Ferrofluid-based annular squeeze film bearing with the effects of roughness and micromodel patterns of porous structures

Based on the ferrohydrodynamic theory by R.E. Rosensweig and roughness effects by Christensen's stochastic theory, a mathematical model of ferrofluid lubricated flat (parallel) annular disks (plates or surfaces) squeeze film bearing, is developed with the effects of porosity at the upper disk, circumferential or radial roughness at the lower disk and radially variable magnetic field. The validity of the Darcy's law is assumed for the porous matrix. The resultant modified Reynolds-Darcy equation is solved in terms of Bessel function. Expressions for dimensionless load-carrying capacity are obtained and computed. The results for circumferential roughness pattern show that dimensionless load-carrying capacity increases when thickness & permeability of the porous matrix decreases, and effect of surface roughness & width of the annular part increases. The effects of micromodel patterns of two different porous structures are also discussed. Slightly better performances of the bearing are observed for globular sphere permeability model. A comparative study is also made when lower disk is circumferentially rough or radially rough or smooth for globular sphere model.