Lubricant Fluid Films With Directional Variable Viscosity

1974 ◽  
Vol 96 (2) ◽  
pp. 267-274 ◽  
Author(s):  
N. Tipei ◽  
S. M. Rohde
Keyword(s):  
Rheological Model ◽  
Velocity Vector ◽  
Variable Viscosity ◽  
Slider Bearing ◽  
Fluid Films ◽  
Viscous Forces ◽  
Lubricating Film

A new rheological model for lubricants containing additives having long molecules is presented. The viscosity of the fluid is assumed to depend on the angle between the viscous forces and the velocity vector at each point in the lubricating film. The characteristics and consequences of this model are discussed qualitatively and quantitatively. Results far a finite slider bearing lubricated with such a lubricant are presented.

scholarly journals SPH modelling of hydrodynamic lubrication: laminar fluid flow–structure interaction with no-slip conditions for slider bearings

2020 ◽  
Author(s):  
Marco Paggi ◽  
Andrea Amicarelli ◽  
Pietro Lenarda
Keyword(s):  
Reynolds Equation ◽  
Stokes Equations ◽  
Hydrodynamic Lubrication ◽  
Flow Direction ◽  
Navier Stokes ◽  
Slider Bearing ◽  
Fluid Films ◽  
Slip Conditions ◽  
Application Fields ◽  
New Research

Abstract The FOSS CFD-SPH code SPHERA v.9.0.0 (RSE SpA) is improved to deal with “fluid–solid body” interactions under no-slip conditions and laminar regimes for the simulation of hydrodynamic lubrication. The code is herein validated in relation to a uniform slider bearing (i.e. for a constant lubricant film depth) and a linear slider bearing (i.e. for a film depth with a linear profile variation along the main flow direction). Validations refer to comparisons with analytical solutions, herein generalized to consider any Dirichlet boundary condition. Further, this study allows a first code validation of the “fluid–fixed frontier” interactions under no-slip conditions. With respect to the most state-of-the-art models (2D codes based on Reynolds’ equation for fluid films), the following distinctive features are highlighted: (1) 3D formulation on all the terms of the Navier–Stokes equations for incompressible fluids with uniform viscosity; (2) validations on both local and global quantities (pressure and velocity profiles; load-bearing capacity); (3) possibility to simulate any 3D topology. This study also shows the advantages of using a CFD-SPH code in simulating the inertia and 3D effects close to the slider edges, and it opens new research directions overcoming the limitations of the codes for hydrodynamic lubrication based on the Reynolds’ equation for fluid films. This study finally allows SPHERA to deal with hydrodynamic lubrication and improves the code for other relevant application fields involving fluid–structure interactions (e.g. transport of solid bodies by floods and earth landslides; rock landslides). SPHERA is developed and distributed on a GitHub public repository.

Thermohydrodynamic Analysis of Surface Roughness in the Flow Field

2005 ◽  
Vol 127 (2) ◽  
pp. 293-301
Author(s):  
Joon Hyun Kim ◽  
Joo-Hyun Kim
Keyword(s):  
Surface Roughness ◽  
Flow Field ◽  
Film Thickness ◽  
Shear Zone ◽  
Rough Surfaces ◽  
Hydrodynamic Pressure ◽  
Computational Procedure ◽  
Fluid Films ◽  
Lubricating Film ◽  
Fluid Film Thickness

The study deals with the development of a thermohydrodynamic (THD) computational procedure for evaluating the pressure, temperature, and velocity distributions in fluid films with a very rough geometry. A parametric investigation is performed to predict the bearing behaviors in the lubricating film with the absorbed layers and their interfaces as determined by rough surfaces with Gaussian distribution. The layers are expressed as functions of the standard deviations of each surface to characterize flow patterns between both rough surfaces. Velocity variations and heat generation are assumed to occur in the central (shear) zone with the same bearing length and width. The coupled effect of the surface roughness and shear zone dependency on the hydrodynamic pressure and temperature has been found in the noncontact mode. The procedure confirms the numerically determined relationship between the pressure and film gap, provided that its roughness magnitude is smaller than the fluid film thickness.

Influence of the Thermal Field on the Resistance Law in the Turbulent Bearing-Lubrication Theory

1984 ◽  
Vol 106 (3) ◽  
pp. 368-374 ◽  
Author(s):  
F. Di Pasquantonio ◽  
R. Sala
Keyword(s):  
Pressure Distribution ◽  
Thermal Field ◽  
Type Equation ◽  
Research Programme ◽  
Mass Conservation ◽  
Staggered Grid ◽  
Arbitrary Distribution ◽  
Slider Bearing ◽  
Lubricating Film ◽  
Plane Normal

In recent years, a joint theoretical and experimental research programme has been carried out by ANSALDO, ENEL, and the Department of Mechanics of the Milan Polytechnic. The purpose of this paper is to investigate the effects of the thermal field on the resistance law. In particular, a study is made of the behavior of the lubricating film of an infinite and inclined-plane slider-bearing, using a turbulence model similar to that employed by Launder and Leschziner. In our method, the complete boundary layer equations of mass, momentum, and energy are solved numerically, by a finite-difference technique in the plane normal to the sliding surface. The equations are discretized on a staggered grid, in which the scalar quantities (pressure, viscosity, and temperature) are located at the nodes and the velocity components between them. Having assumed arbitrary distribution of velocity at the inlet and pressure distribution, the set of conservation equations can be solved at the downstream stations. Since the velocity field obtained does not satisfy the global mass conservation law at every station, a Poisson-type equation for pressure correction is derived by imposing such a mass conservation condition. Velocity and pressure distribution at the inlet are then corrected, and a new computation performed. This iterative procedure is repeated until the solution is no longer significantly modified. The numerical results show that the resistance coefficients obtained taking into account the thermal field, are lower than those obtained in isothermal conditions.

Flying Characteristics of the “Zero-Load” Slider Bearing

1983 ◽  
Vol 105 (3) ◽  
pp. 484-490 ◽  
Author(s):  
J. W. White
Keyword(s):  
Data Storage ◽  
High Performance ◽  
Storage System ◽  
Disk Surface ◽  
Air Bearing ◽  
Slider Bearing ◽  
Storage And Retrieval ◽  
High Stiffness ◽  
Lubricating Film ◽  
Low Load

One of the most critical elements making up a disk storage system is the air bearing interface located between the magnetic transducer and the disk surface on which data is stored and retrieved. The air film provided between the slider which houses the transducer and the disk serves to eliminate contact and wear of the solid surfaces and in addition must be extremely thin (on the order of 1/4 micron) in order to achieve a high density of data storage. Two of the most sought after properties of this lubricating film are a low generated load and high fluid stiffness. Low load allows the slider to be in contact with the disk when it is started and stopped, while high stiffness tends to provide a nearly uniform air bearing clearance which is important for reliable and efficient data storage and retrieval. The Zero-Load slider incorporates both low load and high stiffness in a single bearing. In this paper, the flying characteristics of the Zero-Load slider are discussed and its potential is explored. Numerical simulations which are presented for both static and dynamic operation indicate that the Zero-Load slider should be a strong contender for application in high performance disk files.

Modeling a Porous Slider Bearing With an External Reservoir

2007 ◽  
Author(s):  
Joshua D. Johnston ◽  
Minel J. Braun ◽  
Gerald W. Young
Keyword(s):  
Porous Medium ◽  
Analytical Solution ◽  
Pressure Profile ◽  
Slider Bearing ◽  
Darcy Model ◽  
Lubricating Film ◽  
Load Carrying ◽  
Bearing System

This work considers a porous slider bearing above an external reservoir. The bearing system consists of a lubricating film, porous medium, and a reservoir. The Darcy model is used for flow inside the porous medium. The moving slider bearing establishes a pressure profile that circulates fluid between the lubricating region and the reservoir. Simplifications are made to allow for a semi-analytical solution to be constructed that can be easily solved using a standard computational package. It is shown that the fluid is circulated inside the bearing to allow for a load-carrying capability as well as for no external lubricant supply.

The Influence of Surface Tension on Bearings Lubricated With Bubbly Liquids

1980 ◽  
Vol 102 (1) ◽  
pp. 91-96 ◽  
Author(s):  
E. H. Smith
Keyword(s):  
Surface Tension ◽  
Bubble Surface ◽  
Load Carrying Capacity ◽  
Slider Bearing ◽  
Bubbly Liquids ◽  
Viscous Forces ◽  
Tilting Pad ◽  
Load Carrying ◽  
Bearing Load ◽  
Order Of Magnitude

An order of magnitude analysis of the Rayleigh-Plesset equation of motion of a bubble surface reveals that inertia and viscous forces can be ignored in realistic bearing configurations and that surface tension plays an important role. The influence of gas bubbles in liquid lubrication is examined with particular reference to the steadily-loaded plane-inclined slider-bearing. Load carrying capacity is virtually unaffected by lubricant gasification. The centre of pressure can be considerably modified, depending partially on the value of a new dimensionless group—the configuration number φ. It appears that the tilting-pad thrust bearing will sometimes be unstable in operation, resulting in bearing failure.

An Asymptotic Expansion Approach to Modeling the Heat Transfer in a Reservoir-Extended Porous Slider Bearing

2008 ◽  
Author(s):  
Joshua D. Johnston ◽  
Minel J. Braun ◽  
Gerald W. Young
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Asymptotic Expansion ◽  
Fluid Flow ◽  
Thermal Effects ◽  
Transfer Problem ◽  
Slider Bearing ◽  
Lubricating Film ◽  
Velocity Flow ◽  
Bearing System

This work is a thermal simulation extension to the modeling of the fluid flow inside a reservoir-extended porous slider bearing [1]. The bearing system consists of a lubricating film, porous medium, and a reservoir. The velocity flow field generated by the modeling of the fluid flow is used as an input to solve the heat transfer problem. The small parameter used in the asymptotic expansion is the ratio of the reservoir depth to the length of the slider. The thermal effects upon the operation of this system are discussed.

Measurement of Load-Carrying Capacity of Thin Lubricating Films

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Xia Li ◽  
Feng Guo ◽  
Shuyan Yang ◽  
P. L. Wong
Keyword(s):  
Film Thickness ◽  
Carrying Capacity ◽  
Constant Load ◽  
Experimental Results ◽  
Hydrodynamic Theory ◽  
Load Carrying Capacity ◽  
Slider Bearing ◽  
Lubricating Film ◽  
Single Function ◽  
Load Carrying

This paper presents an experimental procedure to evaluate the load-carrying capacity of a fixed-incline slider bearing (dimensionless load W versus convergence ratio K) using a slider-on-disk lubricating film test rig. In general, the applied load is the dependent variable and is directly measured for different convergence ratios such that the relation of the load-carrying capacity W and the convergence ratio K can be obtained. The load and slider inclination are fixed in the present approach, and the film thickness is measured at different speeds. As the dimensionless load can be a function of speed and film thickness, the variation of load-carrying capacity with respect to speed can be obtained even under a constant load and a fixed incline. It is shown that the measured load-carrying capacity is lower than that predicted by the classical hydrodynamic theory. Nevertheless, the experimental results acquire the same trend in the variation of dimensionless loads with convergence ratios. The theory holds that the load-carrying capacity is a single function of the convergence ratio. However, the experimental results show that the dimensionless load-carrying capacity is affected by the inclination angle of the slider, load, and the properties of lubricating oils.

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