Analysis of coupled vibration of many concentric cylinders filled with fluid

The equipment and structures, which are composed of multiple cylinders and contain liquid between them, such as vertical pumps, heat exchangers, the structures in nuclear reactors and so on, are cosidered to cause coupled vibration through liquid. As the method of solving such liquid-coupled vibration, it is important to consider the vibration characteristics of structures in liquid taking elastic deformation into account, and it belongs to the field of hydroelastics. In this study, it was intended to examine the basic property of a liquid-coupled vibration system of multiple cylinders filled with liquid, extending the fundamental theory in the previous paper. As the procedure of analysis, liquid was assumed to be incompressible, nonviscous perfect fluid, and the equation of bending vibration was derived for multiple cylinders taking three-dimensional fluid force into account, then its general solution was obtained. Next, the transfer matrix of the multiple cylinders filled with liquid was derived, and the method of numerical calculation to determine the coupled natural frequency, vibration mode and steady response of the system was established. The propriety of this analysis method was examined by the vibration experiment of a double cylinder model. (Kako, I.)