Influence of analysis modeling on dynamic stability of a beam subjected to a confined annular axial flow

Abstract

The evaluation methodologies of flow induced vibration on the dynamic stability of elastic beam structure are investigated. In this paper, the instability analysis methods of a beam subjected to a confined annular axial flow are dealt with. Such structures are reactor core structures of nuclear power plants, high-speed trains passing thorough a tunnel, and submarine resources production pipeline, so on. The relation between the annular axial flow velocity and the unstable dynamics of structures has to be clarified. We have compared two analysis methods which can evaluate the dynamic instability of such structures. In first analysis method, the fluid is treated as viscous fluid, and is governed by the Navier-Stokes equation, and the beam structure is treated as the Euler-Bernoulli beam. This is called as the viscous flow solution hereafter. In second analysis method, the fluid is treated as ideal fluid. The viscosity effect is added to the equation of motion. This is called as the nonviscous flow solution hereafter. The complex eigenvalue analysis of the fluid structure coupled equation of motion is performed in order to clarify the dynamic instability. Performing the parametric studies, the comparison between both solutions is investigated. Moreover, the numerical solutions are compared with the experiments which have already reported by one of authors. When an annular gap becomes smaller than other dimensions, it is found that the difference in the critical velocity between the viscous flow solution and the nonviscous flow solution is generated.