A number of oil and gas projects encounter significant costs to achieve subsea pipeline stabilization using present methods. The standard procedure to estimate pipeline stability is to consider the worst combination of amplitude and direction of the current and waves that the pipe will undergo during its operational lifetime. To calculate the hydrodynamic forces a common approach is to consider only the component of the fluid velocity perpendicular to the pipe axis according to the independence principle. The hydrodynamic coefficients are then taken from a case where the fluid flow is perpendicular to the pipe for similar flow characteristics.

A substantial amount of research has been carried out to assess the hydrodynamic forces on pipelines with the current and wave directions collinear and perpendicular to the pipe. However, only limited information is available on pipeline hydrodynamic forces for highly oblique current and wave flow. A Computational Fluid Dynamics (CFD) analysis was carried out to investigate the effect on pipeline hydrodynamic forces for highly oblique collinear and non-collinear current and wave directions. The work was carried out as part of the STABLEpipe JIP (1) (with participation by Woodside, Chevron, The University of Western Australia, and Wood Group Kenny) which aims to achieve a step-change improvement in the approaches to stability design, especially on mobile or erodible sea beds.

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