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See detailNumerical simulations of seasonal and interannual variability of the Black Sea thermohaline circulation
Stanev, Emil; Beckers, Jean-Marie ULg

in Journal of Marine Systems (1999), 22(4), 241-267

The Black Sea general circulation is simulated by a primitive equation model with active free surface. The forcing is seasonally variable and is based on available climatic data. The model reproduces the ... [more ▼]

The Black Sea general circulation is simulated by a primitive equation model with active free surface. The forcing is seasonally variable and is based on available climatic data. The model reproduces the main features of the Black Sea circulation, including the river discharge effects on the mean sea level and the Bosphorus outflow. Model results show that the simulated sea surface elevation increases in spring over the whole sea, reaching a maximum in the Danube delta area. In the same region, a minimum is observed in winter. The amplitude of the seasonal oscillations (about 8-12 cm over the whole basin) is of the same order of magnitude as the maximum horizontal variations (about 15-18 cm between the coastal areas and the basin interior). This strong signal formed mostly by river discharges, along with the seasonal variability in the other forcing functions and the local dynamics creates a well-pronounced interannual variability. The performance of the model in simulating the seasonal and interannual variability is critically analyzed, with a special attention on the cold intermediate water formation and the circulation in the upper 150 m. The simulations demonstrate that the source of intermediate waters is on the shelf, and that the water mass in the core of cold intermediate layer changes with time as a response to the periodic forcing at sea surface. This type of variability is characterized by pronounced interannual changes, proving that important differences could exist between water mass structure in different years, even when using identical atmospheric forcings each year. (C) 1999 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailNumerical simulations of the sound propagation in non rectilinear streets
Billon, Alexis ULg; Picaut, Judicaël; Valeau, Vincent et al

Conference (2009, October)

At high frequencies, the sound propagation can be approximated by the propagation of sound particles which are reflected and absorbed at the boundaries. This propagation follows then a transport process ... [more ▼]

At high frequencies, the sound propagation can be approximated by the propagation of sound particles which are reflected and absorbed at the boundaries. This propagation follows then a transport process. In urban canyons, this transport process can be reduced to a diffusion process. The resultant model allows one to obtain the spatial distribution of the acoustical energy in a street in a few seconds using a classical finite elements program. This diffusion model has been previously validated in rectilinear streets for different geometrical and acoustical parameters. In this paper, more complex geometries such as varying cross-sections, bents and streets crossings are dealt with. As the diffusion model only models the reverberated sound field, diffraction effects on the direct sound field at streets corners are added. The obtained results are then compared to scale model experiments. [less ▲]

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See detailNumerical simulations of the wind of magnetic massive star HD191612
ud-Doula, A.; Nazé, Yaël ULg

Poster (2010)

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See detailNUMERICAL SIMULATIONS OF THIXOFORMING PROCESSES: DEVELOPMENT AND COMPARISON OF SEVERAL SEMI-SOLID CONSTITUTIVE LAWS
Koeune, Roxane ULg; Ponthot, Jean-Philippe ULg

(2011)

ABSTRACT This paper deals with the development, and the comparison, of several constitutive laws in the frame of the simulation of thixoforming processes. The comparison is based on the simulation of a ... [more ▼]

ABSTRACT This paper deals with the development, and the comparison, of several constitutive laws in the frame of the simulation of thixoforming processes. The comparison is based on the simulation of a simple academic test that is well representative of the thixotropic behavior: a simple shear test, with shear-rate step-up and step-down. [less ▲]

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See detailNumerical simulations of tissue ingrowth and differentiation around a loaded titanium implant in a bone chamber
Van Oosterwyck, Hans; Geris, Liesbet ULg; Vander Sloten, Jos et al

in Proceedings of the symposium on integrated systems in dental healthcare (2003)

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See detailNumerical simulations of torsional flutter oscillations of a bluff body: Energy issues, GraSMech poster session
Andrianne, Thomas ULg; Dimitriadis, Grigorios ULg

Poster (2012, May)

The possibility of harvesting energy from aeroelastic phenomena is assessed through numerical simulations. The unsteady aerodynamics around an aeroelastic structure are modeled using the Discrete Vortex ... [more ▼]

The possibility of harvesting energy from aeroelastic phenomena is assessed through numerical simulations. The unsteady aerodynamics around an aeroelastic structure are modeled using the Discrete Vortex Method (DVM). The Torsional Flutter oscillations of a rectangular cylinder are studied in this work. The phenomenon is characterized by Limit Cycle Oscillations (LCOs) around the pitch axis of the rectangle. The complete bifurcation behaviour is investigated numerically and compared to wind tunnel measurements for validation. The energy issues are investigated in terms of the sensibility of the energy output to variations in the structural damping. [less ▲]

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See detailA Numerical Simulator for VITRUV
Lebouquin, J.-B.; Herwats, Emilie ULg; Carvalho, M.-I. et al

in Richichi, A.; Delplancke, F.; Paresce, F. (Eds.) et al The Power of Optical/IR Interferometry: Recent Scientific Results and 2nd Generation Instrumentation (2008)

VITRUVsim is a numerical tool with as much as possible physics included. Inputs are the source parameters (flux, morphology, position...) and outputs are sequences of observed fringes and/or reduced ... [more ▼]

VITRUVsim is a numerical tool with as much as possible physics included. Inputs are the source parameters (flux, morphology, position...) and outputs are sequences of observed fringes and/or reduced visibilities. VITRUVsim is written in a portable and free language. [less ▲]

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See detailNumerical solution of DAEs in flexible multibody dynamics using Lie group time integrators
Bruls, Olivier ULg; Cardona, Alberto; Arnold, Martin

in Proceedings of the First Joint International Conference on Multibody System Dynamics (2010, May)

This paper studies a family of Lie group time integrators for the simulation of flexible multibody systems. The method provides an elegant solution to the rotation parameterization problem and, as an ... [more ▼]

This paper studies a family of Lie group time integrators for the simulation of flexible multibody systems. The method provides an elegant solution to the rotation parameterization problem and, as an extension of the classical generalized-alpha method for dynamic systems, it can deal with constrained equations of motion. Here, second-order accuracy of the Lie group method is demonstrated for constrained problems. The convergence analysis explicitly accounts for the nonlinear geometric structure of the Lie group. The performance is illustrated on two critical benchmarks of rigid and flexible systems with large rotation amplitudes. Second-order accuracy is evidenced in both of them. The remarkable simplicity of the new algorithms opens some interesting perspectives for real-time applications, model-based control and optimization of multibody systems. [less ▲]

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See detailNumerical solution of DAEs in flexible multibody dynamics with applications in control and mechatronics
Bruls, Olivier ULg

Scientific conference (2010, October 21)

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See detailNumerical solution of the transfer of diffuse radiation in spherically symmetric emission nebulas
Manfroid, Jean ULg

in Bulletin de la Société Royale des Sciences de Liège (1975), 44

The equation of transfer of the diffuse radiation in a spherically symmetric nebula is transformed following a method proposed by Chandrasekhar. Numerical equations are obtained in terms of finite ... [more ▼]

The equation of transfer of the diffuse radiation in a spherically symmetric nebula is transformed following a method proposed by Chandrasekhar. Numerical equations are obtained in terms of finite differences, and a resolution scheme is given. [less ▲]

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See detailNumerical solutions on non steady-state conditions of lubrication in internal combustion engine bearing
NELIS, M.; Bozet, Jean-Luc ULg

in Proc. 6th International Congress on Tribology (1994), 4

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See detailNumerical study of coupling between optical fibers
Guenneau, S.; Nicolet, A.; Zolla, F. et al

in Proceedings of the 5th International Workshop on Electric and Magnetic Fields, EMF 2000 (2000)

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See detailA Numerical Study of Fiber Glass Drawing Process
Chouffart, Quentin ULg; Terrapon, Vincent ULg

Scientific conference (2012, October 19)

The industrial glass fiber process is very sensitive to disturbances as they can lead to fibers break during the extrusion step. To identify and better characterize the relevant underlying physics and the ... [more ▼]

The industrial glass fiber process is very sensitive to disturbances as they can lead to fibers break during the extrusion step. To identify and better characterize the relevant underlying physics and the possible causes of fiber break, the glass behavior from the die exit to the winder is investigated numerically. In a first step, simulations of the glass fiber extrusion process are performed where the fluid is considered Newtonian. The full Navier-Stokes equations including the energy equation for the temperature are solved with a finite-element method. The solution is then compared to previous results from the literature. In a second step, we conducted a sensitivity analysis of the key process variables, such as glass height above the tip, viscosity and flow rate at the tip exit, winder velocity... Additionally, the importance of an accurate physical representation of the heat transfers, i.e., conduction within the fiber, radiation of the fiber, and convection around the fiber, is investigated. This model shows very good agreement with cases from the literature. It was found that bushing temperature and fiber environment have a significant impact on forming fiber shape. This demonstrates that numerical simulations can provide a useful tool to adjust the process operating window. [less ▲]

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See detailNumerical study of shear band instability and effect of cavitation on the response of a specimen under undrained biaxial loading
Sieffert, Yannick; Buzzi, Olivier; Collin, Frédéric ULg

in International Journal of Solids and Structures (2014), 51(9), 16861696

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See detailNumerical study of the fatigue crack in welded beam-to-column connection using cohesive zone model
Lequesne, Cédric ULg; Plumier, André ULg; Degée, Hervé ULg et al

in Proceedings of the International Conference on Fracture and Damage Mechanics V (2006)

The fatigue behaviour of the welded beam-to-column connections of steel moment resisting frame in seismic area must be evaluated. The cohesive zone model is an efficient solution to study such connections ... [more ▼]

The fatigue behaviour of the welded beam-to-column connections of steel moment resisting frame in seismic area must be evaluated. The cohesive zone model is an efficient solution to study such connections by finite elements. It respects the energetic conservation and avoids numerical issues. A three-dimensional cohesive zone model element has been implemented in the home made finite element code Lagamine [1]. It is coupled with the fatigue continuum damage model of Lemaître and Chaboche [2]. The cohesive parameters are identified by the inverse method applied on a three points bending test modelling. [less ▲]

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See detailA numerical study of the influence of the dirunal cycle on the surface energy and water budgets
Delire, Christine; Gérard, Jean-Claude ULg

in Journal of Geophysical Research (1995), 100

Global models including atmospheric, oceanic, and biogeochemical processes are needed for the study of possible environmental changes, but they require efficient approximations of physical processes in ... [more ▼]

Global models including atmospheric, oceanic, and biogeochemical processes are needed for the study of possible environmental changes, but they require efficient approximations of physical processes in order to reduce the computing time. The need to resolve the dirunal cycle when treating such problems is questionable. The Interaction Soil Biosphere Atmosphere (ISBA) model describing soil-vegetation-atmosphere interactions is used to analyze the importance of the dirunal cycle on the surface energy and water budjets. Stand-alone simulations are first performed using the Hydrologic Atmospheric Pilot EXperiment-MOdélisation du BILan HYdrique (HAPEX-MOBILHY) and Amazonian Region Micrometeorological Experiment (ARME) data sets to assess the need of an explicit dirunal variation of the atmospheric forcing for different sites. As a reference, the run is forced by measured values of atmospheric variables and radiative fluxes. As a test, ISBA is run forced by the 24-hour means of these atmospheric and radiative forcings. The surface and deep water content, the total evaporation, and the net radiation flux are correctly evaluated without the diurnal cycle. In contrast, the interception reservoir is highly overestimated. The model is then coupled with a one-dimensional atmospheic model in which, as test, the solar flux at the top of the atmosphere is replaced by a daily constant mean insolation. The superficial soil moisture content and the total evapotranspiration flux are correctly estimated. The surface temperature and the sensible heat flux are not satisfactorily predicted. Thus it appears that neglecting the diurnal cycle is adequate when considering the hydrologic balance of the surface but not the surface temperature. [less ▲]

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See detailNumerical Study of the Shielding properties of Macroscopic Hybrid Ferromagnetic/Superconductor Hollow Cylinders
Lousberg, Grégory ULg; Fagnard, Jean-François ULg; Ausloos, Marcel ULg et al

in IEEE Transactions on Applied Superconductivity (2010), 20(1), 33

We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material.We use an axisymmetric finite-element ... [more ▼]

We study the magnetic shielding properties of hybrid ferromagnetic/superconductor (F/S) structures consisting of two coaxial cylinders, with one of each material.We use an axisymmetric finite-element model in which the electrical properties of the superconducting tube are modeled by a nonlinear E-J power law with a magnetic-field-dependent critical current density whereas the magnetic properties of the ferromagnetic material take saturation into account. We study and compare the penetration of a uniform axial magnetic field in two cases: 1) a ferromagnetic tube placed inside a larger superconducting tube (Ferro-In configuration) and 2) a ferromagnetic tube placed outside the superconducting one (Ferro-Out configuration). In both cases, we assess how the ferromagnetic tube improves the shielding properties of the sole superconducting tube. The influence of the geometrical parameters of the ferromagnetic tube is also studied: It is shown that, upon an optimal choice of the geometrical parameters, the range of magnetic fields that are efficiently shielded by the hightemperature superconductor tube alone can be increased by a factor of up to 7 (2) in a Ferro-Out (Ferro-In) configuration. The optimal configuration uses a 1020 carbon steel with a thickness of 2 mm and a height that is half that of the superconducting cylinder (80 mm). [less ▲]

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See detailNumerical study of the thermo-hydro-mechanical behavior of GMZ bentonite
Chen, L.; Wang, J.; Liu, Y. et al

Conference (2012, October)

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See detailNumerical study to identify the material parameters of a damage model
Schwartz, Renée ULg; Castagne, Sylvie; Habraken, Anne ULg

in Computer Methods in Materials Science (2007), 7(2), 237-242

In the continuous casting (CC) process, transversal cracks happen. This type of macroscopic damage is due to the process loading in the bending and unbending area of the CC line. In order to study this ... [more ▼]

In the continuous casting (CC) process, transversal cracks happen. This type of macroscopic damage is due to the process loading in the bending and unbending area of the CC line. In order to study this damage, a 2D model was developed. It simulates the intergranular crack at the mesoscopic level. Already validated for a microalloyed steel with C level < 0.1 wt%, this model must be extended to peritectic and stainless steels. The first step is to identify the model parameters for these grades. The type and the quantity of hot tensile tests required to identify a single set of parameters for the damage law must be determined. So, simulations of hot tensile tests of notched samples are needed. The computed stress and strain histories are applied on the representative mesoscopic cell and the moment of rupture is determined in function of the input parameters. Thanks to inverse modelling, the parameters of the damage law are adapted in order to get one single set of parameters with only two different geometries of notch. [less ▲]

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