Analysis of Laminar Flow Over a Non-Conventional Random Rough Surface Based on Lattice Boltzmann Method

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
Ping Zhou ◽  
Dongming Guo ◽  
Renke Kang ◽  
Zhuji Jin
Keyword(s):  
Laminar Flow ◽  
Rough Surface ◽  
Flow Model ◽  
Rough Surfaces ◽  
Average Flow ◽  
Random Rough Surface ◽  
Surface Slopes ◽  
Boltzmann Method ◽  
Polishing Pads ◽  
Average Flow Model

The average flow model offers a great convenience for the analysis of laminar flow over rough surfaces and is widely used in simulation studies. Flow factors used in the average flow model are generally expressed as a function of statistical properties of a single level rough surface with gentle slopes. However, for a nonconventional surface with multilevel roughness or high local surface slopes, such as polishing pads used in chemical mechanical planarization (CMP), it has not been verified whether this model is still applicable as expected. Generally, computations based on the Reynolds equation are carried out repeatedly for the same problem regarding different but statistically identical rough surfaces, and the average flow model is applicable if stable flow factors (statistical average) are obtained. However, due to the complex topography and high local surface slopes of polishing pads used in CMP, the Reynolds equation is no longer valid, and thus a new method needs to be developed to estimate the applicability of the average flow model and to calculate the flow factors accurately. In this study, aiming to research the flow over a nonconventional random rough surface such as the slurry flow in CMP, a new strategy is developed to research the incompressible laminar flow through a narrow gap between various nonconventional rough surfaces by combining the lattice Boltzmann method (LBM) and numerical simulation of random rough surface. With this strategy, it is convenient to simulate the flow field in a narrow gap between various random rough surfaces and obtain the flow factors. In addition, an analytical formula for calculating the flow factors of a dual-level rough surface, i.e., surface composed of two different types of microstructure, is introduced and verified through a comparison with the results obtained using the presented numerical simulation strategy.

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.

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.

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

scholarly journals Tungsten Based Spectrally Selective Absorbers with Anisotropic Rough Surface Texture

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 2018
Author(s):  
Niloufar Pirouzfam ◽  
Kursat Sendur
Keyword(s):  
Rough Surface ◽  
Near Infrared ◽  
Rough Surfaces ◽  
Operating Conditions ◽  
Selective Absorption ◽  
Absorption Region ◽  
Correlation Lengths ◽  
Spectrally Selective ◽  
Random Rough Surface ◽  
Random Rough Surfaces

Spectrally selective absorbers have received considerable interest due to their applications in thermophotovoltaic devices and as solar absorbers. Due to extreme operating conditions in these applications, such as high temperatures, thermo-mechanically stable and broadband spectrally selective absorbers are of interest. This paper demonstrates anisotropic random rough surfaces that provide broadband spectrally selective absorption for the thermo-mechanically stable Tungsten surfaces. Anisotropic random rough surface has different correlation lengths in the x- and y-directions, which means their topography parameters have directional dependence. In particular, we demonstrate that spectral absorptance of Tungsten random rough surfaces at visible (VIS) and near-infrared (NIR) spectral regions are sensitive to correlation length and RMS height variations. Our results indicate that by optimizing random rough surface parameters, absorption values exceeding 95% can be obtained. Moreover, our results indicate that anisotropic random rough surfaces broaden the bandwidth of the high absorption region. It is shown that in VIS and NIR regions, the absorption enhancements of up to 47% and 52% are achieved for the isotropic and anisotropic rough surfaces, respectively.

Sign in / Sign up

Export Citation Format

Share Document