Subsea Cable Laying Problem

Abstract

Subsea cable laying process is a difficult task for an engineer due to many uncertain situations which occur during the operation. It is very often that the cable being laid out is not perfectly fit on the route being planned, which results in the formation of slack. In order to control wastages during installation, the slack needs to be minimized and the movement of a ship/vessel needs to be synchronized with the cable being laid out. The current problem was addressed using a mathematical model by considering a number of defining parameters such as the external forces, the cable properties and geometry. Due to the complexity, the model is developed for a steady-state problem assuming velocity of the vessel is constant, seabed is flat and the effect of wind and wave is insignificant. Non-dimensional system is used to scale the engineering parameters and grouped them into only two main parameters which are the hydrodynamic drag of the fluid and the bending stiffness of the cable. There are two solutions generated in this article; numerical and asymptotic solutions. The result of these solutions suggests that the percentage of slack can be reduced by the increase of the prescribed cable tension, and also the increase in either the drag coefficient of the sea water or the bending stiffness of the cable, similarly will result in lower slack percentage.