Computational investigation of ship propulsion performance in rough seas

In this paper, the performance of a merchant vessel propulsion system during acceleration is evaluated under different sea state conditions. The various parts of the main propulsion system have been modelled by using a mean value approach for the engine model with differential equations to calculate the engine crankshaft and turbocharger shaft speeds. Ship propulsion system has been modelled by using differential equations to calculate vessel speed and speed of advance. The output of the engine model has been validated under steady conditions according to the main engine shop test performance data. The calm water resistance is calculated following the ship sea trials results, whilst Wageningen polynomials have been used to simulate the propeller performance for the given hull resistance and speed. In order to estimate the added resistance for different weather conditions, the recommended procedures by International Standards have been followed. Then, the propulsion system performance is evaluated, both in calm water and waves, to investigate the main engine response during acceleration. Based on the simulation results, the propulsion system performance is discussed in respect for the engine response and vessel hydrodynamic performance, predicting the maximum vessel speed for the available engine power and speed.