Corotational cable elements for the study of fluid-structure interaction

The present work deals with the development of a numeric procedure adapted to the study of the nonlinear motion of a flexible structure (i.e. a suspended cable) interacting with a fluid flow. The large displacements and rotations related to the behaviour of flexible systems require a particular Finite Element formulation to describe the exact position and orientation of each part of the system during the motion. The numerical procedure here presented reposes on a step-by-step response calculation method and on cable finite elements capable to compute the interaction forces induced by a steady or random fluid flow (wind). Two different Finite Elements are superimposed to model this kind of system: an isoparametric element (“aerodynamic element”) is adopted to evaluate the aerodynamic forces at the nodes in the varied dynamic configuration occupied by the structure in motion; in addition, a corotational beam element (“mechanical element”) is used to compute the mechanical response of the cable itself, taking into account its flexural and torsional properties and considering large nodal displacements and rotations. The elements and integration procedure are here applied to some numerical examples; the results are compared to those of a different approach.