Development of rational design methodology of deep sea riser

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We completed a computer code to numerically simulate the behaviors of deep sea riser.Both finite difference and finite element modeling have been studied for the code ; the latter was employed. Riser body is divided into numerous segments. Local bending and torsion are represented by the relative displacement of neighboring segments which are assumed rigid. Nevertheless each segment is assumed to extend and compress responding to tension and compression.We derive the equation of motion of a system of the segments from Lagrangean function of a system written in the Euler angle of each segment. Hydrodynamic forces on the segments, added mass and drag force, are computed assuming that the relative flow occurs in the plane normal to the axis of the segment cylinder and has no component into the axis.Our computer code was validated by comparing the simulated motion, tension and bending moment, with the measured ones obtained in the experiments. The experiment are with the hang-off condition of a riser and the forced motion given by the supporting platform floating in waves.We designed a deep sea riser by using the computer code we developed.