Molecular Gas Film Lubrication analyses of sliders with nanometers spacing : Effects of Accommodation coefficients on pressure and shear stress

2003 ◽  
Vol 2003.41 (0) ◽  
pp. 243-244
Author(s):  
Hidekazu SHIMADA ◽  
Kiyomi YAMANE ◽  
Hiroshige MATSUOKA ◽  
Shigehisa FUKUI
Keyword(s):  
Shear Stress ◽  
Molecular Gas ◽  
Spacing Effects ◽  
Accommodation Coefficients ◽  
Molecular Gas Film Lubrication ◽  
Film Lubrication

A Database for Couette Flow Rate Considering the Effects of Non-Symmetric Molecular Interactions

2002 ◽  
Vol 124 (4) ◽  
pp. 869-873 ◽  
Author(s):  
Wang-Long Li
Keyword(s):  
Couette Flow ◽  
Molecular Interactions ◽  
Flow Rate ◽  
Molecular Gas ◽  
Mems Devices ◽  
Magnetic Head ◽  
Linearized Boltzmann Equation ◽  
Accommodation Coefficients ◽  
Molecular Gas Film Lubrication ◽  
Film Lubrication

A complete database for Couette flow rate (QCD,α1,α2,0.1⩽α1,α2⩽1.0,0.01⩽D⩽100, where D=inverse Knudsen number) for ultra-thin gas film lubrication problems is advanced. When the accommodation coefficients (AC) of the two lubricating surfaces are different α1≠α2, the Couette flow rate in the modified molecular gas film lubrication (MMGL) equation should be corrected. The linearized Boltzmann equation (under small Mach number conditions) is solved numerically for the case of non-symmetric molecular interactions α1≠α2. The Couette flow rate is then calculated, and the database is constructed. The present database can be easily implemented in the MMGL equation. In addition, the present database extends the previously published results for 0.1⩽α1,α2⩽0.7. The database for low ACs is valuable in the analysis and applications of MEMS devices (bushings of electrostatic micro motors, micro bearings, magnetic head/disk interfaces, etc.), and their future development.

Thermo-Molecular Gas-Film Lubrication (t-MGL) Considering Temperature Distributions and Accommodation Coefficients: Analyses by Quasi-Free-Molecular t-MGL Equation

2018 ◽  
Author(s):  
Shigehisa Fukui ◽  
Fumiya Shinohara ◽  
Ryota Asada ◽  
Hiroshige Matsuoka
Keyword(s):  
Specular Reflection ◽  
Flow Region ◽  
Molecular Flow ◽  
Molecular Gas ◽  
Gas Temperature ◽  
Accommodation Coefficients ◽  
Ambient Gas ◽  
Molecular Gas Film Lubrication ◽  
Local Temperature Distribution ◽  
Film Lubrication

In the present paper, the flying characteristics of a step slider flying in either air or He with a local temperature distribution of the disk are analyzed using the thermo-molecular gas-film lubrication (t-MGL) equation in the quasi-free-molecular flow region (quasi-free-molecular t-MGL equation: t-MGLqfm eq.). The gas temperature in the t-MGLqfm equation, τG, is assumed to be that in the free molecular limit, τGfm, defined by temperatures and accommodation coefficients at the disk, τW0, α0, and those at the slider, τW1, α1, respectively. The decreases in static spacing for the slider flying in He are significant. Moreover, the spacing decreases as the accommodation coefficients of the disk, α0, decreases, that is, as the ratio of specular reflection increases. The spacing fluctuation caused by a running wavy disk varies according to both the ambient gas (air/He) and the boundary accommodation coefficients.

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