Inertia effects in evaluating dynamic coefficients for thick lubricant film

In general, the dynamic coefficients of a journal or a thrust bearing are evaluated by applying the perturbation method to the steady state Reynolds equation. Since the Reynolds equation neglects the inertia of the lubricant in a thin film, the dynamic coefficients for the thick film must be evaluated in a different way. In this study, the dynamic coefficients evaluated by a CFD package and experiments are compared to those evaluated by applying the perturbation method to the Reynolds equation for the thick fluid film. A disk damper of an HDD is used to evaluate the dynamic coefficients experimentally. The difference of the dynamic coefficients obtained in a different way becomes larger with the thickness of the fluid film due to the inertia of the lubricant in the film.