Session: 02-05-01 Extreme Loads and Responses

Submission Number: 155494

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 and subsea power-transmission cables. Static stability (or absolute stability) and dynamic stability are two widely adopted approaches for the on-bottom stability design. The absolute stability method requires pipelines to be statically stable on the seabed, whereas the dynamic stability method allows oscillations of pipelines that make the pipelines penetrate deeper into the soil.

It has been demonstrated that the cables that have a relatively smaller diameter comparing with the oil-and-gas pipelines will experience smaller peak wave forces than those indicated by DNV-RP-F109 (2021) at large KC conditions (Teng et al. 2022). Therefore, the specific weight S_G required for the absolute stability design can be reduced by 10~30% under extreme storm events. Recent research outcomes based on the UWA-Woodside linkage project provide a dataset of the Fourier-type hydrodynamic force coefficients for small-diameter pipelines. These force coefficients can be used for the dynamic on-bottom stability analysis. This paper will demonstrate how much the dynamic stability design will benefit from the new Fourier-type coefficients.

The dynamic stability analysis is conducted via an in-house software named Dynamic On-bottom Stability Analyzing Tool – 2 Dimensional (DOSAT2D), which is composed of a dynamic response solver, a flow kinematic solver, a hydrodynamic force solver and a pipe-soil interaction solver. The accumulated lateral displacement and the penetration depth under a three-hour storm will be simulated with the present simulation tool. The simulated results by using the new and the existing Fourier-type force coefficients will be compared.

[1] Det Norske Veritas AS (2021) On-bottom stability design of submarine pipelines. Recommended Practice, DNV-RP-F109.

[2] Teng Y, Griffiths T, An H, Draper S, Tang G, Mohr H, White D, Fogliani A, Cheng L (2022) Hydrodynamic forces on subsea cables immersed in wave boundary layers. Coastal Engineering, 174, 104101.

Presenting Author: Yunfei Teng South China University of Technology

Presenting Author Biography: Yunfei has been working on pipeline hydrodynamics for 10 years. He is now working as an associate professor in Dalian University of Technology in China.