“…Childs [5,6] proposed a finite-length method to calculate the dynamic coefficients of annular seals based on the Hirs' turbulent lubrication equations and perturbation method, and this method has been widely applied to the analysis of the stable motion of rotor-bearing-seal system. Kanemori and Iwatsubo [7,8] conducted groups of experiments to research the dynamic coefficients of long annular seals at various rotating speeds, whirling speeds, and pressure drops, they found the experimental results coincided fairly well with Childs' theory. However, the Childs' linear model will be no longer applicable in the case of large disturbance.…”