Numerical Simulation of Surface Roughness Effects in Laminar Lubrication Using the Lattice-Boltzmann Method

[+] Author and Article Information
Gunther Brenner, Ahmad Al-Zoubi, Merim Mukinovic

Institute of Applied Mechanics, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, Germany

Hubert Schwarze, Stefan Swoboda

Institute of Tribology and Energy Conversion Machinery, Clausthal University of Technology, 38678 Clausthal-Zellerfeld, Germany

J. Tribol 129(3), 603-610 (Mar 15, 2007) (8 pages) doi:10.1115/1.2736452 History: Received October 05, 2005; Revised March 15, 2007

The effect of surface texture and roughness on shear and pressure forces in tribological applications in the lubrication regime is analyzed by means of lattice-Boltzmann simulations that take the geometry of real surface elements into account. Topographic data on representative surface structures are obtained with high spatial resolution with the application of an optical interference technique. The three-dimensional velocity field past these surfaces is computed for laminar flow of Newtonian fluids in the continuum regime. Subsequently, pressure and shear flow factors are obtained by evaluating the velocity field in accordance with the extended Reynolds equation of Patir and Cheng (1978, ASME J. Tribol., 100, pp. 12–17). The approach allows an efficient determination of the hydrodynamic characteristics of microstructured surfaces in lubrication. Especially, the influence of anisotropy of surface texture on the hydrodynamic load capacity and friction is determined. The numerical method used in the present work is verified for a simplified model configuration, the flow past a channel with sinusoidal walls. The results obtained indicate that full numerical simulations should be used to accurately and efficiently compute the characteristic properties of film flows past rough surfaces and may therefore contribute to a better understanding and prediction of tribological problems.

Copyright © 2007 by American Society of Mechanical Engineers
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Figure 1

Sketch of computational domain for the calculation of pressure and shear flow factors

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Figure 2

Sketch of the velocity stencil (D2Q9) in two dimensions (left) and of bounce-back boundary condition and solid wall (right)

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Figure 3

Detail of a scanned surface element before and after the mapping to a voxel grid

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Figure 4

Geometry of the verification test case and boundary conditions

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Figure 5

Velocity distribution in a wavy channel for various microinertial Reynolds numbers as compared to (29)

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Figure 6

Pressure flow factors for the flow in a wavy channel for various microinertial Reynolds numbers

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Figure 7

Shear and pressure flow factor for the flow in a wavy channel; comparison of numerical and theoretical results of (10-11)

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Figure 8

Scanned surface element of the crankshaft bearing (left) and bearing shell (right) surfaces

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Figure 11

Computed shear flow factors for the flow past configurations A (left) and B (right) and both flow directions as function of the h¯T∕σ ratio

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Figure 12

Computed pressure flow factors for the flow past configuration B, dependence of Reynolds number

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Figure 9

Detail of the isosurfaces of the streamwise velocity component for the pressure-driven flow past the crankshaft element with anisotropic surface roughness: Left, flow in x direction; right, flow in y direction

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Figure 10

Computed pressure factors for the flow past configurations A (left) and B (right) and both flow directions as function of the h¯T∕σ ratio



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