An Average Flow Model of Rough Surface Lubrication With Inter-Asperity Cavitation

2000 ◽  
Vol 123 (1) ◽  
pp. 134-143 ◽  
Author(s):  
Susan R. Harp ◽  
Richard F. Salant
Keyword(s):  
Numerical Experiments ◽  
Reynolds Equation ◽  
Flow Model ◽  
Present Model ◽  
Cavitation Number ◽  
Local Surface ◽  
Cavitation Model ◽  
Surface Separation ◽  
Surface Statistics ◽  
Average Flow Model

An average Reynolds equation capable of predicting the effects of roughness induced inter-asperity cavitation is introduced. The average Reynolds equation is based on the JFO cavitation model and the Patir and Cheng flow factor method. The flow factors are calculated in numerical experiments as functions of the local surface separation, surface statistics, and cavitation number. The model is extended into a universal average Reynolds equation capable of predicting the combined effects of inter-asperity cavitation and macroscopic cavitation. Both the Patir and Cheng method and the present model are verified in numerical experiments.

scholarly journals An Average Flow Model of the Reynolds Roughness Including a Mass-Flow Preserving Cavitation Model

2005 ◽  
Vol 127 (4) ◽  
pp. 793-802 ◽  
Author(s):  
Guy Bayada ◽  
Sébastien Martin ◽  
Carlos Vázquez
Keyword(s):  
Mass Flow ◽  
Numerical Experiments ◽  
Reynolds Equation ◽  
Flow Model ◽  
Two Dimensional ◽  
Scale Analysis ◽  
Cavitation Model ◽  
Average Flow ◽  
One Dimensional ◽  
Average Flow Model

An average Reynolds equation for predicting the effects of deterministic periodic roughness, taking Jakobsson, Floberg, and Olsson mass flow preserving cavitation model into account, is introduced based upon the double scale analysis approach. This average Reynolds equation can be used both for a microscopic interasperity cavitation and a macroscopic one. The validity of such a model is verified by numerical experiments both for one-dimensional and two-dimensional roughness patterns.

Pressure and Shear Flow in a Rough Hydrodynamic Bearing, Flow Factor Calculation

1997 ◽  
Vol 119 (3) ◽  
pp. 549-555 ◽  
Author(s):  
L. Lunde ◽  
K. To̸nder
Keyword(s):  
Finite Element Method ◽  
Surface Roughness ◽  
Finite Element ◽  
Shear Flow ◽  
Reynolds Equation ◽  
Flow Model ◽  
The Finite Element Method ◽  
Average Flow ◽  
Hydrodynamic Bearing ◽  
Average Flow Model

The lubrication of isotropic rough surfaces has been studied numerically, and the flow factors given in the so-called Average Flow Model have been calculated. Both pressure flow and shear flow are considered. The flow factors are calculated from a small hearing part, and it is shown that the flow in the interior of this subarea is nearly unaffected by the bearing part’s boundary conditions. The surface roughness is generated numerically, and the Reynolds equation is solved by the finite element method. The method used for calculating the flow factors can be used for different roughness patterns.

Mixed Lubrication Analyses by a Macro-Micro Approach and a Full-Scale Mixed EHL Model

2004 ◽  
Vol 126 (1) ◽  
pp. 81-91 ◽  
Author(s):  
Q. Jane Wang ◽  
Dong Zhu ◽  
Herbert S. Cheng ◽  
Tonghui Yu ◽  
Xiaofei Jiang ◽  
...  
Keyword(s):  
Pressure Distribution ◽  
Numerical Experiments ◽  
Flow Model ◽  
Elastohydrodynamic Lubrication ◽  
Full Scale ◽  
Asperity Contact ◽  
Average Pressure ◽  
Average Flow ◽  
Simplified Approach ◽  
Average Flow Model

This paper presents an improvement of a simplified approach, namely, the macro-micro approach, used to model the mixed elastohydrodynamic lubrication problems in counterformal contacts, and its comparison with Zhu and Hu’s full-scale mixed-EHL model. In this approach, Patir and Cheng’s average flow model is employed to obtain the distribution of piecewise average pressure. A contact-embedment method that incorporates the detail of asperity contact pressure into the overall pressure distribution is utilized to reveal the severity of surface interaction. Numerical experiments are conducted, and the results are compared with those obtained by means of the full-scale mixed-EHL. The regime of the application of this macro-micro approach is explored.

An Analysis of the Lubrication Characteristics of Mechanical Seals with Parallel Sealing Faces Using an Average Flow Model

2015 ◽  
Vol 656-657 ◽  
pp. 615-621
Author(s):  
Mikiko Oyabu ◽  
Jun Tomioka
Keyword(s):  
Correction Factor ◽  
Relative Motion ◽  
Flow Model ◽  
Present Model ◽  
Hydrodynamic Pressure ◽  
Mechanical Seal ◽  
Mechanical Seals ◽  
Average Flow ◽  
Lubrication Characteristics ◽  
Average Flow Model

A new average flow model to analyze the lubrication characteristics of mechanical seals with parallel sealing faces is proposed. The present model determines the flow factors considering the side leakage under the operating condition equivalent to that in the mechanical seal. The correction factor for the expected hydrodynamic pressure generated by the relative motion of rough surfaces is also defined. The results are compared with those based on the Patir’s average flow model and show that the present model can be effective for the analysis of the lubrication characteristics of mechanical seals with parallel sealing faces.

Some Aspects of Determining the Flow Factors

1989 ◽  
Vol 111 (3) ◽  
pp. 525-531 ◽  
Author(s):  
Yuanzhong Hu ◽  
Lingqing Zheng
Keyword(s):  
Boundary Conditions ◽  
Flow Model ◽  
Rough Surfaces ◽  
Simulation Approach ◽  
Random Surfaces ◽  
Grid Systems ◽  
Average Flow ◽  
Surface Statistics ◽  
Average Flow Model

The uncertainty in calculated results of the flow factors greatly limits the application of the average flow model [1] which otherwise is an approach with broad prospects for studying the lubrication behavior of rough surfaces. The effects of boundary conditions, grid systems, and surface statistics on the flow factors are discussed in the paper, and the reason why the calculated results for the flow factors obtained by different researchers widely differ from each other is revealed. The research shows that ∂p/∂y over the micro-bearing has an effect on the calculated value of flow factors; the influence of the sideflow arises from the simulation approach itself, in which a micro-bearing is used for determining flow factors; the grid systems and the procedure to generate random surfaces may change the statistics of the surfaces used in calculation and affect the results thereby.

scholarly journals Surface Roughness Effects in Hydrodynamic Lubrication: The Flow Factor Method

1983 ◽  
Vol 105 (3) ◽  
pp. 458-463 ◽  
Author(s):  
J. H. Tripp
Keyword(s):  
Surface Roughness ◽  
Reynolds Equation ◽  
Flow Model ◽  
Hydrodynamic Lubrication ◽  
Perturbation Expansion ◽  
Ensemble Averaging ◽  
Roughness Effects ◽  
Average Flow ◽  
Point Correlation ◽  
Average Flow Model

The average flow model of Patir and Cheng [1, 2] for obtaining an average Reynolds equation in the presence of two dimensional surface roughness is extended and generalized. Expectation values of the flow factors appearing in the formalism are calculated by means of a perturbation expansion of the pressure in a nominal parallel film. Terms in the series are evaluated using the unperturbed Green function, which permits ensemble averaging to be performed directly on the solution. Calculations are carried to second order, which involves only two point correlation functions of the two rough surfaces. Perturbation results agree well with results of the earlier numerical simulation until surface contact becomes important when both approaches are inadequate. The theory displays the dependence of the flow factors on the roughness parameters in simple closed form, leading to improved understanding of the average flow method.

An Evaluation of the Average Flow Model [1] for Surface Roughness Effects in Lubrication

1980 ◽  
Vol 102 (3) ◽  
pp. 360-366 ◽  
Author(s):  
J. L. Teale ◽  
A. O. Lebeck
Keyword(s):  
Surface Roughness ◽  
Flow Model ◽  
Two Dimensional ◽  
Roughness Effects ◽  
Important Conclusion ◽  
Average Flow ◽  
One Dimensional ◽  
Dimensional Flow ◽  
Two Dimensional Flow ◽  
Average Flow Model

The average flow model presented by Patir and Cheng [1] is evaluated. First, it is shown that the choice of grid used in the average flow model influences the results. The results presented are different from those given by Patir and Cheng. Second, it is shown that the introduction of two-dimensional flow greatly reduces the effect of roughness on flow. Results based on one-dimensional flow cannot be relied upon for two-dimensional problems. Finally, some average flow factors are given for truncated rough surfaces. These can be applied to partially worn surfaces. The most important conclusion reached is that an even closer examination of the average flow concept is needed before the results can be applied with confidence to lubrication problems.

Adhesive Contact Between Atomistic Surfaces Using a Continuum Analysis

2009 ◽  
Author(s):  
Simon Medina ◽  
Daniele Dini ◽  
Andrew V. Olver
Keyword(s):  
Adhesive Contact ◽  
Atomic Scale ◽  
Local Surface ◽  
Total Surface Energy ◽  
Complete Representation ◽  
Surface Separation ◽  
Continuum Analysis ◽  
Pressure Profiles ◽  
Dynamics Simulations ◽  
Adhesive Forces

We have previously shown that, for non-adhesive conditions, an atomic scale contact can be adequately represented by a continuum analysis despite the physical shortcomings at this scale. Here we have extended the approach to include effects of the adhesive forces that become significant at this level of contact. Adhesive forces are obtained directly from the surface separation across the contact rather than through a total surface energy approach; this allows a complete representation of local surface features. The pull-off characteristics and pressure profiles have been obtained for several different atomistic AFM tip profiles and compared to those obtained from molecular dynamics simulations presented in the literature [1].

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