Shape optimisation of an integrated bulb-keel

Abstract: The objective of the thesis was to shape optimise an integrated bulb-keel using a numericaloptimisation method and to validate how well the used methods suit this kind of problem. Thealgorithm used for the optimisation was a Non-dominated Sorting Genetic Algorithm, NSGAII.The optimisation was limited to the bulb part of the keel and 7 design variables were usedtogether with 4 inequality constraints. The hydrodynamic performance of the keel wasevaluated using a RANS viscous solver and the objective function used in the optimisationwas the ratio of drag coefficient over lift coefficient CD/CL.The numerical CFD calculations were validated with experimental wind tunnel tests, which isa crucial part when investigating new types of numerical flow problems. The CFDcalculations were also verified using a Least Square Root method in order to obtain thenumerical error. The comparison between the wind tunnel results and the CFD results showedthat the CL/CD-ratio was predicted very similarly for the numerical and experimental tests.The optimised keel design had a CD/CL-ratio improvement of around 4% compared to theinitial keel design. Finally the keels were mounted on a hull of a 40-foot yacht and tested in avelocity prediction program (VPP) in order to get a more understandable performanceindicator of the keels.