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Détail de l'auteur
Auteur Junke Guo
Documents disponibles écrits par cet auteur
Affiner la rechercheMotion of spheres falling through fluids / Junke Guo in Journal of hydraulic research, Vol. 49 N° 1 (Janvier/Fevrier 2011)
in Journal of hydraulic research > Vol. 49 N° 1 (Janvier/Fevrier 2011) . - pp. 32-41
Titre : Motion of spheres falling through fluids Type de document : texte imprimé Auteurs : Junke Guo, Auteur Année de publication : 2011 Article en page(s) : pp. 32-41 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Added mass force Fluid-solid interaction Particle acceleration Powder technology Sphere drag 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 : Motion of spheres falling through fluids is a classic problem in fluid mechanics. The problem is solved for steady motion and other special cases such as for small and large Reynolds numbers, but not yet for transitional flow motion because of the complicated drag law. Recently, a series approximation for the transitional motion at zero initial velocity was proposed by applying a nonlinear perturbation method and Rubey's universal drag law to the Boussinesq-Basset-Oseen equation. This research presents a simple closed-form solution to the problem for arbitrary Reynolds numbers at nonzero initial velocity. The proposed solution is confirmed with experimental literature data and reproduces all well-known asymptotic values. The results can be directly used for particle size analysis in hydraulics laboratories; they may also help understanding the fluid-particle interactions in environmental engineering, meteorology, and powder technology.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.informaworld.com/smpp/content~db=all~content=a933339750~frm=titlelink [article] Motion of spheres falling through fluids [texte imprimé] / Junke Guo, Auteur . - 2011 . - pp. 32-41.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 49 N° 1 (Janvier/Fevrier 2011) . - pp. 32-41
Mots-clés : Added mass force Fluid-solid interaction Particle acceleration Powder technology Sphere drag 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 : Motion of spheres falling through fluids is a classic problem in fluid mechanics. The problem is solved for steady motion and other special cases such as for small and large Reynolds numbers, but not yet for transitional flow motion because of the complicated drag law. Recently, a series approximation for the transitional motion at zero initial velocity was proposed by applying a nonlinear perturbation method and Rubey's universal drag law to the Boussinesq-Basset-Oseen equation. This research presents a simple closed-form solution to the problem for arbitrary Reynolds numbers at nonzero initial velocity. The proposed solution is confirmed with experimental literature data and reproduces all well-known asymptotic values. The results can be directly used for particle size analysis in hydraulics laboratories; they may also help understanding the fluid-particle interactions in environmental engineering, meteorology, and powder technology.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.informaworld.com/smpp/content~db=all~content=a933339750~frm=titlelink
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. 49 N° 6 (Novembre/Décembre 2011) . - pp. 744-749
Titre : Time-dependent clear-water scour for submerged bridge flows Type de document : texte imprimé Auteurs : Junke Guo, Auteur Année de publication : 2012 Article en page(s) : pp. 744-749 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bridge scour Clear-water scour Pressure flow Real-time monitoring Submerged flow Time-dependent scour 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 : The current design of bridge foundations based on equilibrium scour depths is much larger than the real maximum scour depth since peak flood periods are often too short to reach equilibrium conditions. Based on a tested hypothesis on the time rate of scour, this research presents a power-exponential equation for the time-dependent clear-water scour depth including a nonzero initial condition for submerged bridge flows. For zero initial conditions, the proposed equation is reduced to a log or power law during the initial phase and an exponential decay near the equilibrium condition. The proposed equation reduces design depths according to design flows and their peak periods, translating into significant savings in the construction of bridge foundations. With a real-time monitoring system, the proposed equation also predicts time-series scour depths during floods, helping bridge managers formulate timely corrective strategies.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.616364 [article] Time-dependent clear-water scour for submerged bridge flows [texte imprimé] / Junke Guo, Auteur . - 2012 . - pp. 744-749.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 49 N° 6 (Novembre/Décembre 2011) . - pp. 744-749
Mots-clés : Bridge scour Clear-water scour Pressure flow Real-time monitoring Submerged flow Time-dependent scour 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 : The current design of bridge foundations based on equilibrium scour depths is much larger than the real maximum scour depth since peak flood periods are often too short to reach equilibrium conditions. Based on a tested hypothesis on the time rate of scour, this research presents a power-exponential equation for the time-dependent clear-water scour depth including a nonzero initial condition for submerged bridge flows. For zero initial conditions, the proposed equation is reduced to a log or power law during the initial phase and an exponential decay near the equilibrium condition. The proposed equation reduces design depths according to design flows and their peak periods, translating into significant savings in the construction of bridge foundations. With a real-time monitoring system, the proposed equation also predicts time-series scour depths during floods, helping bridge managers formulate timely corrective strategies.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.616364
in Journal of hydraulic research > Vol. 49 N° 4 (Juillet/Août 2011) . - pp 424-436
Titre : Wave–current interaction at an angle. 1, Experiment Type de document : texte imprimé Auteurs : Pradeep C. Fernando, Auteur ; Junke Guo, Auteur ; Pengzhi Lin, Auteur Année de publication : 2011 Article en page(s) : pp 424-436 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bed roughness Bed shear stress Theoretical model Velocity distribution Wave–current interaction 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 : This research presents an experimental study in a spatial wave basin for nonlinear interaction of regular waves with a perpendicular shear current over a movable bed. Detailed measurements were collected for current velocity profiles under different conditions, from which the bed shear stress and apparent roughness heights were determined. These combined with the measured velocities were used to validate theoretical models for wave–current interaction at an angle. It is found that for small wave heights all models agree well with the measured mean current velocities in the combined flow, while for larger wave heights only two models are reasonably close to the measurements for current velocities. For very large waves none of the models adequately describes the near-surface current velocities, which deviate significantly from the log-law. For the bed shear stress and the apparent roughness, only one model describes the measured data well.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2010.547036 [article] Wave–current interaction at an angle. 1, Experiment [texte imprimé] / Pradeep C. Fernando, Auteur ; Junke Guo, Auteur ; Pengzhi Lin, Auteur . - 2011 . - pp 424-436.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 49 N° 4 (Juillet/Août 2011) . - pp 424-436
Mots-clés : Bed roughness Bed shear stress Theoretical model Velocity distribution Wave–current interaction 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 : This research presents an experimental study in a spatial wave basin for nonlinear interaction of regular waves with a perpendicular shear current over a movable bed. Detailed measurements were collected for current velocity profiles under different conditions, from which the bed shear stress and apparent roughness heights were determined. These combined with the measured velocities were used to validate theoretical models for wave–current interaction at an angle. It is found that for small wave heights all models agree well with the measured mean current velocities in the combined flow, while for larger wave heights only two models are reasonably close to the measurements for current velocities. For very large waves none of the models adequately describes the near-surface current velocities, which deviate significantly from the log-law. For the bed shear stress and the apparent roughness, only one model describes the measured data well.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2010.547036
in Journal of hydraulic research > Vol. 49 N° 4 (Juillet/Août 2011) . - pp. 437-449
Titre : Wave–current interaction at an angle. 2, Theory Type de document : texte imprimé Auteurs : Pradeep C. Fernando, Auteur ; Pengzhi Lin, Auteur ; Junke Guo, Auteur Année de publication : 2011 Article en page(s) : pp. 437-449 Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Bed roughness Bed shear stress Theoretical model Velocity distribution Wave–current interaction 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 : A theoretical model is presented to describe the current velocity within and outside a wave–current boundary layer and to quantify the associated bed shear stresses for wave–current interaction at an arbitrary angle. The model assumes that the wave-induced bed shear stress in the combined flow varies sinusoidally with time while the current-induced bed shear stress follows an eddy viscosity concept. The computational procedure is given for both depth-averaged and reference-point current-based computations. Unlike other analytical models proposing different coefficients for different problems, the present model uses the same set of equations and coefficients to describe wave–current flows at any angle under any flow regime. This model agrees better with both field measurements and laboratory data than existing theoretical models. The model indicates that the wave–current interaction angle is not significant for wave–current flow properties.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.574388 [article] Wave–current interaction at an angle. 2, Theory [texte imprimé] / Pradeep C. Fernando, Auteur ; Pengzhi Lin, Auteur ; Junke Guo, Auteur . - 2011 . - pp. 437-449.
Hydraulique
Langues : Anglais (eng)
in Journal of hydraulic research > Vol. 49 N° 4 (Juillet/Août 2011) . - pp. 437-449
Mots-clés : Bed roughness Bed shear stress Theoretical model Velocity distribution Wave–current interaction 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 : A theoretical model is presented to describe the current velocity within and outside a wave–current boundary layer and to quantify the associated bed shear stresses for wave–current interaction at an arbitrary angle. The model assumes that the wave-induced bed shear stress in the combined flow varies sinusoidally with time while the current-induced bed shear stress follows an eddy viscosity concept. The computational procedure is given for both depth-averaged and reference-point current-based computations. Unlike other analytical models proposing different coefficients for different problems, the present model uses the same set of equations and coefficients to describe wave–current flows at any angle under any flow regime. This model agrees better with both field measurements and laboratory data than existing theoretical models. The model indicates that the wave–current interaction angle is not significant for wave–current flow properties.
DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.tandfonline.com/doi/abs/10.1080/00221686.2011.574388
