Ship's Seakeeping Prediction Based On Realistic Wave Spectrum And CFD

Accurate prediction of ship's dynamic response in waves, is a hot and frontier topic in the shipping industry and ship hydrodynamic field at home and abroad. The current radar wave measurement system is the only ship equipment that can get the real-time wave information in ship's sailing area and has already obtained the authentication from the Germanischer Lloyd and the Det Norske Veritas. On the other hand, compared with the real ship test, the ship model pool test and the potential flow theory, SCFD (Ship Computational Fluid Dynamics) has a unique advantage, and it has made fruitful achievements in the field of seakeeping. The above two research fruits were fully absorbed to present a new ship seakeeping prediction model based on SCFD and realistic wave spectrum gotten form wave radar.SCFD is a branch of CFD with a narrow application scope, so "CFD" was adopted to be used in the title to avoid misunderstanding.One type of ship equipped with wave observation radar as the object was taken, and a lot of real-measured wave data and ship motion time series were acquired, and it takes the lead in using wavelet time series -Echo State Networks method, and 10 hours' accurate real wave spectrum prediction based on radar wave information had been gotten. Based on that, a combination of moving mesh and sliding mesh to optimize called the SCFD model was used, to conduct a ship motion comparative test of the target based on universal spectrum like Jonswap spectrum and predicted spectrum. The results showed that the predicted spectrum is better than the universal spectrum, the optimized SCFD model has high reliability and the seakeeping prediction of their combination and the measured values are in good agreement.Based on the optimized SCFD mode, the numerical simulation of vessels pitching, heaving and rolling on the middle and high sea condition in different course speed was realized and their response spectrum was gotten. In this paper, the problem of green water?slamming and added resistance in middle and high sea was studied and the relationship between these strong nonlinear dynamic effects and the course speed was given. The continuous monitoring of the slamming and green water points was achieved and a quantitative analysis gist of the frequency and intensity of slamming and green water was provided.The loss of pure stability of ships along with the wave has been a difficult problem in the study of ship's seakeeping, as well as a focus of international maritime organization (IMO). Based on the SCFD method, the stability of ships in the situation where the ships loses its pure stability worst was studied, and the situation is named "ride the wave" (wavelength is equal to the captain, crest is located in the middle of vessel). The numerical simulations of the flow field of the model "riding the wave" in still water and three different waves with different height was carried out, and the curves of the ship's stability was obtained. The results showed that when the ship sailing "ride the wave", the larger the wave angle is, the more serious the pure stability of ships loses; and because the speed of the ship which is riding the waves is high, the influence of ship wave can't be ignored. Research results provided a new way for the precise calculation of stability loss of ship which is sailing along with waves.