An efficient time-domain analysis of very large multi-body floating structures

摘要

While the frequency-domain approach represents a very useful approximation for VLFS, the application of the time-domain approach has certain advantages which allow more realistic evaluation of loads and motions. These include the capability to include nonlinearities which may arise from the structure, such as connectors between modules and nonlinear viscous damping due to eddy-making. A time-domain method is developed for the analysis of the loads and motions of a VLFS which is based on a numerically efficient frequency-domain approach recently developed by Garrison (1998). Numerical efficiency is of great importance in the frequency-domain analysis of VLFS as well as the time-domain approach. Frequency-domain results are presented to demonstrate the validity of the approximations which is based on neglecting the hydrodynamic interaction between distant modules and these results are then used as a basis for an efficient time-domain approach. The approach is shown to be an accurate and practical and does not preclude the extension to the inclusion of drift forces, an option that is lost in the case of frequency-domain methods based on the Haskind's relations approach.