Application of Average Flow Model to Lubrication Between Rough Sliding Surfaces

1979 ◽  
Vol 101 (2) ◽  
pp. 220-229 ◽  
Author(s):  
Nadir Patir ◽  
H. S. Cheng
Keyword(s):  
Shear Stress ◽  
Shear Flow ◽  
Flow Model ◽  
Stress Factors ◽  
Surface Pattern ◽  
Roughness Effects ◽  
Local Pressure ◽  
Average Flow ◽  
Flow Factor ◽  
Average Flow Model

The Average Flow Model introduced in an earlier paper is extended to include sliding contacts by deriving the shear flow factor for various roughness configurations. Similar to the pressure flow factors, the shear flow factor is obtained through numerical flow simulation on a model bearing having numerically generated roughness. The flow factors for isotropic and directional surfaces are expressed as empirical relationships in terms of h/σ, a surface pattern parameter γ defined as the ratio of x and y correlation lengths, and the variance ratio Vr1 which is the ratio of variance of surface 1 to that of the composite roughness. Expressions for the mean shear stress and horizontal force components due to local pressure in rough bearings are derived through the definition of shear stress factors, also obtained through simulation. The application of the average Reynolds equation to analyze roughness effects in bearings is demonstrated on a finite slider. The effects of the operating parameters as well as the roughness parameters on mean hydrodynamic load, mean viscous friction and mean bearing inflow are illustrated.

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.

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.

Initial Pressure Influence on Pressure Flow Factor Used in Mixed-Lubrication Model

2011 ◽  
Vol 86 ◽  
pp. 65-69
Author(s):  
Fan Ming Meng ◽  
Yuan Pei Chen
Keyword(s):  
Analytical Solution ◽  
Pressure Distribution ◽  
Flow Model ◽  
Initial Pressure ◽  
Mixed Lubrication ◽  
Average Pressure ◽  
Pressure Flow ◽  
Average Flow ◽  
Flow Factor ◽  
Average Flow Model

The average flow model proposed by Patir and Cheng offers a great convenience for the mixed-lubrication analysis of rough surfaces. The pressure flow factor introduced by Patir and Cheng helps to analyze the influence of roughness on the average pressure and average flow of a lubricant between surfaces. This paper reports how to reasonably choose initial pressure in computing the pressure flow factor. The numerical results show that the pressure distribution and further pressure flow factor value are sensitive to an initial pressure in solving the pressure flow factor, and the initial pressure of a constant value is not suitable for the pressure flow factor calculation for a measured surface with many sample points. Meanwhile, the pressure flow code is demonstrated by the comparison of the pressure obtained numerically with the analytical solution of pressure.

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.

A Simple Method to Calculate Contact Factor Used in Average Flow Model

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Fanming Meng ◽  
Q. Jane Wang ◽  
Diann Hua ◽  
Shuangbiao Liu
Keyword(s):  
Density Distribution ◽  
Probability Density ◽  
Method Validation ◽  
Present Method ◽  
Flow Model ◽  
Probability Density Distribution ◽  
Simple Method ◽  
Average Flow ◽  
Non Gaussian ◽  
Average Flow Model

The average flow model proposed by Patir and Cheng offers a great convenience for the analysis of rough surfaces in lubrication. The contact factor introduced by Wu and Zheng helps to solve a difficulty in local film evaluation using the average flow model. This paper reports a simple method to calculate the contact factor. Method validation is demonstrated by the comparison of the contact factors for Gaussian surfaces obtained with the present method and the fitting formula of Wu and Zheng. The proposed method cannot only easily compute the contact factor values for Gaussian surfaces; it can also be used for those of non-Gaussian and measured surfaces, especially those with unknown probability density distribution of the roughness height.

A mass-conservative average flow model based on finite element method for complex textured surfaces

2013 ◽  
Vol 56 (10) ◽  
pp. 1909-1919 ◽  
Author(s):  
Yi Xie ◽  
YongJian Li ◽  
ShuangFu Suo ◽  
XiangFeng Liu ◽  
JingHao Li ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Flow Model ◽  
Textured Surfaces ◽  
Average Flow ◽  
Model Based ◽  
Average Flow Model ◽  
Element Method
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