TIME DECREMENT SIMULATION OF EXPEDITIOUS OCEANIC CABLE-BODY INSTALLATION

In the simulation of cable-body deployment problems, the final state, i.e. predetermined locations at ocean bottom, are more restrained than the initial state. Thus it was hypothesized that it is possible to re verse the time integration process, i.e. given desired coordinates, st resses and velocities in the final state, small steps backward in time can be taken and the values of all variables predicted needed to achi eve that final state. Solving the cable governing equation backwards i n time and space is mathematically ill-posed. The difficulties in obta ining stable time decrement solutions are described from both numerica l and physical points of view. Several approaches are considered and d escribed. Details are given for the most successful approach which def ines a well-postulated conjugate problem whose solution is close to th e solution of the original problem. Three illustrative examples of the deployment of cable-bodies from a surface vessel are given to demonst rate the validity of the method. (C) 1997 Civil-Comp Ltd and Elsevier Science Ltd.