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See detailDam break flow modelling with uncertainty analysis
Dewals, Benjamin ULg; Archambeau, Pierre ULg; Erpicum, Sébastien ULg et al

Conference (2011, November)

The failure of a large dam may result in catastrophic floods in the downstream valley. However, past experience has revealed that loss of life and damage can be drastically reduced if crisis management is ... [more ▼]

The failure of a large dam may result in catastrophic floods in the downstream valley. However, past experience has revealed that loss of life and damage can be drastically reduced if crisis management is planned in advanced, including early-warning systems, organized communication and structural measures. This requires a fairly good knowledge of the inundation characteristics likely to be induced in case of a failure. Predictions of flood waves induced by dam failure are affected by a considerable level of uncertainty. Due to the extreme nature of such events, numerical models can hardly be calibrated and validated. Flow resistance parameterizations are designed for ranges of flow properties which significantly differ from those occurring during dam break flows. Large amounts of debris may also be transported by the flow and the details of the failure scenario remain usually unknown, such as sequence of dislodgement of dam wall fragments or breach formation time (e.g., Dewals et al. 2011). Nonetheless, most dam break flow studies so far have been conducted without systematic uncertainty nor sensitivity analyses. This is partly due to the high computational cost of the multidimensional flow models used to simulate dam break flows on natural topography. We present here the simulation of a real dam break flow with a systematic analysis of the uncertainty resulting from the roughness coefficient, the failure hydrograph and topographic data. The flow simulations have been conducted with the model WOLF 2D developed at the University of Liege. It solves the fully dynamic shallow-water equations based on a finite volume scheme and a self-developed flux-vector splitting (Erpicum et al. 2010a; Erpicum et al. 2010b). Monte-Carlo simulations have been used to perform the uncertainty analysis. The two-dimensional flow model is computationally too costly to perform a high number of repeated runs, as needed for Monte Carlo simulations. Therefore, a “reduced complexity model” has been set up, in the form of multidimensional Hermite polynomials. The method developed by Isukapalli et al. (Isukapalli et al. 2004) indicates the number of simulations of the complete model needed to calibrate the polynomials, as well as the parameter values to be used in these calibration runs. The methodology has been tested for a real dam break which occurred in Spain in 1982 (Alcrudo and Mulet 2007) and for which a number of observations are available (mainly maximum water depths at different locations in a town). The presentation will show the applicability and efficiency of the methodology, which is readily available for real-world analyses. Such uncertainty analysis for dam break flows disclose crucial information for practical risk management. In particular, they reveal that the uncertainty ranges on maximum water depth and time of arrival of the front are not symmetric (overestimation vs. underestimation) and very unevenly distributed in space. [less ▲]

Detailed reference viewed: 27 (12 ULg)
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Peer Reviewed
See detailDam break flow modelling with uncertainty analysis
Dewals, Benjamin ULg; Erpicum, Sébastien ULg; Pirotton, Michel ULg et al

in Gourbesville, Philippe; Cunge, Jean; Caignaert, Guy (Eds.) Advances in Hydroinformatics (2013)

Handling uncertainties in dam break flow modelling is of primary interest. Therefore, a procedure is presented here to conduct systematic analysis of the uncertainties resulting from the roughness ... [more ▼]

Handling uncertainties in dam break flow modelling is of primary interest. Therefore, a procedure is presented here to conduct systematic analysis of the uncertainties resulting from the roughness coefficient, the breaching hydrograph and topographic data. The flow simulations have been conducted with the model WOLF 2D developed at the University of Liege. This two-dimensional flow model is computationally too costly to perform a high number of repeated runs, as needed for Monte Carlo simulations. Therefore, a “reduced complexity model” has been set up, in the form of multidimensional Hermite polynomials. This method, developed by Isukapalli et al. (2004) and first applied to dam break flow by Niemeyer (2007), involves a reduced number of runs of the complete model to calibrate the polynomials. This paper shows the applicability and efficiency of the methodology, but it also discusses previously unreported shortcomings of the approach, together with hints to overcome them. Results of such uncertainty analysis for dam break flow modelling disclose crucial information for practical risk management. In particular, they reveal that the uncertainty ranges on maximum water depth and time of arrival of the front are not symmetric (overestimation vs. underestimation) and very unevenly distributed in space. [less ▲]

Detailed reference viewed: 41 (7 ULg)
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See detailDam rehabilitation study with process oriented numerical flow models
Erpicum, Sébastien ULg; Archambeau, Pierre ULg; Detrembleur, Sylvain ULg et al

in Proceedings of the 5th International Conference on Dam Engineering (2007)

In the global framework of climate change, hydraulic structures rehabilitation is an up-to-date subject requiring appropriate design and impact studies. In this scope, upgrading the release facilities of ... [more ▼]

In the global framework of climate change, hydraulic structures rehabilitation is an up-to-date subject requiring appropriate design and impact studies. In this scope, upgrading the release facilities of dams is an important point when both up and downstream consequences, often irreversible, of badly controlled rising of water in the reservoir, become awarded. Suitable numerical models, coupled with contemporary computational possibilities, allow engineers to forecast the complex situations induced on real structures by extreme events with increasing representativeness and accuracy. In this field, WOLF software, a process oriented free surface flows computation package completely set up by the HACH, has proved its efficiency and reliability for years by numerous theoretical, experimental as well as on real structures applications. In this paper, the rehabilitation study of the Nisramont dam (Belgium) is presented. Due to its temporary primary tasks, the stilling basin downstream of the crest spillway has been designed for a short time use. It’s the same with the 3 bottom outlets, which were never equipped with valves and are thus unusable for the reservoir management. In order to secure the structure and to make it comply with its definitive working objectives, while taking into account climate change observations, the HACH has been entrusted with evaluating up to date critical flood discharges and with designing a system in accord with these new values for the rehabilitation of the bottom outlets and the evacuation of the floods. Several construction options have been compared and optimized by means of the hydrodynamic software WOLF. [less ▲]

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Peer Reviewed
See detailDam treatment with insulin-like growth factor-I monoclonal antibodies induce an alteration of fetal development
Renaville, Robert ULg; Devolder, Anne; Sneyers, Myriam et al

in Archives Internationales de Physiologie, de Biochimie et de Biophysique (1992), 100

Detailed reference viewed: 5 (0 ULg)
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See detailDam-break flow computation based on an efficient flux-vector splitting
Erpicum, Sébastien ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Journal of Computational & Applied Mathematics (2010), 234

Dam-break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. In this paper, a 2D finite volume multiblock flow solver, able to deal with ... [more ▼]

Dam-break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. In this paper, a 2D finite volume multiblock flow solver, able to deal with natural topography variation, is presented in details. The model is based on an efficient Flux Vector Splitting method developed by the authors. A number of validation examples are comprehensively described. [less ▲]

Detailed reference viewed: 159 (57 ULg)
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See detailDam-break flow computation using high resolution DEM
Erpicum, Sébastien ULg; Dewals, Benjamin ULg; Archambeau, Pierre ULg et al

in Hogge, Michel; Van Keer, R.; Noels, L. (Eds.) et al Proceedings of the 4th International Conference on Advanced Computational Methods in Engineering (2008)

Dam-break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. High resolution Digital Elevation Models (DEMs) available today provide ... [more ▼]

Dam-break flow computation is a task of prime interest in the scope of risk analysis processes related to dams and reservoirs. High resolution Digital Elevation Models (DEMs) available today provide extremely dense and accurate topography information in the valley downstream of these structures, even in urban area. In this paper, a 2D finite volume flow solver, able to deal with these DEMs, is presented in details. Validation examples are comprehensively described. [less ▲]

Detailed reference viewed: 67 (7 ULg)
Peer Reviewed
See detailDam-break flow computation using high resolution DEM
Dewals, Benjamin ULg

Conference (2008, May 26)

Detailed reference viewed: 17 (2 ULg)
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See detailDam-break flow numerical modeling considering structural impacts on buildings
Erpicum, Sébastien ULg; Archambeau, Pierre ULg; Dewals, Benjamin ULg et al

in Proc. 33rd IAHR Congress: Water Engineering for a Sustainable Environment (2009)

Detailed reference viewed: 13 (2 ULg)
See detailDamage and fracture of ductile materials submitted to high strain rates. An implicit thermomechanically coupled approach with element erosion
Jeunechamps, Pierre-Paul ULg; Ponthot, Jean-Philippe ULg

in Proceedings of “PACAM XI, 11th Pan-American Congress of Applied Mechanics (2009)

Detailed reference viewed: 22 (0 ULg)
See detailDamage and fracture of materials submitted to high strain rates. A thermomechanically coupled approach with element erosion
Jeunechamps, Pierre-Paul ULg; Ponthot, Jean-Philippe ULg

in Proceedings of “Dynamic behaviour of materials”, Workshop in memory of Prof. J.R. Klepaczko (2009)

Detailed reference viewed: 11 (1 ULg)
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See detailDamage and Fracture of Materials Submitted to High Strain Rates. A Thermomechanically Implicit Coupled Approach with Element Erosion
Jeunechamps, Pierre-Paul; Boman, Romain ULg; Papeleux, Luc ULg et al

in Proceedings of the 3rd International Conference on Impact Loading of Lightweight Structures (2011, June 28)

Detailed reference viewed: 18 (8 ULg)
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See detailDamage and functional recovery of the Atlantic cod (Gadus morhua) inner ear hair cells following local injection of gentamicin
Faucher, Karine ULg; Aas-Hansen, Øyvind; Damsgård, Borge et al

in International Journal of Audiology (2009), 48(7), 456-464

This study addresses the ultrastructural and functional damage and subsequent recovery of the inner ear in the Atlantic cod following intrasaccular gentamicin injection. Inner ear damage was assessed ... [more ▼]

This study addresses the ultrastructural and functional damage and subsequent recovery of the inner ear in the Atlantic cod following intrasaccular gentamicin injection. Inner ear damage was assessed using SEM and measurements of AEP following 250-Hz pure-tone stimuli. Data from gentamicin-treated fish were compared with control (no injection) and sham (injection of saline) fish. Control fish had normal response thresholds associated with welldeveloped hair cell bundles in their macula sacculi. Sham fish had higher response thresholds compared with control fish during the first week post-intervention, but response thresholds were subsequently normal. Treated fish displayed significant inner ear damage associated with an increased average AEP threshold on the third day following treatment. Thereafter, inner ear tissue displayed signs of progressive regeneration until it was comparable to controls from the 14th day. Response thresholds were similar to those of control fish from the 17th day following treatment. These observations suggest that the macula sacculi of Atlantic cod can regenerate towards a near-complete functional and ultrastructural recovery within 17-21 days following ototoxic gentamicin treatment. [less ▲]

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See detailDamage around tunnels in indurated clay: hydro-mechanical modelling aspects
Levasseur, Séverine ULg; Charlier, Robert ULg; Frieg, Bernd et al

in Li, Xiangling; Jing, Lanru; Blaser, Petra (Eds.) Impact of Thermo-Hydro-Mechanical-Chemical (THMC) processes on the safety of underground radioactive waste repositories (2009, September)

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See detailA damage constitutive law for steel elevated temperature. Identification of the parameters
Castagne, Sylvie; Talamona, D.; Habraken, Anne ULg

in International Journal of Material Processing (2007), (1), 23-43

This paper presents a methodology of damage analysis at elevated temperature using the finite element method. Both the model and the methodology to identify parameters are summarized. The mechanical ... [more ▼]

This paper presents a methodology of damage analysis at elevated temperature using the finite element method. Both the model and the methodology to identify parameters are summarized. The mechanical properties are established using compression tests at elevated temperature. An elasto-visco-plastic model depending on temperature is identified. A metallographic analysis is used to determine the original size and morphology of the austenitic grains. The experimental damage analyses consist in acoustic tests in order to determine the apparition of the first crack during compression. Finite element simulations of these experiments allow the determination of the damage parameters using a reverse method. [less ▲]

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See detailDamage detection and local resonances model in CFRP composite material by vibrothermography
Demy, Philippe ULg; Golinval, Jean-Claude ULg; Simon, Daniel

Scientific conference (2012, September)

Vibrothermography (VT) is an active non destructive technique able to detect singularities like delamination, even if the defect internal faces are in contact. Under sonic or ultrasonic mechanical ... [more ▼]

Vibrothermography (VT) is an active non destructive technique able to detect singularities like delamination, even if the defect internal faces are in contact. Under sonic or ultrasonic mechanical vibrations, a delamination may behave like a heat source principally due to friction between the rubbing faces and/or stress concentration in the area. The present article focuses on the understanding of the underlying phenomenon so-called "local resonances" and its correlation with the presence of temperature peaks observed at certain frequencies. For this purpose, a simplified finite element modal analysis of the delamination model is compared with the heating rate vs. frequency data's acquired by an infrared camera. Then, some conclusive results of sine sweep and chirp testing will be presented and discussed in regards to this theory. [less ▲]

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See detailDamage Detection in Civil Engineering Structure Considering Temperature Effect
Nguyen, Viet Ha; Mahowald, Jean; Maas, Stefan et al

in Proceedings of IMAC XXXII Dynamics of Coupled Structures (2014, February)

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different ... [more ▼]

This paper concerns damage identification of a bridge located in Luxembourg. Vibration responses were captured from measurable and adjustable harmonic swept sine excitation and hammer impact. Different analysis methods were applied to the data measured from the structure showing interesting results. However, some difficulties arise, especially due to environmental influences (temperature and soil-behaviour variations) which overlay the structural changes caused by damage. These environmental effects are investigated in detail in this work. First, the modal parameters are identified from the response data. In the next step, they are statistically collected and processed through Principal Component Analysis (PCA) and Kernel PCA. Damage indexes are based on outlier analysis. [less ▲]

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See detailDamage detection in composites by vibrothermography and local resonances
Demy, Philippe ULg; Golinval, Jean-Claude ULg; Simon, Daniel

in Mechanics & Industry (2013), 14(2), 137-143

Vibrothermography is an active thermographic technique able to detect singularities like delamination in composite materials. Carbon fibre laminates are increasingly used, especially in aviation industry ... [more ▼]

Vibrothermography is an active thermographic technique able to detect singularities like delamination in composite materials. Carbon fibre laminates are increasingly used, especially in aviation industry where defect detection is directly related to safety. Physical causes of the internal heating mechanism linked to defect interaction with the elastic waves may be friction, viscoelastic hysteresis or plasticity. The method can efficiently detect flaws on complex geometries and only requires that both internal faces or edges are free to vibrate. The purpose of this work is to determine the relation between the observed heating right above a delamination by an IR camera and the frequency of a sinusoidal excitation between 8 and 27 kHz. The results clearly show specific heating peaks at certain frequencies. The comparison with local resonance frequencies of the delamination computed by simplified FEM shows similarities with the appearance of heating peaks. An experimental study having as goal to exploit the presence of those peaks and thus to increase the sensitivity of the method shows the interest for a high sweep sinusoidal excitation of the chirp type. The final objective of this research is to set up a serviceable short and reliable vibrothermographic test for non-destructive testing of composite materials. [less ▲]

Detailed reference viewed: 43 (6 ULg)