Analytical and experimental studies on dynamic response of a SES air cushion plenum experiencing forced oscillation

Abstract

In this study, a series of experiments is conducted in which a plenum experiences forced oscillation. The oscillating system is driven by a periodic force arising from regular volumetric fluctuations analogous to fixed-height water waves entering a surface-effect ship (SES) plenum below a heave deck. An analytical study is then conducted in which a MATLAB Simulink model is created to incorporate the same parameters taken into account during the experiments. The results of both the experiments and the simulation demonstrated that as the frequency associated with the plenum volume's forced oscillations approaches the natural frequency of the mass/plenum system, the vibration magnitude of the heave deck increases as predicted. Resonance is observed in vibrations of the heave deck. The mean hover height of the heave deck increases predictably and remains high at higher frequencies when the forced oscillations' frequency approaches the natural frequency of the mass/plenum system. Higher frequency oscillations lead to air accumulation in the plenum. Since there was a significant difference between the experimentally-measured (and simulated) natural frequency and the theoretical natural frequency of a similar, but rigid-walled plenum, it appeared that the natural frequency of the heave deck above the plenum is reduced by the flexibility of the seals and water surface under a SES.