Experimental Study of Cavitation in an Oscillatory Oil Squeeze Film

Abstract

A displacement-controlled parallel-plate squeeze film test apparatus was designed and built to study the cavitation of oil films. Simultaneous pressure measurement and high-speed photography were conducted in the experiment. The study was aimed at comparing the measured results with the prediction of a recently proposed cavitation model (Sun, et al. (1) ). Among the findings are: (a) When cavitation did not occur, the measured pressure traces agreed well with the theory of non-cavitated oil squeeze film. In particular, tensile stresses of significant magnitudes were measured in the oil film. (b) When cavitation occurred, the measured pressure traces agreed well with the prediction of the new cavitation model. In particular, tensile stresses were measured in the oil film just before the arrival of the expanding cavitation front. (c) The measured cavitation duration correlated well with the new cavitation model. But the measured growth of the cavitation region was faster, and its maximum size was larger, than the model prediction. An analysis of the size effect of the cavitation nuclei, which were likely the entrained air bubbles, provided plausible explanations for the non-occurrence or occurrence of cavitation, as well as for some of the discrepancies between the measured results and model predictions.

KEY WORDS:

• Dynamic Cavitation
• Tensile Stresses
• Parallel-Plate Squeeze Film Bearing
• Displacement-Controlled Oscillations

ACKNOWLEDGMENTS

The research was jointly supported by China's State Key Basic Research Development Program, under Grant G1998020317-4.2; and Shanghai's Baiyulan Foundation for Talents in Science and Technology, under Grant 200328. The authors also gratefully acknowledge Prof. Fang Minglun, Senior Provost of Shanghai University, for his encouragement as well as space and equipment support.

Review led by Josiah Knight

Notes

We became aware of this work after our experiment was concluded, from Professor Hori's recent publication, Hydrodynamic Lubrication, Springer-Verlag, pp 145-149 (2006).

*The pressure presented in all the figures is in the absolute scale (NOT as gauge pressure).

*A quote from Professor Hori (Ibid., p. 3) may be relevant: “Cavitation is not the result of growth of a single bubble, but of many bubbles that originate at various points and quickly grow, and … cover almost the whole area … of the squeeze surface.”