An Integrated Probability Based Propulsor Hull Matching Methodology

Abstract

Traditionally, designers of marine propulsors select a discrete number of critical design points for which to optimize the propulsor geometry. The design procedure carefully weighs the needs to be fuel efficient, to minimize cavitation, to maintain structural integrity, and to provide enough thrust to reach the desired speed, including the need to overcome any resistance humps. The current work proposes a new, alternative propulsorhull matching methodology that is able to systematically consider the full range of expected operating conditions. A joint probability density function is used to represent the probabilistic operational space as a function of ship speed and sea state, and is used as a weighting function to select the propulsor that will minimize the annual fuel consumption while satisfying a set of constraints. The new probabilistic design approach is able to automatically locate the globally optimal solution by considering the probability of occurrence along with system performance characteristics. Hence, it is able to avoid the inherent ambiguity of selecting the proper design points. The proposed methodology is general to the design of marine propulsors for any type of vessel and engine system. It is applied in the current study for the sizing of waterjets for a surface effect ship.