Shape optimisation of an integrated bulb-keel
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Typ
Examensarbete för masterexamen
Master Thesis
Master Thesis
Program
Publicerad
2011
Författare
Ljungqvist, Kasper
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The objective of the thesis was to shape optimise an integrated bulb-keel using a numerical optimisation method and to validate how well the used methods suit this kind of problem. The algorithm 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 used together with 4 inequality constraints. The hydrodynamic performance of the keel was evaluated using a RANS viscous solver and the objective function used in the optimisation was the ratio of drag coefficient over lift coefficient CD/CL. The numerical CFD calculations were validated with experimental wind tunnel tests, which is a crucial part when investigating new types of numerical flow problems. The CFD calculations were also verified using a Least Square Root method in order to obtain the numerical error. The comparison between the wind tunnel results and the CFD results showed that 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 the initial keel design. Finally the keels were mounted on a hull of a 40-foot yacht and tested in a velocity prediction program (VPP) in order to get a more understandable performance indicator of the keels.
Beskrivning
Ämne/nyckelord
Transport , Farkostteknik , Transport , Vehicle Engineering