This paper presents a practical hydrodynamic optimization tool for the design of a modern container ship. In stead of using complex and computationally expensive CFD solvers with standard optimization methods, the present tool adopts the variable fidelity method that uses lower-fidelity models and a scaling function to approximate the higherfidelity models to reduce computational cost. The method aims to maximize the use of lower-fidelity, cheaper models in iterative procedures with occasional, but systematic, recourse to higher-fidelity, more expensive models for monitoring the progress of the algorithm. The method is globally convergent to the solution of the original, highfidelity problem. For purposes of illustration, the potential flow solvers with nonlinear and linear free surface boundary conditions are used as high-fidelity model and lower-fidelity model, respectively, in the present hydrodynamic optimization tool to determine the optimal hull form of a modern container ship for a given speed with displacement constraint.
Hydrodynamic optimization is an important aspect of ship design. In order to perform hydrodynamic design optimization, an objective function that compares the merit of different designs quantitatively needs to be defined. This objective function depends on design variables, and the changes in flow variables due to them. The aim is then to minimize (or maximize) this objective function subject to PDE (Partial Differential Equations that govern the flow) constraints, geometry constraints, and physical constraints. The CFD-based hull-form hydrodynamic optimization consists of CFD solver/solvers that can be used to compute the flow field and evaluate the objective function and its gradient if required by the optimization technique, hull geometry modeling and modification that are linked to the design variables, optimization technique that can be used to minimize the objective function under given constraints.
