Numerical Analysis Of Vibration And Acoustic Radiation Characteristics Of Stiffened Cylindrical Shells

The finite length stiffened cylindrical shells is the main structure style in hull part of vessel both in air and water, and the structure noise of these vessels comes from the vibration of shell cause by the exciting force of internal machine and the acoustic radiation in the surrounding media. Therefore, it has great theoretic significance and practice value to do research on vibration and acoustic radiation of finite length stiffened cylindrical shells.This thesis takes use of FEM to discrete structure and simulate fluid using BEM, and using FEM software ANSYS and BEM application to establish a model of vibration and acoustic radiation of finite length stiffened cylindrical shell both in air and water. To calculate the vibration and acoustic radiation of stiffened cylindrical shell in air, we take use of ANSYS to obtain the vibration response of structure, and then calculate the acoustic response by inputting the velocity response of structure surface into BEM application. For the situation in water, coupled vibration response is obtained by using ANSYS to do finite element discretion of both water and structure, and then obtain the acoustic response by inputting the structure surface velocity into the BEM application.This thesis discussed the influence to structure nature frequency, mode shape, velocity of surface, acoustic pressure at surface, field point pressure and radiation power by changing the parameter of longitudinal rib, rings rib, thickness of plate and fluid media. And discussed the law of acoustic radiation of changing the parameter of ribs and thickness and fluid media. The calculation result shows that: the shell thickness has the most important effect on the vibration and acoustic radiation characteristics of increasing the natural frequencies and decreasing the sound radiation. The influence of the stiffeners has no clear trends and has no important influence on radiated sound power. The longitudinal ribs have more influence than the ring ribs on the sound radiation. The sound power radiated by the cylindrical shell in water is much more than that in air.