The hydrodynamic coefficients of a journal bearing set with the bearing subjected to axial oscillation are determined in this work. The Navier-Stokes equations were used to account for the axial component of the relative motion between the journal and the bearing. Numerical solution of the Navier-Stokes equations yielded the pressure distribution within the cavity of the bearing. This pressure distribution was then integrated over the surface of the bearing to obtain the two orthogonal force components. The derivatives of these force components were then taken with respect to the displacement and velocity of the journal that are co-linear with these forces. This yielded the hydrodynamic coefficients.
To conduct a parametric study, the bearing design parameters were chosen such that the Sommerfeld number was equal to one. The axial oscillation of the bearing was modeled as a purely sinusoidal motion, with an amplitude of one millimeter and a frequency range of 0-304 rads/s.
This study shows that for a bearing axial frequency up to 304 rads/s the bearing dynamic coefficients exhibit an increase in their deviation from the values of a stationary bearing.
This study further shows that at the frequency of 300 rads/s the stiffness and damping coefficients vary dramatically over the course of cycle for the bearing set described in this work. This study shows Kxy changes from 1.711073 to 5.235242 back to 1.711073 again to 5.235242 and then back to 1.711073 as the bearing completes one-half cycle of travel.