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Lubrication theory

About: Lubrication theory is a research topic. Over the lifetime, 1713 publications have been published within this topic receiving 50261 citations. The topic is also known as: Fluid bearing.


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Journal ArticleDOI
TL;DR: In this article, the effect of external pressure disturbance, being displaced with a constant speed along the free surface of a viscous thin film, is studied theoretically in the lubrication approximation in one and two-dimensional geometries.
Abstract: The effect of an external pressure disturbance, being displaced with a constant speed along the free surface of a viscous thin film, is studied theoretically in the lubrication approximation in one- and two-dimensional geometries. In the comoving frame, the imposed pressure field creates a stationary deformation of the interface – a wake – that spatially vanishes in the far region. The shape of the wake and the way it vanishes depend on both the speed and size of the external source and the properties of the film. The wave resistance, namely the force that has to be externally furnished in order to maintain the wake, is analysed in detail. For finite-size pressure disturbances, it increases with the speed, up to a certain transition value, above which a monotonic decrease occurs. The role of the horizontal extent of the pressure field is studied as well, revealing that for a smaller disturbance the latter transition occurs at a higher speed. Eventually, for a Dirac pressure source, the wave resistance either saturates for a one-dimensional geometry, or diverges for a two-dimensional geometry.

12 citations

Book ChapterDOI
01 Jan 2006
TL;DR: In this article, four basic forms of this type of lubrication are identified: the formation of an ultra-viscous layer close to the worn surface, the shielding of an oxidized metal surface by a mono-molecular layer of adsorbed linear surfactants, the separation of contacting surfaces by entrapped layers of finely divided and perhaps amorphous debris and the suppression of metal to metal contact at extreme pressures by the temperature-dependent formation of sacrificial films of corrosion product on worn metallic surfaces.
Abstract: Publisher Summary In many practical applications there are cases where the operating conditions are such that neither hydrodynamic nor EHL lubrication is effective. The models of lubrication which are thought to operate under such conditions are discussed in this chapter. The traditional name for this type of lubrication is “boundary lubrication” or “boundary and extreme-pressure lubrication.” Boundary and EP lubrication is a complex phenomenon. The lubrication mechanisms involved can be classified in terms of relative load capacity and limiting frictional temperature. Lubrication by chemical and physical interaction between an oil-based lubricant and a surface (usually metal) is essential to the operation of most practical machinery. Four basic forms of this lubrication are identified: the formation of an ultra-viscous layer close to the worn surface, the shielding of an oxidized metal surface by a mono-molecular layer of adsorbed linear surfactants, the separation of contacting surfaces by entrapped layers of finely divided and perhaps amorphous debris and the suppression of metal to metal contact at extreme pressures by the temperature-dependent formation of sacrificial films of corrosion product on worn metallic surfaces.

12 citations

Journal ArticleDOI
TL;DR: It is demonstrated how to systematically determine the evolution of the entire film profile from the meniscus to the apparent contact line, which allows a categorization of the range of behaviors for a transversely uniform profile in a two-dimensional parameter space.
Abstract: On a tilted heated substrate, surface tension gradients can draw liquid up out of a reservoir. The resulting film thickness profile is controlled by two parameters, which depend on the tilt of the substrate, the imposed temperature gradient, and the thickness of a postulated thin precursor layer. The evolution of this film in time is studied using a lubrication model. A number of distinct behaviors are possible as the substrate tilt angle and other parameters are varied. Recent results for the multiple stationary profiles possible near the meniscus are used, and the interaction of these profiles with the advancing front is examined. We demonstrate how to systematically determine the evolution of the entire film profile from the meniscus to the apparent contact line. This allows a categorization of the range of behaviors for a transversely uniform profile in a two-dimensional parameter space. In addition to capillary fronts and double shock structures, new combinations that arise for certain ranges of larg...

12 citations

Journal ArticleDOI
TL;DR: In this paper, a theoretical analysis based on the lubrication theory is presented to study the calendering mechanism, where the material to be calendered is described by the constitutive relationship of a micropolar fluid.
Abstract: A theoretical analysis based on the lubrication theory is presented to study the calendering mechanism. The material to be calendered is described by the constitutive relationship of a micropolar fluid. An exact solution and numerical solution of the problem is calculated. The roll-separating force, power function and exiting sheet thickness are computed numerically using Runge-Kutta method. The influence of the material parameters on the pressure distribution, pressure gradient and related quantities of engineering interest in calendering process is analyzed through graphs. POLYM. ENG. SCI., 2017. © 2017 Society of Plastics Engineers

12 citations

Journal ArticleDOI
TL;DR: Lubrication expressions for the friction coefficients of a spherical particle moving in a fluid between and along two parallel solid walls are explicitly evaluated in the low-Reynolds-number regime to determine lubrication expression for the particle free motion under an ambient Poiseuille flow.
Abstract: Lubrication expressions for the friction coefficients of a spherical particle moving in a fluid between and along two parallel solid walls are explicitly evaluated in the low-Reynolds-number regime. They are used to determine lubrication expression for the particle free motion under an ambient Poiseuille flow. The range of validity and the accuracy of the lubrication approximation is determined by comparing with the corresponding results of the accurate multipole procedure. The results are applicable for thin, wide and long microchannels, or quasi-two-dimensional systems.

12 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202325
202265
202155
202062
201970
201864