Hydrodynamics of a floating barge adjacent to fixed structure in transient wave fronts

Physical experiments are carried out in the wave flume to investigate the effects of transient wave fronts acting on multiple floating bodies. Two identical barges are considered with one being allowed to sway freely and the other fixed. A time-frequency analysis method based on the improved empirical mode decomposition and the Hilbert–Huang transform is developed to help analyze the localized characteristics of non-stationary wave fronts and the corresponding barge responses. A series of problems of particular concern are investigated systematically, and rich results and discussions are provided. Transient wave fronts behaving in a chirp waveform are observed. Two types of wave peaks with respect to transversal waves are recognized in the gap between two barges, whose occurrence locations are derived mathematically. The barge motion is found to be composed of the mean trend and oscillatory components, where the trend component is largely determined by the mooring system, and the oscillatory component is more relevant to the wave property. In shorter incident waves, the motion of weather-side barge can evidently amplify the wave amplitude between two barges. Both amplitudes of the barge motion and maximum wave elevation in the gap generally increase with the reduction in the gap width. Physical understandings revealed in this study are significant to help guarantee the operation safety of offshore side-by-side floating structures in practice.