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2 International Journal of Applied Mechanics and Engineering

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Hydrodynamic squeeze-film characteristic in porous annular disks using the Brinkman model

Lin J. R., Liao W. H.

International Journal of Applied Mechanics and Engineering

2003

Vol. 8, no 3

413-424

Based on the Brinkman model (BM) with the assumption that the pressure gradient across the porous region is an unknown function, the effects of viscous shear stresses upon the squeezing-film motion in porous annular disks are considered. Using the Brinkman equations and applying the continuity conditions at the interface for the velocities, shear stresses and pressures, two coupled modified Reynolds equations governing the squeeze-film pressure are obtained. The film pressure equation is solved and applied to evaluate the load-carrying capacity and the height-time relationship. According to the results obtained, the BM predicts quite a different squeezing action to those derived by the slip-flow model (SFM) and the Darcy model (DM). Comparing with the SFM, the viscous shear effects of the BM increase the load-carrying capacity and the response time. But, these trends are reversed as compared to the DM. On the whole, the effects of viscous shear stresses are more pronounced for moderate-value permeability parameters and a higher-value radius ratio. A design example for porous annular disks is also illustrated for engineering applications.

The effects of couple stresses in the squeeze film behavior between isotropic rough rectangular plates

Lin J. R.

International Journal of Applied Mechanics and Engineering

2001

Vol. 6, no 4

1007-1024

On the basis of the Stokes microcontinuum theory and the Christensen stochastic model, a theoretical study of squeeze film performance for isotropic rough rectangular plates with couple stress fluids as lubricants is presented. A stochastic non-Newtonian Reynolds-type equation is derived and solved analytically for the mean film presure distribution. Squeeze film characteristics are then evaluated. According to the results, bearing surfaces with isotropic roughness pattern result in poor bearing characteristics as compared to the smooth-surface case. However. the isotropic rough plates with a non-Newtonian couple stress fluid provide a significant increase in the mean load-carrying capacity, and compensate the response time by more than the reduction caused by surface roughness.