ABSTRACT
This paper presents the methodology that has been used in the design stage to analyse the vibrations of a Coastal Patrol Vessel (CPV), caused by two ship propellers and 30 mm gun. The analysis is performed by the finite element method, with mesh size defined by spacing of transverse frames and longitudinals. The lowest natural frequencies of vibration of whole ship are determined to estimate the risk of main resonances. Propeller excitation forces are determined using specialized in-house computer program, calibrated by the measurements of hull pressure pulses performed in the cavitation tunnel. Forced harmonic vibration analysis due to the propeller excitation is then performed. Structural reinforcements are proposed in order to satisfy vibration criteria defined by ISO 6954. Free vibration analysis of the gun foundation is performed in order to meet gun manufacturer’s requirements. In addition, transient dynamic response of ship structure, caused by gun firing force time history is also presented.
