Measurements of Squeeze-Film Bearing Forces and Pressures,Including the Effect of Fluid Inertia

Squeeze-film dampers are commonly applied to high-speed rotating machinery, such as aircraft engines, to reduce vibration problems. The Reynolds theory of hydrodynamic lubrication has been used for the design and modeling of dampers in rotor dynamic systems despite typical modified Reynolds numbers in applications between ten and fifty. Lubrication theory is strictly valid for Reynolds numbers much less than one, which means that fluid viscous forces are much greater than inertia forces. Theoretical papers which account for fluid inertia in squeeze films have predicted large discrepancies from lubrication theory, but these results have not found wide acceptance by workers in the field. Recently, experimental results on the behavior of rotor dynamic systems have been reported which strongly support the existence of large fluid inertia forces. In the present paper, direct measurements of damper forces and pressures are presented for tile first time at high Reynolds number. Reynolds numbers up to 13 are obtained at eccentricity ratios 0.2, 0.5, and 0.8. Lubrication theory underpredicts the measured forces by up to a factor of two (100 percent error). Qualitative agreement is found with predictions of improved theories which include fluid inertia forces.