Documents disponibles écrits par cet auteur

Effect of drop in pipe wall stiffness on water-hammer speed and attenuation / Fadi E. Hachem in Journal of hydraulic research, Vol. 50 N° 2 (Mars/Avril 2012) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 50 N° 2 (Mars/Avril 2012) . - pp. 218-227 Titre : Effect of drop in pipe wall stiffness on water-hammer speed and attenuation Type de document : texte imprimé Auteurs : Fadi E. Hachem, Auteur ; Anton J. Schleiss, Auteur Année de publication : 2012 Article en page(s) : pp. 218-227 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Geophone  Monitoring  Steel-lined  tunnel  Wall  stiffness  Water-hammer  Wave  attenuation  Wave  speed Résumé : The effect of local drop of wall stiffness in pressurized waterways on the pressure wave speed and the wave attenuation during transients is investigated experimentally. A new signal-processing procedure to identify the presence of a weak reach is introduced and validated by physical experimentation based on assessing the pressure and vibration records acquired at both ends of a multi-reach steel test pipe. Water-hammer was generated by closing a downstream valve, whereas the weak reaches were simulated by replacing the steel portions with aluminium and PVC material. The wave speed and wave attenuation factor during transients are considered as global indicators of local and large changes in stiffness of the pipe wall. The method is capable of locating the stiffness weakness along the test pipe if one PVC reach is used. The error in estimating the position of such a reach relative to the real position of its mean value varies up to 23%. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2012.656838 [article] Effect of drop in pipe wall stiffness on water-hammer speed and attenuation [texte imprimé] / Fadi E. Hachem, Auteur ; Anton J. Schleiss, Auteur . - 2012 . - pp. 218-227. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 50 N° 2 (Mars/Avril 2012) . - pp. 218-227 Mots-clés : Geophone  Monitoring  Steel-lined  tunnel  Wall  stiffness  Water-hammer  Wave  attenuation  Wave  speed Résumé : The effect of local drop of wall stiffness in pressurized waterways on the pressure wave speed and the wave attenuation during transients is investigated experimentally. A new signal-processing procedure to identify the presence of a weak reach is introduced and validated by physical experimentation based on assessing the pressure and vibration records acquired at both ends of a multi-reach steel test pipe. Water-hammer was generated by closing a downstream valve, whereas the weak reaches were simulated by replacing the steel portions with aluminium and PVC material. The wave speed and wave attenuation factor during transients are considered as global indicators of local and large changes in stiffness of the pipe wall. The method is capable of locating the stiffness weakness along the test pipe if one PVC reach is used. The error in estimating the position of such a reach relative to the real position of its mean value varies up to 23%. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2012.656838

Entrainment of floating granules behind a barrier / Azin Amini in Journal of hydraulic research, Vol. 47 N° 6 (2009) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 47 N° 6 (2009) . - pp. 711-715 Titre : Entrainment of floating granules behind a barrier Titre original : Entraînement de granules flottants derrière une barrière Type de document : texte imprimé Auteurs : Azin Amini, Auteur ; Boillat, Jean-Louis, Auteur ; Anton J. Schleiss, Auteur Article en page(s) : pp. 711-715 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Critical  shear  stress  Floating  granule  Interfacial  shear  Multiphase  model  Pollution  Retaining  barrier  Shields  diagram Index. décimale : 627 Ingénierie des cours d'eau naturels, des ports, des rades et des cotes. Installations de navigation, de dragage, de récupération et de sauvetage. Barrages et centrales électriques hydrauliques Résumé : To simulate the retaining capacity of an oil barrier in an uniform flow field, experiments were carried out in a laboratory flume at Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Hydraulic Constructions (LCH) by using Light Expanded Clay Aggregates (LECA) and plastic particles. It was demonstrated that under appropriate assumptions for the effects of buoyancy and gravity forces, the Shields approach is suitable to predict both the entrainment of suspended granules behind a barrier and the start of leakage underneath. The phenomenon was also simulated numerically with a multiphase model using a CFD code, Fluent, and the results were compared to those of the physical experiments. The “Eulerian model” multiphase model of FLUENT was selected to simulate the phenomenon. The numerical model successfully predicts the evolution of the slick shape behind the barrier for various flow conditions. The amount of LECA that leaked from the barrier agreed well with the experimental observations. Pour simuler la capacité de fixation d'une barrière à huile dans un écoulement uniforme, des expériences ont été effectuées dans un canal de laboratoire à l'Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de Constructions Hydrauliques (LCH) en utilisant des Light Expanded Clay Agrégats (LECA) et des particules en plastique. Il a été démontré que dans le cadre d'hypothèses appropriées pour les effets de flottabilité et les forces de gravité, l'approche de Shields permet de prédire tant l'entraînement de granulés en suspension derrière une barrière que le début de fuite par en dessous. Le phénomène a été également simulé numériquement avec un modèle multiphase utilisant le code de CFD Fluent, et les résultats ont été comparés à ceux des expériences physiques. Le "modèle Eulerien" multiphase de FLUENT a été sélectionné pour simuler le phénomène. Le modèle numérique prédit avec succès l'évolution de la forme de la nappe derrière la barrière pour différentes conditions d'écoulement. Le montant de LECA qui a fuit de la barrière correspondait bien avec les observations expérimentales. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.journalhydraulicresearch.com [article] Entrainment of floating granules behind a barrier = Entraînement de granules flottants derrière une barrière [texte imprimé] / Azin Amini, Auteur ; Boillat, Jean-Louis, Auteur ; Anton J. Schleiss, Auteur . - pp. 711-715. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 47 N° 6 (2009) . - pp. 711-715 Mots-clés : Critical  shear  stress  Floating  granule  Interfacial  shear  Multiphase  model  Pollution  Retaining  barrier  Shields  diagram Index. décimale : 627 Ingénierie des cours d'eau naturels, des ports, des rades et des cotes. Installations de navigation, de dragage, de récupération et de sauvetage. Barrages et centrales électriques hydrauliques Résumé : To simulate the retaining capacity of an oil barrier in an uniform flow field, experiments were carried out in a laboratory flume at Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratory of Hydraulic Constructions (LCH) by using Light Expanded Clay Aggregates (LECA) and plastic particles. It was demonstrated that under appropriate assumptions for the effects of buoyancy and gravity forces, the Shields approach is suitable to predict both the entrainment of suspended granules behind a barrier and the start of leakage underneath. The phenomenon was also simulated numerically with a multiphase model using a CFD code, Fluent, and the results were compared to those of the physical experiments. The “Eulerian model” multiphase model of FLUENT was selected to simulate the phenomenon. The numerical model successfully predicts the evolution of the slick shape behind the barrier for various flow conditions. The amount of LECA that leaked from the barrier agreed well with the experimental observations. Pour simuler la capacité de fixation d'une barrière à huile dans un écoulement uniforme, des expériences ont été effectuées dans un canal de laboratoire à l'Ecole Polytechnique Fédérale de Lausanne (EPFL), Laboratoire de Constructions Hydrauliques (LCH) en utilisant des Light Expanded Clay Agrégats (LECA) et des particules en plastique. Il a été démontré que dans le cadre d'hypothèses appropriées pour les effets de flottabilité et les forces de gravité, l'approche de Shields permet de prédire tant l'entraînement de granulés en suspension derrière une barrière que le début de fuite par en dessous. Le phénomène a été également simulé numériquement avec un modèle multiphase utilisant le code de CFD Fluent, et les résultats ont été comparés à ceux des expériences physiques. Le "modèle Eulerien" multiphase de FLUENT a été sélectionné pour simuler le phénomène. Le modèle numérique prédit avec succès l'évolution de la forme de la nappe derrière la barrière pour différentes conditions d'écoulement. Le montant de LECA qui a fuit de la barrière correspondait bien avec les observations expérimentales. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.journalhydraulicresearch.com

Experimental study of velocity fields in rectangular shallow reservoirs / Erica Camnasio in Journal of hydraulic research, Vol. 49 N° 3 (Mai/Juin 2011) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 49 N° 3 (Mai/Juin 2011) . - pp. 352-358 Titre : Experimental study of velocity fields in rectangular shallow reservoirs Type de document : texte imprimé Auteurs : Erica Camnasio, Auteur ; Enrico Orsi, Auteur ; Anton J. Schleiss, Auteur Année de publication : 2011 Article en page(s) : pp. 352-358 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Flow  pattern  Geometrical  effect  Instability  Large  scale  turbulent  structure  Shallow  reservoir  Velocity  measurement Index. décimale : 627 Ingénierie des cours d'eau naturels, des ports, des rades et des cotes. Installations de navigation, de dragage, de récupération et de sauvetage. Barrages et centrales électriques hydrauliques Résumé : Velocity fields in rectangular shallow reservoirs with different length-to-width and expansion ratios were investigated in an experimental study, to evaluate the effect of geometry on the flow field. A wide range of combinations of these two non-dimensional geometric parameters were tested at constant hydraulic conditions. Ultrasound velocity profilers were used to measure the horizontal velocity components across the entire reservoir surface, allowing for the visualization of streamlines and of the instantaneous and average velocities. Five different types of flow patterns were identified, depending on the values of the length-to-width ratio and expansion ratio of the reservoir. Asymmetrical flow patterns were found to develop for certain combinations of these geometric parameters despite the perfect reservoir symmetry. A critical comparison of these new experimental results with those of other works is provided. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.574387 [article] Experimental study of velocity fields in rectangular shallow reservoirs [texte imprimé] / Erica Camnasio, Auteur ; Enrico Orsi, Auteur ; Anton J. Schleiss, Auteur . - 2011 . - pp. 352-358. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 49 N° 3 (Mai/Juin 2011) . - pp. 352-358 Mots-clés : Flow  pattern  Geometrical  effect  Instability  Large  scale  turbulent  structure  Shallow  reservoir  Velocity  measurement Index. décimale : 627 Ingénierie des cours d'eau naturels, des ports, des rades et des cotes. Installations de navigation, de dragage, de récupération et de sauvetage. Barrages et centrales électriques hydrauliques Résumé : Velocity fields in rectangular shallow reservoirs with different length-to-width and expansion ratios were investigated in an experimental study, to evaluate the effect of geometry on the flow field. A wide range of combinations of these two non-dimensional geometric parameters were tested at constant hydraulic conditions. Ultrasound velocity profilers were used to measure the horizontal velocity components across the entire reservoir surface, allowing for the visualization of streamlines and of the instantaneous and average velocities. Five different types of flow patterns were identified, depending on the values of the length-to-width ratio and expansion ratio of the reservoir. Asymmetrical flow patterns were found to develop for certain combinations of these geometric parameters despite the perfect reservoir symmetry. A critical comparison of these new experimental results with those of other works is provided. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.574387

Hydraulic design of A-type Piano Key Weirs / Marcelo Leite Ribeiro in Journal of hydraulic research, Vol. 50 N° 4 (Juillet/Août 2012) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 50 N° 4 (Juillet/Août 2012) . - pp. 400-408 Titre : Hydraulic design of A-type Piano Key Weirs Type de document : texte imprimé Auteurs : Marcelo Leite Ribeiro, Auteur ; Michael Pfister, Auteur ; Anton J. Schleiss, Auteur Année de publication : 2012 Article en page(s) : pp. 400-408 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Capacity  Discharge  Flood  Piano  Key  Weir  Spillway Résumé : Piano Key Weirs (PKWs) are an alternative to linear overflow structures, increasing the unit discharge for similar heads and spillway widths. Thus, they allow to operate reservoirs with elevated supply levels, thereby providing additional storage volume. As they are relatively novel structures, few design criteria are available. Hence, physical model tests of prototypes are required. This study describes comprehensive model tests on a sectional set-up of several A-type PKWs, in which the relevant parameters were systematically varied. Considering data of former studies, a general design equation relating to the head–discharge ratio is derived and discussed. The latter is mainly a function of the approach flow head, the developed crest length, the inlet key height, and the transverse width. To extend its application range, case study model tests were analysed to provide a design approach if reservoir approach flow instead of channel flow is considered. ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/full/10.1080/00221686.2012.695041 [article] Hydraulic design of A-type Piano Key Weirs [texte imprimé] / Marcelo Leite Ribeiro, Auteur ; Michael Pfister, Auteur ; Anton J. Schleiss, Auteur . - 2012 . - pp. 400-408. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 50 N° 4 (Juillet/Août 2012) . - pp. 400-408 Mots-clés : Capacity  Discharge  Flood  Piano  Key  Weir  Spillway Résumé : Piano Key Weirs (PKWs) are an alternative to linear overflow structures, increasing the unit discharge for similar heads and spillway widths. Thus, they allow to operate reservoirs with elevated supply levels, thereby providing additional storage volume. As they are relatively novel structures, few design criteria are available. Hence, physical model tests of prototypes are required. This study describes comprehensive model tests on a sectional set-up of several A-type PKWs, in which the relevant parameters were systematically varied. Considering data of former studies, a general design equation relating to the head–discharge ratio is derived and discussed. The latter is mainly a function of the approach flow head, the developed crest length, the inlet key height, and the transverse width. To extend its application range, case study model tests were analysed to provide a design approach if reservoir approach flow instead of channel flow is considered. ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/full/10.1080/00221686.2012.695041

Optimization of the flood protection effect of a hydropower multi-reservoir system / Frédéric M. Jordan in JRBM : International journal of river basin management, Vol. 10 N° 1 (Janvier 2012) 

Public ISBD [article]  in JRBM : International journal of river basin management > Vol. 10 N° 1 (Janvier 2012) . - pp. 65-72 Titre : Optimization of the flood protection effect of a hydropower multi-reservoir system Type de document : texte imprimé Auteurs : Frédéric M. Jordan, Auteur ; Boillat, Jean-Louis, Auteur ; Anton J. Schleiss, Auteur Année de publication : 2012 Article en page(s) : pp. 65-72 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Flood  risk  management  Multi-reservoir  systems  Preventive  operation  of  hydropower  schemes  Flood  forecast Résumé : The use of existing hydroelectricity multi-reservoir systems for flood protection may be an efficient approach in many catchment areas. The assessment of the protection potential offered by the hydropower plants during floods requires a comprehensive analysis of the catchment area, including the simulation of flood scenarios. A methodology for the optimization of turbine and bottom outlet operations of multi-reservoir systems during floods is presented. Based on a theoretical catchment configuration, the most relevant parameters in view of reducing of the peak flows in rivers located downstream of the reservoirs are analysed in a systematic way with the help of hydrological forecasts. The influence of the drained areas, the installed turbine capacities, the emergency rules and the location of the reservoirs on the flood control in such a complex catchment area is highlighted. The optimization approach is applied in the Upper Rhone River basin in Switzerland, where 10 major hydropower schemes with large reservoirs are located. The results regarding peak flow reduction at the catchment outlet are in good agreement with the theoretical values obtained with the developed methodology. ISSN : 1571-5124 En ligne : http://www.tandfonline.com/doi/full/10.1080/15715124.2011.650868 [article] Optimization of the flood protection effect of a hydropower multi-reservoir system [texte imprimé] / Frédéric M. Jordan, Auteur ; Boillat, Jean-Louis, Auteur ; Anton J. Schleiss, Auteur . - 2012 . - pp. 65-72. Hydraulique Langues : Anglais (eng) in JRBM : International journal of river basin management > Vol. 10 N° 1 (Janvier 2012) . - pp. 65-72 Mots-clés : Flood  risk  management  Multi-reservoir  systems  Preventive  operation  of  hydropower  schemes  Flood  forecast Résumé : The use of existing hydroelectricity multi-reservoir systems for flood protection may be an efficient approach in many catchment areas. The assessment of the protection potential offered by the hydropower plants during floods requires a comprehensive analysis of the catchment area, including the simulation of flood scenarios. A methodology for the optimization of turbine and bottom outlet operations of multi-reservoir systems during floods is presented. Based on a theoretical catchment configuration, the most relevant parameters in view of reducing of the peak flows in rivers located downstream of the reservoirs are analysed in a systematic way with the help of hydrological forecasts. The influence of the drained areas, the installed turbine capacities, the emergency rules and the location of the reservoirs on the flood control in such a complex catchment area is highlighted. The optimization approach is applied in the Upper Rhone River basin in Switzerland, where 10 major hydropower schemes with large reservoirs are located. The results regarding peak flow reduction at the catchment outlet are in good agreement with the theoretical values obtained with the developed methodology. ISSN : 1571-5124 En ligne : http://www.tandfonline.com/doi/full/10.1080/15715124.2011.650868

Scour formation due to simultaneous circular impinging jet and wall jet / Mojtaba Mehraein in Journal of hydraulic research, Vol. 50 N° 4 (Juillet/Août 2012) 

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Water-surface oscillations in channels with axi-symmetric cavities / Tobias Meile in Journal of hydraulic research, Vol. 49 N° 1 (Janvier/Fevrier 2011) 

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