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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Fri, 24 May 2024 20:18:04 GMT2024-05-24T20:18:04ZWall effects on the transportation of a cylindrical particle in power-law fluids
http://hdl.handle.net/10985/8454
Wall effects on the transportation of a cylindrical particle in power-law fluids
DESPEYROUX, Antoine; AMBARI, Abdelhak; BEN RICHOU, Abderrahim
The present work deals with the numerical calculation of the Stokes-type drag undergone by a cylindrical particle perpendicularly to its axis in a power-law fluid. In unbounded medium, as all data are not available yet, we provide a numerical solution for the pseudoplastic fluid. Indeed, the Stokes-type solution exists because the Stokes’ paradox does not take place anymore. We show a high sensitivity of the solution to the confinement, and the appearance of the inertia in the proximity of the Newtonian case, where the Stokes’ paradox takes place. For unbounded medium, avoiding these traps, we show that the drag is zero for Newtonian and dilatant fluids. But in the bounded one, the Stokes-type regime is recovered for Newtonian and dilatant fluids. We give also a physical explanation of this effect which is due to the reduction of the hydrodynamic screen length, for pseudoplastic fluids. Once the solution of the unbounded medium has been obtained, we give a solution for the confined medium numerically and asymptotically. We also highlight the consequence of the confinement and the backflow on the settling velocity of a fiber perpendicularly to its axis in a slit. Using the dynamic mesh technique, we give the actual transportation velocity in a power-law “Poiseuille flow”, versus the confinement parameter and the fluidity index, induced by the hydrodynamic interactions.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/10985/84542011-01-01T00:00:00ZDESPEYROUX, AntoineAMBARI, AbdelhakBEN RICHOU, AbderrahimThe present work deals with the numerical calculation of the Stokes-type drag undergone by a cylindrical particle perpendicularly to its axis in a power-law fluid. In unbounded medium, as all data are not available yet, we provide a numerical solution for the pseudoplastic fluid. Indeed, the Stokes-type solution exists because the Stokes’ paradox does not take place anymore. We show a high sensitivity of the solution to the confinement, and the appearance of the inertia in the proximity of the Newtonian case, where the Stokes’ paradox takes place. For unbounded medium, avoiding these traps, we show that the drag is zero for Newtonian and dilatant fluids. But in the bounded one, the Stokes-type regime is recovered for Newtonian and dilatant fluids. We give also a physical explanation of this effect which is due to the reduction of the hydrodynamic screen length, for pseudoplastic fluids. Once the solution of the unbounded medium has been obtained, we give a solution for the confined medium numerically and asymptotically. We also highlight the consequence of the confinement and the backflow on the settling velocity of a fiber perpendicularly to its axis in a slit. Using the dynamic mesh technique, we give the actual transportation velocity in a power-law “Poiseuille flow”, versus the confinement parameter and the fluidity index, induced by the hydrodynamic interactions.The drainage of non-Newtonian fluids in the quasi-steady motion of a sphere towards a plane
http://hdl.handle.net/10985/8477
The drainage of non-Newtonian fluids in the quasi-steady motion of a sphere towards a plane
DESPEYROUX, Antoine; AMBARI, Abdelhak
In the lubrication limit, the time needed for the drainage of the liquid film between two particles or between particles and walls is of industrial importance, because it controls the dynamics and aggregation of nondilute suspensions. This problem is also of fundamental interest in the application of the dynamic surface force apparatus to nanorheology. Even if this problem has an exact solution in Newtonian fluid when the sphere moves steadily and slowly towards or away from a plane wall, this problem remains, to our knowledge, without any exact analytical solution in non-Newtonian fluids with negligible viscoelastic components. But Rodin, using the method of asymptotic expansions, gives an asymptotic solution to this problem in the lateral unbounded power-law fluid. Therefore, in this study, we give a numerical result using the dynamic mesh technique and an asymptotic analytical formula valid in the lubrication regime, for a fluidity index 0.5<n⩽1.8. The comparison between the two results confirms their mutual validity.
http://dx.doi.org/10.1007/s10404-011-0906-2
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/84772012-01-01T00:00:00ZDESPEYROUX, AntoineAMBARI, AbdelhakIn the lubrication limit, the time needed for the drainage of the liquid film between two particles or between particles and walls is of industrial importance, because it controls the dynamics and aggregation of nondilute suspensions. This problem is also of fundamental interest in the application of the dynamic surface force apparatus to nanorheology. Even if this problem has an exact solution in Newtonian fluid when the sphere moves steadily and slowly towards or away from a plane wall, this problem remains, to our knowledge, without any exact analytical solution in non-Newtonian fluids with negligible viscoelastic components. But Rodin, using the method of asymptotic expansions, gives an asymptotic solution to this problem in the lateral unbounded power-law fluid. Therefore, in this study, we give a numerical result using the dynamic mesh technique and an asymptotic analytical formula valid in the lubrication regime, for a fluidity index 0.5<n⩽1.8. The comparison between the two results confirms their mutual validity.Slow motion of a sphere towards a plane through confined non-Newtonian fluid
http://hdl.handle.net/10985/8481
Slow motion of a sphere towards a plane through confined non-Newtonian fluid
DESPEYROUX, Antoine; AMBARI, Abdelhak
The time needed for the contact of two spheres or a sphere with a rigid plane is mainly controlled by the hydrodynamic drainage of the film located in the gap as long as its thickness is out of range of the Van der Waals interactions. In fact, this time controls the dynamics of aggregation of concentrated dispersions. This fundamental problem has an exact solution in Newtonian fluid which has been used to confirm the validity of the numerical dynamic mesh method employed in this geometrically unsteady problem. Following this validation, we applied it to calculate the correction factor of the drag undergone by a sphere approaching a plane, at constant Reynolds number, in a cylindrical tube filled with a non-Newtonian fluid having negligible viscoelastic component and roughly behaving as a power-law fluid. After a justification for using this useful model, we studied the influence of the lateral confinement on the frontal correction factor of the drag. In the lubrication limit, we recall the asymptotic solution of Rodin to this problem in lateral unbounded power law fluid. The comparison of both asymptotical and numerical results confirms their validity. The results obtained in this study may find an application to Dynamic Surface Force Apparatus for nanorheology.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/10985/84812012-01-01T00:00:00ZDESPEYROUX, AntoineAMBARI, AbdelhakThe time needed for the contact of two spheres or a sphere with a rigid plane is mainly controlled by the hydrodynamic drainage of the film located in the gap as long as its thickness is out of range of the Van der Waals interactions. In fact, this time controls the dynamics of aggregation of concentrated dispersions. This fundamental problem has an exact solution in Newtonian fluid which has been used to confirm the validity of the numerical dynamic mesh method employed in this geometrically unsteady problem. Following this validation, we applied it to calculate the correction factor of the drag undergone by a sphere approaching a plane, at constant Reynolds number, in a cylindrical tube filled with a non-Newtonian fluid having negligible viscoelastic component and roughly behaving as a power-law fluid. After a justification for using this useful model, we studied the influence of the lateral confinement on the frontal correction factor of the drag. In the lubrication limit, we recall the asymptotic solution of Rodin to this problem in lateral unbounded power law fluid. The comparison of both asymptotical and numerical results confirms their validity. The results obtained in this study may find an application to Dynamic Surface Force Apparatus for nanorheology.Conséquences du confinement dans le transfert de chaleur sur une sphère dans un fluide non newtonien
http://hdl.handle.net/10985/6606
Conséquences du confinement dans le transfert de chaleur sur une sphère dans un fluide non newtonien
DESPEYROUX, Antoine; AMBARI, Abdelhak; BEN RICHOU, Abderrahim; CHAMPMARTIN, Stephane
Le phénomène de transfert de chaleur ou de masse sur une particule sphérique en situation d’interactions hydrodynamiques et thermiques ou massiques est d’un intérêt majeur pour de nombreux problèmes rencontrés dans les procédés industriels faisant intervenir des particules en suspension [1]. Nous avons contribué par ce travail à l’étude de l’influence du confinement sur les phénomènes de transfert en présence d’un fluide de type loi de puissance. La comparaison des résultats numériques avec les calculs asymptotiques effectués par nous-mêmes et ceux obtenus par Acrivos confirment la validité des calculs. Dans le cas des fluides non newtoniens, il apparaît que la rhéofluidification est favorable aux phénomènes de transfert contrairement au cas rhéoépaississant.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/10985/66062010-01-01T00:00:00ZDESPEYROUX, AntoineAMBARI, AbdelhakBEN RICHOU, AbderrahimCHAMPMARTIN, StephaneLe phénomène de transfert de chaleur ou de masse sur une particule sphérique en situation d’interactions hydrodynamiques et thermiques ou massiques est d’un intérêt majeur pour de nombreux problèmes rencontrés dans les procédés industriels faisant intervenir des particules en suspension [1]. Nous avons contribué par ce travail à l’étude de l’influence du confinement sur les phénomènes de transfert en présence d’un fluide de type loi de puissance. La comparaison des résultats numériques avec les calculs asymptotiques effectués par nous-mêmes et ceux obtenus par Acrivos confirment la validité des calculs. Dans le cas des fluides non newtoniens, il apparaît que la rhéofluidification est favorable aux phénomènes de transfert contrairement au cas rhéoépaississant.