Free surface in-port coupling hydrodynamic force ship motion forecasting method and forecasting system

The invention discloses a ship motion forecasting method and forecasting system for coupling hydrodynamic force in a free-surface harbor, and the method comprises the steps: decomposing a watershed of the free-surface harbor into a free-surface harbor internal sub-domain and a free-surface harbor external sub-domain, and giving a velocity potential equation and boundary conditions of the watershed based on a linear potential flow theory; applying a matching condition on the boundary surfaces of the internal and external sub-domains; calculating a boundary integral equation; dispersing boundaries of the internal and external sub-domains into units, solving a velocity potential, and obtaining pressure through a Bernoulli equation according to the obtained velocity potential; performing integral calculation on the pressure to obtain hydrodynamic force acting on the ship body; therefore, a six-degree-of-freedom motion equation of the ship is obtained, and the ship motion is forecasted. On the basis of a drainage