A Procedure for the Dynamic Positioning Estimation in Initial Ship-Design

Abstract

The importance of Dynamic Positioning (DP) is growing because of the increase in the number of offshore construction sites requiring DP for their operations. Due to the high complexity of the calculation process, a few institutions are able to estimate the station-keeping capability of vessels. Since the DP capability of a vessel is directly connected to the hull form as well as the propulsion and manoeuvring system, it is obvious that DP is a major design task. Hence, it should be taken into account during the early ship design phase. The paper describes the background studies, methodology, and mechanism associated with the formulation and development of a reliable design tool to calculate DP capability, versatile enough to be integrated into the initial ship design stage of a vessel. The process includes the creation of the general concept of the solver module with the capacity to estimate empirically the external loads on the vessel due to the wind, current, and waves. The static force balance is obtained by suitably predicting thrust requirements for the propulsion system, bearing in mind the power and positional constraints. The optimization of the design variables for the station-keeping criteria targets the highest capability at the lowest possible energy expenditure. Finally, the results are automatically presented in the form of standard DP plots. As a method of cross-checking on the reliability, verification of the DP tool is done with the help of available data from several DP vessels. The studies of relevant parameters during the development of the DP tool gave rise to some valid topics requiring further analysis. These are also outlined as a measure for future considerations to increase the reliability of the methods as well as the estimation tool. Keywords