Experimental study on hydrodynamic characteristics of a moored square cylinder under freak wave (II: Frequency-domain study). (1st January 2021)

• Record Type: Journal Article
• Authors: Pan, Wenbo; Liang, Chen; Zhang, Ningchuan; Huang, Guoxing
• Is Part Of: Ocean engineering. Volume 219(2021)
• Publication Date: 2021-01-01
• Subjects: Hydrodynamic characteristics -- Square cylinder -- Freak wave -- Random wave -- Frequency-domain; Ocean engineering -- Periodicals; Ocean engineering; Periodicals; 620.4162
• DOI: 10.1016/j.oceaneng.2020.108452
• Languages: English
• ISSNs: 0029-8018

Abstract

Abstract: Previous studies indicated that the occurrence of freak wave has a significant impact on the time-domain characteristics of a moored floater dynamic response. In this study, extensive investigations have been performed to figure out further dynamic response characteristics of a moored square cylinder under freak wave in frequency-domain. In the experiments, the wave sequences with and without the freak wave are defined as freak and random waves, respectively. The results show that, the freak wave parameter α 1 and spectral peak period have significant impacts on the dynamic response characteristics of the moored floater in frequency-domain. The effect of freak wave on surge and mooring tension of the floater is figured out through the low frequency components (0–0.5 f p ) which leads to significant increase with α 1 . Followed the occurrence of freak wave, surge increases sharply and oscillates for longer than 20 wave periods in low frequency. Without the occurrence of freak wave, however, both amplitude and oscillating of surge is significantly weaker. The mooring tension response is subjected to surge and hence the trend of variation is similar to surge. Highlights: Under freak and random wave, extensive tests were conducted to measure the floater motion and mooring tensionsynchronously. Wavelet analysis method is adopted to compute the time-frequency spectra of the dynamic responses. The freak wave parameter α1 plays a key role on the surge of the floater and the mooring tension. Followed the occurrence of freak wave, the surge increases sharply and oscillates for longer than 20 wave periods in low frequency.