Optimal heuristic design of a high efficient SWATH-type vessel

The paper illustrates the shape optimization of the immersed part of the hulls of a SWATH (Small Waterplane Area Twin Hull) vessel, a particular type of catamaran that has already been used as passenger ship and fast ferry. The optimization tool aims to find the best combination of parameters, such as the shape of the immersed hulls, their distance, and draft that induces the lowest hydrodynamic resistance. This application refers to the same design vessel that has fixed displacement and cruise speed defined for specific mission requirements. Size limits are also imposed by operability requirements.The optimization makes use of a genetic evolutionary algorithm, a stochastic global search method based on the Darwinian concept of natural selection. The optimization environment has been created in Matlab and is based on a parametric geometry definition module, able to define a series of hull forms through the CST technique (Class Function/Shape Function Transformation). For the evaluation of the hydrodynamic resistance, CFD simulations are implemented in STAR-CCM+.The main reasons that motivate this research are the integration of computer-assisted parametric definition of vessels hull shapes with the CFD techniques for the prediction of hydrodynamic performances, and to assemble an optimization tool able to facilitate the design procedure through the creation of complete performance databases of customized hulls.As the amount of the total resistance reduction with an improved hull shape is impressive, the usefulness of applying automated CFD optimization techniques in the design is remarkable and should persuade the reader to consider this alternative in the design stages of a boat.