Experiments on the Nonlinear Dynamics of Parallel Plates Subjected to Squeeze-Film Forces

Squeeze film dynamical effects are relevant in many industrial components, bearings and seals being the most conspicuous applications. But they also arise in other industrial contexts, for instance when dealing with the seismic excitation of spent fuel racks. The significant nonlinearity of the squeeze-film forces prevents the use of linearised flow models, therefore a fully nonlinear formulation must be used for adequate computational predictions. Because it can accommodate laminar and turbulence flow effects, a simplified bulk-flow model — based on gap-averaged Navier-Stokes equations and incorporating all relevant inertial and dissipative terms — was previously developed by the authors (Antunes & Piteau, 2010), assuming a constant skin-friction coefficient. In this paper we introduce an improved theoretical formulation, fully developed elsewhere (Piteau & Antunes, 2010), such that the dependence of the friction coefficient on the local flow velocity is explicitly accounted for, so that it can be applied to laminar, turbulent and mixed flows. The main part of the paper is then devoted to the presentation and discussion of the results from an extensive series of experiments performed at CEA/Saclay. The test rig consisted on a long gravity-driven instrumented plate of rectangular shape colliding with a planar surface. Theoretical results stemming from both analytical flow models are compared with the experimental measurements, in order to assert the strengths and drawbacks of the simpler original model, as well as the improvements brought by the new but more involved flow formulation.