The Effect of Perturbation Amplitudes on Eight Force Coefficients of Journal Bearings

Abstract

This paper investigates the relationship between eight linear oil-film force coefficients of circular journal bearings and the perturbation amplitudes. The force coefficients are calculated by the finite perturbation method and compared with those calculated by the infinitesimal perturbation method. Numerical experiments show that the calculated results from both finite perturbation and infinitesimal perturbation methods are very close (with a variation less than 0.1 %) when the perturbation amplitudes are less than 0.02c (displacement) or 0.02ωc (velocity) for normal bearing eccentricities. For eccentricities between 0.2 and 0.8, the calculated coefficients by the finite perturbation method will differ less than 2.5 % from the results by the infinitesimal perturbation method if the perturbation amplitude is less than 0.05c or 0.04ωc. The bearing coefficients calculated by the finite perturbation method under different perturbation amplitudes are presented graphically.