MODELLING AND SIMULATION OF SUBSEA UMBILICAL DYNAMICS: A NUMERICAL APPROACH

In this paper, we describe the mathematical method we used to model and simulate the dynamics of a subsea umbilical. The subsea umbilical dynamics are modelled as a tensioned beam with hydrodynamic forces and other forces acting on it. The forces and moments acting on the umbilical were considered in 3-D (three-dimension) numerical form using the Newtonian method so as to obtain a model that will predict the motion of the umbilical cable in subsea environment. The derived model consists of three (3) uncoupled, non-linear, partial differential equations (i.e., a set of two 4th-order and one 2nd-order non-linear partial differential equations). The equations were non-dimensionalized and simulated using Mathematica. The results of the simulations are presented in this paper. Based on our simulation of the effect of tension on the subsea umbilical, we conclude that an increase in tension results in an increase in the frequency of oscillations of the umbilical cable in the normal and transverse directions keeping the effects of current/water forces constant