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Aerated flow characteristics of skimming flow over stepped chutes / Masayuki Takahashi 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. 427-434 Titre : Aerated flow characteristics of skimming flow over stepped chutes Type de document : texte imprimé Auteurs : Masayuki Takahashi, Auteur ; Iwao Ohtsu, Auteur Année de publication : 2012 Article en page(s) : pp. 427-434 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Aerated  flow  Friction  factor  Skimming  flow  Specific  energy  Stepped  chute Résumé : Stepped chutes effectively dissipate the energy of supercritical flow of steep channels. In general, stepped chute flows are characterized by self-aeration. For their hydraulic design, it is important to know the aerated flow depth, the aerated flow velocity, the air concentration, and the specific energy. Herein, quasi-uniform aerated skimming flow is systematically investigated over a range of chute angles from 19° to 55° for a wide range of step heights and discharges. Air concentration and aerated flow velocity profiles are presented, and the depth-averaged air concentration and the friction factor are determined. The specific energy is determined based on the aerated flow characteristics, revealing the effects of chute angle and step height on the specific energy of aerated skimming flow. This quantity was compared with the conventional specific energy of clear-water flows. ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/full/10.1080/00221686.2012.702859 [article] Aerated flow characteristics of skimming flow over stepped chutes [texte imprimé] / Masayuki Takahashi, Auteur ; Iwao Ohtsu, Auteur . - 2012 . - pp. 427-434. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 50 N° 4 (Juillet/Août 2012) . - pp. 427-434 Mots-clés : Aerated  flow  Friction  factor  Skimming  flow  Specific  energy  Stepped  chute Résumé : Stepped chutes effectively dissipate the energy of supercritical flow of steep channels. In general, stepped chute flows are characterized by self-aeration. For their hydraulic design, it is important to know the aerated flow depth, the aerated flow velocity, the air concentration, and the specific energy. Herein, quasi-uniform aerated skimming flow is systematically investigated over a range of chute angles from 19° to 55° for a wide range of step heights and discharges. Air concentration and aerated flow velocity profiles are presented, and the depth-averaged air concentration and the friction factor are determined. The specific energy is determined based on the aerated flow characteristics, revealing the effects of chute angle and step height on the specific energy of aerated skimming flow. This quantity was compared with the conventional specific energy of clear-water flows. ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/full/10.1080/00221686.2012.702859

An experimental study of effects of step roughness in skimming flows on stepped chutes / Gonzalez, Carlos A. in Journal of hydraulic research, Vol. 46 extra issue (2008) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 46 extra issue (2008) . - p. 24-35 Titre : An experimental study of effects of step roughness in skimming flows on stepped chutes Titre original : Etude expérimentale des effets de la rugosité des marches sur les écoulements d'écumage dans les évacuateurs en gradins Type de document : texte imprimé Auteurs : Gonzalez, Carlos A., Auteur ; Masayuki Takahashi, Auteur ; Chanson, Hubert, Auteur Article en page(s) : p. 24-35 Note générale : Hydraulique Résumé en Français Langues : Anglais (eng) Mots-clés : Stepped  chute  Skimming  flow  Step  roughness  Air-water  flow  Physical  modelling  Flow  resistance  Form  drag  Energy  dissipation  Gabion  stepped  spillway 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 : On a spillway chute, a stepped design increases the rate of energy dissipation on the chute itself and reduces the size of a downstream energy dissipater. Up to date, the effects of step roughness on the flow properties remain unknown despite the practical relevance to damaged concrete steps, rock chutes and gabions weirs. New measurements were conducted in a large-size laboratory facility with two step conditions (smooth and rough) and three types of step roughness. Detailed air-water flow properties were measured systematically for several flow rates. The results showed faster flow motion on rough step chutes. Although the finding is counter-intuitive, it is linked with the location of the inception point of free-surface aeration being located further downstream than for a smooth stepped chute for an identical flow rate. In the aerated flow region, the velocities on rough-step chutes were larger than those of smooth chute flows for a given flow rate and dimensionless location from the inception point of free-surface aeration both at step edges and between step edges. The results suggest that design guidelines for smooth (concrete) stepped spillway may not be suitable to rough stepped chutes including gabion stepped weirs, and older stepped chutes with damaged steps. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.journalhydraulicresearch.com/ [article] An experimental study of effects of step roughness in skimming flows on stepped chutes = Etude expérimentale des effets de la rugosité des marches sur les écoulements d'écumage dans les évacuateurs en gradins [texte imprimé] / Gonzalez, Carlos A., Auteur ; Masayuki Takahashi, Auteur ; Chanson, Hubert, Auteur . - p. 24-35. Hydraulique Résumé en Français Langues : Anglais (eng) in Journal of hydraulic research > Vol. 46 extra issue (2008) . - p. 24-35 Mots-clés : Stepped  chute  Skimming  flow  Step  roughness  Air-water  flow  Physical  modelling  Flow  resistance  Form  drag  Energy  dissipation  Gabion  stepped  spillway 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 : On a spillway chute, a stepped design increases the rate of energy dissipation on the chute itself and reduces the size of a downstream energy dissipater. Up to date, the effects of step roughness on the flow properties remain unknown despite the practical relevance to damaged concrete steps, rock chutes and gabions weirs. New measurements were conducted in a large-size laboratory facility with two step conditions (smooth and rough) and three types of step roughness. Detailed air-water flow properties were measured systematically for several flow rates. The results showed faster flow motion on rough step chutes. Although the finding is counter-intuitive, it is linked with the location of the inception point of free-surface aeration being located further downstream than for a smooth stepped chute for an identical flow rate. In the aerated flow region, the velocities on rough-step chutes were larger than those of smooth chute flows for a given flow rate and dimensionless location from the inception point of free-surface aeration both at step edges and between step edges. The results suggest that design guidelines for smooth (concrete) stepped spillway may not be suitable to rough stepped chutes including gabion stepped weirs, and older stepped chutes with damaged steps. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.journalhydraulicresearch.com/

Developing flow in skimming flow regime on embankment stepped spillways / Masayuki Takahashi 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. 437-439 Titre : Developing flow in skimming flow regime on embankment stepped spillways Type de document : texte imprimé Auteurs : Masayuki Takahashi, Auteur ; Iwao Ohtsu, Auteur Année de publication : 2012 Article en page(s) : pp. 437-439 Note générale : Hydraulique Langues : Anglais (eng) ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/full/10.1080/00221686.2012.704959 [article] Developing flow in skimming flow regime on embankment stepped spillways [texte imprimé] / Masayuki Takahashi, Auteur ; Iwao Ohtsu, Auteur . - 2012 . - pp. 437-439. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 50 N° 4 (Juillet/Août 2012) . - pp. 437-439 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/full/10.1080/00221686.2012.704959

High-precision finite element analysis of elastoplastic dynamic responses of super-high-rise steel frames / Makoto Ohsaki in Earthquake engineering structural dynamics, Vol. 38 N°5 (Avril 2009) 

Public ISBD [article]  in Earthquake engineering structural dynamics > Vol. 38 N°5 (Avril 2009) . - pp. 635-654 Titre : High-precision finite element analysis of elastoplastic dynamic responses of super-high-rise steel frames Type de document : texte imprimé Auteurs : Makoto Ohsaki, Auteur ; Tomoshi Miyamura, Auteur ; Masayuki Takahashi, Auteur Article en page(s) : pp. 635-654 Note générale : Génie Civil Langues : Anglais (eng) Mots-clés : Large-scale  structure;  Dynamic  collapse  analysis;  Finite  element  analysis;  E-simulator;  Steel  frame Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A new framework is presented for analysis of dynamic collapse behavior of steel frames using large-scale parallel finite element method based on the domain decomposition method. The analysis software is based on ADVC as a part of the E-Simulator that takes advantage of recent development of computer science and high-performance parallel computing in computational mechanics. By making an analysis model with fine meshing, a complicated sequence of local buckling of columns and beams can be simulated. Numerical results are shown for dynamic collapse analysis of single-story and 5-story frame models to show that the global and local behaviors are simultaneously simulated by a high-precision finite element analysis. Eigenvalue analysis is also carried out for a 31-story frame to demonstrate that dynamic analysis can be carried out for a structure discretized to solid elements with more than 70 million DOFs. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/122198910/abstract [article] High-precision finite element analysis of elastoplastic dynamic responses of super-high-rise steel frames [texte imprimé] / Makoto Ohsaki, Auteur ; Tomoshi Miyamura, Auteur ; Masayuki Takahashi, Auteur . - pp. 635-654. Génie Civil Langues : Anglais (eng) in Earthquake engineering structural dynamics > Vol. 38 N°5 (Avril 2009) . - pp. 635-654 Mots-clés : Large-scale  structure;  Dynamic  collapse  analysis;  Finite  element  analysis;  E-simulator;  Steel  frame Index. décimale : 624.1 Infrastructures.Ouvrages en terre. Fondations. Tunnels Résumé : A new framework is presented for analysis of dynamic collapse behavior of steel frames using large-scale parallel finite element method based on the domain decomposition method. The analysis software is based on ADVC as a part of the E-Simulator that takes advantage of recent development of computer science and high-performance parallel computing in computational mechanics. By making an analysis model with fine meshing, a complicated sequence of local buckling of columns and beams can be simulated. Numerical results are shown for dynamic collapse analysis of single-story and 5-story frame models to show that the global and local behaviors are simultaneously simulated by a high-precision finite element analysis. Eigenvalue analysis is also carried out for a 31-story frame to demonstrate that dynamic analysis can be carried out for a structure discretized to solid elements with more than 70 million DOFs. ISSN : 0098-8847 En ligne : http://www3.interscience.wiley.com/journal/122198910/abstract