Nonlinear fluid forces in cylindrical squeeze films. part II: Finite length

Two nonlinear models of finite-length cylindrical squeeze films are develop ed. The first finite-length model is formed using length-correction factors on a short cylindrical model, while the second finite-length model is cons tructed using side-leakage factors with an infinitely long model. Each mode l has seven force terms which are nonlinear functions of instantaneous cyli nder position. The two models are evaluated through experimental measuremen ts using two geometrical configurations where 50.6 mm and 25 mm diameter cy linders undergo 160 cases of radial and offset-linear motions. Comparing th e theoretical predictions of squeeze force waveforms with measurements, and also with previous models by Lu & Rogers, shows that the present finite-le ngth models are quite reasonable. By investigating each force term, the pre sent models are modified slightly and better predictions are obtained for m ost test cases. Without empirical corrections, the models tend to underesti mate the unsteady inertia terms and are unable to predict the frequency dep endence of the viscous terms. (C) 2001 Academic Press.