Abstract
Vibration analysis is a crucial process in ship design to guarantee crew’s comfortability and to save operating costs by predicting problematical resonance in advance. This study focuses on idealizing fluid mass in tanks by positioning point mass element and quad elements inside the tanks. Also, the added mass effect induced sea water surrounding a ship was included in the present study. The natural frequency obtained from free and forced ship vibration analysis were compared and assessed in the manner of ISO regulation. Finally, it was concluded that the quad element was more adequate to idealize fluid entities in tanks since it was difficult in arranging point mass elements at each grid points properly.
Highlights
Ship design is a sustainable process which each stage correlates each other
The virtual mass method in NASTRAN using fluid-structure interaction has been used as an adequate technique to consider an added mass effect caused by sea water [3]
MFLUID card was used to consider the added mass effect induced by the sea water contacted with the outer shell plates
Summary
Ship design is a sustainable process which each stage correlates each other. A design assessment should be conducted to achieve the optimum level and to satisfy demands of the ship owner for the purpose of operational costs. A ship is accelerated in the ocean, sea water surrounding the ship simultaneously has to be accelerated. This is called an inertial effect known as added mass effect which has a tendency to make natural frequencies decrease [1]. The virtual mass method in NASTRAN using fluid-structure interaction has been used as an adequate technique to consider an added mass effect caused by sea water [3]. This study investigates the global ship vibration of a 1500-ton fishery research vessel using finite element method and summarizes the dynamic structural response depending on methodologies. Added mass induced from sea water was calculated by the virtual mass method which utilizes MFLUID card in NASTRAN. Free and forced vibration analysis were conducted to compare two methodologies and its results were evaluated based on the Guidance Note and ISO standards [5-6]
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