DESIGN OF SHIPS FITTED WITH TWO-STROKE ENGINES IN VIEW OF LOW VIBRATION LEVEL

This paper presents a practical procedure for the consideration of excitation forces generated by slow-running main engines in global ship vibration analyses. The structure of the main engine is incorporated into the finite-element-model of the ship's hull. The excitation forces are calculated directly from the indicator diagram of the actual engine. A computer programme distributes the excitation forces of the different orders on the relevant nodes of the finite-element-model. A comparison between calculated and measured amplitudes reveals good agreement. Following this approach, the most economical measures to reduce the vibration level to the necessary extent can be defined as early as in the design stage. However, overreactions with regard to the measures are avoided. In this way investments effecting the vibrational behaviour are minimised.