An investigation on the influence of the supporting structure on the dynamics of the rotor system

This work presents a methodology to analyse the influence of the foundation or supporting structure on the rotor-bearings system. The mathematical procedure applies a modal approach using modal parameters of generalised mass, damping ratio and natural frequencies. The Finite Elements Method is used to model the rotor. The linear model of the foundation is obtained by FEM and a modal approach is applied to reduce the degree of freedom order of the foundation model. The modal parameters of the foundation are estimated using the frequency response functions and their respective Fourier Transforms, obtained experimentally. An analysis of the frequency response of the complete system is accomplished considering physical co-ordinates for the rotor-bearings system and principal co-ordinates for the foundation. Convergence of the presented methodology is verified and the effect of the flexible foundation on the complete system response is analysed.