Documents disponibles écrits par cet auteur

Pressure buildup mechanism in a textured inlet of a hydrodynamic contact / Samuel Cupillard in Transactions of the ASME . Journal of tribology, Vol. 130 n°2 (Mars/Avril 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 130 n°2 (Mars/Avril 2008) . - 10 p. Titre : Pressure buildup mechanism in a textured inlet of a hydrodynamic contact Type de document : texte imprimé Auteurs : Samuel Cupillard, Auteur ; Cervantes, Michel J., Auteur ; Sergei Glavatskih, Auteur Année de publication : 2008 Article en page(s) : 10 p. Note générale : Tribology Langues : Anglais (eng) Résumé : A flow analysis is carried out for an inclined slider bearing with the aim of showing the governing mechanism at conditions where an optimum in load carrying capacity is achieved. The effects of surface texture on pressure buildup and load carrying capacity are explained for a textured slider bearing geometry. Numerical simulations are performed for laminar, steady, and isothermal flows. The energy transferred to the fluid from the moving wall is converted into pressure in the initial part of the converging contact and into losses in the second part. The convergence ratio can be increased, in order to get the greatest pressure gradient, until the limiting value where flow recirculation begins to occur. The texture appears to achieve its maximum efficiency when its depth is such that the velocity profile is stretched at its maximum extent without incurring incoming recirculating flow. The wall profile shape controlling the velocity profile can be optimized for many hydrodynamic contacts. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1468026 [article] Pressure buildup mechanism in a textured inlet of a hydrodynamic contact [texte imprimé] / Samuel Cupillard, Auteur ; Cervantes, Michel J., Auteur ; Sergei Glavatskih, Auteur . - 2008 . - 10 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 130 n°2 (Mars/Avril 2008) . - 10 p. Résumé : A flow analysis is carried out for an inclined slider bearing with the aim of showing the governing mechanism at conditions where an optimum in load carrying capacity is achieved. The effects of surface texture on pressure buildup and load carrying capacity are explained for a textured slider bearing geometry. Numerical simulations are performed for laminar, steady, and isothermal flows. The energy transferred to the fluid from the moving wall is converted into pressure in the initial part of the converging contact and into losses in the second part. The convergence ratio can be increased, in order to get the greatest pressure gradient, until the limiting value where flow recirculation begins to occur. The texture appears to achieve its maximum efficiency when its depth is such that the velocity profile is stretched at its maximum extent without incurring incoming recirculating flow. The wall profile shape controlling the velocity profile can be optimized for many hydrodynamic contacts. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleid=1468026

Pulsating turbulent flow in a straight asymmetric diffuser / Cervantes, Michel J. in Journal of hydraulic research, Vol. 46 extra issue (2008) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 46 extra issue (2008) . - p. 112-128 Titre : Pulsating turbulent flow in a straight asymmetric diffuser Titre original : Ecoulement turbulent pulsé dans un diffuseur asymétrique droit Type de document : texte imprimé Auteurs : Cervantes, Michel J., Auteur ; Fredrik T. Engstrom, Auteur Article en page(s) : p. 112-128 Note générale : Hydraulique Résumé en Français Langues : Anglais (eng) Mots-clés : Unsteady  Turbulent  Boundary  Diffuser 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 : Pulsating turbulent flow is studied for four regimes: steady, quasi-steady, relaxation, and quasi-laminar in a rectangular straight asymmetric diffuser, a generic model of the diffuser found at the end of most Kaplan and Francis type hydropower turbines. The flow entering the diffuser is a developing duct flow at Reynolds number 20 000, based on mean streamwise velocity and hydraulic diameter. The time averaged velocity and turbulent quantities are not affected by the forced oscillation. The regimes prevail in the diffuser, but are shifted due to the decreasing friction velocity. The oscillating quantities are affected by the adverse pressure gradient in the same way as the time averaged quantities, but with a decreasing effect for higher forcing frequencies. The amplitude of the oscillating wall shear stress is found to be signicantly lower than the Stokes solution in the quasi-laminar regime. The regime is confirmed by the behaviour of several other quantities. The pressure recovery is found to be 30 % higher in the relaxation regime than in the other regimes. Results are compared with experiments in channels and turbulent boundary layers, with and without an adverse pressure gradient, and with large-eddy simulations. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.journalhydraulicresearch.com [article] Pulsating turbulent flow in a straight asymmetric diffuser = Ecoulement turbulent pulsé dans un diffuseur asymétrique droit [texte imprimé] / Cervantes, Michel J., Auteur ; Fredrik T. Engstrom, Auteur . - p. 112-128. Hydraulique Résumé en Français Langues : Anglais (eng) in Journal of hydraulic research > Vol. 46 extra issue (2008) . - p. 112-128 Mots-clés : Unsteady  Turbulent  Boundary  Diffuser 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 : Pulsating turbulent flow is studied for four regimes: steady, quasi-steady, relaxation, and quasi-laminar in a rectangular straight asymmetric diffuser, a generic model of the diffuser found at the end of most Kaplan and Francis type hydropower turbines. The flow entering the diffuser is a developing duct flow at Reynolds number 20 000, based on mean streamwise velocity and hydraulic diameter. The time averaged velocity and turbulent quantities are not affected by the forced oscillation. The regimes prevail in the diffuser, but are shifted due to the decreasing friction velocity. The oscillating quantities are affected by the adverse pressure gradient in the same way as the time averaged quantities, but with a decreasing effect for higher forcing frequencies. The amplitude of the oscillating wall shear stress is found to be signicantly lower than the Stokes solution in the quasi-laminar regime. The regime is confirmed by the behaviour of several other quantities. The pressure recovery is found to be 30 % higher in the relaxation regime than in the other regimes. Results are compared with experiments in channels and turbulent boundary layers, with and without an adverse pressure gradient, and with large-eddy simulations. DEWEY : 627 ISSN : 0022-1686 En ligne : http://www.journalhydraulicresearch.com

Unsteadiness and viscous losses in hydraulic turbines / Cervantes, Michel J. in Journal of hydraulic research, Vol. 44 N°2 (2006) 

Public ISBD [article]  in Journal of hydraulic research > Vol. 44 N°2 (2006) . - 249-258 p. Titre : Unsteadiness and viscous losses in hydraulic turbines Titre original : Instabilités et pertes visqueuses dans des turbines hydrauliques Type de document : texte imprimé Auteurs : Cervantes, Michel J., Auteur ; Gustavsson, L. Hakan, Auteur Article en page(s) : 249-258 p. Note générale : Hydraulique Langues : Anglais (eng) Mots-clés : Unsteadiness  Viscous  losses  Scale-up  formula  Unsteadiness  Pertes  visqueuses  Balance  vers  le  haut  de  formule 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 variation of the mechanical energy for the mean, oscillating and turbulent flows are considered. Their mean point out the contribution of the unsteadiness to the viscous losses and the turbulent production. A two-dimensional turbulent pulsating flow is investigated for different unsteady regimes to illustrate the effects of unsteadiness on the overall losses. La variation de l'énergie mécanique pour le moyen, l'oscillation et les écoulements turbulents sont considérés. Leur moyen précisent la contribution de l'unsteadiness aux pertes visqueuses et à la production turbulente. Un écoulement de palpitation turbulent bidimensionnel est étudié pour différents régimes instables pour illustrer les effets de l'unsteadiness sur les pertes totales. DEWEY : 627 ISSN : 0022-1686 RAMEAU : Turbines hydrauliques En ligne : michel.cervantes@ltu.se [article] Unsteadiness and viscous losses in hydraulic turbines = Instabilités et pertes visqueuses dans des turbines hydrauliques [texte imprimé] / Cervantes, Michel J., Auteur ; Gustavsson, L. Hakan, Auteur . - 249-258 p. Hydraulique Langues : Anglais (eng) in Journal of hydraulic research > Vol. 44 N°2 (2006) . - 249-258 p. Mots-clés : Unsteadiness  Viscous  losses  Scale-up  formula  Unsteadiness  Pertes  visqueuses  Balance  vers  le  haut  de  formule 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 variation of the mechanical energy for the mean, oscillating and turbulent flows are considered. Their mean point out the contribution of the unsteadiness to the viscous losses and the turbulent production. A two-dimensional turbulent pulsating flow is investigated for different unsteady regimes to illustrate the effects of unsteadiness on the overall losses. La variation de l'énergie mécanique pour le moyen, l'oscillation et les écoulements turbulents sont considérés. Leur moyen précisent la contribution de l'unsteadiness aux pertes visqueuses et à la production turbulente. Un écoulement de palpitation turbulent bidimensionnel est étudié pour différents régimes instables pour illustrer les effets de l'unsteadiness sur les pertes totales. DEWEY : 627 ISSN : 0022-1686 RAMEAU : Turbines hydrauliques En ligne : michel.cervantes@ltu.se