Dynamics of the Interaction of Mooring Line With the Sea Bed

Lumped Mass method is a proven numerical approach to analyze the problems of mooring lines. The two-dimensional method was originally developed by Walton and Polachek (1959) for various conditions of frequency and amplitude. Nakajima et al (1982) carried out investigation on the dynamics of mooring lines. In this paper, the interaction of mooring line with the ocean bottom is highlighted and the resulted reduction in dynamic tension is discussed. The line is divided into finite number of lumped masses and linear springs without mass. The damping, associated with the interaction of vibrating chain with the sea bed which is considered to be elastic, is incorporated in the computations. In normal case some part of mooring line will be on the surface of sea floor. Modification to the lumped mass method is done in view of the changed external forces with the change of mode of velocity amplitude along the length of the chain embedded in the sea bottom media. The validation of the modified Lumped Mass method is confirmed by comparing the dynamics of chain on elastic foundation by N.C. Perkins (1990). The sea floor conditions can be found varied for different locations of anchoring and the properties of themore » sea bottom media influences energy dissipation when the mooring line is interacting with it. The dynamic behavior of chain will be different depending upon the change in sea bottom conditions.« less