Theoretical and experimental prediction of the response of compliant risers

The general three-dimensional linearized dynamic equations of a compliant riser, idealized as a rotationally nonuniform rod, around a nonlinear static configuration in the presence of general current and monochromatic wave excitation are formulated. Nonlinear forces such as quadratic drag are harmonically linearized by minimizing the mean square error between the linear approximation and the nonlinear force. The theory is implemented in a computer program which allows analysis of a variety of compliant riser configurations. Numerical examples for catenary risers are included. Comparisons of our theoretical predictions with experimental results obtained from a 1.5-m catenary compliant riser model excited monochromatically at the top parallel to a constant current are also presented to evaluate our ability to predict the response of compliant riser systems.