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Adjacent Fluid
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A. Mongruel – One of the best experts on this subject based on the ideXlab platform.

Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016CoAuthors: 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 micropillars, 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…

Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016CoAuthors: 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 micropillars, 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.

Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016CoAuthors: 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 micropillars, 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…

Squeeze flow between a sphere and a textured wall
Physics of Fluids, 2016CoAuthors: 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 micropillars, 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.

Signature of coalescence during scalar mixing in a Rankine vortex
arXiv: Fluid Dynamics, 2020CoAuthors: 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 mixinglimited reactive flows. The analysis is useful to understand scalar dispersion in vortical flow structures.

The impact of stretchingenhanced mixing and coalescence on reactivity in mixinglimited reactive flows
Physics of Fluids, 2020CoAuthors: Sabyasachi Sen, Joris Heyman, Tanguy Le Borgne, Prajwal Singh, Aditya BandopadhyayAbstract:We analyze the dynamics of solute mixing and reaction in a mixinglimited 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 stretchingenhanced diffusion in mixinglimited reactive flows.