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The impact of heterogeneity and pore network characteristics on single and multi-phase fluid propagation in complex porous media:An X-ray computed tomography study

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Petroleum Science 2024年第3期21卷 1719-1738页

作者： Shohreh Iraji Tales Rodrigues De Almeida Eddy Ruidiaz Munoz Mateus Basso Alexandre Campane Vidal Department of Mechanical Engineering (FEM) State University of Campinas (UNICAMP) Department of Geology and Natural Resources Geosciences Institute (IG) State University of Campinas (UNICAMP) LRAP/coppe/coppeTEC/UFRJ Center of Energy and Petroleum Studies (CEPETRO) State University of Campinas (UNICAMP)

This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media, providing insights into the factors affecting fluid propagation in such systems. Specifically, high-resolution or micro X-ray computed tomography(CT) imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada, considered flow analogous to the Brazilian Pre-salt carbonate reservoirs. The petrophysical results comprised two distinct stromatolite depositional facies, the columnar and the fine-grained facies. By generating pore network model(PNM), the study quantified the relationship between key features of the porous system, including pore and throat radius, throat length, coordination number, shape factor, and pore volume. The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores. Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length. Additionally, a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields. The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others. The relation between saturation profiles, porosity profiles, and the number of fluid flow patterns for the samples was evident. Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB) observed.

关键词： Pore network model Heterogeneous porous media Flow patterns Dead-end pores

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A neural branch-and-price for truck scheduling in cross-docks

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Science China Mathematics 2024年第6期67卷 1341-1358页

作者： Rahimeh Neamatian Monemi Shahin Gelareh Nelson Maculan Wei-Kun Chen Sharkey Predictim Globe Villeneuve d’Ascq59650France Département R&T IUT de BéthuneUniversitéd’ArtoisBéthuneF-62000France Federal University of Rio de Janeiro COPPE-PESCRio de JaneiroRJ 21941-972Brazil School of Mathematics and Statistics Beijing Institute of TechnologyBeijing100081China

In this paper,we address the complex problem of dock-door assignment and truck scheduling within cross-docking operations.This is a problem that requires frequent resolution throughout the operational day,as disruptions often invalidate the optimal plan.Given the problem's highly combinatorial nature,finding an optimal solution demands significant computational time and resources.However,the distribution of data across problem instances over a lengthy planning horizon remains consistently stable,with minimal concern regarding distribution shift.These factors collectively establish the problem as an ideal candidate for a learn-to-optimize solution strategy.We propose a Dantzig-Wolfe reformulation,solving it via both a conventional branch-and-price approach and a neural branch-and-price approach,the latter of which employs imitation learning.Additionally,we introduce some classes of valid inequalities to enhance and refine the pricing problem through a branch-and-cut scheme.Our computational experiments demonstrate that this methodology is not only feasible but also presents a viable alternative to the traditional branch-and-price algorithms typically utilized for such challenges.

关键词： cross-docking MILP modeling Dantzig-Wolfe decomposition graph convolutional network

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Impact of Cascade Disconnection of Distributed Energy Resources on Bulk Power System Stability:Modeling and Mitigation Requirements

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Journal of Modern Power Systems and Clean Energy 2023年第2期11卷 412-420页

作者： Fabricio Andrade Mourinho Tatiana Mariano Lessa Assis Electrical Engineering Department of the Federal University of Rio de Janeiro(coppe/UFRJ) Rio de JaneiroRJBrazil

This work presents a new approach to establishing the minimum requirements for anti-islanding protection of distributed energy resources(DERs)with focus on bulk power system stability.The proposed approach aims to avoid cascade disconnection of DERs during major disturbances in the transmission network and to compromise as little as possible the detection of real islanding situations.The proposed approach concentrates on the rate-of-change of frequency(RoCoF)protection function and it is based on the assessment of dynamic security regions with the incorporation of a new and straightforward approach to represent the disconnection of DERs when analyzing the bulk power system stability.Initially,the impact of disconnection of DERs on the Brazilian Interconnected Power System(BIPS)stability is analyzed,highlighting the importance of modeling such disconnection in electromechanical stability studies,even considering low penetration levels of DERs.Then,the proposed approach is applied to the BIPS,evidencing its benefits when specifying the minimum requirements of anti-islanding protection,without overestimating them.

关键词： Anti-islanding protection bulk power system stability distributed energy resource(DER) dynamic security region(DSR)

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Phenomenological model for torsional galloping of an elastic flat plate due to hydrodynamic loads

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Journal of Hydrodynamics 2014年第1期26卷 57-65页

作者： FERNANDES Antonio Carlos ARMANDEI Mohammadmehdi Department of Naval and Ocean Engineering COPPE/UFRJ

This study investigates the torsional galloping phenomenon, an instability type flow-induced oscillation, in an elastic stru-cture due to hydrodynamic loads into the water current. The structure applied here is a rectangular flat plate with an elastic axis in its mid-chord length. The elasticity is provided by torsion spring. The flat plate has only one degree of freedom which is rotation in pure yaw about its axis. It is observed that as the current speed is higher than a critical velocity, the flat plate becomes unstable. The instability leads to torsional galloping occurrence, as a result of which the flat plate begins to yaw about the elastic axis. By testing two different chord lengths each with several torsion spring rates, the flat plate behavior is investigated and three different responses are recognized. Then, a phenomenological model is developed with the original kernel in the form of the van der Pol-Duffing equa-tion. The model explains these three responses observed experimentally.

关键词： torsional galloping flow-induced oscillation phenomenological model van der Pol-Duffing equation

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Synthesis Gas Production from Natural Gas on Supported Pt Catalysts

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Journal of Natural Gas Chemistry 2006年第1期15卷 21-27页

作者： Mariana M. V. M. Souza Octávio R. Macedo Neto Martin Schmal NUCAT/PEQ/coppe

Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.

关键词： methane steam reforming CO2 reforming partial oxidation auto-thermal reforming platinum catalyst ceria zirconia

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PREDICTION OF VORTEX-INDUCED VIBRATION OF LONG FLEXIBLE CYLINDERS MODELED BY A COUPLED NONLINEAR OSCILLATOR:INTEGRAL TRANSFORM SOLUTION

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Journal of Hydrodynamics 2012年第6期24卷 888-898页

作者： GU Ji-jun AN Chen LEVI Carlos SU Jian Ocean Engineering Program COPPEUniversidade Federal do Rio de Janeiro Nuclear Engineering Program COPPEUniversidade Federal do Rio de Janeiro

The Generalized Integral Transform Technique （GITT） was applied to predict dynamic response of Vortex-Induced Vibration （VIV） of a long flexible cylinder. A nonlinear wake oscillator model was used to represent the cross-flow force acting on the cylinder, leading to a coupled system of second-order Partial Differential Equations （PDEs） in temporal variable. The GITT approach was used to transform the system of PDEs to a system of Ordinary Differential Equations （ODEs）, which was numerically solved by using the Adams-Moulton and Gear method （DIVPAG） developed by the International Mathematics and Statistics Library （IMSL）. Numerical results were presented for comparison to those given by the finite difference method and experimental results, allowing a critical evaluation of the technique performance. The influence of variation of mean axial tension induced by elongation of flexible cylinder was evaluated, which was shown to be not negligible in numerical simulation of VIV of a long flexible cylinder.

关键词： Vortex-Induced Vibration （VIV） nonlinear wake oscillator flexible cylinder integral transform

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A Review of Greenhouse Gas Emissions by Hydropower Reservoirs

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Journal of Geoscience and Environment Protection 2023年第9期11卷 203-215页

作者： Marco Aurélio Dos Santos coppe/UFRJ Rio de Janeiro Brazil

Hydroelectric reservoirs have environmental impacts as many other sources of energy. Regarding hydropower, these effects include flooding cultivated and forest areas, changes in water quality, negative impacts on water biodiversity, conflict with indigenous people and fish migration. In the nineties, researchers put in evidence of another important impact of dam construction: the greenhouse gases generated by flooding organic matter by reservoir flooding. Scientists argue that like natural human water bodies, the hydropower reservoirs emit biogenic gases into the atmosphere. The diffusive gas flux is associated with the difference between gas partial pressure of each chemical substance considering the aquatic system and the atmosphere. Ebullition is a process where some chemical substances are not soluble in water and bubbles are formed in the sediment at the bottom of the reservoir. Ebullition is often the dominant pathway of CH4 that is released from aquatic ecosystems. The phenomenon is episodic and irregular and depends mainly on hydrostatic pressure and other physical influences, such as currents, temperature gradients and the bathymetry of the water body. At hydropower reservoirs, other pathways for gas emanation to the atmosphere are the degassing by water passing through turbines of the powerhouse and the gas diffusion across the river downstream dam. This paper gives a review of the state-of-the-art and advances in the research of greenhouse gas emissions and removals from hydropower reservoirs.

关键词： Hydropower Reservoirs Carbon Emission Methane Carbon Dioxide

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Phasor-domain Dynamic Model of Asymmetric Current Injection Controller for Converter-interfaced Generator

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Journal of Modern Power Systems and Clean Energy 2021年第6期9卷 1269-1278页

作者： Victor A.F.Almeida Glauco N.Taranto José M.T.Marinho Electrical Engineering Department of the Federal University of Rio de Janeiro(coppe/UFRJ) Petrobras S.A.

This paper presents a controller model of asymmetric current injection for converter-interfaced generators suitable for root-mean-square(RMS)phasor-domain,fundamentalfrequency,three-phase,and dynamic simulation tools.The effectiveness of the proposed controller is assessed with simulations in test systems with high percentage of converter-interfaced generation.The simulations focus on the operation of protection relays that use negative-sequence quantities in their directional elements.This paper also presents and compares two strategies to limit reactive negative-sequence currents,and active and reactive positive-sequence currents.A tutorial test system and a regional system part of the actual Brazilian Interconnected Power System are used to assess the correctness of the proposed controller in three-phase fundamental-frequency RMS dynamic simulations.

关键词： Converter-interfaced generator three-phase model power system protection negative-sequence current injection negative-sequence current protection unbalanced fault three-phase root-mean-square(RMS)dynamic simulation

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Stability analysis of the fluttering and autorotation of flow-induced rotation of a hinged flat plate

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Journal of Hydrodynamics 2013年第5期25卷 755-762页

作者： MIRZAEISEFAT Sina FERNANDES Antonio Carlos Department of Naval Architecture and Marine Engineering University of Michigan coppe/UFRJ Federal University of Rio de Janeiro

This work describes investigations performed on the interaction of uniform current and freely rotating plate about a fixed vertical axis. Fluttering and autorotation are two different motions that may occur during the flow induced rotation. The dimensional analysis proves that the motion in flow induced rotation motion is governed essentially by the dimensionless moment of inertia and Reynolds number. Certain combinations define the stability boundaries between fluttering and autorotation. Fluttering is oscillation of body about a vertical axis and the autorotation is a name given to the case when the body turns continuously about the vertical axis First, the loads and moment coefficients are calculated by experiments and streamline theory for different angles of attack for a fixed fiat plate. Then for dynamic case, a bifurcation diagram is presented based on experiments to classify different motion states of flow induced rotation. Finally, a dynamical model is proposed for stability analysis of flow induced rotation of a flat plate.

关键词： flow-induced rotation autorotation fluttering stability analysis

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On the viability of wearing evaluation by Thin Layer Activation in the presence of non-occupationally exposed individuals

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Nuclear Science and Techniques 2022年第3期33卷 103-112页

作者： Michel de Almeida Franca Julio Cezar Suita Paulo Fernando Ferreira Frutuoso e Melo Celso Marcelo Franklin Lapa Graduate Program of Nuclear Engineering COPPEFederal University of Rio de JaneiroRio de JaneiroRJ 21941914Brazil Instituto de Engenharia Nuclear(IEN-CNEN) Rio de Janeiro 21941614Brazil Comissao Nacional de Energia Nuclear(SEASE/DRS/CNEN) Rio de Janeiro 22290040Brazil

Thin Layer Activation is a nuclear technique that has key advantages over other wear measuring techniques for mechanical systems,especially for in site experiments on equipment important to safety in nuclear plants.Still,it incurs radioactive dose and,thus,must be proved radiologically safe before use,otherwise,the utilization of this technique may be hindered inviable.Proving said technique is safe previous to any operational/monetary cost is key,providing a methodology for this early assertion is the main contribution of this work—here,only non-occupationally exposed individuals are considered.This work offers a methodology,through a case study,to ascertain the Thin Layer Activation parameters to obtain safe levels of radioactive dose while maintaining statistically reliable results.This methodology consists of using simulations,through the Monte Carlo Method,to obtain the floors and ceilings for the previously mentioned activation parameters based on operation and work conditions on site.

关键词： Thin Layer Activation Safety evaluation Simulation Equipment wearing

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