Dynamic Stability Analysis of Small-Diameter Pipelines Using New Fourier-Type Hydrodynamic Force Coefficients

On-bottom stability analysis is essential for the safety of pipelines, including both oil-and-gas pipelines with relatively large diameters and subsea cables/umbilicals with relatively small diameters. The dynamic stability analysis allows oscillations of pipelines that make the pipelines penetrate deeper into the soil and become more stable under storms. Recent research from the University of Western Australia (Griffiths et al. 2025) provides a new set of Fourier-type hydrodynamic force coefficients for small-diameter pipelines. These coefficients can be used for estimating the time-dependent hydrodynamic forces acting on subsea cables/umbilicals, which outperforms the coefficients proposed by Danish Hydraulic Institute (DHI, 1986) for oil-and-gas pipelines. This paper demonstrates how much the dynamic stability design benefits from the UWA set of coefficients when small-diameter cables are concerned. The dynamic stability analysis is conducted via a new software named Dynamic On-bottom Stability Analysis Tool – 2 Dimensional (DOSAT-2D) developed by South China University of Technology. Results show that the lift force reduction of small-diameter pipelines leads to noticeable benefit for the dynamic stability.