Nonlinear dynamics of flexible slender structures moving in a limited space with application in nuclear reactors

This paper deals with the modelling and dynamic analysis of thin or slender flexible bodies characterized by axial motion, contacts and friction interaction. Such mechanical systems can be found in cable applications, in petroleum drilling industry, in biomedical applications and in nuclear equipments. An original combination of the absolute nodal coordinate formulation and the classical finite element method is used for the modelling of flexible slender structures moving inside flexible tubes and channels considering the overall system vibration. In a nuclear power plant, it allows to analyse mainly the influence of guide thimbles vibration on the control rod drop. The novelty of the introduced methodology is also in the original usage of the absolute nodal coordinate formulation in the problems of nuclear engineering. All the interaction phenomena such as effect of fluid flow, contact forces, gravitation and buoyancy forces are considered in the mathematical model. The particular application of the presented methodology on the problem of the nuclear control rod drop through vibrating bowed guide thimble helps to formulate interesting conclusions on the rod drop time affected by vibrating guide thimbles.