Simulation Based Design of Fast Multihull Ships

The numerical optimization of the initial design of a fast catamaran (HSSL-B) is carried out through two Simulation Based Design (SBD) frameworks, based on advanced free-surface RANS solvers and Global Optimization (GO) algorithms. Their successful application in a real industrial problem has been the result of a close collaboration between code developers, users and industry, both in the detailed formulation of the optimization problem and in the analysis of the results, that helped in overcoming challenges arising from the complexity of the application, as well as of the mathematical/numerical models and their interaction with the optimization algorithms. The fluid-dynamic analysis of the flow past the catamaran proved to be interesting too and the use of RANS solvers resulted fundamental in dealing with the multihull interference problem. In the case investigated the separation distance was small and the viscous flow quite distorted by the proximity of the hulls, so that only viscous solvers could correctly capture the flow details. Sinkage and trim effects, due to the high speed range and again to the small separation distance investigated, are also relevant. Preliminary results show for both the SBDs similar geometrical trends.