A Stochastic Model for Evaluation of Seakeeping Performance

摘要

The stochastic process model of the long-term statistics of ship responses is proposed. We have investigated the correlation between the wave height and the standard deviations of the ship responses at sea. Analysing the monitored ship response data on board of a container ship and a bulk carrier, we have found that these standard deviations have three stochastic properties: the Markov property, regression to equilibrium, and linearity of fluctuation. The stochastic process model of the ship responses is constructed based on these properties. This model is given by the stochastic differential equations, and the probability density function is obtained by the Fokker-Planck equation. Generally, the stochastic differential equation is difficult but this model is not difficult because it has only three parameters. Furthermore, we explain long-term prediction and simulation of ship responses by this stochastic model and introduce a method of evaluating the monitoring data of ship responses on board.