The Research On Vibration And Sound Radiation From A Cylindrical Shell And The Noise Active Control Based On Mode Theory

The single and double cylindrical shell is the major structure of the underwater vehicles. It has very important theoretic value and practicality to research the vibration and sound radiation and the active control of sound radiation from a cylindrical shell. This paper studies the vibration and sound radiation from the viewpoint of modal theory, then discusses the active control of sound radiation.Firstly, this paper investigates the relationships between structural modes and radiation modes of a single cylindrical shell simply supported at both ends based on modal theory and uses FEM and BEM method to research the relationships in numerical calculation.Then, according to the numerical analysis theory, a method is presented for the selection of a set of sensor locations from lots of candidate sets, which takes the condition number of the matrix as the objective function. Then a modal filter matrix is derived, by which the acoustic radiation mode velocity can be extracted from the response of allotted measurement points. The acoustic power of a structure can be calculated through a weighted sum of acoustic radiation mode velocities. Numerical examples illustrate the method is viable and discusses the relationship between the acceleration of structural measure points and the acoustic power.Last, using transfer function method, a method is presented for active control of sound radiation based on the acoustic radiation modes. Numerical examples show the method is a viable method and discusses the mechanism of the active control.As for the double cylindrical shell, the vibration relationship between inner shell and outer shell is derived based on the comparability of vibration. Then the paper studies the vibration and sound radiation of double cylindrical shell and the active of sound radiation.