Experimental verification of finite element model for vibration of a narrow gap, fluid coupled, concentric flexible cylinders

Abstract

The influence of a fluid environment on the dynamic characteristics of structure has been of interest for hundreds of years. Analyses have varied from classical formulations, numerical discretization, or experimentation. In this study, both experimental and numerical analysis by Finite Element (FE) are conducted in an attempt to quantify the effects of the actual or real fluid versus the idealized nonviscous fluid (as assumed in the FE) as a function of cylinder dimensions. The analytical model employed 3D linear finite element displacement technique on a plate structure and eight‐node brick fluid elements. Solutions obtained are for undamped, linear elastic and small displacement response of the system. The FE method's accuracy and applicability is demonstrated by comparison of numerically computed natural frequencies and mode shapes to experimental data. Numerical solution sensitivity to parameter variations such as cylinder wall thickness, gap width and boundary conditions, and the relative significance of nonlinear and viscous effects observed in the experimental results are discussed. [Support by the Babcock and Wilcox Company and the Clinch River Breeder Reactor Project is acknowledged.]