitivity analysis of thermal phenomena in APB (Annular Pressure Buildup) in oil wells
Authors: Luiz Elias da Silva Filho  , Thiago Barbosa da Silva  , Catarina Nogueira de Araújo Fernandes  , William Wagner Matos Lira  , João Paulo Lima Santos  , Charlton Okama de Souza  , Emilio Cesar Cavalcante Melo da Silva
Published: January 2025

This paper presents a sensitivity analysis aimed at understanding how certain parameters of the thermal problem affect the increase in Annular Pressure Buildup (APB) in oil wells. The structure of an oil well experiences high-temperature gradients throughout its lifespan, directly affecting its components such as casings, cement, and rock formation. Among the undesirable effects caused by temperature variation, APB stands out, related to the expansion of fluids confined between casings, being a severe phenomenon that can lead to well collapse. This justifies studies aimed at better understanding temperature distributions and, consequently, the increase in pressure in the annular spaces of oil wells. On the other hand, changes in fluid and component temperatures during well operation depend on many factors, such as operating flow rate, inlet pressure and temperature, operating time, formation type, and properties of the produced/injected fluid. Some of these parameters are chosen for inclusion in the parametric analysis proposed in this work. To achieve the proposed objective, the methodology adopted in this work is based on four steps: a) selection of a reference well used for the analyses; b) definition of the variables to be studied and their assumed values; c) generation and simulation of scenarios formed by the combination of chosen variables; and d) selection and description of the sensitivity analysis method to be employed. The main contribution of this work is to present a sensitivity analysis of certain well parameters in annular pressure buildup, allowing inference about the importance of some isolated properties in the thermomechanical response. Additionally, the methodology presented can be applied to other parameters and thus improve understanding of how each property influences well APB.
CO2 injection modeling in a reservoir: Phase transition study
Authors: Rafael de Lima Omena  , Jonathan da Cunha Teixeira  , Ruan da Silva Nobre  , Bernardo José Lucas Ferro Moreira  , Matheus Vinícius Silva Santos
Published: January 2025

The study explores the phase transition of carbon dioxide from liquid to gas after injection and storage in a confined aquifer at a temperature of 30°C. By utilizing a compositional isotropic model and data from the NIST webbook (Linstrom and Mallard, 2024), the simulation analyzes, using compositional mesh model in tNavigator software (by Rock Flow Dynamics), the behavior of CO2 within a confined aquifer, seeking to identify the phase transition of the fluid. The effects of capillarity are neglected, and the main parameters of the reservoir are a pressure of 65 bar at the wellhead and a constant temperature of 31°C throughout the aquifer to evaluate the phase transition close to the supercritical point of CO2. The analysis reveals that the drastic pressure reduction within the confined aquifer leads to the formation of free gas within the reservoir after the closure of injection wells, which becomes a problem, as occurred in the Ordos CCS Project in China, allowing fluid backflow during non-injection (CAI, Yuna et al.). The results showed that the closer the temperature approaches the supercritical point of CO2, the greater the probability of free gas formation within the reservoir. Therefore, the conclusions emphasize the impact of the pressure reduction on the stability of CO2, which will undergo a phase transition from the liquid to the gaseous state, so that free gas is generated within the reservoir. In this way, it is highlighted the importance of understanding phase transition in CO2 injection processes for effective carbon capture and storage strategies.
Evaluation of the Impact of Mineralogy On Oil Recovery Using Digital Petrophysics
Authors: Mirele dos Santos Bispo  , Emily Katarine Ferreira Vale  , Agatha Densy dos Santos Francisco  , Thiago Maia Fontes Pineiro  , José Luis Drummond Alves  , Maira da Costa de Oliveira Lima Santo  , Paulo Couto
Published: January 2025

Exploring pre-salt oil deposits poses a significant challenge for the oil and gas industry. Carbonate rock reservoirs, being more susceptible to diagenetic actions, exhibit considerable complexity due to the heterogeneity of the porous system, making exploration activities in this scenario challenging. Microscale analysis of fluid behavior in porous media from X-ray microtomography images and petrophysical system analyses has become increasingly essential for enhancing techniques applied in this sector. To investigate the impact of mineralogy on oil recovery using desulfated seawater (DSW), two samples of coquinas from the Morro do Chaves Formation, Sergipe-Alagoas Basin, considered analogs to the coquinas of the Itapema Formation in the Santos Basin, Brazilian pre-salt, were utilized. Due to the depositional context of this formation, the coquinas from the Morro do Chaves Formation contain terrigenous minerals, primarily quartz, in their composition. This study aims to understand how different percentages of these terrigenous minerals associated with carbonate minerals can influence reservoir oil recovery. For this purpose, 3D image analyses obtained by micro-CT at different saturation phases: dry, water-saturated formation, oil-aged, and at various contact times with DSW were employed. To confirm observations acquired through images, the contact angle of the system was measured, where samples aged in oil came into contact with recovery water. Image analyses were conducted using profiles of both porosity and fluid saturation present in the pores. As a result, indications were observed that terrigenous minerals influence rock wettability. The sample containing higher percentages of these minerals demonstrated an affinity with oil, while the other, lacking these minerals, exhibited water-wettability. Different interpretations, however, could be identified: desulfated seawater did not benefit oil recovery, as the sample with a high content of terrigenous material showed the highest efficiency in removing residual oil; another interesting aspect found in this sample was the tendency for gas entrapment, as the percentage of pores filled with air remained practically constant during the process.
An Eulerian-like interface-capturing approach for modeling the fouling process by crystallization
Authors: Andrés Mauricio Nieves Chacón  , Renato Simões Silva  , Regina Célia Cerqueira de Almeida
Published: January 2025

Calcium carbonate (CaCO3) is an inverse solubility salt commonly scaled in heat exchangers when the fouling mechanism by crystallization occurs. Several models have been proposed to predict the fouling behavior, considering the growth of fouling mass as the difference between deposition and removal rates. Despite the different alternatives suggested in the literature to approximate these rates, there has been limited discussion regarding the fouling layer growth interface capture within a continuous domain during the time-dependent crystallization process. Hence, in this work, we propose an Eulerian interface-capturing approach for modeling the fouling process by crystallization (EICAFC). This scheme will be implemented using the standard Galerkin Finite Element Method with linear interpolation polynomials. The EICAFC procedure will be outlined employing the Bohnet fouling model. Results about fouling thickness, mass accumulation, fouling resistance, and the EICAFC performance will be discussed.
Application of Artificial Neural Networks in predicting the thermal performance of grooved heat pipes
Authors: Thiago Antonini Alves  , Thomas Siqueira Pereira  , Yara de Souza Tadano  , Hugo Valadares Siqueira
Published: January 2025

Heat pipes are versatile, relatively easy to construct, and capable of exchanging large amounts of heat between small temperature differences, even without external pumping. On the other hand, these devices have complex equations, which usually complicates their development, generating more extended periods of research and expenses. Methods that use computational intelligence, such as Artificial Neural Networks (ANN), have the ideal characteristics for use in problems of this type. ANN are algorithms that can solve complex problems using only experimental data, even without knowledge about the physics of the problem, limited only by the quality of the data used and the available computational power. In many cases, the results found using ANN have lower error percentages than those obtained using conventional methods. The database used was generated from an experimental investigation of the thermal behavior of heat pipes with a wicked structure of axial grooves and using water as the working fluid. The results were used to train two different Artificial Neural Networks. The Neural Networks used were the Multi-Layer Perceptron (MLP) and the Extreme Learning Machine (ELM). Filling ratio, slope, and dissipated power were used as inputs to the networks, and as output, we have the expected thermal resistance of the heat pipe. The results show that both ANN were able to generalize the problem, presenting errors of less than 25%. It is also possible to note that the MLP presents better results, with an error of about 18%. These values show that ANN are viable as a tool to improve the development of grooved heat pipes.
Numerical Study of the Effects of Residual Stress in Welded Pipe Joints
Authors: Gustavo Teixeira da Silva  , Lucas Pereira de Gouveia  , Eduardo Toledo de Lima Junior  , João Paulo de Lima Santos
Published: January 2025

In general, welding processes can be understood as the establishment of the union of parts, generally metallic, using a heat source to promote the fusion of materials, with or without the presence of pressure efforts. Studies related to the distributions and levels of residual resistance arising from the thermal cycles involved in welding processes are of vital importance for evaluating and guaranteeing the integrity of welded pipes. This work proposes the implementation of a routine in PYTHON language to automate the production of thermomechanical coupling welding models using the ABAQUS® CAE finite element tool, considering the heat distribution model of the welding source according to Goldak et al. (1984), better known as the double ellipsoid model. The studies are produced considering an ambient temperature of 20 °C and another with preheating of the tubes to 300 °C. The results achieved by this study are related solely to analyzes of the residual stress fields in a thin walled tube joint manufactured in AISI 304 stainless steel, welded using TIG (Tungsten Inert Gas) processes in a single pass. Thus, this study seeks to analyze the hoop and axial residual stress distributions on the internal or external walls of post-welded tubes in angular positions 0°, 90°, 180° and 270°, whether or not there is uniform preheating of the pre-welding pipes. The results show that, in general, residual stresses differ slightly with the angular position, being relatively high when compared to the yield stress of the steel, and therefore have a considerable impact on reducing the mechanical strength of the welded joint. It should also be noted that when considering the preheating of the pipes there is a significant decrease in the peak temperatures reached in the transfer process, in the cooling rates and in the residual stress levels of the joints, especially in the most critical regions, located in the proximity from the center of the weld beads.
Thermal Parameter Estimation of Sandwich Panel using Numerical Solution of Inverse Heat Conduction Problem
Authors: Geraldo José Belmonte dos Santos  , Adilson Brito de Arruda Filho  , Sasha Kaline Santana Botelho  , Maicon Souza Sena  , Paulo Roberto Lopes Lima
Published: January 2025

In this work, a numerical formulation to solution of the inverse heat transfer problem, based in the implicit finite difference method and Monte Carlo method, is developed to estimate the thermal properties of the sandwich panel. It is realized the sensitivity analysis of the parameters and the thermal contact resistance along the layers interface is used. Experimental results of temperature are used in the numerical formulation to determine the thermal properties (conductivity and the specific heat) of the layers materials and to predict the thermal behavior of the panel. The results obtained show that the formulation estimates with adequate accuracy the material thermal proprieties.
Numerical modeling of localization bands with mesh-independence using lumped damage mechanics
Authors: David Leonardo Nascimento de Figueiredo Amorim  , Daniel Victor da Cunha Teles  , Rafael Nunes da Cunha  , Ricardo Picón  , Julio Flórez-López
Published: January 2025

The Lumped Damage Mechanics for continuous media has been successful in describing the nonlinear physical behavior of engineering problems. The approach utilizes basic concepts from fracture and classic damage mechanics. In this regard, material degradation in two-dimensional media is computed from the evolution of localization bands concentrated on the finite elements faces. The growth of these bands occurs based on the Griffith criterion. In this work, a nonlinear evolution law with exponential softening is adopted in order to accurately describe quasi-brittle failure behavior. Numerical solutions show mesh-independence of the proposed approach as well as the reproduction of the size-effect phenomenon. Finally, it was possible to reproduce experimental behavior in terms of equilibrium trajectory and cracking pattern of the failure region.
Seismic vulnerability of steel tubular structures based on local Buckling driving variables
Authors: Rúbia Mara Bosse  , Scarlet Montilla Barrios  , Gustavo de Miranda Saleme Gidrão  , Ricardo Picón  , André Teófilo Beck  , Júlio Flórez-López
Published: January 2025

Performance-Based Earthquake Engineering (PBEE) is computationally demanding, due to the multiple high-fidelity non-linear dynamic structural response analyses required to compute fragility curves. In this manuscript we propose an efficient procedure to obtain fragility curves of complex tubular structures prone to fail due to local buckling using a model based on the Lumped Damage Mechanics. A state variable characterizing local buckling is employed as engineering demand parameter in PBEE. This state variable is a scalar, derived from lumped damage mechanics and taking values between 0 and 1, which characterizes the degree of local buckling (LB). A procedure to identify and define global collapse mechanisms using the local buckling state variable at the nodes is proposed, which serves as the EDP for computing the structure's fragility curves. To evaluate the seismic vulnerability, incremental dynamic analyses are conducted. The main results demonstrate efficiency of the mechanical model in a PBEE framework, and that the internal variables indicating local buckling can be considered objective indicators of collapse for Tubular complex steel frames. Results show how to identify the global failure mechanisms that are more likely to appear for each frame.
Efektivitas Pendistribusian Dana Zakat terhadap Program Pendidikan pada BAZNAS kabupaten Majene
Authors: Muhammad Hilal Mubarak
Published: January 2025

Penelitian ini dilatarbelakangi oleh permasalahan kemiskinan yang tengah di hadapi oleh masyarakat, dimana kemiskinan tersebut salah satu penyebab munculnya permasalahan pada perekonomian masyarakat. Sehingga tidak mampu untuk memenuhi kebutuhan pokok termasuk dalam aspek pendidikan. Pokok permasalahan dari penelitian ini adalah (1) Bagaimana mekanisme dari pendistribusian dana zakat terhadap program pendidikan di BAZNAS kabupaten Majene, (2) Bagaimana Implementasi teori efektivitas dari Richard M. Steers dengan pendistribusian dana zakat terhadap program pendidikan di BAZNAS kabupaten Majene. Penelitian ini menggunakan jenis penelitian lapangan dengan sumber data dari Jurnal, artikel, buku, maupun hasil penelitian yang relevan untuk di bahas. Penelitian ini menyimpulkan bahwa Mekanisme Distribusi zakat yang telah dilakukan oleh BAZNAS kabupaten Majene sudah sesuai dengan prosedur dengan terdapatnya Visi-misi, Struktur Organisasi serta Berrbagai Program kerja yang inovatif agar sampai kepada tangan para Mustahik dengan Mudah. Distribusi zakat Konsumtif maupun produktif yang diberikan oleh pihak BAZNAS kabupaten Majene melalu program “Majene Cerdas” kepada mustahik di kabupaten majene secraa keseluruhan dapat meningkatkan kualitas pendidikan dan kesejahteraan mustahik. Sehingga pendistribusian dana zakat pada program pendidikan yang dilakukan oleh BAZNAS kabupaten majene ini sudah efektif dalam meningkatkan kesejahteraan mustahik, hal ini dibuktikan dengan meningkatnya keinginan warga Majene yang melanjutkan pendidikan nya ke tahap perguruan tinggi.
Kualitas Hewan Kurban Pemakan Sampah di TPA Antang Kota Makassar
Authors: Ativa Nurhadi  , Usman Jafar  , Fatmawati  , Halim Talli  , Kurniati
Published: January 2025

Penelitian ini merupakan penelitian kualitatif dengan jenis penelitian lapangan (field research). Studi lapangan dilaksanakan dengan mengumpulkan data primer melalui observasi,wawancara dan dokumentasi. Selain data yang diperoleh dari lapangan , diperkuat juga dengan data berupa literatur seperti buku, dan artikel-artikel ilmiah yang membahas mengenai penelitian ini. Kemudian, teknik pengolahan dan analisi data dilakukan dengan reduksi data, penyajian data, dan penarikan kesimpulan. Hasil penelitian ini menunjukkan, 1)Peran Pemerintah telah dilihat dengan mengeluarkan kebijakan, bahwasanya penggembalaan sapi di TPA itu dilarang, karena makanan yang di konsumsi oleh sapi tidak layak, namun hal demikian dihiraukan oleh penggembala, aturan telah dijelaskan pada UU kesehatan hewan ternak, dan ancaman penyakit pada hewan ternak. Adapun Aturan pemerintah daerah pada pencegahan penyakit pada hewan kurban yang akan dikurbankan pasal 21A. 2)Penggembalaan sapi di TPA Juga berdampak pada masyarakat baik dari segi kesehatan dan lingkungan, banyak dari mereka yang merasa khawatir karena adanya daging sapi yang berasal dari TPA, Dalam hasil penelitian juga dijelaskan oleh Dokter Hewan bahwa banyaknya zat-zat yang terkontaminasi pada sapi yang ada di TPA, seperti plastik, zat-zat logam berat, yang dapat menyebabkan bahaya pada manusia. 3)Islam memerintahkan melakukan ibadah kurban haruslah sesuai dengan syariat yang telah ditentukan baik itu bersifat sunah maupun wajib. Hewan kurban yang tidak sesuai kriteria yang ditentukan seperti, yang sudah tidak sehat dagingnya tidak sah dijadikan kurban. Begitu pula dengan hewan yang hidup ditempat yang tidak layak dan mengkonsumsi makanan yang tidak sesuai dengan sapi pada umumnya seperti sapi yang ada di TPA Antang.
Peranan Solidaritas Perempuan Anging Mammiri dalam Pemenuhan Hak Perempuan Buruh Migran di Sulsel Perspektif Hukum Islam
Authors: Nurfianalisa  , Kurniati  , Asni  , Siti Aisyah  , Abd. Halim Talli
Published: January 2025

Tujuan umum penelitian adalah untuk menganalisis peran Solidaritas Perempuan Anging Mammiri dalam pemenuhan hak perempuan buruh migran di Sulsel perspektif hukum Islam. Adapun tujuan khususnya yaitu: 1) Untuk mengetahui bentuk pemenuhan hak perempuan buruh migran Solidaritas Perempuan Anging Mammiri di Sulsel. 2) Untuk mengetahui upaya Solidaritas Perempuan Anging Mammiri dalam pemenuhan hak perempuan buruh migran korban Trafficking. 3) Untuk mengetahui pandangan hukum Islam terhadap peran Solidaritas Perempuan Anging Mammiri. Jenis penelitian yang digunakan adalah penelitian kualitatif (field research) untuk menggambarkan kondisi faktual di lapangan dengan pendekatan penelitian yang digunakan adalah teologi normatif syar’i dan pendekatan yuridis empiris. Selanjutnya, metode pengumpulan data yang digunakan adalah observasi, wawancara, dokumentasi, dan penelusuran referensi. Teknik pengolahan data dan analisis data dilakukan dengan melalui tiga tahapan, yaitu reduksi data, pemeriksaan data, sistematika data, verifikasi dan kesimpulan data. Hasil penelitian ini menunjukkan, 1) Bentuk pemenuhan hak perempuan buruh migran oleh lembaga Solidaritas Perempuan Anging Mammiri menggunakan tiga pendekatan uatama, yakni pengorganisasian, advokasi, dan kampanye kesadaran. 2) Upaya pemenuhan hak korban Trafficking yang dilakukan lembaga SP Anging Mammiri melalui tiga langkah utama, yang pertama pendidikan dan peningkatan kapasitas, kedua penanganan kasus litigasi maupun nonlitigasi, dan ketiga reintegrasi sosial. 3) Perspektif Hukum Islam terhadap peran lembaga SP Anging Mammiri sejalan dengan prinsip utama Hukum Islam yang meliputi Maqashid syariah yang melindungi hak-hak dasar seperti jiwa, kehormatan, dan harta.