Surge motion of a semi-submersible in freak waves

Abstract

The surge responses of a semi-submersible under freak wave sequences are studied in time domain. In the present study, a measured New Year Wave sequence is applied to the reference semi-submersible, and its surge responses are analysed to reveal the interaction with freak waves. To investigate the influences of the relative phases, crest amplitudes and the three sister waves, a series of freak wave sequences with different wave parameters have been generated by embedding a freak wave sequence into a random wave sequence. Focuses are paid to the magnitudes of the surge responses, which are directly related to the forces of mooring lines. The surge motion amplitude is observed to be significantly influenced by the freak waves. Main conclusions are drawn regarding the influence of freak waves and their wave parameters on the surge motion responses.

Keywords:

• Freak wave
• surge response
• semi-submersible

Acknowledgements

This work was financially supported by National Natural Science Foundation of China (grant no. 51239007) and Shanghai Yang Fan Program (grant no. 15YF1406100). Wenhua Zhao is supported by the Shell EMI offshore engineering initiative at the University of Western Australia. The sources of support are gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by National Natural Science Foundation of China [grant number 51239007]; Shanghai Yang Fan Program [grant number 15YF1406100]. Wenhua Zhao is supported by the Shell EMI offshore engineering initiative at the University of Western Australia.