A Motion Analysis of a Riser Upper Joint Interacting With a Floating Vessel

Riser motions (acceleration and velocity) should be estimated for the determination of forces on the riser in waves. They are predominantly influenced by vessel motions. Previous analyses involving waves or water depth have not presented details of in-depth approach or extensive numerical results and have ignored motion phase angles. In this paper, a method of prediction and analysis with numerical results is presented for the absolute or relative riser motions and for vessel motion. Mathematical derivations directly relate the equations of the vessel motion to the riser motions. Effects of phase angles and water depth on motions of a (semi-submersible) vessel and a riser are shown to be significant and should be accounted for in the determination of the riser motions.