Wall effects on a rotating sphere

Liu, Qianlong; Prosperetti, Andréa

doi:10.1017/s002211201000128x

Cited by 99 publications

(97 citation statements)

References 43 publications

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“…In order to increase the accuracy of the method, in this work the part of the flow domain containing particles was discretized with a grid finer by a factor of 2 in each direction with respect to the grid used elsewhere in the computational domain similarly to an earlier paper (Liu & Prosperetti 2010). Matching between the Stokes solution and the finite-difference solution was carried out at the nodes adjacent to the particle surface, i.e.…”

Section: Numerical Methods and Validationmentioning

confidence: 99%

Pressure-driven flow in a channel with porous walls

Liu

Prosperetti

2011

J. Fluid Mech.

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The finite-Reynolds-number three-dimensional flow in a channel bounded by one and two parallel porous walls is studied numerically. The porous medium is modelled by spheres in a simple cubic arrangement. Detailed results on the flow structure and the hydrodynamic forces and couple acting on the sphere layer bounding the porous medium are reported and their dependence on the Reynolds number illustrated. It is shown that, at finite Reynolds numbers, a lift force acts on the spheres, which may be expected to contribute to the mobilization of bottom sediments. The results for the slip velocity at the surface of the porous layers are compared with the phenomenological Beavers-Joseph model. It is found that the values of the slip coefficient for pressure-driven and shear-driven flow are somewhat different, and also depend on the Reynolds number. A modification of the relation is suggested to deal with these features. The Appendix provides an alternative derivation of this modified relation.

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Section: Numerical Methods and Validationmentioning

confidence: 99%

Pressure-driven flow in a channel with porous walls

Liu

Prosperetti

2011

J. Fluid Mech.

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“…When a sphere is rotating in a viscous fluid such as water, its angular velocity induces a diffusion of momentum in a boundary layer. This results in a viscous torque applied to the pebble (Liu and Prosperetti, 2010), which opposes its rotation:…”

Section: Interactions Between Pebbles and The Flowmentioning

confidence: 99%

Bedrock incision by bedload: insights from direct numerical simulations

Aubert¹,

Langlois²,

Allemand³

2016

Earth Surf. Dynam.

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Abstract. Bedload sediment transport is one of the main processes that contribute to bedrock incision in a river and is therefore one of the key control parameters in the evolution of mountainous landscapes. In recent years, many studies have addressed this issue through experimental setups, direct measurements in the field, or various analytical models. In this article, we present a new direct numerical approach: using the classical methods of discrete-element simulations applied to granular materials, we explicitly compute the trajectories of a number of pebbles entrained by a turbulent water stream over a rough solid surface. This method allows us to extract quantitatively the amount of energy that successive impacts of pebbles deliver to the bedrock, as a function of both the amount of sediment available and the Shields number. We show that we reproduce qualitatively the behaviour observed experimentally by Sklar and Dietrich (2001) and observe both a "tool effect" and a "cover effect". Converting the energy delivered to the bedrock into an average long-term incision rate of the river leads to predictions consistent with observations in the field. Finally, we reformulate the dependency of this incision rate with Shields number and sediment flux, and predict that the cover term should decay linearly at low sediment supply and exponentially at high sediment supply.

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“…The viscous drag increased by less than 5% even for a surface as close as one particle radius [21,69], for rotation about an axis parallel to the surface. For rotation perpendicular to the surface [69], it is difficult to experimentally observe any effect until the probe particle touches the surface [15]. In the next Chapter, we discuss in more detail wall effects on a rotating particle.…”

Section: Tear Filmmentioning

confidence: 94%

“…In addition, for a particle between two plane walls, the viscous torque on a sphere of radius a rotating between two plane boundaries 3a apart would experience a viscous torque only ∼1.05 times greater than the same sphere rotating in an infinite domain [69]. As illustrated in Figure 4.3, the particle rotating at a constant speed is centred inside the spherical wall, in this special case, wall effects of concentric spheres can be expressed analytically, and is given by:…”

Section: Early Workmentioning

confidence: 99%

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High Resolution Measurements of Viscoelastic Properties of Complex Biological Systems Using Rotating Optical Tweezers

Zhang¹

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The aim of this thesis is to investigate the viscoelastic properties of systems on the microscale at extremely low sample volumes and in highly limited spaces with high temporal resolution. A method based on both passive and active rotational tweezers is presented, which enables measurements of viscoelasticity with high resolution and within a broadband frequency range.Cellular mechanics and rheological properties play an important role in biological processes (e.g., transport of intracellular organelles by molecular motors, cellular processes, endocytic trafficking, axonal retrograde transport in neurons and secretory pathways). All these activities occur in cytoplasm which behaves both as an elastic solid and as a viscous fluid, and is considered viscoelastic. Therefore, the quantitative characterization of viscoelasticity in cells can help us to understand cellular mechanisms.This thesis begins by introducing optical tweezers elucidating transfer of both linear and angular momentum of light and describing methods to apply and measure optical torques on birefringent particles. Microspherical vaterite particles are synthesized for our experiments using a method developed and refined in our lab. These particles are composed of the calcium carbonate mineral vaterite and are birefringent. Next I describe both theoretical and experimental methods of determining viscoelasticity by measuring the angular diffusion of displacement of a trapped vaterite

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Wall effects on a rotating sphere

Cited by 99 publications

References 43 publications

Pressure-driven flow in a channel with porous walls

Pressure-driven flow in a channel with porous walls

Bedrock incision by bedload: insights from direct numerical simulations

High Resolution Measurements of Viscoelastic Properties of Complex Biological Systems Using Rotating Optical Tweezers

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