Dynamic responses of a riser under combined excitation of internal waves and background currents

• Main Authors: Min Lou, Chenglong Yu
• Format: Article
• Language: English
• Published: Elsevier 2014-09-01
• Series: International Journal of Naval Architecture and Ocean Engineering
• Subjects: Dynamic response; Internal waves; Background currents; Taylor-goldstein equation; Newmark-β method
• Online Access: http://www.sciencedirect.com/science/article/pii/S2092678216301716

In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-β method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode.