MOB Transit Draft Transient Dynamics and Stability

摘要

Over the last year and a half, the transit draft behavior of the U.S. Navy Mobile Offshore Base (MOB) has been investigated. This has been a multi-faceted effort which has consisted of analytic experimental and numerical approaches. The analytical effort has been completed at the University of New Orleans Marine Dynamics Lab. The model tests have been completed at the U.S. Naval Academy's Hydromechanics Lab. The analytical study has also been subdivided into various aspects, which are more completely described in a previous paper (Falzarano, et al., 1999). The focus of this paper is on parametric excitation that results when the top of the lower hull is alternately wetted and dried when a wave passes as the vessel heaves and pitches in head seas. In this work, we investigate the sensitivity of the parametric stability to the representation the radiated wave hydrodynamic force. Specifically, we compare an approximate constant coefficients representation of the radiated wave hydrodyanmic force to the more accurate impulse response function representation of the radiated wave hydrodynamic force.