Experimental Investigation on the Wave Elevation around a Semisubmersible in Monochromatic and Irregular Waves

Abstract

In the present work, the wave elevation around a floating semisubmersible was experimentally studied in monochromatic and irregular waves. The effect of the direction of incident waves was considered by introducing five directions: head sea, quartering head sea, beam sea, quartering following sea, and following sea. In monochromatic wave tests, the normalized wave elevation, harmonic components, mean, and skewness of wave elevation were used to analyze the response of disturbed wave elevation. In irregular wave tests, a response amplification factor, ratio of the significant height of diffracted and radiated waves to that of incident waves, was used to analyze the amplification effect of diffraction. The wave run-up in monochromatic wave tests was found to respond significantly on the weather side and mildly on the lee side. However, a strong response of wave run-up on the lee side was observed in irregular waves. Moreover, a phenomenon of near-trapping associated with a large magnification of wave crest height was discovered and confirmed in between two upstream columns. The near-trapping phenomenon was only observed in monochromatic wave tests, and this phenomenon was not witnessed in irregular wave tests. The energy distribution of disturbed waves was also investigated by using the wave energy density spectrum. The energy distribution was dominated by the diffraction in cases in which strong diffraction occurred.