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See detailNumerical computations of hypersonic boundary layer roughness induced transition on a at plate
Serino, Gennaro ULg; Pinna, Fabio; Rambaud, Patrick et al

Scientific conference (2012, January)

The work is focused on numerical simulations of roughness induced transition for hypersonic ow on a at plate wall mounted roughness element. Numerical simulations are compared to experimental results in ... [more ▼]

The work is focused on numerical simulations of roughness induced transition for hypersonic ow on a at plate wall mounted roughness element. Numerical simulations are compared to experimental results in order to resemble the physics highlighted in the tests. In particular, stress has been placed on the detection of the vortices in the wake behind the roughness element and on the onset of transition. [less ▲]

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See detailNumerical Continuation of Aeroelastic Systems: Shooting vs Finite Difference Approach
Dimitriadis, Grigorios ULg

in Limit Cycle Oscillation and Other Amplitude-Limited Self Excited Vibrations (2008, May)

Nonlinearity in aeroelastic systems has become an important area of research. It is widely recognised that nonlinearities due to the structure, control system or aerodynamic forces can affect aeroelastic ... [more ▼]

Nonlinearity in aeroelastic systems has become an important area of research. It is widely recognised that nonlinearities due to the structure, control system or aerodynamic forces can affect aeroelastic systems, such as aircraft, and can cause oscillatory phenomena that cannot be predicted using a purely linear analysis. An important class of methods for predicting such phenomena from the equations of motion of a nonlinear aeroelastic system is numerical continuation. There are several techniques for the application of numerical continuation, each with its advantages and disadvantages. Here, the finite differences and shooting approaches are implemented and compared. Both approaches are applied to a simple pitchplunge nonlinear aeroelastic mathematical system. [less ▲]

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See detailNumerical determination of 3D temperature fields in steel joints
Franssen, Jean-Marc ULg

in Fire & Materials (2004), 28(2-4, MAR-AUG), 63-82

A numerical study was undertaken to investigate the temperature field in steel joints and to compare the temperatures in the joints with the temperatures of the adjacent steel members on the hypothesis ... [more ▼]

A numerical study was undertaken to investigate the temperature field in steel joints and to compare the temperatures in the joints with the temperatures of the adjacent steel members on the hypothesis that the thermal protection is the same on the joint and in the members. Very brief information is given on the numerical model, supplemented with parametric studies made in order to determine the required level of discretization in the time and in the space domain. A simplified assumption for representing the thermal insulation is also discussed and validated. Different numerical analyses are performed, with a variation of the following parameters: (i) type of joints, from very simple to more complex configurations, with welds and/or bolts, all of them representing joints between elements located in the same plane; (ii) unprotected joints or protected by one sprayed material; (iii) ISO, hydrocarbon or one natural fire scenario. The fact that the thermal attack from the fire might be less severe because the joints are usually located in the corner of the compartment is not taken into account. Copyright (C) 2004 John Wiley Sons, Ltd. [less ▲]

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See detailNumerical determination of 3D temperature fields in steel joints
Franssen, Jean-Marc ULg; Brauwers, Luc

in Proceedings of the 2nd International workshop Structures in Fire (2002, March)

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See detailNumerical discretization of rotated diffusion operators in ocean models
Beckers, Jean-Marie ULg; Burchard, Hans; Deleersnijder, Eric et al

in Monthly Weather Review (2000), 128(8), 2711-2733

A method to improve the behavior of the numerical discretization of a rotated diffusion operator such as, for example, the isopycnal diffusion parameterization used in large-scale ocean models based on ... [more ▼]

A method to improve the behavior of the numerical discretization of a rotated diffusion operator such as, for example, the isopycnal diffusion parameterization used in large-scale ocean models based on the so-called z-coordinate system is presented. The authors then focus exclusively on the dynamically passive tracers and analyze some different approaches to the numerical discretization. Monotonic schemes are designed but are found to be rather complex, while simpler, linear schemes are shown to produce unphysical undershooting and overshooting. It is suggested that the choice of an appropriate discretization method depends on the importance of the rotated diffusion in a given simulation, whether the field to be diffused is dynamically active or not. [less ▲]

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See detailNumerical dosimetry of elf fields by using dual formulations
Scorretti, Riccardo; V Sabariego, Ruth ULg; Geuzaine, Christophe ULg et al

in Proceedings of 10th International Conference of the European Bioelectromagnetics Association (EBEA2011) (2011)

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See detailNumerical Evaluation of Load induced Thermal Strain in restraint Structures compared with an Experimental Study on reinforced Concrete Columns
Schneider, Ulrich; Schneider, Martin; Franssen, Jean-Marc ULg

in Conference Proceedings Fire and Materials 2009 (2009)

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See detailNumerical evaluation of the fire behaviour of a concrete tunnel integrating the effects of spalling
Franssen, Jean-Marc ULg; Hanus, François ULg; Dotreppe, Jean-Claude ULg

in Proceedings of the Fire Design of Concrete Structures from Materials Modelling to Structural Performance Workshop (2007)

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See detailNumerical evidence of mixing in rooms using the free path temporal distribution
Billon, Alexis ULg; Embrechts, Jean-Jacques ULg

in Journal of the Acoustical Society of America (2011), 130(3), 13811389

The ergodic propriety of a room has strong effects on its reverberation. If the room is ergodic, the reverberation can be broken up in two steps: a deterministic process followed by a stochastic one. The ... [more ▼]

The ergodic propriety of a room has strong effects on its reverberation. If the room is ergodic, the reverberation can be broken up in two steps: a deterministic process followed by a stochastic one. The late reverberation can be then modeled by a reverberation algorithm instead of more computationally consuming methods. In this study, the free path temporal distribution obtained by ray-tracing is used as an indicator of the room’s mixing: the energetic average of the path lengths is computed at each time step. Ergodic rooms are thus characterized by rapidly convergent distributions. The free path value becomes independent of time. On the other hand, path selection mechanism and orbits are observed in non-ergodic rooms. The transition time from the deterministic process to the stochastic one is also studied through the evaluation of the room’s time constant. It is shown that its value depends only on the mean free path and the boundaries scattering value. An empirical expression is obtained which agrees well with simulations carried out in a concert hall. This transition time from a deterministic model to a stochastic one can be used to speed up the acoustical predictions and auralizations in ergodic rooms. [less ▲]

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See detailNumerical Exploration of Oscillation Modes in Rapidly Rotating Stars
Ballot, Jérôme; Lignières, François; Reese, Daniel ULg

in Goupil, M.; Belkacem, K.; Neiner, C. (Eds.) et al Studying Stellar Rotation and Convection (2013)

In this chapter, we show that two-dimensional oscillation codes help us to improve our knowledge of the effects of rapid rotation on acoustic (p) and gravity (g) modes. We first discuss how to solve the ... [more ▼]

In this chapter, we show that two-dimensional oscillation codes help us to improve our knowledge of the effects of rapid rotation on acoustic (p) and gravity (g) modes. We first discuss how to solve the full problem of stellar oscillations in rapidly rotating stars by including the effects of the Coriolis force as well as those of the centrifugal distortion. We illustrate the development and the validation of a 2-D code using the Two-dimensional Oscillation Program (TOP) as an example. We then describe what strategies are being developed to explore the p- and g-mode spectra, how effective these methods are, and what intrinsic difficulties they face. In the last part of this chapter, we present results obtained with these techniques. [less ▲]

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See detailNumerical investigation and experimental validation of physically-based advanced GTN model for DP steels
Fansi Tchonko, Joseph ULg; Balan, Tudor; Lemoine, Xavier et al

in Materials Science & Engineering : A (2013), 569

This numerical investigation of an advanced Gurson-Tvergaard-Needleman (GTN) model is an extension of the original work of [Ben Bettaieb, M., Lemoine, X., Bouaziz, O., Habraken, A.-M., Duchêne, L ... [more ▼]

This numerical investigation of an advanced Gurson-Tvergaard-Needleman (GTN) model is an extension of the original work of [Ben Bettaieb, M., Lemoine, X., Bouaziz, O., Habraken, A.-M., Duchêne, L., Numerical modeling of damage evolution of DP steels on the basis of X-ray tomography measurements, Mechanics of Materials 43 (2011) 139-156]. The current damage model extends the previous version by integrating the three damage mechanisms: nucleation, growth and coalescence of voids. Physically-based void nucleation and growth laws are considered, including an effect of the kinematic hardening. [less ▲]

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See detailA numerical investigation in the transition zone of the NW African upwelling
Elmoussaoui, A.; Djenidi, Salim ULg; Kostianoy, A. et al

in Bulletin de la Société Royale de Liège (1996), 65

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See detailNumerical investigation of continuous fiber glass drawing
Chouffart, Quentin ULg; Simon, Philippe; Terrapon, Vincent ULg

in Idelsohn, Sergio R; Papadrakakis, Manolis; Schrefler, Bernhard A (Eds.) Proceedings of the V International Conference on Computational Methods for Coupled Problems in Science and Engineering (2013, June)

The physics of glass fiber drawing is studied through numerical simulations and experimental measurements, with a focus on the fluid region, from the hole tip at the bushing plate to the glass transition ... [more ▼]

The physics of glass fiber drawing is studied through numerical simulations and experimental measurements, with a focus on the fluid region, from the hole tip at the bushing plate to the glass transition point. The influence of the different heat transfer mechanisms is investigated to understand their respective impact on fiberization, such as fiber radius attenuation and internal stresses. Numerical predictions are then compared to experimental data measurements obtained from a dedicated fiberization unit. Numerical and experimental results show a good agreement. In particular, it is found that the ambient air temperature and the radiation have an important impact on the fiber cooling rate. Moreover, for a prescribed fiber diameter, internal stresses are lower when operating at a higher temperature. [less ▲]

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See detailNumerical Investigation of Continuous Fiber Glass Drawing Process
Chouffart, Quentin ULg; Simon, Philippe; Terrapon, Vincent ULg

Conference (2014, May 30)

The manufacturing process of glass fibers used for the reinforcement of composite material consists in drawing a glass melt at high temperature through the bushing plate into fibers using a winder. This ... [more ▼]

The manufacturing process of glass fibers used for the reinforcement of composite material consists in drawing a glass melt at high temperature through the bushing plate into fibers using a winder. This process is sensitive to numerous disturbances that can cause the fiber to break during the drawing process. In order to understand the origin of these failures and improve the process efficiency, it is important to understand the physics of the forming fiber. We investigate here the underlying physics of the forming of a single fiber through numerical simulations. In particular, we focus on the region from the hole tips at the bushing plate to the glass transition point. The influence of key parameters (e.g. operating windows, and heat transfers mechanisms) on the fiber radius attenuation and the internal stresses is investigated through a sensitivity analysis. In addition, the impact of the temperature variations at the bushing plate is investigated. Finally, we show how the forming stress is influenced by these parameters. It is found that the internal stress can be minimizing by varying the operating windows. On the other hand, results also demonstrate that the heat pattern of the bushing plate is one of the most important causes for disturbance in the process. [less ▲]

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See detailNumerical Investigation of Cooling in the Continuous Fiber Glass Drawing Process
Chouffart, Quentin ULg; Terrapon, Vincent ULg; Simon, Philippe

in Proceedings of the 15th International Heat Transfer Conference (2014, August)

The manufacturing process of glass fibers used for the reinforcement of composite material consists in drawing a glass melt at high temperature through an array of thousands of small orifices (i.e., the ... [more ▼]

The manufacturing process of glass fibers used for the reinforcement of composite material consists in drawing a glass melt at high temperature through an array of thousands of small orifices (i.e., the bushing plate) into fibers using a winder. This process is sensitive to numerous disturbances that can cause a fiber to break during the drawing process. This paper analyzes how the stress in the fiber depends on the controlling parameters of the process. The approach relies on numerical simulations and sensitivity analysis. Both a semi-analytical one-dimensional model and a more complex two-dimensional axisymmetric model are used. It is first found that radial variations across the fiber are small compared to changes in the axial direction and that the one-dimensional approximation is accurate enough to describe the major trends in the process. Sensitivity analyses on some physical parameters controlling the heat transfers and on process parameters are then performed to identify strategies to reduce the axial stress. In particular, it is shown that, for a given fiber diameter, the stress is minimized if the glass melt temperature and the drawing velocity are increased. This approach is then applied to quantify the effect of inhomogeneous heat patterns on a bushing plate with a large number of fibers. [less ▲]

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See detailNumerical investigation of cut-edge effect using the Gurson-Tvergaard-Needleman model
Lemoine, Xavier; Tudor, Balan; Habraken, Anne ULg

in Procedia Engineering (2014, October)

In this contribution, the formability of sheet metal cut edges is investigated using damage model.Classical forming limit diagrams are known not to apply properly to the cut edges. However, with mild ... [more ▼]

In this contribution, the formability of sheet metal cut edges is investigated using damage model.Classical forming limit diagrams are known not to apply properly to the cut edges. However, with mild steels the sheet edges usually behave better than the Forming Limit Diagram prédictions, so this phenomenon has not been given sufficient attention. In contrast, for Advanced High Strengh Steels the cut edges exhibit reduced formability as compared to the plain sheet;this effect is very sensitive to the quality of the cutting process. The current investigation is aimed to evaluate the ability of available damage models to predict this effect on sample applications. The Gurson-Tvergaard-Needleman model is used and the material parameters for a Dual Phase are considered [1]. The effect of the cutting process is described by means of initial fields of equivalent plastic strain and porosity. The geometrical distribution and typical values for these two initial fields are devised based on literature . Numerical simulations of flat notched tensile tests are used within the FE code Abaqus/Explicit to illustrate the impact of the initial fields on the moment and the location of the failure initiation. The influence of the mesh size in the cutting-affected area is also investigated. The hole expansion test and a flat bending test are further simulated to investigate the influence of the cut edge. [less ▲]

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See detailNumerical investigation of flow patterns in rectangular shallow reservoirs
Dufresne, Matthieu; Dewals, Benjamin ULg; Erpicum, Sébastien ULg et al

in Engineering Applications of Computational Fluid Mechanics (2011), 5(2), 247-258

The present work gives findings profitable for the person who wants to evaluate an asymmetric detach-reattach flow. In this study, the capability of a two-dimensional shallow-water numerical model to ... [more ▼]

The present work gives findings profitable for the person who wants to evaluate an asymmetric detach-reattach flow. In this study, the capability of a two-dimensional shallow-water numerical model to simulate the symmetric and asymmetric flows that can take place in rectangular shallow reservoirs varying the lateral expansion ratio and the dimensionless length is investigated. For a large lateral expansion ratio, the use of two protocols of simulation highlighted a high sensitivity of the simulated flow pattern to the initial condition. Comparison between simulated results and experimental data showed a good agreement for the critical shape parameter (combination of the lateral expansion ratio and the dimensionless length) between symmetric and asymmetric flows. A good agreement was also found for the value of the shorter reattachment length of asymmetric flows. For small lateral expansion ratios, the agreement was not so good. The model was used for even larger lateral expansion ratios in order to numerically extend the experimental dataset. This predictive work showed that the shape parameter, whose expression was only based on experiments carried out for small lateral expansion ratios, was also relevant for larger values. Moreover, the predicted values of the shorter reattachment length were also consistent with a regression only based on experimental results. [less ▲]

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See detailNumerical investigation of impact of non lethal kinetic projectiles onto human thorax
Nsiampa Ndompetelo, ULg; Robbe, Cyril ULg; Papy, Alexandre

in 6th European Symposium on Non-Lethal Weapons 2011 proceedings (2011, May 16)

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See detailNumerical investigation of photonic crystal fibers by spectral and multipole methods
Nicolet, A.; Guenneau, S.; Zolla, F. et al

in Asymptotics, Singularities and Homogenisation in Problems of Mechanics, Proceedings of the IUTAM Symposium (Liverpool, July 2002) (2003)

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See detailNumerical investigations on web panels stiffened by one or two trapezoidal stiffeners
Degée, Hervé ULg; Boissonnade, N.; Maquoi, René ULg

in Proceedings of the 5th International Conference on Coupled Instabilities in Metal Structures (2008)

This paper focuses on the behaviour of I-girder web panels subjected to combined bending and shear and stiffened by longitudinal trapezoidal stiffeners. This implies to account for the coupling between ... [more ▼]

This paper focuses on the behaviour of I-girder web panels subjected to combined bending and shear and stiffened by longitudinal trapezoidal stiffeners. This implies to account for the coupling between local panel buckling between stiffeners and global buckling of the whole stiffened panel. The study is restricted to panels with one or two longitudinal stiffeners, for which the well-known orthotropic plate approach may not be relevant. For such configurations, the most recent design rules available may either not address this specific problem or be too conservative. This contribution provides information on the behaviour of such girders based on numerical simulations. Results of extensive non-linear FEM calculations are presented and discussed. The effects of aspect ratio, web slenderness and position of stiffeners are studied. Numerical results are compared to design loads obtained according to Eurocode 3 Part 1.5. The parameter study shows that several aspects of the code may be improved and proposals in this respect are given and validated through the numerical results. In particular, the beneficial effect of closed longitudinal stiffeners is highlighted. It is shown that the high level of torsional rigidity exhibited by welded trapezoidal stiffeners may significantly increase the overall resistance of the web panel. [less ▲]

Detailed reference viewed: 32 (2 ULg)