Simulation of ship motion and deck-wetting due to steep random seas

Abstract

The extreme motion and load of ships have been assessed using a linear frequency domain method or a linear energy spectral method and RAOs, which may be too approximate to be used for estimation of ship motion in severest seas. The new technology uses simulation in the time domain to deal with the non-linear responses to the random seas. However, the current simulation technique has been successful only up to the sea state of 7 (“high seas”), defined by the significant wave height of 9 meters. The above cannot provide the extreme wave loads and motions for seas higher than the sea state 7. The ultimate goal of this work would be to develop a new technique that can simulate responses to the seas of states 8 and 9. The objective of the present study is to simulate the vertical relative motion and wave topping of a moored ship in the time domain by varying the significant wave heights. The analysis was able to predict with a fair accuracy the relative motion characteristics of a freely floating body in the head and beam sea conditions. The resonance aspects and its significance in the overall response are also analyzed.