Numerical and Experimental Investigation of Parametric Roll
The main purpose of this Master thesis is to provide insights about the
sensitivity of parametric roll occurrence. Parametric roll resonance may lead
to large roll angles experienced by the ship typically in longitudinal waves. It
is related to the periodic change of stability when the ship's wave encounter
frequency is approximately twice the rolling natural frequency and the damping
of the ship to dissipate the parametric roll energy is not sucient to avoid
the onset of a resonant condition. This study contains a brief description of
this physical phenomenon and presents the state of the art in terms of theoretical,
numerical and physical modeling.
Using free decay tests, a parameter analysis is carried out, including linear
and quadratic damping corrections. The inuence of the parametric roll
occurrence relative to appendages such as skeg or bilge keels is carried out
using the 6DoF potential ow solver. The numerical results are presented as
a function in time, showing the amplitudes in heave, roll and pitch.
A 1.5DoF model is chosen to investigate the parametric roll resonance on
a shing vessel. The inuence on the occurrence and features of the phenomenon
are analyzed using this model. Hence the reliability and applicability
of the simplied approach is discussed. Comparing the 1.5DoF model
results with experimental results of scaled model testing of the same shing
vessel, a validation of the model is performed, showing that the model is
consistent with the experiments.
Place, publisher, year, edition, pages
Institutt for marin teknikk , 2013. , 84 p.
IdentifiersURN: urn:nbn:no:ntnu:diva-22272Local ID: ntnudaim:9174OAI: oai:DiVA.org:ntnu-22272DiVA: diva2:648727
Greco, Marilena, Professor