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Peer Reviewed
See detailNumerical approach of contact using an augmented lagrangian method
Bille, J.Ph.; Cescotto, Serge ULg; Habraken, Anne ULg et al

in 2nd Contact Mechanics Int. Symp., CMIS (1994, September)

Detailed reference viewed: 13 (6 ULg)
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See detailNumerical approach of contact with friction between two bodies in large deformations
Habraken, Anne ULg; Radu, Jean-Pol ULg; Charlier, Robert ULg

in Proc. of the Contact Mechanics Int. Symp. (1992, October)

Detailed reference viewed: 4 (0 ULg)
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See detailNumerical assessment of concrete damage: procedures and pitfalls
Stroeven, Piet; He, Huan ULg

in Heron (2011), 56(3), 123-140

The paper focuses on the quality of predicting the damage characteristics of the loaded engineering structure by subjecting section images of cores supposedly drawn from the concrete of the structure to ... [more ▼]

The paper focuses on the quality of predicting the damage characteristics of the loaded engineering structure by subjecting section images of cores supposedly drawn from the concrete of the structure to quantitative image analysis by sweeping test lines. Automation of this data acquisition stage is shown, generally leading to information that is biased to an unknown degree. This is accomplished mathematically and graphically according to Underwood. When the Stroeven/Saltikov (S/S)-concept of a partially linear-planar model for damage is accepted and (four-connexity) digitization is accomplished in a direction adjusted to the prevailing orientation direction of the cracks, the paper shows that orthogonal observations in vertical sections are sufficient for the unbiased assessment of total crack length per unit of area (2D), or specific crack surface area (3D), also when digitized images are employed. This is possible in situations where (uniaxial) compressive or tensile stresses dominate. The crack orientation distribution is however always biased when determined on digitized images in an automated set up when pixel directions are not compensated for, such as by the quantified S/S-concept of damage. [less ▲]

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See detailA numerical comparison of control strategies applied to an existing ice storage system
Lemort, Vincent ULg

in Energy Conversion and Management (2006), 47(20), 3619-3631

While ice storage systems are designed according to a defined strategy for warm day loads, it is interesting to consider other conventional control strategies for mid-season day loads. Three different ... [more ▼]

While ice storage systems are designed according to a defined strategy for warm day loads, it is interesting to consider other conventional control strategies for mid-season day loads. Three different charging-discharging control strategies are applied to an existing cooling plant and compared in terms of operating costs and energy consumption. A cooling plant model is built. A time stage equal to 15 min is considered to simulate numerically a whole charging-discharging process and compare the different control strategies. These simulations take into account existing technical constraints and set points. EES software is used. The operating costs of the cooling plant are evaluated by taking into account both the energy and the demand cost rate. It is shown that an ice storage system can allow savings of operating costs. However, they can increase energy consumption. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailNumerical computation of nonlinear normal modes of nonconservative systems
Renson, Ludovic ULg; Kerschen, Gaëtan ULg

in Proceedings of the ASME IDETC/CIE 2013 (2013, August)

Since linear modal analysis fails in the presence of nonlinear dynamical phenomena, the concept of nonlinear normal modes (NNMs) was introduced with the aim of providing a rigorous generalization of ... [more ▼]

Since linear modal analysis fails in the presence of nonlinear dynamical phenomena, the concept of nonlinear normal modes (NNMs) was introduced with the aim of providing a rigorous generalization of linear normal modes to nonlinear systems. Initially defined as periodic solutions, numerical techniques such as the continuation of periodic solutions were used to compute NNMs. Because these methods are limited to conservative systems, the present study targets the computation of NNMs for nonconservative systems. Their definition as invariant manifolds in phase space is considered. Specifically, the partial differential equations governing the manifold geometry are considered as transport equations and an adequate finite element technique is proposed to solve them. The method is first demonstrated on a conservative nonlinear beam and the results are compared to standard continuation techniques. Then, linear damping is introduced in the system and the applicability of the method is demonstrated. [less ▲]

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See detailNumerical computation of one-photon mazer resonances for arbitrary field modes
Bastin, Thierry ULg; Solano, E.

in Computer Physics Communications (2000), 124

We present a novel approach for solving numerically one-dimensional scattering problems and apply it for computing the emission probability of an ultracold atom interacting with an arbitrary field mode of ... [more ▼]

We present a novel approach for solving numerically one-dimensional scattering problems and apply it for computing the emission probability of an ultracold atom interacting with an arbitrary field mode of a high-Q cavity. Our method is efficient, stable and succeeds when other numerical integration methods fail. It also replaces and improves advantageously the WKB approximation. The cases of sinusoidal, sech2 and Gaussian field modes are studied and compared. Divergences with previous works, where WKB was used, are found. [less ▲]

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See detailNumerical computation of the electrostatic interaction energy between methanol and the dyad water-imidazole
Dehareng, Dominique ULg; Dive, Georges ULg; Lamotte-Brasseur, Josette ULg et al

in Theoretica Chimica Acta (1989), 76(2), 85-94

The electrostatic interaction energy between methanol and the dyad water-imidazole has been computed numerically at three levels of approximation from 3D grids of the charge density of one partner and the ... [more ▼]

The electrostatic interaction energy between methanol and the dyad water-imidazole has been computed numerically at three levels of approximation from 3D grids of the charge density of one partner and the electrostatic potential of the other. The minimum positions and energy values thus obtained compare well with those calculated analytically. The numerical procedure is especially interesting for the prediction of the stable conformers. [less ▲]

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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 ▲]

Detailed reference viewed: 65 (7 ULg)
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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 crashworthiness analysis of an offshore wind turbine monopile impacted by a ship
Bela, Andreea ULg; Le Sourne, Hervé; Buldgen, Loïc ULg et al

in Shenoi, R Ajit; Soares, Carlos Guedes (Eds.) Analysis and Design of Marine Structures (2015, March)

The consequences of collision events can range from minor structural damages of the supporting structure to complete collapse of the wind turbine, which may lead to disruptions of the electricity ... [more ▼]

The consequences of collision events can range from minor structural damages of the supporting structure to complete collapse of the wind turbine, which may lead to disruptions of the electricity production and, at worst, to sinking of the striking ship with probability of loss of human lives or/and pollution. For all these reasons, a collision risk analysis becomes mandatory at the pre-design stage in order to identify the collision scenarios having the greatest probabilities of occurrence, to estimate the consequences of collision events and to ensure safe operations through the wind farm service life. The goal of this paper is to outline the behavior of the monopile foundations during ship collision by performing non-linear finite element simulations. Many collision scenarios are analyzed in order to study the sensitivity of the monopile to various parameters like impact striking ship velocity, nacelle mass, wind direction, soil stiffness, vertical location of the impact point, wind orientation … The internal energy dissipated by deformation of the monopile, the crushing force and the indentation of the crushed area are compared for different situations, as well as the overall displacements of the supporting structure. [less ▲]

Detailed reference viewed: 49 (16 ULg)
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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)

Detailed reference viewed: 22 (1 ULg)
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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 ▲]

Detailed reference viewed: 39 (6 ULg)
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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)

Detailed reference viewed: 48 (7 ULg)
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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)

Detailed reference viewed: 78 (9 ULg)
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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)

Detailed reference viewed: 76 (5 ULg)
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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 ▲]

Detailed reference viewed: 55 (7 ULg)
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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 ▲]

Detailed reference viewed: 93 (30 ULg)