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See detailModeling of a Magnetic Shunt and an Aluminum Screen Using the Perturbation Finite Element Method
Ferreira da Luz, Mauricio V.; Dular, Patrick ULg; V Sabariego, Ruth ULg et al

in Proceedings of the 14th Biennial IEEE Conference on Electromagnetic Field Computation (CEFC2010) (2010)

In this paper the perturbation technique is developed for modeling of the magnetic shunt and an aluminum screen in large power transformers. The problem is first studied using either a simplified ... [more ▼]

In this paper the perturbation technique is developed for modeling of the magnetic shunt and an aluminum screen in large power transformers. The problem is first studied using either a simplified analytical or a finite element model. A more elaborated model is then defined to take into account its structural details. The calculation of iron losses and of the minimum clearance between bus bars leading current and magnetizable steel parts for a frequency range is performed. The modeling takes into account the eddy currents in magnetic shunt laminations due to the magnetic field in the shunt. [less ▲]

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See detailModeling of a pilot plant for the CO2-reactive absorption in amine solvent for power plant flue gases
Léonard, Grégoire ULg

Master's dissertation (2009)

During the combustion of fossil fuels in power plants, large carbon dioxide quantities are produced and released into the atmosphere. Carbon dioxide is a greenhouse gas and its role in the current global ... [more ▼]

During the combustion of fossil fuels in power plants, large carbon dioxide quantities are produced and released into the atmosphere. Carbon dioxide is a greenhouse gas and its role in the current global warming is widely accepted by the scientific community. Many projects have been launched in the last few years that aimed at developing processes for the mitigation of carbon-dioxide emissions. Among the different carbon capture and storage technologies (CCS), the post-combustion capture of CO2 in power plants seems promised to a large development. The objective of the present work is to model a pilot installation that should be built in the next few months. This pilot installation will be retrofitted in an existing coal-fired power plant in order to treat 5000 Nm³/h flue gas in two process trains. It is planed that 90% of the CO2 present in the flue gas can be removed, which corresponds to a capture rate of about 1 ton CO2/h. The role of this simulation is to facilitate the comprehension of the capture phenomena and to highlight the key process parameter and their influence on the obtained results. Furthermore, some technical improvements are studied that aim at a reduction of the energy consumption of the CO2-capture process. The simulation tool Aspen Plus has been employed to model the pilot installation. It has been assumed for the simulation requirement that the equilibrium state was achieved for each stage of the mass transfer columns. Mass transfer limitations and reaction kinetics have then been neglected. The model described in this work has been successfully developed for one process train treating a flue gas flow of 2500 Nm³/h. The solvent is monoethanolamine (MEA), which is the most employed solvent in CO2-capture technologies. The CO2-recovery rate has been fixed to 90%. The most relevant process parameter that have been studied with the developed model are the solvent flow rate, the solvent concentration, and the stripper pressure. An optimum for the solvent flow rate has been identified at 11,75 m³/h, corresponding to a thermal energy consumption of 3,76 GJ/ton CO2. When increasing the stripper pressure, the thermal energy consumption decreased up to 16%. The fact that a pressure increase in the stripper leads to a temperature increase and the strong temperature dependence of the CO2-partial pressure explained this reduction of the thermal energy consumption. However, an increase of the stripper pressure induces solvent degradation problems, corrosion and a more complex equipment design. The MEA-concentration has been varied between 27 and 37 wt-%. When using a more concentrated solvent solution, the solvent is easier to regenerate. Consequently, the thermal energy consumption of the process decreased up to 12,5%. However, corrosion problems limit the use of concentrated solvents so that the MEA-concentration in capture-processes is generally adjusted to 30 wt-%. Furthermore, two process modifications have been tested successfully. First, a partial evaporation of the regenerated solvent after the stripper outlet has been studied. The gaseous product of this partial evaporation was compressed and recycled to the stripper. A decrease by 25% of the thermal energy consumption could be achieved. However, compression work has to be furnished. When calculating the improvement on the basis of exergy, then the exergy of the capture process decreased by 18%. The second modification that has been studied is a solvent intercooling between two absorber stages. It has been observed that intercalating the intercooler between absorber bottom stages gives better results than between absorber top stages. Simulation results have shown that the thermal energy consumption decreased by up to 6%. In the case of a flue gas pre-cooling before the absorber inlet, about the same reduction of the thermal energy requirement could be achieved. Finally, a thermal energy consumption of 2,82 GJ/ton CO2 has been achieved in the best case, corresponding to a process exergy reduction by approximately 18%. The developed model allows further improvements so that the optimization of the CO2-capture process could be pursued. Since a detailed study of the process model could help the planning of an experimental test phase, the test-campaigns with the new pilot plant could be optimized. [less ▲]

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See detailModeling of a Power Transformer Using the Perturbation Finite Element Method
Ferreira da Luz, Mauricio V.; Dular, Patrick ULg; Leite, Jean V. et al

in 18th Conference on the Computation of Electromagnetic Fields (COMPUMAG2011) (2011, July)

In this paper the perturbation technique is developed for modeling a power transformer. The paper analyses the influence of frames on the magnetic field behaviour and on the core losses calculation. Two ... [more ▼]

In this paper the perturbation technique is developed for modeling a power transformer. The paper analyses the influence of frames on the magnetic field behaviour and on the core losses calculation. Two types of frames are considered: frame manufactured with steel and frame of the steel with a copper layer. The model considers the eddy currents in copper layer of the frame and its effects on the magnetic field behaviour of the core. [less ▲]

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See detailModeling of aerodynamic forces in flapping flight with the Unsteady Vortex Lattice Method
Lambert, Thomas ULg

Master's dissertation (2015)

This thesis concerns the extensive study and comparison of two approaches commonly used to compute the aerodynamic forces with the unsteady vortex lattice method. The first approach was introduced by Katz ... [more ▼]

This thesis concerns the extensive study and comparison of two approaches commonly used to compute the aerodynamic forces with the unsteady vortex lattice method. The first approach was introduced by Katz and Plotkin and is based on Bernoulli's equations, the second approach was based Joukowski's equations for the computation of forces. This report is divided in two main sections: the study of one wing undergoing simple movements (steady, pure harmonic pitching and pure harmonic plunging) and the study of two separate wings undergoing a combination of flapping and pitching such as seen in avian flight. For the simple test cases, the results obtained with both methods of computation were first compared to an analytical solution for a (quasi) 2D case. Then the comparison of both methods was made for finite wings. For the 3D problem a convergence study was done with respect to the chordwise discretisation of the airfoils. This section showed that for all the cases, the two methods give almost the same answer and therefore they could be considered as equivalent. The convergence study realised for finite wings showed however that Joukowski's method converges quicker than Katz's for symmetric airfoils, but it is the other way around when it comes to cambered airfoils. The study of the flapping and pitching motion is based on the work of N. Abdul Razak. The influence of pitch leading was extensively studied as this phenomenon presents a flow attached at all time, so these kinematics are well suited for the vortex lattice method. Both pure flapping and pitch lagging were also discussed but more briefly. For pitch leading, the study showed that in general both methods give the same results for the drag and the lift. Moreover, the UVLM solutions were very close to the experimental ones, especially for the drag. The convergence showed a small advantage for the Katz method for the coarser meshes, but in the end both methods appear to reach convergence for the same discretisation. [less ▲]

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See detailModeling of Antimicrobial Lipopeptides in interaction with lipidic membranes
Loison, Claire; Nasir, Mehmet Nail ULg; Besson, Françoise et al

Conference (2015, May)

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See detailModeling of coalescence behavior in high-viscosity systems
Pungsang, P; Chuttrakul, P; Scherübel, P et al

Conference (2014)

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See detailModeling of cobalt and copper speciation in metalliferous soils from Katanga (Democratic Republic of Congo)
Pourret, Olivier; Lange, Bastien; Houben, David et al

in Journal of Geochemical Exploration (2015), 149

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See detailModeling of contact between stiff bodies in automotive transmission systems
Virlez, Geoffrey ULg; Bruls, Olivier ULg; Duysinx, Pierre ULg

in Samin, Jean-Claude; Fisette, Paul (Eds.) Proceedings of MULTIBODY DYNAMICS 2011, ECCOMAS Thematic Conference (2011, July 05)

Many transmission components contain moving parts which can enter in contact. The TORSEN differentials are mainly composed of gear pairs and thrust washers. The friction involved by contacts between these ... [more ▼]

Many transmission components contain moving parts which can enter in contact. The TORSEN differentials are mainly composed of gear pairs and thrust washers. The friction involved by contacts between these two kind of parts is essential in the working principle of such differentials. In this paper, two different contact model are presented. The former uses an augmented Lagrangian technique and is defined between a rigid body and a flexible structure. The second contact formulation is a continuous impact modeling based on a restitution coefficient. [less ▲]

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See detailModeling of Crack Propagation in Weld Beam-to-Column Connection Submitted to Cyclic Loading with Cohesive Zone Model
Lequesne, Cédric ULg; Plumier, André ULg; Duchene, Laurent ULg et al

in Journal of ASTM International (2010), 7(5),

During the earthquakes in Japan and California in the 1990s, cracks appeared in some weld beam-to-column connections of heavy rigid frame steel buildings. This prompted the necessary assessment of the ... [more ▼]

During the earthquakes in Japan and California in the 1990s, cracks appeared in some weld beam-to-column connections of heavy rigid frame steel buildings. This prompted the necessary assessment of the performance of weld connections in terms of rotation capacity and crack propagation. In the present study, experimental tests were performed where weld connections were submitted to cyclic loadings with increasing amplitude until a macro crack event was reached. However the crack phenomenon depends on many parameters: the geometry, the material, the welding process…. For this reason, it was interesting to develop a finite element modeling of these connections in order to complete these experiments and perform a parametric study. This paper describes the finite element model development, its material parameter identification and its comparison with experimental results. The weld connections were modeled by using three-dimensional mixed solid elements. The constitutive laws applied were elastoplastic with isotropic hardening identified for the base metal and the weld metal. Crack propagation was modeled by a cohesive zone model. The parameters of this cohesive zone model were identified by an inverse method with the modeling of three point bending tests of precracked samples performed on the base and weld metals. The fatigue damage generated by the cyclic loading was computed by the fatigue continuum damage model of Lemaitre and Chaboche, which was coupled with the cohesive zone model. [less ▲]

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See detailModeling of damage to crack transition using a coupled discontinuous Galerkin/cohesive extrinsic law framework
Wu, Ling ULg; Becker, Gauthier; Noels, Ludovic ULg

Conference (2013, June)

One current challenge related to computational fracture mechanics is the modelization of ductile fracture and in particular the damage to crack transition. In this paper we propose to achieve this goal by ... [more ▼]

One current challenge related to computational fracture mechanics is the modelization of ductile fracture and in particular the damage to crack transition. In this paper we propose to achieve this goal by combining 1. A non-local damage model 2. The hybrid discontinuous Galerkin (DG)/extrinsic cohesive law (ECL) formulation As classical damage models for finite element formulations lose the solution uniqueness and face the strain localization problem when strain softening of materials is involved, the damage model is herein formulated in a so-called implicit non-local approach, following the developments in [1]. In this formulation, a new non-local variable, the non-local accumulated plastic strain eg, representative of an internal variable and its derivatives, results from the resolution of a new boundary value problem. Besides the advantage of using C0 elements, although the elements have now one additional degree of freedom per node, this approach also possesses the feature of being fully non-local. The hybrid DG/ECL method was recently proposed [2] to circumvent the drawbacks of the cohesive element methods. Indeed, with this DG/ECL method, prior to fracture, the flux and stabilization terms arising from the DG formulation at interelement boundaries are enforced via interface elements in a way that guarantees consistency and stability, contrarily to traditional extrinsic cohesive zone methods. Upon the onset of fracture, the traction–separation law (TSL) governing the fracture process becomes operative without the need to modify the mesh topology as the the cohesive elements required to integrate the TSL are already present. This DG/ECL method has been shown to be an efficient numerical framework that can easily be implement in parallel with excellent scalability properties to model fragmentation, dynamic crack propagation in brittle and smallscale yielding materials, for 3D problems and for thin structures [3,4]. In this work, the DG/ECL method is extended to account for the damage process, as described in the non-local setting. One main advantage of the DG/ECL formulation is the existence of interface elements in which the damage model can be solved, the hydrostatic pressure can be resolved, and through which discontinuities can easily be introduced with a physically-based criterion. [less ▲]

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See detailModeling of Dendritic Cell-based vaccination Immunotherapy using Artificial Neural Networks
Mehrian, Mohammad ULg; Arabameri, Abazar; Sedghi, Alireza et al

in Modeling of Dendritic Cell-based vaccination Immunotherapy using Artificial Neural Networks (2013)

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See detailModeling of elasto-viscoplastic behaviour of steels at high temperatures
Charles, J. F.; Habraken, Anne ULg; Lecomte-Beckers, Jacqueline ULg

in Baajens; Huetink (Eds.) Proceedings of Simulation of Materials Processing, Methods and Applications. Esaform (1998)

Hot compression tests at constant strain rate and temperature allow to reach stress-strain curves. These experimental data are then used to calibrate a Norton Hoff elastoviscoplastic model (Gavrus ... [more ▼]

Hot compression tests at constant strain rate and temperature allow to reach stress-strain curves. These experimental data are then used to calibrate a Norton Hoff elastoviscoplastic model (Gavrus & Massoni 1995). The implementation of this model (Habraken et al. 1997) in the large strain non linear finite element code LAGAMINE is summarised in this paper. Then finite element thermo-mechanical analysis of previous compression tests and independant ones are performed to validate the produced material constitutive model. These simulations give the stress, strain rate and temperature fields of the sample, necessary to predict recrystallisation phenomena. A summary of the recrystallisation models proposed by the literature as well as the simple one implemented in the LAGAMINA code will be presented. So experimental, numerical and metallographic studies of hot compression tests aim the definition of an accurate predictive thermo-mechanic metallurgical model able to simulate forging processes. [less ▲]

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See detailModeling of Electro-mechanical coupling in MEMS
Rochus, Véronique ULg; Duysinx, Pierre ULg; Golinval, Jean-Claude ULg

Scientific conference (2002)

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See detailModeling of Electro-Mechanical Coupling Problem using the Finite Element Formulation
Rochus, Véronique ULg; Rixen, Daniel J.; Golinval, Jean-Claude ULg

Conference given outside the academic context (2003)

A modeling procedure is proposed to handle strong electro-mechanical coupling appearing in micro-electromechanical systems (MEMS). The finite element method is used to discretize simultaneously the ... [more ▼]

A modeling procedure is proposed to handle strong electro-mechanical coupling appearing in micro-electromechanical systems (MEMS). The finite element method is used to discretize simultaneously the electrostatic and mechanical fields. The formulation is consistently derived from variational principles based on the electromechanical free energy. In classical weakly coupled formulations staggered iteration is used between the electrostatic and the mechanical domain. Therefore, in those approaches, linear stiffness is evaluated by finite differences and equilibrium is reached typically by relaxation techniques. The strong coupling formulation presented here allows to derive exact tangent matrices of the electro-mechanical system. Thus it allows to compute non-linear equilibrium positions using Newton-Raphson type of iterations combined with adaptive meshing in case of large displacements. Furthermore, the tangent matrix obtained in the method exposed in this paper greatly simplifies the computation of vibration modes and frequencies of the cou pled system around equilibrium configurations. The non-linear variation of frequencies with respect to voltage and stiffness can be then be investigated until pull-in appears. In order to illustrate the effectiveness of the proposed formulation numerical results are shown first for the reference problem of a simple flexible capacitor, then for the model of a micro-bridge. [less ▲]

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See detailModeling of Electromagnetic Systems by Coupling of Subproblems – Application to Thin Shell Finite Element Magnetic Models
Dang, Quoc Vuong ULg

Doctoral thesis (2013)

The direct application of the finite element method to realistic electromagnetic problems is challenging, especially when modeling structures with thin conductive and/or magnetic parts. This work presents ... [more ▼]

The direct application of the finite element method to realistic electromagnetic problems is challenging, especially when modeling structures with thin conductive and/or magnetic parts. This work presents a subproblem method for correcting the inaccuracies inherent to classical thin shell models, and to efficiently handle geometrical and material variations in parametric studies. [less ▲]

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See detailModeling of Excavation Damaged Zone through the strain localization approach in Boom clay
Salehnia, Fatemeh ULg; Charlier, Robert ULg; Sillen, Xavier et al

in Proceedings of the 14th Int. Conference of International Association for Computer Methods and Recent Advances in Geomechanics, IACMAG 2014 (2014)

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See detailModeling of InSAR displacements related with the January 2002 eruption of Nyiragongo volcano
Wauthier, Christelle ULg; Cayol, Valérie; Kervyn, François et al

in ECGS Blue Books (2010)

Detailed reference viewed: 112 (1 ULg)