An approach to constrained hydrodynamic optimization of ships

Since their foundation, model basins play an important role in hydrodynamic ship optimization. Their customers (ship yards, ship owners, navies, etc.) come to verify their design targets, but expect in addition advice on possible improvements. Such advice is based on experience and know-how, on careful analysis of model test results, on observations in the testing facilities and, since 15 years, on results of numerical flow simulations.
The rapid development of Computational Fluid Dynamics (CFD), i.e. the prediction of flow phenomena by numerical solution of a mathematical model of the flow, has resulted in a strongly increasing role of flow computations in hydrodynamic ship design. Analysis of the results by an experienced designer provides valuable indications on how to modify the hull form to improve the flow and hence the ship’s performance. In a number of steps, significant improvements are often achieved.
Attempts to improve this process are continuing. The improvement is partly to come from better CFD predictions but also from speeding up the optimization process. In this paper, we will describe the enhancements recently introduced at MARIN.
We advocate a semi-automatic optimization technique that is suitable for routine application in practical ship design projects, the principal features being:

• the completely flexible parameterisation of hull form variations;
• the effective and intuitive system for specifying the deformations;
• automated preprocessing for the CFD tools;
• the important role left for the designer, in selecting variations and analysing results. As we will try to demonstrate, this has opened the way towards a new dimension in CFD-based hull form design.