In this paper, the dynamics of lateral vibration of marine riser in installation is studied. The riser is modeled as an Euler-Bernoulli beam hanging vertically in the floating drilling platforms or vessels and vibrates in the plane of the cross current flow. Wave height and wave period are taken into consideration of the current velocity distribution along the riser axis, i.e., the wave is varying positive and negative periodically respect to time and the value at the sea level is larger than that in deep sea. Besides, in the installation process, length of the riser is varying with time, increasing or decreasing at particular velocity. The riser is subjected to lateral fluid force, induced by cross current flow and axial extension force, induced by weight of blow out preventers. These effects render the riser vibrating at various frequency and amplitude, which would to some extent lead to fatigue and damage to the riser. This is the aim of this work. The governing equations of motion are derived via Hamiltonian's principle. Boundary conditions are modified into the governing equations, thus classic boundary conditions are obtained for numerical calculation. Effects of the weight of blow out preventers, velocity of cross current flow and extending rate of the riser have been discussed. Results show that a larger increasing ratio would destabilize the system; different ratio should be adopted under various current flow load cases. The weight of blow out preventers enhance the stability of the tip of the riser but would destabilize the system at some particular current velocity.
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