The effect of surface roughness on squeeze film behavior between two circular disks with couple stress lubricant is analyzed when the upper disk has porous facing which approaches the lower disk with uniform velocity. The modified Stochastic Reynolds equation is derived on the basis of Stokes micro-continuum theory for couple stress fluid and Christensen Stochastic theory for the rough surface. Closed form solution of the Stochastic Reynolds equation is obtained in terms of Fourier-Bessel series. The importance of roughness and couple stress on bearing characteristics are presented in terms of load carrying capacity, squeeze time, and relative percentage of the load. It is observed that, effect of couple stress fluid, and surface roughness is more pronounced compared to classical case. These predictions enable design engineers to choose suitable parameters.

If you would like to write for this, or any other Emerald publication, then please use our Emerald for Authors service information about how to choose which publication to write for and submission guidelines are available for all. Please visit www.emeraldinsight.com/authors for more information. About Emerald www.emeraldinsight.comEmerald is a global publisher linking research and practice to the benefit of society. The company manages a portfolio of more than 290 journals and over 2,350 books and book series volumes, as well as providing an extensive range of online products and additional customer resources and services.Emerald is both COUNTER 4 and TRANSFER compliant. The organization is a partner of the Committee on Publication Ethics (COPE) and also works with Portico and the LOCKSS initiative for digital archive preservation. AbstractPurpose -This paper aims to study the effects of surface roughness on the characteristics of squeeze film lubrication between curved annular plates. Design/methodology/approach -The modified Reynolds type equation governing the fluid film pressure is derived. The stochastic method for rough surfaces developed by Christensen is to derive stochastic type equation and has been solved for two types of one-dimensional roughness patterns. Closed form expressions of mean squeeze film pressure and mean load carrying capacity are obtained. Findings -The bearing characteristics are computed for various values of roughness parameter. It is found that the effect of radial (circumferential) roughness pattern is to shift the point of maximum pressure towards the inlet (outlet) edge and also observe that the mean load-carrying capacity increases (decreases) for the circumferential (radial) roughness pattern compared with the corresponding smooth case, for both concave and convex pad geometries.Research limitations/implications -The analysis is useful in obtaining suitable mathematical model of physical problems. The one which we have considered here is the idealized form of functioning of bearings in general. Analysis of finer models requires pure numerical schemes, for which the present model is a base. Practical applications -Findings of the present paper have applications in machine elements like clutch plates and collar bearings. Originality/value -Inclusions of surface roughness effect on the characteristics of bearings are original contributions in tribology.

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Characteristic features of squeeze film lubrication between two rectangular plates, of which, the upper plate has a roughness structure, in the presence of a uniform transverse magnetic field are examined. The fluid in the film region is represented by a viscous, incompressible and electrically conducting couple-stress fluid. The thickness of the fluid film region is h and that of the roughness is h s. The pressure distribution in the film region is governed by the modified Reynolds equation, which also incorporates the roughness structure and couple stress fluid. This Reynolds equation is solved using a novel multigrid method for all involved physical parameters. It is observed that the pressure distribution, load carrying capacity and squeeze film-time increase for smaller values of couple-stress parameter and for increasing roughness parameters and Hartmann number compared to the classical case.

The combined effects of couple stresses and surface roughness patterns on the squeeze film characteristics of curved annular plates are studied. The Stokes (1966) couple stress fluid model is included to account for the couple stresses arising due to the presence of microstructure additives in the lubricant. In the context of Christensen's (1969) stochastic theory for the lubrication of rough surfaces, two types of one-dimensional roughness patterns (circumferential and radial) are considered. The governing modified stochastic Reynolds type equations are derived for these roughness patterns. Expressions for the mean squeeze film characteristics are obtained. Numerical computations of the results show that the circumferential roughness pattern on the curved annular plate results in more pressure buildup whereas performance of the squeeze film suffers due to the radial roughness pattern for both concave and convex pads. Further the squeeze film time is longer (shorter) for the circumferential (radial) roughness patterns. Improved squeeze film characteristics are predicted for the couple stress lubricant.

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