Cavitation in a Lubrication Flow between a Moving Sphere and a Boundary

Ashmore, Jacqueline; Pino, C. del; Mullin, T.

doi:10.1103/physrevlett.94.124501

Cited by 50 publications

(61 citation statements)

References 13 publications

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“…Campbell (14) and Ikels (15) attributed the nucleation observed in these conditions to the pressure drop induced by the viscous flow in the space between two separating solid surfaces. Indeed, in highly viscous liquids, bubble formation compatible with this picture has been reported (16)(17)(18). However, this explanation cannot easily account for the nucleation observed in low-viscosity fluids like water and ethanol, because in many cases the theoretical gap between the solids would have to be smaller than the surface roughness.…”

supporting

confidence: 47%

Tribonucleation of bubbles

Lhuissier

Sun

Lohse

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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We report on the nucleation of bubbles on solids that are gently rubbed against each other in a liquid. The phenomenon is found to depend strongly on the material and roughness of the solid surfaces. For a given surface, temperature, and gas content, a trail of growing bubbles is observed if the rubbing force and velocity exceed a certain threshold. Direct observation through a transparent solid shows that each bubble in the trail results from the early coalescence of several microscopic bubbles, themselves detaching from microscopic gas pockets forming between the solids. From a detailed study of the wear tracks, with atomic force and scanning electron microscopy imaging, we conclude that these microscopic gas pockets originate from a local fracturing of the surface asperities, possibly enhanced by chemical reactions at the freshly created surfaces. Our findings will be useful either for preventing undesired bubble formation or, on the contrary, for "writing with bubbles," i.e., creating controlled patterns of microscopic bubbles.Comment: Link to journal article: http://www.pnas.org/content/111/28/10089.abstrac

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supporting

confidence: 47%

Tribonucleation of bubbles

Lhuissier

Sun

Lohse

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…For example, if the two colliding spheres interact at their combined asperity height, the rebound distance may be twice as large as the height of a single asperity. Furthermore, if the filling liquid properties change due to liquid hardening ( Joseph & Hunt 2004) or the occurrence of cavitation (Ashmore et al 2005), this may result in dramatic variations in the rebound , of a Delrin sphere, suggesting a mixed contact. In figure 6, the two bounding e m curves are plotted, using the value e dry Z0.90 measured by Joseph et al (2001).…”

Section: K3mentioning

confidence: 99%

A mixed contact model for an immersed collision between two solid surfaces

Yang

Hunt

2008

Phil. Trans. R. Soc. A.

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Experimental evidence shows that the presence of an ambient liquid can greatly modify the collision process between two solid surfaces. Interactions between the solid surfaces and the surrounding liquid result in energy dissipation at the particle level, which leads to solid-liquid mixture rheology deviating from dry granular flow behaviour. The present work investigates how the surrounding liquid modifies the impact and rebound of solid spheres. Existing collision models use elastohydrodynamic lubrication (EHL) theory to address the surface deformation under the developing lubrication pressure, thereby coupling the motion of the liquid and solid. With EHL theory, idealized smooth particles are made to rebound from a lubrication film. Modified EHL models, however, allow particles to rebound from mutual contacts of surface asperities, assuming negligible liquid effects. In this work, a new contact mechanism, 'mixed contact', is formulated, which considers the interplay between the asperities and the interstitial liquid as part of a hybrid rebound scheme. A recovery factor is further proposed to characterize the additional energy loss due to asperity-liquid interactions. The resulting collision model is evaluated through comparisons with experimental data, exhibiting a better performance than the existing models. In addition to the three non-dimensional numbers that result from the EHL analysis-the wet coefficient of restitution, the particle Stokes number and the elasticity parameter-a fourth parameter is introduced to correlate particle impact momentum to the EHL deformation impulse. This generalized collision model covers a wide range of impact conditions and could be employed in numerical codes to simulate the bulk motion of solid particles with non-negligible liquid effects.

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“…For the lubricated contact to support any load this symmetry must be broken; this may be due to cavitation 18 or, when the pressures are sufficiently large, by elastic deformation. In Ref.…”

mentioning

confidence: 99%

Similarity theory of lubricated Hertzian contacts

2013

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We consider a heavily loaded, lubricated contact between two elastic bodies at relative speed U, such that there is substantial elastic deformation. As a result of the interplay between hydrodynamics and non-local elasticity, a fluid film develops between the two solids, whose thickness scales as U3/5. The film profile h is selected by a universal similarity solution along the upstream inlet. Another similarity solution is valid at the outlet, which exhibits a local minimum in the film thickness. The two solutions are connected by a hyperbolic problem underneath the contact. Our asymptotic results for a soft sphere pressed against a hard wall are shown to agree with both experiment and numerical simulations.

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Cavitation in a Lubrication Flow between a Moving Sphere and a Boundary

Cited by 50 publications

References 13 publications

Tribonucleation of bubbles

Tribonucleation of bubbles

A mixed contact model for an immersed collision between two solid surfaces

Similarity theory of lubricated Hertzian contacts

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