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Forced vibration analysis of the hull girder by propeller excitation and rudder interaction

Abstract:

The hydro-vibration analysis of hull girder has become a very important methodology in the design stages of a ship, for pbkp_redicting resonance problems that can be caused by the encountering wave loads, or due to the interaction between the ship’s drive line and rudder. This paper presents the methodology that has been used to analyze the Hull-girder vibrations induced due to propeller—rudder interaction, in the design stage of a Coastal Patrol Vessel (CPV). The methodology at first analyze the interaction of the propulsion system and the rudder as two separate sub-systems and finally the interaction with the hull girder in a system of forced vibration caused by the excitation of the propeller. The resulting interaction takes into consideration: the excitation of the propeller, natural frequencies of the drive line, natural frequencies of the rudder, natural frequencies of the structure of equipment foundations, added mass, and damping of both the propeller and the hull girder. Vibration levels acting in the vessel structure are compared with the limits proposed by ISO 6954 (2000).