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.

Simulations of air slider bearings with realistic gas-surface scattering

Abstract: We have calculated the pressure distribution for an infinitely wide plane slider air bearing by using a particle-based direct simulation Monte Carlo method. These simulations include a sophisticated gas-surface scattering model and take measured accommodation coefficients as inputs. Our results are in good agreement with the molecular gas lubrication theory of Fukui and Kaneko for both glass and disk-drive surfaces.

A model for thermal Marangoni drying

Abstract: The process of thermal Marangoni drying is considered, which has been recently proposed for use in semiconductor production. The process allows ultraclean drying of semiconductor wafer surfaces at the end of a sequence of wet operations. A theoretical model is presented, which incorporates the movement of a thin liquid film on the semiconductor surface, heat exchange between the semiconductor and outer medium, and the water flow below the meniscus. In the frame of this model, the problem is solved using a combination of lubrication approximation, one-dimensional heat transfer analysis, and spectral-element solution of the two-dimensional Stokes equations. Several examples are given to show how the model can be used to evaluate the efficiency of drying.

Gears: Elastohydrodynamic lubrication and durability

Abstract: The paper presents a brief review of developments in understanding of gear tooth contact lubrication in relation to problems of surface durability and distress. Gear tooth contacts tend to operate under conditions where the lubricating oil film is thin compared with surface roughness. This feature is shown to have a significant effect on scuffing capacity and friction and is also thought to be a factor in micropitting. Recent developments in thin-film micro-elastohydrodynamic lubrication theory are described and these should lead to a better understanding of the behaviour and modes of surface distress in gears. The paper also describes the application of elastohydrodynamic analysis to other transmission components such as high-conformity gears and thrust cones.

Fingering instability in the flow of a power-law fluid on a rotating disc

Abstract: A computational study of the flow of a non-Newtonian power law fluid on a spinning disc is considered here. The main goal of this work is to examine the effect of non-Newtonian nature of the fluid on the flow development and associated contact line instability. The governing mass and momentum balance equations are simplified using the lubrication theory. The resulting model equation is a fourth order non-linear PDE which describes the spatial and temporal evolutions of film thickness. The movement of the contact line is modeled using a constant angle slip model. To solve this moving boundary problem, a numerical method is developed using a Galerkin/finite element method based approach. The numerical results show that the spreading rate of the fluid strongly depends on power law exponent n. It increases with the increase in the shear thinning character of the fluid (n 1). It is also observed that the capillary ridge becomes sharper with the value of n. In order to examine the stability of these ridges, a linear stability theory is also developed for these power law fluids. The dispersion relationship depicting the growth rate for a given wave number has been reported and compared for different power-law fluids. It is found that the growth rate of the instability decreases as the fluid becomes more shear thinning in nature, whereas it increases for more shear thickening fluids.