ABSTRACT

Existing simulation methods are not able to determine in detail the wave loads on a complex sub-sea structure when it is passing through the splash zone. To determine these loads, model tests are necessary. Otherwise only simplified formulations or empirical relations for added mass and damping can be used. The improved Volume Of Fluid (iVOF) method presented in this paper is a potential candidate for the better numerical prediction of the behaviour of a sub-sea structure in the splash zone. The simulated flow around and through the structure looks very realistic and shows a strong resemblance with observations from model tests. The quantitative comparison of the vertical load on the sub-sea structure shows that the total load levels are well predicted. This good initial comparison shows the potential of the iVOF method for the simulation of the behaviour of sub-sea structures in the splash zone. However, significant further development and validation is needed before a fully coupled simulation of a sub-sea structure and its lifting vessel in waves can be carried out. This possibility is also affected by the long simulation times required at the moment. As an intermediate step the method might be used to determine the wave loads and added mass in an uncoupled simulation.

INTRODUCTION

For the development of deep and ultra deep fields, the safe and economical installation of subsea equipment is of vital importance. The practically continuous swells West of Africa result in significant motions of the installation vessels, in other areas the possible wind seas can induce significant wave loads on the subsea structure when it is lowered through the splash zone. These subsea structures have a large variety of shapes and their shape is typically very complex (see Figure 1).

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