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Peer Reviewed
See detailAn efficient dynamic state estimator for large-scale electric power systems
Rousseaux, Patricia ULg

in Proceedings of the IFAC Symposium on Power Systems. Modelling and Control applications (1988)

Detailed reference viewed: 18 (1 ULg)
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See detailEfficient estimation of the high-order response statistics of a wind-excited oscillator with nonlinear velocity feedback
Denoël, Vincent ULg; Carassale, Luigi

in Proceedings of the XIII Conference of the Italian Association for Wind engineering (2014)

Detailed reference viewed: 14 (2 ULg)
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See detailEfficient Evaluation of the Geometrical Validity of Curvilinear Finite Elements
Johnen, Amaury ULg; Remacle, Jean-François; Geuzaine, Christophe ULg

Conference (2011, November 14)

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See detailEfficient finite element assembly of high order Whitney forms
Marsic, Nicolas ULg; Geuzaine, Christophe ULg

in IET Conference Proceedings (2014)

This paper presents an efficient method for the finite element assembly of high order Whitney elements. We start by reviewing the classical assembly technique and by highlighting the most time consuming ... [more ▼]

This paper presents an efficient method for the finite element assembly of high order Whitney elements. We start by reviewing the classical assembly technique and by highlighting the most time consuming part. Then, we show how this classical approach can be reformulated into a computationally efficient matrix - matrix product. We also address the problem of the basis orientation by considering more than one reference space. We conclude by presenting numerical results on a wave guide problem. [less ▲]

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See detailEfficient finite element assembly of high order Whitney forms
Marsic, Nicolas ULg; Geuzaine, Christophe ULg

in IET Science, Measurement & Technology (2015), 9(2), 204-210

This study presents an efficient method for the finite element assembly of high order Whitney elements. The authors start by reviewing the classical assembly technique and by highlighting the most time ... [more ▼]

This study presents an efficient method for the finite element assembly of high order Whitney elements. The authors start by reviewing the classical assembly technique and by highlighting the most time consuming part. Then, they show how this classical approach can be reformulated into a computationally efficient matrix-matrix product. They also address the global orientation problem of the vector valued basis functions. They conclude by presenting numerical results for a three-dimensional wave propagation problem. [less ▲]

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See detailAn efficient flamelet-based combustion model for compressible flows
Saghafian, Amirreza; Terrapon, Vincent ULg; Pitsch, Heinz

in Combustion and Flame (2015), 162(3), 652-667

A combustion model based on a flamelet/progress variable approach for high-speed flows is introduced. In the proposed formulation, the temperature is computed from the transported total energy and ... [more ▼]

A combustion model based on a flamelet/progress variable approach for high-speed flows is introduced. In the proposed formulation, the temperature is computed from the transported total energy and tabulated species mass fractions. Only three additional scalar equations need to be solved for the combustion model. Additionally, a flamelet library is used that is computed in a pre-processing step. This approach is very efficient and allows for the use of complex chemical mechanisms. An approximation is also introduced to eliminate costly iterative steps during the temperature calculation. To better account for compressibility effects, the chemical source term of the progress variable is rescaled with the density and temperature. The compressibility corrections are analyzed in an a priori study. The model is also tested in both Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) computations of a hydrogen jet in a supersonic transverse flow. Comparison with experimental measurements shows good agreement, particularly for the LES case. It is found that the disagreement between RANS results and experimental data is mostly due to the mixing model deficiencies and the presumed probability density functions used in the RANS formulation. A sensitivity study of the proposed model shows the importance of the compressibility corrections especially for the source term of the progress variable. [less ▲]

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See detailAn Efficient Flamelet-based Combustion Model for Supersonic Flows
Saghafian, Amirreza; Terrapon, Vincent ULg; Ham, Frank et al

in 17th AIAA International Space Planes and Hypersonic Systems and Technologies Conference 2011, Vol. 2; No AIAA 2011-2267 (2011, April)

A combustion model based on a Flamelet/Progress Variable approach for high-speed flows is introduced. In the proposed formulation, the temperature is computed from the transported total energy and ... [more ▼]

A combustion model based on a Flamelet/Progress Variable approach for high-speed flows is introduced. In the proposed formulation, the temperature is computed from the transported total energy and tabulated species mass fractions. The combustion is thus modeled by 3 additional scalar equations and a chemistry table that is computed in a pre-processing step. This approach is very efficient and allows the use of complex chemical mechanisms. An approximation is also introduced to eliminate costly iteration steps during the temperature calculation. To better account for compressibility e ects, the source term for the progress variable is rescaled with the pressure. The model is tested in both RANS and LES computations of a hydrogen jet in a supersonic transverse flow. Comparison with experimental measurements shows good agreement, particularly in the LES case. It is also found that the disagreement between RANS results and experimental data is mostly due to the mixing model de ciencies used in RANS. [less ▲]

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See detailAn efficient formulation for the simulation of elastic wave propagation in 1-dimensional collinding bodies
Depouhon, Alexandre ULg; Detournay, Emmanuel; Denoël, Vincent ULg

in Proceedings of the 11th International Conference on Vibration Problems (2013, September 09)

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See detailAn efficient global methodology for hazard analysis of dams complexes and cascades
Dewals, Benjamin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

in Brebbia, C. A.; Popov, V.; Beriatos, E. (Eds.) Risk analysis Vol. 6 (2008)

Hazard analysis of dams arranged in complex or in cascade may involve the assessment of a large number of different scenarios of combined failures. However, a tremendous computation time would be needed ... [more ▼]

Hazard analysis of dams arranged in complex or in cascade may involve the assessment of a large number of different scenarios of combined failures. However, a tremendous computation time would be needed to perform a detailed modelling of the flows generated by all possible scenarios. Therefore, the present paper describes a methodology for analysing the flows induced by the most relevant incidents occurring on a complex or in a cascade of dams and reservoirs. The methodology combines several hydrodynamic models, including the two-dimensional flow solver WOLF 2D and a simplified lumped hydrodynamic model, to simulate the flows induced on the dams complex, the potential breaching in cascade of other dams, as well as the propagation of the flood wave in the whole downstream valley. The application of the methodology to a practical case study involving a complex of five dams is also described. [less ▲]

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See detailEfficient hydraulic numerical modeling with multiblock grids and linked models
Erpicum, Sébastien ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Houille Blanche (2011), 3

In the field of numerical hydraulic engineering, the size of the simulations is one of the current challenges to consider with sufficient precision the large areas involved by practical applications. In ... [more ▼]

In the field of numerical hydraulic engineering, the size of the simulations is one of the current challenges to consider with sufficient precision the large areas involved by practical applications. In this scope, the linking in the same computational domain of different solvers, each one used in the part of the simulation where its characteristics are most suitable, opens the door to huge modeling possibilities. Such optimized hydraulic numerical modeling is presented in this paper with a multiblock multimodel 2D solver and its linking to a 1D model. After a description of the solvers, with emphasis on the linking procedures, theoretical test cases and real applications are presented. [less ▲]

Detailed reference viewed: 34 (11 ULg)
See detailEfficient hydrogen-bond donor activators for the synthesis of bio-based cyclic carbonates from CO2 and vegetable oils: a combined in-situ FT-IR and DFT study
Alves, Margot ULg; Méreau, Raphaël; Grignard, Bruno ULg et al

Conference (2015, July 06)

The present research aims at developing new very efficient organocatalysts for the chemical fixation of carbon dioxide onto epoxides that are precursors of non-isocyanate polyurethanes (NIPUs). Although ... [more ▼]

The present research aims at developing new very efficient organocatalysts for the chemical fixation of carbon dioxide onto epoxides that are precursors of non-isocyanate polyurethanes (NIPUs). Although this area of research is the subject of many works, the catalytic performance must be further enhanced in particular for the carbonatation of vegetable-based precursors while respecting environmental standards. In this context, we developed a new organocatalytic platform based on the combination of ammonium salts with single or double hydrogen bond donor activators that showed unexpected catalytic activity for the fast addition of CO2 onto epoxidized oils under mild conditions. First of all, in situ kinetic studies of the cycloaddition of CO2 onto model epoxidized oils were monitored by FT-IR spectroscopy in order to evaluate the influence of the hydrogen bond structure and various parameters such as the pressure, the temperature, the catalyst loading, and the nature of the epoxide on the reaction kinetics. Thanks to this catalyst screening, we found that ammonium salt/fluorinated hydrogen bond donors bicomponent organocatalysts were by far more efficient than that proposed in the literature under mild conditions (60°C, 2MPa). Then, the reaction mechanism of the organocatalyzed cycloaddition of propylene oxide onto CO2 was elucidated by performing Density Functional Theory (DFT). Our theoretical results highlighted the key role of the hydrogen bond interaction between the epoxide and the activators for the enhancement of the catalytic platform’s efficiency. [less ▲]

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See detailEfficient Immunoselection of Cytolytic Effectors with a Magnetic Cell Sorter
Jacobs, Nathalie ULg; Moutschen, Michel P; Boniver, Jacques ULg et al

in Research in Immunology (1993), 144(2), 141-50

This paper describes a rapid and efficient method for the sorting of in vitro activated cytolytic effectors cells. For cytotoxic assays, a large number of cells with conserved function must be rapidly ... [more ▼]

This paper describes a rapid and efficient method for the sorting of in vitro activated cytolytic effectors cells. For cytotoxic assays, a large number of cells with conserved function must be rapidly obtained. Immunomagnetic sorting was chosen because it is faster than flow cytometry sorting. The MACS system requires the use of paramagnetic beads of small diameter (100-150 nm), reputed to interfere minimally with cell function. In order to generate the cytolytic effectors, peripheral blood lymphocytes were cultivated in the presence of interleukin-2 (50 U/ml) and anti-CD3 monoclonal antibody (BMA030, 100 ng/ml) for 4 days. Cell separation was based on the membrane expression of the CD3 complex. The purity obtained for positive (CD3+) cell sorting with the MACS was higher than 95%. The purity of negative (CD3-) cell fraction was more variable, but further purification by flow cytometry rapidly yielded purity higher than 95%. Cytotoxic assays were performed against four target cell lines (K562, Daudi, HL60 and U937) and proliferation assays showed that both negatively and positively selected populations had conserved their function acquired during culture in the presence of anti-CD3 mAb and IL2. [less ▲]

Detailed reference viewed: 37 (11 ULg)
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See detailAn efficient implicit approach for the thermomechanical behavior of materials submitted to high strain rates
Jeunechamps, Pierre-Paul ULg; Ponthot, Jean-Philippe ULg

in Journal de Physique IV (2006), 134

In the present paper, three solutions are proposed to simulate fast phenomena with finite element method at best. At first, material constitutive laws of Johnson-Cook and Zerilli-Armstrong types are ... [more ▼]

In the present paper, three solutions are proposed to simulate fast phenomena with finite element method at best. At first, material constitutive laws of Johnson-Cook and Zerilli-Armstrong types are implemented. These well-known laws are efficient for the description of material behavior at high velocities, especially for material used in automotive or aeronautics industry. The second contribution of this paper is the coupling of an implicit Chung-Hulbert algorithm taking into account the inertial effects with a staggered scheme for solving the thermal problem. The last input of this paper is the use of EAS (Enhanced Assumed Strain) finite elements to better capture complex strain modes, especially bending that is not accurately evaluated with classical finite elements. These EAS finite elements are used in the scope of thermomechanical dynamic phenomena implemented in a modular C++ environment at the University of Liege in the home made software METAFOR. [less ▲]

Detailed reference viewed: 40 (5 ULg)
See detailAn Efficient Implicit Scheme for the Treatment of Contact between Deformable Bodies
GRAILLET, D.; Ponthot, Jean-Philippe ULg

in . Proceedings of "NUMIFORM'98, Simulation of Materials Processing: Theory, Methods and Applications (1998, June)

Detailed reference viewed: 7 (1 ULg)
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See detailAn Efficient Implicit Scheme for the Treatment of Contact Between Deformable Bodies
Ponthot, Jean-Philippe ULg; GRAILLET

in Idelsohn, S.; Onate; Dvorkin (Eds.) Proceedings of "World Congress on Computational Mechanics IV (1998)

Detailed reference viewed: 4 (0 ULg)
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See detailAn Efficient Implicit Scheme for the Treatment of Frictional Contact between Deformable Bodies
GRAILLET, D.; Ponthot, Jean-Philippe ULg

in Proceedings of "First ESAFORM Conference on Material Forming" (1998)

Detailed reference viewed: 7 (3 ULg)
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See detailEfficient Implicit Schemes for Finite Element Impact Simulation
Ponthot, Jean-Philippe ULg; Graillet, D.

in International Journal of Crashworthiness (1999), 4(3), 273-285

Detailed reference viewed: 11 (4 ULg)
See detailEfficient Implicit Schemes for High-Speed Dynamics and Crash Simulation. Application to shock-absorber devices
Hogge, Michel ULg; GRAILLET, D.; Ponthot, Jean-Philippe ULg

in Proceedings of «ACOMEN’98», Advanced Computational Methods in Engineering: Invited Papers (1998, September)

Detailed reference viewed: 28 (1 ULg)
See detailEfficient implicit schemes for the treatment of the contact between deformable bodies. Application to shock absorber devices
GRAILLET, D.; Stainier, Laurent ULg; Ponthot, Jean-Philippe ULg

in Proceedings of the Fifth National Belgian Congress on Theoretical and Applied Mechanics (2000)

Detailed reference viewed: 22 (8 ULg)