In designing the mooring system of a very large floating structure (VLFS) it is essential to estimate the slowly varying drift force in random seas. For a small vessel Hsu's method or Newman's approximation may be used to simulate this slowly varying drift force. However based on experiments and/or field observations it was found that the slowly varying drift force acting on a VLFS could be reduced to a great extent from the simulated values based on those methods. Thus the conventional methods are not applicable for a VLFS. This discovery led to the development of several methods for estimating the slowly varying drift force on a VLFS e.g. Namba et al. (J Soc Nav Archit Jpn 186:235-242 1999) and Shimada and Maruyama (J Soc Nav Archit Jpn 190:347-351 2001). However Namba's method is only applicable to a pontoon-type VLFS with a shallow draft and Shimada's method is too simplified to account for the general shape of a VLFS and elastic deformation. These methods have been expanded in this article and by our proposed method any shape of VLFS and the effect of elastic deformation of the VLFS can be included. Formulations and several numerical examples are given.
All Science Journal Classification (ASJC) codes
- Ocean Engineering
- Mechanics of Materials
- Mechanical Engineering