Multi-Objective Optimization for Ship Hull Form Design




Kim, Hyunyul

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Hydrodynamic optimization is an important aspect of ship design. The aim of this dissertation is to develop a computational fluid dynamics (CFD)-based computational tool for the hydrodynamic design of ship hull forms. The main components of this hull-form hydrodynamic optimization tool consist of a hull geometry modeling and modification module, an optimization module, and a CFD module. This CFD-based multi-objective optimization tool can automatically modify the shape of a ship hull by minimizing some user-defined objective functions associated with the hydrodynamic performance of the ship with the aid of CFD information. This dissertation covers three main topics. The first topic is the development of a geometry modeling method to produce the initial hull form and to modify the hull surface during optimization cycles. Three hull-form modeling methods are developed, which are NURBS representation, parametric representation, and the combination of the NURBS and parametric representation to represent a complex geometry and to satisfy different design requirements. The second topic is the development of various optimization algorithms. Both single- and multi-objective optimization algorithms are implemented. Several optimization algorithms are employed and compared with one another in various hull form optimization applications. Finally, a CFD module is developed to compute the flow field and evaluate the hydrodynamic performance of the new hull forms obtained during optimization cycles. A lower-fidelity CFD tool (computer code SSF) and a high-fidelity CFD tool (computer code FEFLO) are integrated into the CFD module to allow fast evaluation of the objective functions during design cycles and accurate analysis of the flow about the final optimal hull. The CFD-based multi-objective optimization tool developed under this dissertation has been validated and applied in the design of various types of ships. A diverse set of optimal hull forms can be obtained using the present hydrodynamic optimization tool and significant improvement in hydrodynamic performance can be achieved.



Optimization algorithms, Hull form optimization, Multi objective, CFD, Surface modification, Wave drag reduction