Numerical Evaluation of Hydrodynamic Forces on Bottom-Mounted Subsea Cables

The design of subsea cables from the structural analysis point of view strongly depends on the required cable weight for stability, and therefore, depends on on-bottom stability analysis. This paper focuses on the nearbed oscillatory-flow induced hydrodynamic forces on small-diameter subsea cables, installed on the seabed. CFD simulations were conducted for a wide range of Keulegan-Carpenter number and Stokes number (3 ≤𝐾𝐶 ≤ 193, 1.3 × 102 ≤ 𝛽 ≤ 9.3 × 103
) to investigate the effect of the near-bed hydrodynamic conditions to the wave-induced hydrodynamic forces, and therefore, on the on-bottom cable weight requirement for stability. The horizontal and lift peak hydrodynamic forces are evaluated through the coefficients and compared with data from literature and from industry standards. A case study with the practical calculation of onbottom absolute horizontal and vertical stability for a typical three-core subsea cable is also presented. It is demonstrated that reduction of the required cable weight can be achieved if the near-bed hydrodynamic conditions are considered, which can affect the overall cable cost.