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.

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.

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.

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.

On Mixed Squeeze Films of Infinite Width Plates

1991 ◽  
Vol 113 (2) ◽  
pp. 378-383
Author(s):  
Wu Chengwei
Keyword(s):  
Flow Model ◽  
Damping Coefficient ◽  
Squeeze Film ◽  
Average Flow ◽  
One Dimensional ◽  
Contact Rigidity ◽  
Squeeze Film Damping ◽  
Longitudinal Roughness ◽  
Roughness Amplitude ◽  
Average Flow Model

A mixed squeeze film model between two rough squeezing plates is established in the present paper. The squeeze behavior in the presence of full and partial fluid film between two rough surfaces is analyzed by using Patir and Cheng’s average flow model and Greenwood and Tripp’s roughness contact model. For one-dimensional squeeze films, transverse and isotropic surface roughness (γ ≤ 1) leads to an increasing squeeze film damping coefficient and a longer sinkage time in comparison with smooth surfaces. But, longitudinal roughness (γ > 1) leads to a decreasing squeeze film damping coefficient and a shorter sinkage time. When the roughness orientation parameter γ is kept constant, increasing roughness amplitude causes an early roughness contact and an increasing contact rigidity.

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.

scholarly journals Some numerical experiments on firn ventilation with heat transfer

1993 ◽  
Vol 18 ◽  
pp. 161-165 ◽  
Author(s):  
M.R. Albert
Keyword(s):  
Heat Transfer ◽  
Surface Pressure ◽  
Thermal Effects ◽  
Numerical Experiments ◽  
Temperature Gradients ◽  
Pressure Amplitude ◽  
Two Dimensional ◽  
One Dimensional ◽  
Thermal Signature ◽  
Spatially Varying

Preliminary estimates of the thermal signature of ventilation in polar firn are obtained from two-dimensional numerical calculations. The simulations show that spatially varying surface pressure can induce airflow velocities of 10−5m s−1at 1.5 m depth in uniform firn, and higher velocities closer to the surface. The two-dimensional heat-transfer results generally agree with our earlier one-dimensional conclusions that the thermal effects of ventilation tend to decrease the temperature gradient in the top portions of the pack. Field observations of ventilation through temperature measurements are most likely to be observed when the firn temperature at depths on the order of 10 m is close to the air temperature, since steep temperature gradients can mask the thermal effects of ventilation. Preliminary indications are that, as long as surface-pressure amplitude is sufficient to move the air about in the top tens of centimeters in the snow, the resulting temperature profile during ventilation is fairly insensitive to the frequency of the surface-pressure forcing for pressure frequencies in the range 0.1–10.0 Hz.

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.

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