Numerical and Experimental Investigation of Parametric Roll
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- Institutt for marin teknikk 
The main purpose of this Master thesis is to provide insights about thesensitivity of parametric roll occurrence. Parametric roll resonance may leadto large roll angles experienced by the ship typically in longitudinal waves. Itis related to the periodic change of stability when the ship's wave encounterfrequency is approximately twice the rolling natural frequency and the dampingof the ship to dissipate the parametric roll energy is not sucient to avoidthe onset of a resonant condition. This study contains a brief description ofthis 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 linearand quadratic damping corrections. The inuence of the parametric rolloccurrence relative to appendages such as skeg or bilge keels is carried outusing the 6DoF potential ow solver. The numerical results are presented asa function in time, showing the amplitudes in heave, roll and pitch.A 1.5DoF model is chosen to investigate the parametric roll resonance ona shing vessel. The inuence on the occurrence and features of the phenomenonare analyzed using this model. Hence the reliability and applicabilityof the simplied approach is discussed. Comparing the 1.5DoF modelresults with experimental results of scaled model testing of the same shingvessel, a validation of the model is performed, showing that the model isconsistent with the experiments.