A proper use of sea trials data for marine propulsion simulations

Simulation in engineering plants design should be used as a powerful tool in order to investigate several design options in different working conditions. From this point of view, simulation techniques are powerful only if they are reliable. Numerical simulation codes are generally based on algebraic and differential equations that are usually tested at the design working point of the represented dynamical systems; instead the validity of the models to represent off design conditions is generally not well documented, due to lack of information. Therefore one of the most difficult tasks in simulation problems is developing complete numerical models, able to represent the entire working area of the considered system. The availability of full-scale experimental data to test and update mathematical models becomes essential for the simulation developer, which could be able to improve the fidelity of the simulation models, for similar applications, on the base on proved experience. The paper is focused on the validation process of the propulsion simulation code for a naval vessel, developed at Genoa University. The simulation code has been used by the automation provider in order to design and test the real propulsion control system on board. To validate and to improve the code simulation results have been compared with sea trials data. Simulation output regarding some dynamic models, as for instance the engine model, was very reliable in the working points near the design conditions, generally at the high engine loads. On the contrary, as it was expected, the major discrepancies occurred at the lower engine loads, in particular where the design characteristics, necessary for the numerical model development, were assumed or extrapolated because their knowledge was not yet available during the design phase. In particular, the engine simulation setup, based on a proper analysis of sea trials data, is briefly described in this paper, in order to underline the importance to plan a proper campaign of specific measurements on board, to be used in marine simulation field.