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Author:Ljungqvist, Kasper
Title:Shape optimisation of an integrated bulb-keel
Formoptimering av en integrerad bulbköl
Publication type:Master's thesis
Publication year:2011
Pages:89 + [20]      Language:   eng
Department/School:Sovelletun mekaniikan laitos
Main subject:Laivanrakennusoppi   (Kul-24)
Supervisor:Matusiak, Jerzy
Instructor:Larsson, Lars ; Vesting, Florian ; Orych, Michal
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  3944   | Archive
Keywords:keel
bulb
NSGA-II
optimisation
CFD
RANS
integrated bulb-keel
Abstract (eng): 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, NSGA-II.
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 uncertainty.
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.
ED:2011-09-13
INSSI record number: 42756
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