The wave buoy analogy - estimating high-frequency wave excitations

The paper deals with the wave buoy analogy where a ship is considered as a wave buoy, so that measured ship responses are used as a basis to estimate wave spectra and associated sea state parameters. The study presented follows up on a previous paper, Nielsen [Nielsen UD. Response-based estimation of sea state parameters — influence of filtering. Ocean Engineering 2007;34:1797–810.], where time series of ship responses were generated from a known wave spectrum for the purpose of the inverse process — the estimation of the underlying wave excitations. Similar response generations and vice versa processes are carried out in the present paper; however with one of the responses being the relative motion which is a type of response that is sensitive to high-frequency excitations. Based on the present study it is shown that by including the relative motion, the frequency-wise energy distribution can be estimated reasonably well, even considering high-frequency wave components of a wind sea wave spectrum.