NORMAL INSTANTANEOUS SQUEEZE FILM FORCE FOR A FINITE-LENGTH CYLINDER

A theoretical model for the normal instantaneous squeeze film force fo r a finite length cylinder is developed in this paper. The model assum es large unidirectional cylinder motion along a sleeve diameter. Based on the assumption of a parabolic flow field, a normal squeeze film mo del for an infinitely long cylinder is first obtained. Combining the i nfinitely long model with side-leakage factors, a finite length model is then obtained. The model shows that the instantaneous squeeze film force consists of three position-dependent nonlinear terms: namely a v iscous term, an unsteady inertia term and a convective inertia term. F rom experimental measurements using water and a clearance to radius ra tio of 0.032, the viscous term of the theoretical model should be corr ected by a factor involving the instantaneous squeeze film Reynolds nu mber and the absolute value of instantaneous eccentricity. The synthes ized squeeze force waveforms obtained using the corrected equation wit h averaged weighting coefficients agree very well with the experimenta l waveforms for eccentricity ratios up to 0.9 and a wide frequency ran ge. The corrected equation is suitable for the calculation of the norm al instantaneous squeeze film force given the instantaneous position, velocity, and acceleration of the cylinder center.