The coupled radial-axial deformations analysis of flexible pipes conveying fluid

This paper presents large deformation analysis of pipes conveying fluid in which two complicated behaviours are taken into consideration. The first is the coupling between radial and axial deformations of pipe wall, and the other is the interaction between a deformed pipe and transported fluid having the variable internal flow velocity. The coupled radial–axial deformation theory of the pipes and the continuity theory of flow inside the moving deformed pipes are developed to undertake these coupling behaviours. All strong and weak forms of governing equations are obtained by carrying out the virtual work formulation. The hybrid-finite element method is used to solve the highly non-linear static problems, which configure the initial large deflection and large strain conditions of the pipes. The state-space finite element model for use in analyses of non-linear vibration and system stability is established as well as the suggested numerical solution procedures. The numerical studies of the pipes under circumstances of intense radial loads such as deep-water risers demonstrate that even a slight change of the radial deformation has a significant effect in increasing non-linear responses, and reducing stabilities of the pipes