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A continuum description of dense granular lubrication flow / John Tichy in Transactions of the ASME . Journal of tribology, Vol. 130 n°3 (Juillet 2008) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 130 n°3 (Juillet 2008) . - 8 p. Titre : A continuum description of dense granular lubrication flow Type de document : texte imprimé Auteurs : John Tichy, Auteur ; Yves Berthier, Auteur ; Ivan Iordanoff, Auteur Année de publication : 2008 Article en page(s) : 8 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Flow  (Dynamics)  Lubrication  Particulate  matter  Shear  (Mechanics)  Equations  Stress  Gravity  (Force)  Force  Engineering  simulation Résumé : The present paper applies a recent continuum theory due to Aranson and Tsimring (2002, “Continuum Theory of Partially Fluidized Granular Flows ,” Phys. Rev. E, 65, p. 061303) for the dense granular flow of particles in sustained contact to lubrication flows. Such third body granular flow may apply to some solid lubrication mechanisms. The continuum theory is unique in that it addresses solidlike behavior and the transition to fully fluidized behavior. The continuum studies are complemented by a discrete particle dynamics model of Iordanoff (2005, “Numerical Study of a Thin Layer of Cohesive Particles Under Plane Shearing ,” Powder Technol., 159, pp. 46–54). Three problems are treated: (1) flow due to the gravity of a layer of granular material down an inclined plane, (2) simple shear flow of a layer confined between sliding parallel surfaces, and (3) lubrication flow of a layer confined between a curved surface and a sliding plane. The perspective of this paper is that a continuum model will be more useful than a discrete model in engineering design of solid lubrication systems for the foreseeable future. In the inclined plane problem, the discrete simulations are used to provide material property parameters to the continuum model. In the simple shear problem, for validation, predictions of the continuum model are compared to those of the discrete element computer simulations. Finally, the continuum theory is applied to a more complex lubrication flow. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleID=1468057 [article] A continuum description of dense granular lubrication flow [texte imprimé] / John Tichy, Auteur ; Yves Berthier, Auteur ; Ivan Iordanoff, Auteur . - 2008 . - 8 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 130 n°3 (Juillet 2008) . - 8 p. Mots-clés : Flow  (Dynamics)  Lubrication  Particulate  matter  Shear  (Mechanics)  Equations  Stress  Gravity  (Force)  Force  Engineering  simulation Résumé : The present paper applies a recent continuum theory due to Aranson and Tsimring (2002, “Continuum Theory of Partially Fluidized Granular Flows ,” Phys. Rev. E, 65, p. 061303) for the dense granular flow of particles in sustained contact to lubrication flows. Such third body granular flow may apply to some solid lubrication mechanisms. The continuum theory is unique in that it addresses solidlike behavior and the transition to fully fluidized behavior. The continuum studies are complemented by a discrete particle dynamics model of Iordanoff (2005, “Numerical Study of a Thin Layer of Cohesive Particles Under Plane Shearing ,” Powder Technol., 159, pp. 46–54). Three problems are treated: (1) flow due to the gravity of a layer of granular material down an inclined plane, (2) simple shear flow of a layer confined between sliding parallel surfaces, and (3) lubrication flow of a layer confined between a curved surface and a sliding plane. The perspective of this paper is that a continuum model will be more useful than a discrete model in engineering design of solid lubrication systems for the foreseeable future. In the inclined plane problem, the discrete simulations are used to provide material property parameters to the continuum model. In the simple shear problem, for validation, predictions of the continuum model are compared to those of the discrete element computer simulations. Finally, the continuum theory is applied to a more complex lubrication flow. En ligne : http://tribology.asmedigitalcollection.asme.org/article.aspx?articleID=1468057

On squeeze film damping in microsystems / Victor Marrero in Transactions of the ASME . Journal of tribology, Vol. 132 N° 3 (Juillet 2010) 

Public ISBD [article]  in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Titre : On squeeze film damping in microsystems Type de document : texte imprimé Auteurs : Victor Marrero, Auteur ; Diana-Andra Borca-Tasciuc, Auteur ; John Tichy, Auteur Année de publication : 2011 Article en page(s) : 06 p. Note générale : Tribology Langues : Anglais (eng) Mots-clés : Compressibility  Compressible  flow  Liquid  films  Lubrication  Micromechanical  devices Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Classical hydrodynamic lubrication theory has been one of the most successful and widely used theories in all of engineering and applied science. This theory predicts that the force resisting the squeezing of a fluid between two parallel plates is inversely proportional to the cube of the fluid thickness. However, recent reports on liquid squeeze film damping in microsystems appear to indicate that experimentally measured damping force is proportional to the inverse of the fluid thickness to the first power—a large fundamental discrepancy from classical theory. This paper investigates potential limitations of lubrication theory in microsystems by theoretical and computational methods. The governing equations for a Newtonian incompressible fluid are solved subject to two-dimensional, parallel surface squeezing by an open-source computational fluid dynamics program called parallel hierarchic adaptive stabilized transient analysis (PHASTA), and by a classical similarity solution technique. At low convective Reynolds numbers, the damping force is determined as a function of the ratio of a reference film thickness H to a reference direction B along the film. Good agreement with classical lubrication theory is found for aspect ratios H/B as high as 1 despite the fact that lubrication theory requires that this ratio be “small.” A similarity analysis shows that when instantaneous convective Reynolds number is of order 10–100 (a range present in experiment), calculated damping deviates significantly from lubrication theory. This suggests that nonlinearity associated with high Reynolds numbers could explain the experimentally observed discrepancy in damping force. Dynamic analysis of beams undergoing small vibrations in the presence of a liquid medium further supports this finding. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...] [article] On squeeze film damping in microsystems [texte imprimé] / Victor Marrero, Auteur ; Diana-Andra Borca-Tasciuc, Auteur ; John Tichy, Auteur . - 2011 . - 06 p. Tribology Langues : Anglais (eng) in Transactions of the ASME . Journal of tribology > Vol. 132 N° 3 (Juillet 2010) . - 06 p. Mots-clés : Compressibility  Compressible  flow  Liquid  films  Lubrication  Micromechanical  devices Index. décimale : 621.5 Energie pneumatique. Machinerie et outils. Réfrigération Résumé : Classical hydrodynamic lubrication theory has been one of the most successful and widely used theories in all of engineering and applied science. This theory predicts that the force resisting the squeezing of a fluid between two parallel plates is inversely proportional to the cube of the fluid thickness. However, recent reports on liquid squeeze film damping in microsystems appear to indicate that experimentally measured damping force is proportional to the inverse of the fluid thickness to the first power—a large fundamental discrepancy from classical theory. This paper investigates potential limitations of lubrication theory in microsystems by theoretical and computational methods. The governing equations for a Newtonian incompressible fluid are solved subject to two-dimensional, parallel surface squeezing by an open-source computational fluid dynamics program called parallel hierarchic adaptive stabilized transient analysis (PHASTA), and by a classical similarity solution technique. At low convective Reynolds numbers, the damping force is determined as a function of the ratio of a reference film thickness H to a reference direction B along the film. Good agreement with classical lubrication theory is found for aspect ratios H/B as high as 1 despite the fact that lubrication theory requires that this ratio be “small.” A similarity analysis shows that when instantaneous convective Reynolds number is of order 10–100 (a range present in experiment), calculated damping deviates significantly from lubrication theory. This suggests that nonlinearity associated with high Reynolds numbers could explain the experimentally observed discrepancy in damping force. Dynamic analysis of beams undergoing small vibrations in the presence of a liquid medium further supports this finding. DEWEY : 621.5 ISSN : 0742-4787 En ligne : http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JOTRE900013 [...]