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Marco Ellero - One of the best experts on this subject based on the ideXlab platform.
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Normal Lubrication Force between spherical particles immersed in a shear-thickening fluid
Physics of Fluids, 2018Co-Authors: Adolfo Vázquez-quesada, Norman J. Wagner, Marco ElleroAbstract:In this work, the inverse bi-viscous model [Vazquez-Quesada et al., “Planar channel flow of a discontinuous shear-thickening model fluid: Theory and simulation,” Phys. Fluids 29, 103104 (2017)] is used to describe a shear-thickening fluid. An analytical velocity profile in a planar Poiseuille flow is utilized to calculate an approximate solution to the generalized Lubrication Force between two close spheres interacting hydrodynamically in such a medium. This approximate analytical expression is compared to the exact numerical solution. The flow topology of the shear-thickening transition within the interparticle gap is also shown and discussed in relation to the behaviour of the Lubrication Force. The present result can allow in the future to perform numerical simulations of dense particle suspensions immersed in a shear-thickening matrix based on an effective Lubrication Force acting between pairwise interacting particles. This model may find additional values in representing experimental systems consisting of suspensions in shear thickening media, polymer coated suspensions, and industrial systems such as concrete.In this work, the inverse bi-viscous model [Vazquez-Quesada et al., “Planar channel flow of a discontinuous shear-thickening model fluid: Theory and simulation,” Phys. Fluids 29, 103104 (2017)] is used to describe a shear-thickening fluid. An analytical velocity profile in a planar Poiseuille flow is utilized to calculate an approximate solution to the generalized Lubrication Force between two close spheres interacting hydrodynamically in such a medium. This approximate analytical expression is compared to the exact numerical solution. The flow topology of the shear-thickening transition within the interparticle gap is also shown and discussed in relation to the behaviour of the Lubrication Force. The present result can allow in the future to perform numerical simulations of dense particle suspensions immersed in a shear-thickening matrix based on an effective Lubrication Force acting between pairwise interacting particles. This model may find additional values in representing experimental systems consist...
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analytical solution for the Lubrication Force between two spheres in a bi viscous fluid
Physics of Fluids, 2016Co-Authors: Adolfo Vazquezquesada, Marco ElleroAbstract:An analytical solution for the calculation of the normal Lubrication Force acting between two moving spheres embedded in a shear-thinning fluid represented by a bi-viscous model is provided. The resulting Force between the suspended spheres exhibits a consistent transition between the Newtonian constant-viscosity limits and it reduces to the well-known standard Newtonian Lubrication theory for viscosity-ratio approaching one. Effects of several physical parameters of the theory are analyzed under relevant physical conditions, i.e., for a prototypical case of two non-colloidal spheres immersed in a non-Newtonian fluid with rheology parameterized by a bi-viscosity model. Topological results for high/low-viscosity regions in the gap between spheres are also analyzed in detail showing a rich phenomenology. The presented model enables the extension of Lubrication dynamics for suspensions interacting with non-Newtonian matrices and provides a clean theoretical framework for new numerical computations of flow of...
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Analytical solution for the Lubrication Force between two spheres in a bi-viscous fluid
Physics of Fluids, 2016Co-Authors: Adolfo Vázquez-quesada, Marco ElleroAbstract:An analytical solution for the calculation of the normal Lubrication Force acting between two moving spheres embedded in a shear-thinning fluid represented by a bi-viscous model is provided. The resulting Force between the suspended spheres exhibits a consistent transition between the Newtonian constant-viscosity limits and it reduces to the well-known standard Newtonian Lubrication theory for viscosity-ratio approaching one. Effects of several physical parameters of the theory are analyzed under relevant physical conditions, i.e., for a prototypical case of two non-colloidal spheres immersed in a non-Newtonian fluid with rheology parameterized by a bi-viscosity model. Topological results for high/low-viscosity regions in the gap between spheres are also analyzed in detail showing a rich phenomenology. The presented model enables the extension of Lubrication dynamics for suspensions interacting with non-Newtonian matrices and provides a clean theoretical framework for new numerical computations of flow of dense complex particulate systems.
Laurent Lacaze - One of the best experts on this subject based on the ideXlab platform.
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Numerical Modeling of a Granular Collapse Immersed in a Viscous Fluid
Advances in Hydroinformatics, 2018Co-Authors: Edouard Izard, Laurent Lacaze, Thomas Bonometti, Annaïg PedronoAbstract:Numerical simulations can help to further understand particles-fluid flows which are encountered in many industrial and natural applications. An immersed boundary and a soft-sphere discrete element methods are coupled to resolve the fluid flow around moving non-deformable particles and to solve the Lagrangian motion of the particles, including grain–grain interactions, respectively. A Lubrication Force is added to the equation of the grains motion to properly capture rebound interactions in a fluid. An a priori simple configuration of gravity-driven grains-fluid mixture flows, namely, the unsteady collapse of a granular column in an incompressible Newtonian fluid, is investigated by three-dimensional simulations. The scale of the system is \({\mathcal{O}}\left( {10^{3} } \right)\) particles. In the present simulations, the collapse dynamics is controlled by the viscous time in agreement with the experimental classification of granular regimes in a fluid proposed by du Pont et al. Phys. Rev. Lett. 90, 044301 (2003). Good agreement is found with experiments of Rondon et al. Phys. Fluids, 23(7), 073301 (2011) regarding the final form of the granular deposit, which may be triangular or trapezoidal depending on aspect ratio and initial packing fraction. In addition, the fluid pressure at the bottom of the granular column, as well as the lengths of the granular deposits, measured in present simulations are in quantitative agreement with experiments. The phenomenon of pore pressure feedback is captured for the first time in simulation results.
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simulation of an avalanche in a fluid with a soft sphere immersed boundary method including a Lubrication Force
The Journal of Computational Multiphase Flows, 2014Co-Authors: Edouard Izard, Thomas Bonometti, Laurent LacazeAbstract:The present work aims at reproducing the local dynamics of a dense granular media evolving in a viscous fluid from the grain scale to that of thousands of grains, encountered in environmental multiphase flows. To this end a soft-sphere collision/immersed-boundary method is developed. The methods are validated alone through various standard configurations including static and dynamical situations. Then, simulations of binary wall-particle collisions in a fluid are performed for a wide range of Stokes number ranging in [10-1, 104]. Good agreement with available experimental data is found provided that a local Lubrication model is used. Finally, three- dimensional simulations of gravity/shear-driven dense granular flows in a viscous fluid are presented. The results open the way for a parametric study in the parameter space initial aspect ratio-initial packing.
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Direct numerical simulation of gravity-driven avalanches immersed in a viscous fluid
Bulletin of the American Physical Society, 2014Co-Authors: Thomas Bonometti, Edouard Izard, Laurent LacazeAbstract:This work deals with direct numerical simulations of sediment transport at the scale of O(10^3) grains. A soft-sphere discrete element method is coupled to an immersed boundary method in order to compute the flow around moving and colliding grains in an incompressible Newtonian fluid. A Lubrication Force is added for representing fluid-particles interaction near contact. The numerical method is shown to adequately reproduce the effective coefficient of restitution measured in experiments of the normal and oblique rebound of a grain on a wall. An analytical model is proposed and highlights the importance of the grain roughness and Stokes number on the rebound phenomenon. Three-dimensional configurations of gravity-driven dense granular flows in a fluid, namely the granular avalanche on an inclined plane and the collapse of a granular column, are performed. The granular flow regimes (viscous, inertial and dry) observed in experiments are identified as a function of the grain-to-fluid density ratio and the Stokes number. In particular, the simulations provide insights on the grain and fluid velocity profiles and Force balance in each regime. In the second case, results agree well with experiments and the pore pressure feedback is observed for the first time in direct numerical simulations.
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Modelling the dynamics of a sphere approaching and bouncing on a wall in a viscous fluid
Journal of Fluid Mechanics, 2014Co-Authors: Edouard Izard, Thomas Bonometti, Laurent LacazeAbstract:The canonical configuration of a solid particle bouncing on a wall in a viscous fluid is considered here, focusing on rough particles as encountered in most of the laboratory experiments or applications. In that case, the particle deformation is not expected to be significant prior to solid contact. An immersed boundary method (IBM) allowing the fluid flow around the solid particle to be numerically described is combined with a discrete element method (DEM) in order to numerically investigate the dynamics of the system. Particular attention is paid to modelling the Lubrication Force added in the discrete element method, which is not captured by the fluid solver at very small scale. Specifically, the proposed numerical model accounts for the surface roughness of real particles through an effective roughness length in the contact model, and considers that the time scale of the contact is small compared to that of the fluid. The present coupled method is shown to quantitatively reproduce available experimental data and in particular is in very good agreement with recent measurement of the dynamics of a particle approaching very close to a wall in the viscous regime St
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Simulation of an Avalanche in a Fluid with a Soft-Sphere/Immersed Boundary Method Including a Lubrication Force
The Journal of Computational Multiphase Flows, 2014Co-Authors: Edouard Izard, Thomas Bonometti, Laurent LacazeAbstract:The present work aims at reproducing the local dynamics of a dense granular media evolving in a viscous fluid from the grain scale to that of thousands of grains, encountered in environmental multiphase flows. To this end a soft-sphere collision/immersed-boundary method is developed. The methods are validated alone through various standard configurations including static and dynamical situations. Then, simulations of binary wall-particle collisions in a fluid are performed for a wide range of Stokes number ranging in [10-1, 104]. Good agreement with available experimental data is found provided that a local Lubrication model is used. Finally, three- dimensional simulations of gravity/shear-driven dense granular flows in a viscous fluid are presented. The results open the way for a parametric study in the parameter space initial aspect ratio-initial packing.
William A. Ducker - One of the best experts on this subject based on the ideXlab platform.
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In Situ control of gas flow by modification of gas-solid interactions.
Physical review letters, 2013Co-Authors: Dongjin Seo, William A. DuckerAbstract:The boundary condition for gas flow at the solid-gas interface can be altered by in situ control of the state of a thin film adsorbed to the solid. A monolayer of ocatadecyltrichlorosilane (OTS) reversibly undergoes a meltinglike transition. When the temperature of an OTS-coated particle and plate is moved through the range of OTS "melting" temperatures, there is a change in the Lubrication Force between the particle and plate in 1 atm of nitrogen gas. This change is interpreted in terms of a change in the flow of gas mediated by the slip length and tangential momentum accommodation coefficient (TMAC). There is a minimum in slip length (290 nm) at 18 °C, which corresponds to a maximum in TMAC (0.44). The slip length increases to 590 nm at 40 °C which corresponds to a TMAC of 0.25. We attribute the decrease in TMAC with increasing temperature to a decrease in roughness of the monolayer on melting, which allows a higher fraction of specular gas reflections, thereby conserving tangential gas momentum. The importance of this work is that it demonstrates the ability to control gas flow simply by altering the interface for fixed geometry and gas properties.
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Gas flow near a smooth plate.
Physical Review E, 2011Co-Authors: Adam P. Bowles, William A. DuckerAbstract:We examine gas flow adjacent to a molecularly smooth, solid, muscovite mica. The fluctuations in Force acting on a glass sphere as a function of proximity to a mica plate were measured in air and were used to obtain the damping. The damping was interpreted as a Lubrication Force. The measured damping as a function of separation in the slip-flow regime corresponds to a slip length of 480 ± 70 nm, which is equivalent to highly specular gas molecule collisions. A slip-flow model fits the data for separations as small as one mean free path.
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Effect of Molecularly-Thin Films on Lubrication Forces and Accommodation Coefficients in Air
The Journal of Physical Chemistry C, 2010Co-Authors: Christopher D. F. Honig, William A. DuckerAbstract:We show that a thin organic film has a significant effect on the Lubrication Force (damping) acting on a smooth sphere approaching a smooth flat plate in a gaseous environment. The Lubrication Forces were determined by the analysis of the width of a power spectrum density of the vibrations of an atomic Force microscope cantilever that is attached to the sphere and immersed in the gas at thermal equilibrium. Because the Lubrication Force is determined by the collisions of gas molecules with both the sphere and the plate, the Lubrication Force was used to determine the thermal accommodation coefficient of the gas on the solids. We find that clean glass surfaces in ambient air at ∼25 °C exhibit a slip length of 630 ± 90 nm per surface and a concomitant accommodation coefficient of 0.19, whereas a glass plate with a ∼1 nm organic film of trimethylsilane exhibits a slip length of 270 ± 90 nm and an accommodation coefficient of 0.43. If left in air for an extended period of time, the slip length on clean glass ...
Adolfo Vázquez-quesada - One of the best experts on this subject based on the ideXlab platform.
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Normal Lubrication Force between spherical particles immersed in a shear-thickening fluid
Physics of Fluids, 2018Co-Authors: Adolfo Vázquez-quesada, Norman J. Wagner, Marco ElleroAbstract:In this work, the inverse bi-viscous model [Vazquez-Quesada et al., “Planar channel flow of a discontinuous shear-thickening model fluid: Theory and simulation,” Phys. Fluids 29, 103104 (2017)] is used to describe a shear-thickening fluid. An analytical velocity profile in a planar Poiseuille flow is utilized to calculate an approximate solution to the generalized Lubrication Force between two close spheres interacting hydrodynamically in such a medium. This approximate analytical expression is compared to the exact numerical solution. The flow topology of the shear-thickening transition within the interparticle gap is also shown and discussed in relation to the behaviour of the Lubrication Force. The present result can allow in the future to perform numerical simulations of dense particle suspensions immersed in a shear-thickening matrix based on an effective Lubrication Force acting between pairwise interacting particles. This model may find additional values in representing experimental systems consisting of suspensions in shear thickening media, polymer coated suspensions, and industrial systems such as concrete.In this work, the inverse bi-viscous model [Vazquez-Quesada et al., “Planar channel flow of a discontinuous shear-thickening model fluid: Theory and simulation,” Phys. Fluids 29, 103104 (2017)] is used to describe a shear-thickening fluid. An analytical velocity profile in a planar Poiseuille flow is utilized to calculate an approximate solution to the generalized Lubrication Force between two close spheres interacting hydrodynamically in such a medium. This approximate analytical expression is compared to the exact numerical solution. The flow topology of the shear-thickening transition within the interparticle gap is also shown and discussed in relation to the behaviour of the Lubrication Force. The present result can allow in the future to perform numerical simulations of dense particle suspensions immersed in a shear-thickening matrix based on an effective Lubrication Force acting between pairwise interacting particles. This model may find additional values in representing experimental systems consist...
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Analytical solution for the Lubrication Force between two spheres in a bi-viscous fluid
Physics of Fluids, 2016Co-Authors: Adolfo Vázquez-quesada, Marco ElleroAbstract:An analytical solution for the calculation of the normal Lubrication Force acting between two moving spheres embedded in a shear-thinning fluid represented by a bi-viscous model is provided. The resulting Force between the suspended spheres exhibits a consistent transition between the Newtonian constant-viscosity limits and it reduces to the well-known standard Newtonian Lubrication theory for viscosity-ratio approaching one. Effects of several physical parameters of the theory are analyzed under relevant physical conditions, i.e., for a prototypical case of two non-colloidal spheres immersed in a non-Newtonian fluid with rheology parameterized by a bi-viscosity model. Topological results for high/low-viscosity regions in the gap between spheres are also analyzed in detail showing a rich phenomenology. The presented model enables the extension of Lubrication dynamics for suspensions interacting with non-Newtonian matrices and provides a clean theoretical framework for new numerical computations of flow of dense complex particulate systems.
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A multiblob approach to colloidal hydrodynamics with inherent Lubrication
The Journal of chemical physics, 2014Co-Authors: Adolfo Vázquez-quesada, Florencio Balboa Usabiaga, Rafael Delgado-buscalioniAbstract:This work presents an intermediate resolution model of the hydrodynamics of colloidal particles based on a mixed Eulerian-Lagrangian formulation. The particle is constructed with a small set of overlapping Peskin's Immersed Boundary kernels (blobs) which are held together by springs to build up a particle impenetrable core. Here, we used 12 blobs placed in the vertexes of an icosahedron with an extra one in its center. Although the particle surface is not explicitly resolved, we show that the short-distance hydrodynamic responses (flow profiles, translational and rotational mobilities, Lubrication, etc) agree with spherical colloids and provide consistent effective radii. A remarkable property of the present multiblob model is that it naturally presents a "divergent" Lubrication Force at finite inter-particle distance. This permits to resolve the large viscosity increase at dense colloidal volume fractions. The intermediate resolution model is able to recover highly non-trivial (many-body) hydrodynamics using small particles whose radii are similar to the grid size $h$ (in the range $[1.6-3.2]\,h$). Considering that the cost of the embedding fluid phase scales like the cube of the particle radius, this result brings about a significant computational speed-up. Our code Fluam works in Graphics Processor Units (GPU's) and uses Fast Fourier Transform for the Poisson solver, which further improves its efficiency.
Edouard Izard - One of the best experts on this subject based on the ideXlab platform.
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Numerical Modeling of a Granular Collapse Immersed in a Viscous Fluid
Advances in Hydroinformatics, 2018Co-Authors: Edouard Izard, Laurent Lacaze, Thomas Bonometti, Annaïg PedronoAbstract:Numerical simulations can help to further understand particles-fluid flows which are encountered in many industrial and natural applications. An immersed boundary and a soft-sphere discrete element methods are coupled to resolve the fluid flow around moving non-deformable particles and to solve the Lagrangian motion of the particles, including grain–grain interactions, respectively. A Lubrication Force is added to the equation of the grains motion to properly capture rebound interactions in a fluid. An a priori simple configuration of gravity-driven grains-fluid mixture flows, namely, the unsteady collapse of a granular column in an incompressible Newtonian fluid, is investigated by three-dimensional simulations. The scale of the system is \({\mathcal{O}}\left( {10^{3} } \right)\) particles. In the present simulations, the collapse dynamics is controlled by the viscous time in agreement with the experimental classification of granular regimes in a fluid proposed by du Pont et al. Phys. Rev. Lett. 90, 044301 (2003). Good agreement is found with experiments of Rondon et al. Phys. Fluids, 23(7), 073301 (2011) regarding the final form of the granular deposit, which may be triangular or trapezoidal depending on aspect ratio and initial packing fraction. In addition, the fluid pressure at the bottom of the granular column, as well as the lengths of the granular deposits, measured in present simulations are in quantitative agreement with experiments. The phenomenon of pore pressure feedback is captured for the first time in simulation results.
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simulation of an avalanche in a fluid with a soft sphere immersed boundary method including a Lubrication Force
The Journal of Computational Multiphase Flows, 2014Co-Authors: Edouard Izard, Thomas Bonometti, Laurent LacazeAbstract:The present work aims at reproducing the local dynamics of a dense granular media evolving in a viscous fluid from the grain scale to that of thousands of grains, encountered in environmental multiphase flows. To this end a soft-sphere collision/immersed-boundary method is developed. The methods are validated alone through various standard configurations including static and dynamical situations. Then, simulations of binary wall-particle collisions in a fluid are performed for a wide range of Stokes number ranging in [10-1, 104]. Good agreement with available experimental data is found provided that a local Lubrication model is used. Finally, three- dimensional simulations of gravity/shear-driven dense granular flows in a viscous fluid are presented. The results open the way for a parametric study in the parameter space initial aspect ratio-initial packing.
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Direct numerical simulation of gravity-driven avalanches immersed in a viscous fluid
Bulletin of the American Physical Society, 2014Co-Authors: Thomas Bonometti, Edouard Izard, Laurent LacazeAbstract:This work deals with direct numerical simulations of sediment transport at the scale of O(10^3) grains. A soft-sphere discrete element method is coupled to an immersed boundary method in order to compute the flow around moving and colliding grains in an incompressible Newtonian fluid. A Lubrication Force is added for representing fluid-particles interaction near contact. The numerical method is shown to adequately reproduce the effective coefficient of restitution measured in experiments of the normal and oblique rebound of a grain on a wall. An analytical model is proposed and highlights the importance of the grain roughness and Stokes number on the rebound phenomenon. Three-dimensional configurations of gravity-driven dense granular flows in a fluid, namely the granular avalanche on an inclined plane and the collapse of a granular column, are performed. The granular flow regimes (viscous, inertial and dry) observed in experiments are identified as a function of the grain-to-fluid density ratio and the Stokes number. In particular, the simulations provide insights on the grain and fluid velocity profiles and Force balance in each regime. In the second case, results agree well with experiments and the pore pressure feedback is observed for the first time in direct numerical simulations.
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Modelling the dynamics of a sphere approaching and bouncing on a wall in a viscous fluid
Journal of Fluid Mechanics, 2014Co-Authors: Edouard Izard, Thomas Bonometti, Laurent LacazeAbstract:The canonical configuration of a solid particle bouncing on a wall in a viscous fluid is considered here, focusing on rough particles as encountered in most of the laboratory experiments or applications. In that case, the particle deformation is not expected to be significant prior to solid contact. An immersed boundary method (IBM) allowing the fluid flow around the solid particle to be numerically described is combined with a discrete element method (DEM) in order to numerically investigate the dynamics of the system. Particular attention is paid to modelling the Lubrication Force added in the discrete element method, which is not captured by the fluid solver at very small scale. Specifically, the proposed numerical model accounts for the surface roughness of real particles through an effective roughness length in the contact model, and considers that the time scale of the contact is small compared to that of the fluid. The present coupled method is shown to quantitatively reproduce available experimental data and in particular is in very good agreement with recent measurement of the dynamics of a particle approaching very close to a wall in the viscous regime St
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Simulation of an Avalanche in a Fluid with a Soft-Sphere/Immersed Boundary Method Including a Lubrication Force
The Journal of Computational Multiphase Flows, 2014Co-Authors: Edouard Izard, Thomas Bonometti, Laurent LacazeAbstract:The present work aims at reproducing the local dynamics of a dense granular media evolving in a viscous fluid from the grain scale to that of thousands of grains, encountered in environmental multiphase flows. To this end a soft-sphere collision/immersed-boundary method is developed. The methods are validated alone through various standard configurations including static and dynamical situations. Then, simulations of binary wall-particle collisions in a fluid are performed for a wide range of Stokes number ranging in [10-1, 104]. Good agreement with available experimental data is found provided that a local Lubrication model is used. Finally, three- dimensional simulations of gravity/shear-driven dense granular flows in a viscous fluid are presented. The results open the way for a parametric study in the parameter space initial aspect ratio-initial packing.
