The Experts below are selected from a list of 18624 Experts worldwide ranked by ideXlab platform
A. Mongruel - One of the best experts on this subject based on the ideXlab platform.
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Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016Co-Authors: Thibault Chastel, A. MongruelAbstract:The motion of a millimetric sphere, translating in a viscous Fluid towards a wettable textured wall, is investigated experimentally. The textures consist of square arrays of cylindrical or square micro-pillars, the height, width, and spacing of which are varied, keeping the periodicity small compared to the sphere radius. An interferometric device is used to measure the sphere vertical displacement, for distances between the sphere and the base of the pillars smaller than 0.1 sphere radius, and with a resolution of 200 nm. At a given distance from the top of the pillars, the sphere velocity is found to be significantly larger than the corresponding velocity for a smooth solid wall. A squeeze flow model of two Adjacent Fluid layers is developed in the lubrication approximation, one Fluid layer having an effective viscosity that reflects the viscous dissipation through the array of pillars. The pressure field in the gap between the sphere and the textured surface is then used to obtain the drag force on the...
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Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016Co-Authors: Thibault Chastel, A. MongruelAbstract:The motion of a millimetric sphere, translating in a viscous Fluid towards a wettable textured wall, is investigated experimentally. The textures consist of square arrays of cylindrical or square micro-pillars, the height, width and spacing of which are varied, keeping the periodicity small compared to the sphere radius. An interferometric device is used to measure the sphere vertical displacement, for distances between the sphere and the base of the pillars smaller than 0.1 sphere radius, and with a resolution of 200 nm. At a given distance from the top of the pillars, the sphere velocity is found to be significantly larger than the corresponding velocity for a smooth solid wall. A squeeze flow model of two Adjacent Fluid layers is developed in the lubrication approximation, one Fluid layer having an effective viscosity that reflects the viscous dissipation through the array of pillars. The pressure field in the gap between the sphere and the textured surface is then used to obtain the drag force on the sphere and hence its velocity. Adjustment of the model to the velocity measurements yields the effective viscosity for a given texture. Finally, a correlation between the effective viscosity and the geometry of the pillar array is proposed.
Thibault Chastel - One of the best experts on this subject based on the ideXlab platform.
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Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016Co-Authors: Thibault Chastel, A. MongruelAbstract:The motion of a millimetric sphere, translating in a viscous Fluid towards a wettable textured wall, is investigated experimentally. The textures consist of square arrays of cylindrical or square micro-pillars, the height, width, and spacing of which are varied, keeping the periodicity small compared to the sphere radius. An interferometric device is used to measure the sphere vertical displacement, for distances between the sphere and the base of the pillars smaller than 0.1 sphere radius, and with a resolution of 200 nm. At a given distance from the top of the pillars, the sphere velocity is found to be significantly larger than the corresponding velocity for a smooth solid wall. A squeeze flow model of two Adjacent Fluid layers is developed in the lubrication approximation, one Fluid layer having an effective viscosity that reflects the viscous dissipation through the array of pillars. The pressure field in the gap between the sphere and the textured surface is then used to obtain the drag force on the...
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Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016Co-Authors: Thibault Chastel, A. MongruelAbstract:The motion of a millimetric sphere, translating in a viscous Fluid towards a wettable textured wall, is investigated experimentally. The textures consist of square arrays of cylindrical or square micro-pillars, the height, width and spacing of which are varied, keeping the periodicity small compared to the sphere radius. An interferometric device is used to measure the sphere vertical displacement, for distances between the sphere and the base of the pillars smaller than 0.1 sphere radius, and with a resolution of 200 nm. At a given distance from the top of the pillars, the sphere velocity is found to be significantly larger than the corresponding velocity for a smooth solid wall. A squeeze flow model of two Adjacent Fluid layers is developed in the lubrication approximation, one Fluid layer having an effective viscosity that reflects the viscous dissipation through the array of pillars. The pressure field in the gap between the sphere and the textured surface is then used to obtain the drag force on the sphere and hence its velocity. Adjustment of the model to the velocity measurements yields the effective viscosity for a given texture. Finally, a correlation between the effective viscosity and the geometry of the pillar array is proposed.
Aditya Bandopadhyay - One of the best experts on this subject based on the ideXlab platform.
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Signature of coalescence during scalar mixing in a Rankine vortex
arXiv: Fluid Dynamics, 2020Co-Authors: Sabyasachi Sen, Prajwal, Joris Heyman, Tanguy Le Borgne, Aditya BandopadhyayAbstract:We analyze the dynamics of solute mixing in a vortex flow. The transport of a passive tracer is considered in a Rankine vortex. The action of a shear flow, in general, is to achieve stretching of Fluid elements. A vortex flow exhibits stretching and folding of Fluid elements in a way which brings Adjacent Fluid elements closer every turn. A strong stretching along the direction of rotation is accompanied by a concomitant thinning in the radial direction leading to a strong diffusive flux which may cause material from neighbouring regions of the mixing interface to aggregate. Through a Lagrangian concentration evolution technique, the diffusive strip method, we obtain the concentration field and pinpoint the signature of coalescence of two neighbouring concentration regions by analyzing the concentration distribution profiles. We link coalescence with reactivity for mixing-limited reactive flows. The analysis is useful to understand scalar dispersion in vortical flow structures.
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The impact of stretching-enhanced mixing and coalescence on reactivity in mixing-limited reactive flows
Physics of Fluids, 2020Co-Authors: Sabyasachi Sen, Joris Heyman, Tanguy Le Borgne, Prajwal Singh, Aditya BandopadhyayAbstract:We analyze the dynamics of solute mixing and reaction in a mixing-limited reactive flow by considering the transport of a tracer in a linear shear flow and in a Rankine vortex. The action of a shear flow, in general, achieves stretching of Fluid elements due to the heterogeneous nature of the flow. A vortex flow exhibits not only stretching but also folding of Fluid elements in a way that brings Adjacent Fluid elements closer at every turn. A strong stretching along the tangential direction is accompanied by a concomitant thinning in the radial direction leading to a strong diffusive flux, which may cause the material from neighboring regions of the mixing interface to aggregate. Through a Lagrangian concentration evolution technique, the diffusive strip method, we obtain the concentration field and pinpoint the signature of coalescence of two neighboring concentration regions by analyzing the concentration distribution profiles. The role of substrate deformation on the reaction kinetics of a classical heterogeneous chemical reaction is also studied where we derive analytical expressions for the coupling between the rate of product formation and the Peclet number in different time limits. Finally, the impact of coalescence on reaction rates is studied for a Rankine vortex, a result that holds important implications for simple bimolecular reactions. This analysis is useful to understand scalar dispersion in vortical flow structures and the consequences of stretching-enhanced diffusion in mixing-limited reactive flows.
Sabyasachi Sen - One of the best experts on this subject based on the ideXlab platform.
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Signature of coalescence during scalar mixing in a Rankine vortex
arXiv: Fluid Dynamics, 2020Co-Authors: Sabyasachi Sen, Prajwal, Joris Heyman, Tanguy Le Borgne, Aditya BandopadhyayAbstract:We analyze the dynamics of solute mixing in a vortex flow. The transport of a passive tracer is considered in a Rankine vortex. The action of a shear flow, in general, is to achieve stretching of Fluid elements. A vortex flow exhibits stretching and folding of Fluid elements in a way which brings Adjacent Fluid elements closer every turn. A strong stretching along the direction of rotation is accompanied by a concomitant thinning in the radial direction leading to a strong diffusive flux which may cause material from neighbouring regions of the mixing interface to aggregate. Through a Lagrangian concentration evolution technique, the diffusive strip method, we obtain the concentration field and pinpoint the signature of coalescence of two neighbouring concentration regions by analyzing the concentration distribution profiles. We link coalescence with reactivity for mixing-limited reactive flows. The analysis is useful to understand scalar dispersion in vortical flow structures.
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The impact of stretching-enhanced mixing and coalescence on reactivity in mixing-limited reactive flows
Physics of Fluids, 2020Co-Authors: Sabyasachi Sen, Joris Heyman, Tanguy Le Borgne, Prajwal Singh, Aditya BandopadhyayAbstract:We analyze the dynamics of solute mixing and reaction in a mixing-limited reactive flow by considering the transport of a tracer in a linear shear flow and in a Rankine vortex. The action of a shear flow, in general, achieves stretching of Fluid elements due to the heterogeneous nature of the flow. A vortex flow exhibits not only stretching but also folding of Fluid elements in a way that brings Adjacent Fluid elements closer at every turn. A strong stretching along the tangential direction is accompanied by a concomitant thinning in the radial direction leading to a strong diffusive flux, which may cause the material from neighboring regions of the mixing interface to aggregate. Through a Lagrangian concentration evolution technique, the diffusive strip method, we obtain the concentration field and pinpoint the signature of coalescence of two neighboring concentration regions by analyzing the concentration distribution profiles. The role of substrate deformation on the reaction kinetics of a classical heterogeneous chemical reaction is also studied where we derive analytical expressions for the coupling between the rate of product formation and the Peclet number in different time limits. Finally, the impact of coalescence on reaction rates is studied for a Rankine vortex, a result that holds important implications for simple bimolecular reactions. This analysis is useful to understand scalar dispersion in vortical flow structures and the consequences of stretching-enhanced diffusion in mixing-limited reactive flows.
Eckehard Specht - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer in indirect heated rotary drums filled with monodisperse spheres: Comparison of experiments with DEM simulations
Powder Technology, 2015Co-Authors: H. Komossa, Siegmar Wirtz, Viktor Scherer, Fabian Herz, Eckehard SpechtAbstract:Abstract Numerical simulations with the discrete element method (DEM) and corresponding experimental investigations were carried out to understand and to quantify the heat transfer in indirect heated rotating drums. Monodisperse glass spheres (diameter 2 mm) were used and the bulk movement was kept within the rolling motion mode (rotational speed between 1 and 9 rpm). The focus is on the heat transfer between the covered wall and the particles in contact with this wall, as well as between the particles on the free bed surface and the Adjacent Fluid. Radiative heat transfer has been neglected due to the low maximum temperature within the system (474 K). Effective heat transfer coefficients for the heat fluxes mentioned were derived from the DEM simulations, considering the actual particle velocities on the free bed surface and on the wall. The particle movement and the heat transfer resulting from the simulations show good agreement with the experiments in general and thus allow the calculation of the effective heat transfer coefficients for the range of parameters considered in the current study.
