ESTIMATION OF THE WAVE-INDUCED ROLL-PITCH ANGLE OF SURFACE VESSELS

Surface vessels such as frigates, destroyers, carriers, battle cruisers, coastal guard ships, and fisheries surveillance are capable of operating in severe weather conditions. One of the most challenges in such conditions is the capsizing phenomenon. In this paper, an engineering model occupied with only five primary design parameters of a vessel including length, breadth, draught, weight, draft, and displacement was suggested to estimate the Roll and Pitch angle of a surface vessel and estimated the capsizing capability in heavy sea states. A dataset of six coastal guard ships was used to process the simulation. The simulation results showed that the typical resonance frequency of the Roll angle is between 0.05 to 0.2Hz while that of the Pitch angle is between 0.1 to 0.18 Hz. The Roll and Pitch angle profiles with respect to frequency were plotted to determine the safe operating condition of these ships. To verify the theoretical model in real sea conditions, an Inertia Moment Unit (IMU) - based device was built and implemented. The experiment was implemented in a fisheries boat in the South China sea to test the performance of the device and the correlation with the suggested profile. The measurement results provide relatively coherent matching with the prediction from the simplified model. For the first time, the results suggest a simple and low-cost method to predict the motion of surface vessels and the marine devices in such ships to operate functionally in heavy sea conditions by the use of five primary ship parameters and one sea state parameter.