Simulation On Ship Heave And Pitch Motions In Head Seas

Ship’s heave and pitch motions have drawn much attention in the field of seakeeping study. Ship heave and pitch motion mathematical model with high accuracy and real-time simulation is required for marine simulator’s behavior reality of Det Norske Veritas (DNV). Using Ordinary Strip Theory (OST), this thesis establishes mathematical model of ship heave and pitch motions and solves the model numerically in regular head waves. The paper aims at its real-time visualization marine simulator system. The main contributions are listed as follows:1. This thesis establishes ship’s heave and pitch motion mathematical model based on OST. With hydrodynamic principle, ship’s heave and pitch motion model is obtained by analysizing the force when heaving and pitching in regular head seas. The model presents the formula for solving the general coefficient in equations.2. Using Tasai’s data, this thesis gets the hydrodynamic coefficient and wave exciting force of the hull. First, the hydrodynamic coefficient and wave exciting force at each station are obtained. The calculations employ the non-dimensional hydrodynamic mass and the ratio between the amplitude in infinity and oscillation amplitude near the strip. Then, numerical integrations result in the add inertia moment, add mass,damping coefficient and wave exciting force of each station. Finally the total hydrodynamic coefficient and wave exciting force of the hull are also acquired.3. The model is validated based on S-175 standard container experimental results. Using Visual Studio 2010, this thesis calculates add mass, damping coefficient and wave exciting force. Forth-order Runge-Kutta algorithm is used to solve the model. The program simulates S-175 standard container motion at different ship speed, wave frequency and wave amplitude. The results are validated through two ways. Firstly, the thesis compares the simulation results and experimental data in Matlab. Then the thesis incorporates the model with marine simulator system, realizes real-time dynamic simulation of ship’s heave and pitch motion. Simulation results manifest that the model is reliable.