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Ajouter le résultat dans votre panierWilfrid noel bond and the bond number / Willi H. Hager in Journal of hydraulic research, Vol. 50 N° 1 (Janvier/Février 2012)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 3-9
Titre : Wilfrid noel bond and the bond number Type de document : texte imprimé Auteurs : Willi H. Hager, Auteur Année de publication : 2012 Article en page(s) : pp. 3-9 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Biography Bond number History Hydraulics Surface tension Viscosity Résumé : Although the Bond number is generally known in fluid mechanics to describe the effects of surface tension and weight of a liquid drop or bubble, W.N. Bond as an individual is currently hardly known. Based on a lucky coincidence, the author was able to find documents, medals and photographs through his grandson. This work describes on the one hand the physical background of Bond's works, mainly relating to the measurement of viscosity and surface tension, the significance and relevance of the Bond number, and the professional and private background of a young and outstanding individual, who tragically passed away due to a serious illness. It is hoped that the basic knowledge of fluid flow is revitalized by this work, and that similar projects may be directed to the understanding of the historical developments of the hydraulic community. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.649839 [article] Wilfrid noel bond and the bond number [texte imprimé] / Willi H. Hager, Auteur . - 2012 . - pp. 3-9.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 3-9
Mots-clés : Biography Bond number History Hydraulics Surface tension Viscosity Résumé : Although the Bond number is generally known in fluid mechanics to describe the effects of surface tension and weight of a liquid drop or bubble, W.N. Bond as an individual is currently hardly known. Based on a lucky coincidence, the author was able to find documents, medals and photographs through his grandson. This work describes on the one hand the physical background of Bond's works, mainly relating to the measurement of viscosity and surface tension, the significance and relevance of the Bond number, and the professional and private background of a young and outstanding individual, who tragically passed away due to a serious illness. It is hoped that the basic knowledge of fluid flow is revitalized by this work, and that similar projects may be directed to the understanding of the historical developments of the hydraulic community. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.649839
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 10-17
Titre : Theory for flow resistance caused by submerged roughness elements Type de document : texte imprimé Auteurs : Fredrik Huthoff, Auteur Année de publication : 2012 Article en page(s) : pp. 10-17 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Dunes Flow resistance Hydraulic roughness Scaling Vegetation Résumé : Herein, a phenomenological theory that unifies the flow resistance caused by a variety of submerged bluff bodies, including cylindrical vegetation, two-dimensional dunes and the roughness elements studied in Schlichting's 1936 experiments, is presented. For the different flow obstructions, scaling relations that relate the equivalent roughness length to the obstructions’ spatial dimensions are derived, by adopting the concepts of the turbulent energy cascade and the momentum thickness in the wake of a bluff body. In the derivation, it is hypothesized that the equivalent roughness height represents the volumetric average of the prevailing turbulence length scale that is present in wakes of the roughness elements. A comparison with experimental literature data indicates that the derived scaling relations capture the dominant dependencies of the equivalent roughness length. These expressions have important engineering applications in large-scale flows where employment of more detailed flow-modelling techniques is not feasible. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.636635 [article] Theory for flow resistance caused by submerged roughness elements [texte imprimé] / Fredrik Huthoff, Auteur . - 2012 . - pp. 10-17.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 10-17
Mots-clés : Dunes Flow resistance Hydraulic roughness Scaling Vegetation Résumé : Herein, a phenomenological theory that unifies the flow resistance caused by a variety of submerged bluff bodies, including cylindrical vegetation, two-dimensional dunes and the roughness elements studied in Schlichting's 1936 experiments, is presented. For the different flow obstructions, scaling relations that relate the equivalent roughness length to the obstructions’ spatial dimensions are derived, by adopting the concepts of the turbulent energy cascade and the momentum thickness in the wake of a bluff body. In the derivation, it is hypothesized that the equivalent roughness height represents the volumetric average of the prevailing turbulence length scale that is present in wakes of the roughness elements. A comparison with experimental literature data indicates that the derived scaling relations capture the dominant dependencies of the equivalent roughness length. These expressions have important engineering applications in large-scale flows where employment of more detailed flow-modelling techniques is not feasible. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.636635
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 18-27
Titre : Pier scour in clear water for sediment mixtures Type de document : texte imprimé Auteurs : Junke Guo, Auteur Année de publication : 2012 Article en page(s) : pp. 18-27 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bridge scour CSU equation Hager number Pier scour Sediment mixture Résumé : The current pier scour design in the USA is mainly based on the CSU equation, yet a recent incisive evaluation indicates a need to change it because substantial advances were made in the last two decades for understanding the pier scour processes. The objective of this research is then to propose a simplified scour mechanism and a physically-based scour depth equation for practical design purposes. A critical review on selected previous studies is first made to form the basis of this research. A simplified scour mechanism is next proposed in terms of the pressure gradient through flow–structure, flow–sediment and sediment–structure interactions. A hypothesis on the equilibrium scour depth equation is then proposed based on the understanding of the scour mechanism and tested by flume data. Finally, the proposed scour depth equation provides a criterion and a rule of thumb for scour design and evaluation. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.644418 [article] Pier scour in clear water for sediment mixtures [texte imprimé] / Junke Guo, Auteur . - 2012 . - pp. 18-27.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 18-27
Mots-clés : Bridge scour CSU equation Hager number Pier scour Sediment mixture Résumé : The current pier scour design in the USA is mainly based on the CSU equation, yet a recent incisive evaluation indicates a need to change it because substantial advances were made in the last two decades for understanding the pier scour processes. The objective of this research is then to propose a simplified scour mechanism and a physically-based scour depth equation for practical design purposes. A critical review on selected previous studies is first made to form the basis of this research. A simplified scour mechanism is next proposed in terms of the pressure gradient through flow–structure, flow–sediment and sediment–structure interactions. A hypothesis on the equilibrium scour depth equation is then proposed based on the understanding of the scour mechanism and tested by flume data. Finally, the proposed scour depth equation provides a criterion and a rule of thumb for scour design and evaluation. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.644418
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 28-34
Titre : Scour upstream of a circular orifice under constant head Type de document : texte imprimé Auteurs : David N. Powell, Auteur ; Abdul A. Khan, Auteur Année de publication : 2012 Article en page(s) : pp. 28-34 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Circular orifice Local scour Scour mechanism Scour shape Vortex action Résumé : The transport mechanism as well as the extent and the shape of the scour upstream of a circular orifice is investigated under steady flow conditions for different sediment sizes and heads on the orifice. The main mechanism of sediment transport is found to be vortex-related, appearing randomly within the scour hole. The scour length, maximum scour width, and maximum scour depth are evaluated for various sediment sizes and under different heads on the orifice. The non-dimensional scour depth profiles along the orifice centreline are found to be similar. The non-dimensional scour depth profiles across the width of the scour hole at various locations upstream of the orifice are found to be similar as well. The flow characteristics related to the scaled centreline longitudinal velocity and the scaled position of the maximum longitudinal velocity are found to approach those for the unbounded orifice at the equilibrium scour condition. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.637821 [article] Scour upstream of a circular orifice under constant head [texte imprimé] / David N. Powell, Auteur ; Abdul A. Khan, Auteur . - 2012 . - pp. 28-34.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 28-34
Mots-clés : Circular orifice Local scour Scour mechanism Scour shape Vortex action Résumé : The transport mechanism as well as the extent and the shape of the scour upstream of a circular orifice is investigated under steady flow conditions for different sediment sizes and heads on the orifice. The main mechanism of sediment transport is found to be vortex-related, appearing randomly within the scour hole. The scour length, maximum scour width, and maximum scour depth are evaluated for various sediment sizes and under different heads on the orifice. The non-dimensional scour depth profiles along the orifice centreline are found to be similar. The non-dimensional scour depth profiles across the width of the scour hole at various locations upstream of the orifice are found to be similar as well. The flow characteristics related to the scaled centreline longitudinal velocity and the scaled position of the maximum longitudinal velocity are found to approach those for the unbounded orifice at the equilibrium scour condition. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.637821
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 35-43
Titre : Combined flow-altering countermeasures against bridge pier scour Type de document : texte imprimé Auteurs : Roberto Gaudio, Auteur ; Ali Tafarojnoruz, Auteur ; Francesco Calomino, Auteur Année de publication : 2012 Article en page(s) : pp. 35-43 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bridge pier Countermeasure Erosion Flow altering Movable bed Scour Résumé : This study presents the results of clear-water tests on the following five combined flow-altering countermeasures against bridge pier scour: (1) submerged vanes and a bed sill, (2) slot and sacrificial piles, (3) a collar and sacrificial piles, (4) a slot and a collar, and (5) a bed sill and a collar. Each countermeasure was designed on the basis of the best configuration recommended in the literature. The results clarify that an improper combination of two countermeasures may be less effective than each individual countermeasure; combinations (1), (2), and (3) do not reduce the scour depth significantly with respect to the single countermeasures; combination (3) increases the scour rate during the first few hours with respect to a single collar; combination (4) may also prevent scour intrusion beneath a collar; and combination (5) in the best configuration reduces the scour depth significantly around the collar with respect to maximum scour depth of the unprotected pier, preventing also the scour hole reaching the pier body. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.649548 [article] Combined flow-altering countermeasures against bridge pier scour [texte imprimé] / Roberto Gaudio, Auteur ; Ali Tafarojnoruz, Auteur ; Francesco Calomino, Auteur . - 2012 . - pp. 35-43.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 35-43
Mots-clés : Bridge pier Countermeasure Erosion Flow altering Movable bed Scour Résumé : This study presents the results of clear-water tests on the following five combined flow-altering countermeasures against bridge pier scour: (1) submerged vanes and a bed sill, (2) slot and sacrificial piles, (3) a collar and sacrificial piles, (4) a slot and a collar, and (5) a bed sill and a collar. Each countermeasure was designed on the basis of the best configuration recommended in the literature. The results clarify that an improper combination of two countermeasures may be less effective than each individual countermeasure; combinations (1), (2), and (3) do not reduce the scour depth significantly with respect to the single countermeasures; combination (3) increases the scour rate during the first few hours with respect to a single collar; combination (4) may also prevent scour intrusion beneath a collar; and combination (5) in the best configuration reduces the scour depth significantly around the collar with respect to maximum scour depth of the unprotected pier, preventing also the scour hole reaching the pier body. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.649548
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 44-51
Titre : Study of sediment motion in scour hole of a circular pier Type de document : texte imprimé Auteurs : Alessio Radice, Auteur ; Chau K. Tran, Auteur Année de publication : 2012 Article en page(s) : pp. 44-51 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bridge pier Local scour Pier–abutment comparison Sediment kinematics Résumé : This research presents results for the sediment kinematics in a clear-water scour experiment with a circular pier. Various process phases were considered, until the scour depth equalled almost twice the pier diameter. The results are consistent with typical literature descriptions of the flow field and with the findings of few previous works where the sediment motion at a local scour was investigated. The relationship between the time-averaged concentration and velocity of sediments in the scour hole was found to be almost space- and time-invariant. In addition, the link was analogous to those found in an earlier work on abutments, providing for the first time evidence that the transport mechanics are identical for the two obstacle types. It is therefore suggested that the present results support the phenomenological description and modelling of various local scour processes. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.641764 [article] Study of sediment motion in scour hole of a circular pier [texte imprimé] / Alessio Radice, Auteur ; Chau K. Tran, Auteur . - 2012 . - pp. 44-51.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 44-51
Mots-clés : Bridge pier Local scour Pier–abutment comparison Sediment kinematics Résumé : This research presents results for the sediment kinematics in a clear-water scour experiment with a circular pier. Various process phases were considered, until the scour depth equalled almost twice the pier diameter. The results are consistent with typical literature descriptions of the flow field and with the findings of few previous works where the sediment motion at a local scour was investigated. The relationship between the time-averaged concentration and velocity of sediments in the scour hole was found to be almost space- and time-invariant. In addition, the link was analogous to those found in an earlier work on abutments, providing for the first time evidence that the transport mechanics are identical for the two obstacle types. It is therefore suggested that the present results support the phenomenological description and modelling of various local scour processes. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.641764
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 52-59
Titre : Uniform laminar wetland flow through submerged and floating plants Type de document : texte imprimé Auteurs : Mingdeng Zhao, Auteur ; Wenxin Huai, Auteur ; Jie Han, Auteur Année de publication : 2012 Article en page(s) : pp. 52-59 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Habitat restoration Laminar flow Porous media Stormwater treatment Vegetation flow Wetland Résumé : Wetland flow is currently actively studied because of its applications in stormwater management, wastewater treatment and habitat restoration. This research applies the well-established poroelastic media flow theory to uniform laminar wetland flow through submerged and floating vegetation, where the linear interaction between the pore water and the vegetation skeleton is considered in the equations of motion. The effects of vegetation porosity on the velocity, the shear stress and the energy distributions in different layers are first derived analytically and interpreted graphically and physically. As special cases, the homogeneous water flow, as also floating, submerged and emergent vegetation flows are then discussed. This research provides qualitative understanding of wetland flow on velocity, shear stress and energy distributions, indicating that a plant applies a significant resistance to the flow system and dissipates most of the flow energy. The results serve a benchmark framework for the future study on turbulent vegetation flow. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.641327 [article] Uniform laminar wetland flow through submerged and floating plants [texte imprimé] / Mingdeng Zhao, Auteur ; Wenxin Huai, Auteur ; Jie Han, Auteur . - 2012 . - pp. 52-59.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 52-59
Mots-clés : Habitat restoration Laminar flow Porous media Stormwater treatment Vegetation flow Wetland Résumé : Wetland flow is currently actively studied because of its applications in stormwater management, wastewater treatment and habitat restoration. This research applies the well-established poroelastic media flow theory to uniform laminar wetland flow through submerged and floating vegetation, where the linear interaction between the pore water and the vegetation skeleton is considered in the equations of motion. The effects of vegetation porosity on the velocity, the shear stress and the energy distributions in different layers are first derived analytically and interpreted graphically and physically. As special cases, the homogeneous water flow, as also floating, submerged and emergent vegetation flows are then discussed. This research provides qualitative understanding of wetland flow on velocity, shear stress and energy distributions, indicating that a plant applies a significant resistance to the flow system and dissipates most of the flow energy. The results serve a benchmark framework for the future study on turbulent vegetation flow. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.641327
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 60-69
Titre : Effect of selected parameters on the depositional behaviour of turbidity currents Type de document : texte imprimé Auteurs : Ehsan Khavasi, Auteur ; Hossein Afshin, Auteur ; Bahar Firoozabadi, Auteur Année de publication : 2012 Article en page(s) : pp. 60-69 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Deposition Inlet Froude number Suspended sediment flux Turbidity current Résumé : Turbidity currents containing kaolin particles were studied experimentally in a channel and the velocity and concentration profiles were measured using an acoustic Doppler velocimeter. These experiments were performed to investigate the depositional behaviour of turbidity currents. The suspended sediment flux was evaluated by experimental and analytical methods and the results of these two methods were in a good agreement. To evaluate the suspended sediment flux, it was necessary to recognize the suspended sediment zone from the upper shear layer region and near the bed depositional area as well. The method of determination of these areas is discussed. The effects of important parameters including the inlet Froude number and bed slope were also studied. Based on these results, it can be concluded that the non-dimensional sediment flux decreases at the vicinity of the hydraulic jump with the inlet Froude number, whereas an increase in the bed slope reduces the non-dimensional sediment flux. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.641763 [article] Effect of selected parameters on the depositional behaviour of turbidity currents [texte imprimé] / Ehsan Khavasi, Auteur ; Hossein Afshin, Auteur ; Bahar Firoozabadi, Auteur . - 2012 . - pp. 60-69.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 60-69
Mots-clés : Deposition Inlet Froude number Suspended sediment flux Turbidity current Résumé : Turbidity currents containing kaolin particles were studied experimentally in a channel and the velocity and concentration profiles were measured using an acoustic Doppler velocimeter. These experiments were performed to investigate the depositional behaviour of turbidity currents. The suspended sediment flux was evaluated by experimental and analytical methods and the results of these two methods were in a good agreement. To evaluate the suspended sediment flux, it was necessary to recognize the suspended sediment zone from the upper shear layer region and near the bed depositional area as well. The method of determination of these areas is discussed. The effects of important parameters including the inlet Froude number and bed slope were also studied. Based on these results, it can be concluded that the non-dimensional sediment flux decreases at the vicinity of the hydraulic jump with the inlet Froude number, whereas an increase in the bed slope reduces the non-dimensional sediment flux. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.641763
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 70-81
Titre : Simulations of the New Orleans 17th Street Canal breach flood Type de document : texte imprimé Auteurs : Sylvie Van Emelen, Auteur ; Soares-Frazão, Sandra, Auteur ; Cyrus K. Riahi-Nezhad, Auteur Année de publication : 2012 Article en page(s) : pp. 70-81 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Breaching Finite volume Katrina Scale model Urban flooding Résumé : The City of New Orleans is surrounded by an intricate network of floodwalls and dikes built to protect it from flooding from the Mississippi River and Lake Pontchartrain. In 2005, following Hurricane Katrina, New Orleans experienced one of the most devastating urban floods in recent history caused by several dike breaches. This work presents an idealized case study of a part of this event on a scale model. It concerns the flow through one of these breaches and flooding in the surrounding urban area. The scale model reproduces part of the remaining dike, the complex morphology caused by the breach and a number of houses around the area. The flow field computed by a two-dimensional depth-averaged finite-volume numerical model is compared with measurements on the scale model. As the transient part of the flood is quite short, the numerical and experimental results were compared under steady-state flow, showing satisfactory agreement. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.642578 [article] Simulations of the New Orleans 17th Street Canal breach flood [texte imprimé] / Sylvie Van Emelen, Auteur ; Soares-Frazão, Sandra, Auteur ; Cyrus K. Riahi-Nezhad, Auteur . - 2012 . - pp. 70-81.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 70-81
Mots-clés : Breaching Finite volume Katrina Scale model Urban flooding Résumé : The City of New Orleans is surrounded by an intricate network of floodwalls and dikes built to protect it from flooding from the Mississippi River and Lake Pontchartrain. In 2005, following Hurricane Katrina, New Orleans experienced one of the most devastating urban floods in recent history caused by several dike breaches. This work presents an idealized case study of a part of this event on a scale model. It concerns the flow through one of these breaches and flooding in the surrounding urban area. The scale model reproduces part of the remaining dike, the complex morphology caused by the breach and a number of houses around the area. The flow field computed by a two-dimensional depth-averaged finite-volume numerical model is compared with measurements on the scale model. As the transient part of the flood is quite short, the numerical and experimental results were compared under steady-state flow, showing satisfactory agreement. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.642578
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 82-88
Titre : Modelling plane open-channel flows by coupled depth-averaged and RANS equations Type de document : texte imprimé Auteurs : Hasan Zobeyer, Auteur ; Peter Steffler, Auteur Année de publication : 2012 Article en page(s) : pp. 82-88 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Depth-averaged equation Non-hydrostatic pressure Non-uniform velocity Open-channel flow RANS equations Résumé : Herein, a coupled depth-averaged (DA) and Reynolds-averaged Navier–Stokes (RANS) model is developed for steady plane open-channel flows with or without the assumption of hydrostatic pressure (HP). Initially, the water surface and the DA velocity are estimated using a DA model by neglecting non-uniform velocity (NUV) and non-HP (NHP). Then, in the RANS model, the horizontal momentum and the continuity equations are solved for the horizontal and vertical velocity components, respectively, with the water surface as a fixed zero-pressure boundary. For the non-hydrostatic RANS model, the pressure Poisson equation is solved for NHP. A correction term is introduced in the Reynolds horizontal momentum equation for mass balance. Once the RANS model results are available, the DA model results are updated iteratively by incorporating the effects of NUV and NHP. The agreement between the model and experimental data is quite satisfactory along with an excellent computational efficiency. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.636636 [article] Modelling plane open-channel flows by coupled depth-averaged and RANS equations [texte imprimé] / Hasan Zobeyer, Auteur ; Peter Steffler, Auteur . - 2012 . - pp. 82-88.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 82-88
Mots-clés : Depth-averaged equation Non-hydrostatic pressure Non-uniform velocity Open-channel flow RANS equations Résumé : Herein, a coupled depth-averaged (DA) and Reynolds-averaged Navier–Stokes (RANS) model is developed for steady plane open-channel flows with or without the assumption of hydrostatic pressure (HP). Initially, the water surface and the DA velocity are estimated using a DA model by neglecting non-uniform velocity (NUV) and non-HP (NHP). Then, in the RANS model, the horizontal momentum and the continuity equations are solved for the horizontal and vertical velocity components, respectively, with the water surface as a fixed zero-pressure boundary. For the non-hydrostatic RANS model, the pressure Poisson equation is solved for NHP. A correction term is introduced in the Reynolds horizontal momentum equation for mass balance. Once the RANS model results are available, the DA model results are updated iteratively by incorporating the effects of NUV and NHP. The agreement between the model and experimental data is quite satisfactory along with an excellent computational efficiency. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.636636
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 89-97
Titre : Initial stage of two-dimensional dam-break waves: laboratory versus VOF Type de document : texte imprimé Auteurs : Mario Oertel, Auteur ; Daniel B. Bung, Auteur Année de publication : 2012 Article en page(s) : pp. 89-97 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Dam-break Drag force Numerical model Physical model PIV VOF Résumé : Since several decades, dam-break waves have been of main research interest. Mathematical approaches have been developed by analytical, physical and numerical models within the past 120 years. During the past 10 years, the number of research investigations has increased due to improved measurement techniques as well as significantly increased computer memories and performances. In this context, the present research deals with the initial stage of two-dimensional dam-break waves by comparing physical and numerical model results as well as analytical approaches. High-speed images and resulting particle image velocimetry calculations are thereby compared with the numerical volume-of-fluid (VOF) method, included in the commercial code FLOW-3D. Wave profiles and drag forces on placed obstacles are analysed in detail. Generally, a good agreement between the laboratory and VOF results is found. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.639981 [article] Initial stage of two-dimensional dam-break waves: laboratory versus VOF [texte imprimé] / Mario Oertel, Auteur ; Daniel B. Bung, Auteur . - 2012 . - pp. 89-97.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 89-97
Mots-clés : Dam-break Drag force Numerical model Physical model PIV VOF Résumé : Since several decades, dam-break waves have been of main research interest. Mathematical approaches have been developed by analytical, physical and numerical models within the past 120 years. During the past 10 years, the number of research investigations has increased due to improved measurement techniques as well as significantly increased computer memories and performances. In this context, the present research deals with the initial stage of two-dimensional dam-break waves by comparing physical and numerical model results as well as analytical approaches. High-speed images and resulting particle image velocimetry calculations are thereby compared with the numerical volume-of-fluid (VOF) method, included in the commercial code FLOW-3D. Wave profiles and drag forces on placed obstacles are analysed in detail. Generally, a good agreement between the laboratory and VOF results is found. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.639981
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 98-104
Titre : Numerical errors in discharge measurements using the KDP method Type de document : texte imprimé Auteurs : Ayaka Kashima, Auteur ; Lee, Pedro J., Auteur ; Roger Nokes, Auteur Année de publication : 2012 Article en page(s) : pp. 98-104 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Differential pressure Discharge measurement Prediction accuracy Transfer matrix Unsteady discharge Résumé : The kinetic differential pressure (KDP) method for measuring unsteady discharge in pressurized fluid conduits is introduced. The method utilizes two pressure measurements to estimate the unsteady discharge at the sampling rate of the pressure sensors. The technique is based on the linear approximation of the one-dimensional governing equations for transient flow. The application of the method is affected by two sources of error: the numerical error due to linear approximation of the one-dimensional governing equation and the modelling error representing the inability of the one-dimensional model to replicate the real transient behaviour. This research provides a first step in the verification of the KDP method by investigating the numerical error caused by the linear approximation. The numerical error is quantified as a function of the measurement location, system and signal characteristics. The method exhibits minor numerical errors if the system resonance is avoided. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.638211 [article] Numerical errors in discharge measurements using the KDP method [texte imprimé] / Ayaka Kashima, Auteur ; Lee, Pedro J., Auteur ; Roger Nokes, Auteur . - 2012 . - pp. 98-104.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 98-104
Mots-clés : Differential pressure Discharge measurement Prediction accuracy Transfer matrix Unsteady discharge Résumé : The kinetic differential pressure (KDP) method for measuring unsteady discharge in pressurized fluid conduits is introduced. The method utilizes two pressure measurements to estimate the unsteady discharge at the sampling rate of the pressure sensors. The technique is based on the linear approximation of the one-dimensional governing equations for transient flow. The application of the method is affected by two sources of error: the numerical error due to linear approximation of the one-dimensional governing equation and the modelling error representing the inability of the one-dimensional model to replicate the real transient behaviour. This research provides a first step in the verification of the KDP method by investigating the numerical error caused by the linear approximation. The numerical error is quantified as a function of the measurement location, system and signal characteristics. The method exhibits minor numerical errors if the system resonance is avoided. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.638211
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 105-113
Titre : Estimation of discharge in compound channels based on energy concept Type de document : texte imprimé Auteurs : Zhonghua Yang, Auteur ; Wei Gao, Auteur ; Wenxin Huai, Auteur Année de publication : 2012 Article en page(s) : pp. 105-113 Note générale : hydraulique Langues : Anglais (eng) Mots-clés : Compound channel Discharge Energy conversation Energy loss Overbank flow Résumé : A new model is developed to estimate the discharge capacity in straight, symmetric, compound open channels based on the energy concept. The energy loss and the transition mechanism in these channels are analysed based on mechanical analysis, in which the momentum transfer mechanism is taken into account as a product of the apparent shear stress. Four representative formulae of apparent shear stress are selected to validate the present model; the results indicate that the performance of the present model depends on our ability to accurately predict the apparent shear stress. The comparisons with experimental data indicate that the most appropriate apparent shear stress formula is that of Moreta and Martín-Vide; however, for the compound channels without roughness differences between the main channel and floodplains, Christodoulou's formula is still recommended for its simplicity. Comparisons with other models indicate that the present models are simple in manipulation and have a reasonable accuracy for engineering purposes. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.638212 [article] Estimation of discharge in compound channels based on energy concept [texte imprimé] / Zhonghua Yang, Auteur ; Wei Gao, Auteur ; Wenxin Huai, Auteur . - 2012 . - pp. 105-113.
hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 105-113
Mots-clés : Compound channel Discharge Energy conversation Energy loss Overbank flow Résumé : A new model is developed to estimate the discharge capacity in straight, symmetric, compound open channels based on the energy concept. The energy loss and the transition mechanism in these channels are analysed based on mechanical analysis, in which the momentum transfer mechanism is taken into account as a product of the apparent shear stress. Four representative formulae of apparent shear stress are selected to validate the present model; the results indicate that the performance of the present model depends on our ability to accurately predict the apparent shear stress. The comparisons with experimental data indicate that the most appropriate apparent shear stress formula is that of Moreta and Martín-Vide; however, for the compound channels without roughness differences between the main channel and floodplains, Christodoulou's formula is still recommended for its simplicity. Comparisons with other models indicate that the present models are simple in manipulation and have a reasonable accuracy for engineering purposes. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.638212
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 114-120
Titre : Discharge coefficients for free and submerged flow over Piano Key weirs Type de document : texte imprimé Auteurs : Abdorreza Kabiri-Samani, Auteur ; Amir Javaheri, Auteur Année de publication : 2012 Article en page(s) : pp. 114-120 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Discharge coefficient Free flow Model experimentation Piano key weir Submerged flow Résumé : A comprehensive experimental investigation was performed to better understand the effect of the weir geometry of a Piano Key weir (PKW) on the discharge coefficient for both free and submerged flow conditions. Experiments were conducted in a 12 m long, 0.4 m wide and 0.7 m deep rectangular glass-walled flume. The effects of the PKW geometry, including weir length and height, up- and downstream key widths as well as up- and downstream apex overhangs on the weir flow discharge coefficient were investigated, so that the governing weir head-discharge relationship resulted. In addition, on the basis of a comprehensive data set, practical discharge coefficient relations associated with the standard weir equation were proposed for both free and submerged flows over PKWs. The present correlations cover various types of PKWs. From the experimental data, optimum values of the primary dimensionless weir parameters result produce the maximum discharge efficiency. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.647888 [article] Discharge coefficients for free and submerged flow over Piano Key weirs [texte imprimé] / Abdorreza Kabiri-Samani, Auteur ; Amir Javaheri, Auteur . - 2012 . - pp. 114-120.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 114-120
Mots-clés : Discharge coefficient Free flow Model experimentation Piano key weir Submerged flow Résumé : A comprehensive experimental investigation was performed to better understand the effect of the weir geometry of a Piano Key weir (PKW) on the discharge coefficient for both free and submerged flow conditions. Experiments were conducted in a 12 m long, 0.4 m wide and 0.7 m deep rectangular glass-walled flume. The effects of the PKW geometry, including weir length and height, up- and downstream key widths as well as up- and downstream apex overhangs on the weir flow discharge coefficient were investigated, so that the governing weir head-discharge relationship resulted. In addition, on the basis of a comprehensive data set, practical discharge coefficient relations associated with the standard weir equation were proposed for both free and submerged flows over PKWs. The present correlations cover various types of PKWs. From the experimental data, optimum values of the primary dimensionless weir parameters result produce the maximum discharge efficiency. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.647888
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 121-128
Titre : Jet diffusion inside a confined chamber Type de document : texte imprimé Auteurs : G. Adriana Camino, Auteur ; David Z. Zhu, Auteur ; Nallamuthu Rajaratnam, Auteur Année de publication : 2012 Article en page(s) : pp. 121-128 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Confined jet Energy dissipation Hydraulics Jet diffusion Recirculating flow Résumé : Assessing the amount of energy dissipation that can be achieved by simple jet diffusion in a confined environment has considerable practical importance. Previous works on jets in confined enclosures have indicated that the entrainment of a recirculating fluid greatly enhances the dissipation of the inflow kinetic energy and reduces the length of the potential core. In the present experimental work, a vertical jet issuing into a rectangular chamber is investigated under two types of confinement and three locations of entry. Detailed velocity measurements for an eccentric jet are obtained to assess the evolution of the axial jet centreline velocity and the turbulent characteristics. These results are compared with classical jet behaviour and jets under other confined conditions. A method to predict the energy dissipation attained by jet diffusion in a confined chamber is also proposed. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.650423 [article] Jet diffusion inside a confined chamber [texte imprimé] / G. Adriana Camino, Auteur ; David Z. Zhu, Auteur ; Nallamuthu Rajaratnam, Auteur . - 2012 . - pp. 121-128.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 121-128
Mots-clés : Confined jet Energy dissipation Hydraulics Jet diffusion Recirculating flow Résumé : Assessing the amount of energy dissipation that can be achieved by simple jet diffusion in a confined environment has considerable practical importance. Previous works on jets in confined enclosures have indicated that the entrainment of a recirculating fluid greatly enhances the dissipation of the inflow kinetic energy and reduces the length of the potential core. In the present experimental work, a vertical jet issuing into a rectangular chamber is investigated under two types of confinement and three locations of entry. Detailed velocity measurements for an eccentric jet are obtained to assess the evolution of the axial jet centreline velocity and the turbulent characteristics. These results are compared with classical jet behaviour and jets under other confined conditions. A method to predict the energy dissipation attained by jet diffusion in a confined chamber is also proposed. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.650423
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 129-133
Titre : Study of velocity field at model sideweir using visualization method Type de document : texte imprimé Auteurs : Gorazd Novak, Auteur ; Franc Steinman, Auteur ; Matej Müller, Auteur Année de publication : 2012 Article en page(s) : pp. 129-133 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Laboratory experiment Model study Open channel flow Sideweir Velocity field Visualization Résumé : A visualization method was employed for accurate non-intrusive measurement of velocity fields at a physical model of a sharp-crested rectangular sideweir under subcritical flow. The experimental observation of velocity vectors at various horizontal planes over the entire width of the main channel confirms that the flow conditions at sideweir are non-uniform. The coefficients of non-uniform velocity distribution were in the range from 1 to 1.1. The present study focuses on the relation between the longitudinal components of the overflow velocities and the corresponding cross-sectional average velocities in the main channel, detailed as a function of flow depth and of location along the sideweir crest. For different sideweir geometries, these coefficients varied between 1 and 1.2. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.648766 [article] Study of velocity field at model sideweir using visualization method [texte imprimé] / Gorazd Novak, Auteur ; Franc Steinman, Auteur ; Matej Müller, Auteur . - 2012 . - pp. 129-133.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 129-133
Mots-clés : Laboratory experiment Model study Open channel flow Sideweir Velocity field Visualization Résumé : A visualization method was employed for accurate non-intrusive measurement of velocity fields at a physical model of a sharp-crested rectangular sideweir under subcritical flow. The experimental observation of velocity vectors at various horizontal planes over the entire width of the main channel confirms that the flow conditions at sideweir are non-uniform. The coefficients of non-uniform velocity distribution were in the range from 1 to 1.1. The present study focuses on the relation between the longitudinal components of the overflow velocities and the corresponding cross-sectional average velocities in the main channel, detailed as a function of flow depth and of location along the sideweir crest. For different sideweir geometries, these coefficients varied between 1 and 1.2. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.648766
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 134-137
Titre : Bubble plume modelling with new functional relationships Type de document : texte imprimé Auteurs : Iran E. Lima Neto, Auteur Année de publication : 2012 Article en page(s) : pp. 134-137 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bubble Entrainment Integral equation Plume Two-phase flow Résumé : In this study, a new parameterization is proposed to be incorporated into the classical integral model for bubble plumes. The virtual origin of the flow, the entrainment coefficient and the momentum amplification factor were obtained by adjusting the model to a wide range of experimental data. This allowed to generate functional relationships based on the gas discharge and the water depth. Model simulations using these novel relationships resulted in a better agreement with experimental data than other approaches for bubble plumes, notably for tests under shallow to intermediate water depths. Therefore, the present model is proposed as a simpler approach to predict the flow induced by bubble plumes for a large range of operational conditions. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.651278 [article] Bubble plume modelling with new functional relationships [texte imprimé] / Iran E. Lima Neto, Auteur . - 2012 . - pp. 134-137.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 134-137
Mots-clés : Bubble Entrainment Integral equation Plume Two-phase flow Résumé : In this study, a new parameterization is proposed to be incorporated into the classical integral model for bubble plumes. The virtual origin of the flow, the entrainment coefficient and the momentum amplification factor were obtained by adjusting the model to a wide range of experimental data. This allowed to generate functional relationships based on the gas discharge and the water depth. Model simulations using these novel relationships resulted in a better agreement with experimental data than other approaches for bubble plumes, notably for tests under shallow to intermediate water depths. Therefore, the present model is proposed as a simpler approach to predict the flow induced by bubble plumes for a large range of operational conditions. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.651278
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 138-141
Titre : Influence of riprap apron shape on spill-through abutments Type de document : texte imprimé Auteurs : Gonzalo Simarro, Auteur ; Sofia Civeira, Auteur ; António H. Cardoso, Auteur Année de publication : 2012 Article en page(s) : pp. 138-141 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Abutment Clear-water scour Experimentation Protection Riprap Scour Résumé : This technical note focuses on the plan geometry of riprap mattresses to protect spill-through abutments against local scour through edge failure. Two non-standard riprap apron geometries are experimentally studied. The performance of the new geometries is evaluated by comparing it with that of the standard design in terms of apron width and total riprap volume needed to guarantee stability. For comparatively short abutments, it is demonstrated that one of the new proposed geometries allows reductions between 15% and 25% in the total riprap volume without any increase in both design complexity and building difficulty. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.650422 [article] Influence of riprap apron shape on spill-through abutments [texte imprimé] / Gonzalo Simarro, Auteur ; Sofia Civeira, Auteur ; António H. Cardoso, Auteur . - 2012 . - pp. 138-141.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 50 N° 1 (Janvier/Février 2012) . - pp. 138-141
Mots-clés : Abutment Clear-water scour Experimentation Protection Riprap Scour Résumé : This technical note focuses on the plan geometry of riprap mattresses to protect spill-through abutments against local scour through edge failure. Two non-standard riprap apron geometries are experimentally studied. The performance of the new geometries is evaluated by comparing it with that of the standard design in terms of apron width and total riprap volume needed to guarantee stability. For comparatively short abutments, it is demonstrated that one of the new proposed geometries allows reductions between 15% and 25% in the total riprap volume without any increase in both design complexity and building difficulty. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.650422
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