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Peer Reviewed
See detailNumerical and Experimental Studies of Simple Geometries in Slamming
Constantinescu, Adrian; Aboulghit, El Malki Aloui; Nême, Alain et al

in International Journal of Offshore and Polar engineering (2011, September)

Detailed reference viewed: 33 (3 ULg)
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See detailNumerical and Experimental Studies of Simple Geometries in Slamming
Constantinescu, A.; Neme, A.; Rigo, Philippe ULg

in ISOPE 2009, The 19th Intern. Offshore and Polar Engg. Conf., Osaka, Japan, 21-26 June 2009 (www.Isope.org) (2009, June)

Detailed reference viewed: 32 (2 ULg)
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See detailNumerical and physical hydraulic modelling of Piano Key Weirs
Erpicum, Sébastien ULg; Machiels, Olivier ULg; Dewals, Benjamin ULg et al

in Proceedings of the 4th Int. Conf. on Water Resources and Renewable Energy Development in Asia (2012, March)

During the last few years, several piano key weirs (PKWs) have been built in France by Electricité de France (EDF). Thanks to the reduced footprint and high release capacities of this new type of weir ... [more ▼]

During the last few years, several piano key weirs (PKWs) have been built in France by Electricité de France (EDF). Thanks to the reduced footprint and high release capacities of this new type of weir, making it particularly suited for concrete dams rehabilitation, lots of other projects in varied countries are under construction or study. The prototype use of PKW requires knowledge about its structural behaviour, hydraulic capacities as well as integration into dams’ environment. This paper aims at presenting numerical and physical modelling works performed at the University of Liege to address the last two points. In particular, large scale physical modelling and parametric scale models enabled to understand the hydraulic behaviour of the structure and to highlight its main geometric parameters as well as their best variation interval depending on various criteria related to the weir design (discharge efficiency, cost…). A 1D numerical model has also been developed based on these experimental investigations. It enables to predict in a few minutes, with 10% accuracy, the discharge capacity of a given PKW geometry on its usual operation head range. This model, available as a freeware on http://www.pk-weirs.ulg.ac.be, constitutes a key tool for the first design of such weirs. Finally, the scale model studies of major projects such as Raviège dam (France) for EDF and Ouldjet Mellegue Project (Algeria) for Coyne et Bellier – Tractebel Engineering enable to confront theoretical predictions with experimental results and to address the problem of PKW integration on dam crests. [less ▲]

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See detailNumerical applications to radiative transfer in expanding envelopes - The two-level atom model
Surdej, Jean ULg

in Astronomy and Astrophysics (1978), 66

The escape probability method developed by Sobolev (1947) is applied to the case of a two-level atom. The numerical applications are based on a previous work concerning a general theory of spectral-line ... [more ▼]

The escape probability method developed by Sobolev (1947) is applied to the case of a two-level atom. The numerical applications are based on a previous work concerning a general theory of spectral-line formation in outward-accelerating and outward-decelerating stellar envelopes. Only the radiative exchanges occurring between the atomic levels are considered, and the statistical-equilibrium equations are solved rigorously in the cases of a transparent medium at rest, an outward-accelerating envelope, and an outward-decelerating envelope. The population of the atomic levels are compared for different physical conditions in each case. It is shown numerically that in the case of an outward-decelerating envelope the contribution of distant atoms to the mean intensity of line radiation appreciably enhances the degree of excitation throughout the envelope. [less ▲]

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See detailNumerical approach of contact using an augmented lagrangian method
Bille, J.Ph.; Habraken, Anne ULg; Charlier, Robert ULg

in Congrès National Belge de Mécanique Théorique et Appliquée (1994)

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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: 12 (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)

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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 ▲]

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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; Brauwers, Luc

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

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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 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: 47 (7 ULg)