Flow and likely scour around three dimensional seabed structures evaluated using RANS CFD

Abstract

When a structure is placed on the seabed, tidal or other marine current induce areas of flow acceleration and deceleration. This may result in movement of the seabed substrate (often sand) near the structure. It would be useful to be able to assess possible scour. For example when considering the protection of wreck and other marine sites of archaeological interest, or the long term durability of marine renewable and offshore structures mounted on the seabed. The first step in the process of scour calculation is to get a good description of the flow around the structure; next a scour pattern can be estimated. The work which was carried out can be divided in 4 mains parts of increasing complexity. The first objective was to produce and compare results on the well documented case of a surface mounted cube. Next, the conclusions of this first part were use to perform several calculations around a variety of cuboids, the CFD results were compared with experimental data obtained recently by the NOC. The third part was a study of scour around
a modeled wreck, using experimental data from a recent thesis. Finally, full scale measurements of the “unknown wreck” were used to complete the study. This work has shown the possibility to correctly describe the flow around 3D structure with a suited turbulence model (as the Shear Stress Transport model). Concerning scour, it has been shown that the wall shear stress alone was not able to predict satisfactorily the onset scour. The turbulence kinetic energy, which seems to have its weight in the scour process, allows a better estimation of the scour pattern.

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Identifiers

ORCID for J. Dix: orcid.org/0000-0003-2905-5403

ORCID for S.R. Turnock: orcid.org/0000-0001-6288-0400

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