Hydrodynamics below a closed fallpipe system
The profile of a rock berm acquired with rock placement operations
M.D.J. Kevelam
C. van Rhee – Mentor
G.H. Keetels – Mentor
D.L. Schott – Mentor
M. Hovestad – Mentor
C. Visser – Mentor
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Abstract
In the offshore industry rock is used for different kind of applications, such as scour protection and pipeline protection. In deep water operations, but also increasingly in shallow water operations, use is made of the method by guiding the rock from the water surface to the seabed with a fallpipe. During a rock placement operation a current through the closed fallpipe and subsequently a jet below the fallpipe is created. The involving processes below the fallpipe are however not well understood. Therefore the goal of this study is to get a better understanding of the hydrodynamic processes below a closed fallpipe system. First the literature was explored and after this, the research phase was started which consists of a threefold. First of all the possibility to use empirical relations, in comparison with computational fluid dynamics (CFD) simulations, for the description of the velocity field below a fallpipe system is looked at. With this the displacement and spreading of rock is determined and as last the rock berm built-up is predicted. The aim of this thesis is to assess the relevant processes of settling stones towards the seabed and tor predict the occurrence of irregular berm shapes due to jet formation below a closed fallpipe.