Numerical simulation of ice sheet – FPSO interaction

Abstract

The present thesis is devoted to investigation of FPSO interaction with level ice. The interaction with level ice is only addressed, disregarding other ice features. The scope of the thesis focuses upon two major problems: (1) numerical modeling of an ice sheet bending and (2) simulation of FPSO surge motion in level ice. The consideration of an ice sheet bending is based on the thin plate theory. The problem is solved by means of finite difference method “manually” implemented in MATLAB. The numerical modeling of an ice sheet bending is intended to investigate ice failure load, which plays essential role for ship’s performance in ice. The numerical model of ice sheet bending has been tested in terms of failure mode prediction by comparison with full-scale results obtained for jacket platform in Bohai Bay, China. A satisfactory agreement of failure mode prediction has been achieved. Failure mode prediction was necessary to estimate ice breaking length. So-called “nodal analysis” concept was proposed for the purpose to determine the interaction contact width. Two output parameters of the numerical model of ice sheet bending – ice failure load and bending failure mode – have been employed for investigation of FPSO surge motion in level ice. The simulated results of FPSO surge motion were compared with model ice tests of moored vessel behaviour in level ice and good compliance has been achieved. The numerical model has well predicted the phenomenon of mooring load increase in the case of low ice drift velocity. The two numerical models developed within the scope of the thesis are believed to be a useful tool for investigation of ice sheet – FPSO interaction.