FORCE COEFFICIENTS FOR OPEN-ENDED SQUEEZE-FILM DAMPERS EXECUTING SMALL-AMPLITUDE MOTIONS ABOUT AN OFF-CENTER EQUILIBRIUM POSITION

Fluid film forces generated by squeeze film dampers (SFD) in response to small amplitude motions about an off centre equilibrium configuration are of considerable importance for stability analyses of rotating machinery employing SFDs with weak or no centering springs. This approach is the basis for calculation of linearized force coefficients obtained by subjecting the journal to small perturbations in velocity and acceleration. The analysis considers the fluid flow in an open ended SFD due to small amplitude motions of the journal centre about the static equilibrium configuration. Simplified governing equations are derived from the full Navier-Stokes equations by order of magnitude tests. Approximate damping and inertia force coefficients for finite length SFDs are derived by implementing a correction factor to the long SFD model solution. This finite length correction is of extreme simplicity and shows excellent agreement with a numerical solution to the differential equations for the pressure including fluid inertia effects. The correction presented tends asymptotically, as the SFD L/D ratio approaches zero, to the existing formulae for the short SFD model. (A)

FORCE COEFFICIENTS FOR OPEN-ENDED SQUEEZE-FILM DAMPERS EXECUTING SMALL-AMPLITUDE MOTIONS ABOUT AN OFF-CENTER EQUILIBRIUM POSITION Academic Article