620 - Ingenieurwissenschaften (Engineering and allied operations)
Wind turbines can be installed on
floating platforms in order to use wind resources, which blow above the deep sea. The presented research investigates the hydrodynamic behaviour of the Olav Olsen Concrete Star floater in free decay motion.
The floater is a new design of a semisubmersible offshore floating platform for wind turbines.
The thesis describes the physical free decay testing of a 1/40 plastic scale model in
a water basin as well as numerical simulations of the same test cases with the aero-hydro-servo-elastic code 3Dfloat. Tests are performed for the heave and pitch degree
of freedom and without mooring lines. The experimental results are compared with
the simulation results in order to find adequate added mass and damping coeffcients
for the numerical model and to validate 3Dfloat for the prediction of heave motions.
The overall added mass coefficient for the vertical direction is found to be CM=2.71
and the damping behaviour is simulated by using a Morison coefficient of CD=8.0
and a considerable amount of additional linear damping. Subsequently, the results
are discussed in order to find possible causes for discrepancies between the results.