Numerical study on local scour characteristics around submarine pipelines in the Yellow River Delta silty sandy soil under waves and currents

• Published in: Deep underground science and engineering (Online) Vol. 3; no. 2; pp. 182 - 196
• Main Authors: Yu, Peng, Hu, Ruigeng, Zhang, Jike, Yang, Qi, Zhao, Jieru, Cao, Lei, Zhu, Chenghao
• Format: Journal Article
• Language: English
• Published: Wiley 01-06-2024
• Subjects: local scour; numerical simulation; submarine pipelines; Yellow River Delta
• ISSN: 2097-0668; 2770-1328
• DOI: 10.1002/dug2.12068

Due to their high reliability and cost‐efficiency, submarine pipelines are widely used in offshore oil and gas resource engineering. Due to the interaction of waves, currents, seabed, and pipeline structures, the soil around submarine pipelines is prone to local scour, severely affecting their operational safety. With the Yellow River Delta as the research area and based on the renormalized group (RNG) k‐ε turbulence model and Stokes fifth‐order wave theory, this study solves the Navier–Stokes (N–S) equation using the finite difference method. The volume of fluid (VOF) method is used to describe the fluid‐free surface, and a three‐dimensional numerical model of currents and waves–submarine pipeline–silty sandy seabed is established. The rationality of the numerical model is verified using a self‐built waveflow flume. On this basis, in this study, the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed in the prototype environment are explored and the influence of the presence of pipelines on hydrodynamic features such as surrounding flow field, shear stress, and turbulence intensity is analyzed. The results indicate that (1) local scour around submarine pipelines can be divided into three stages: rapid scour, slow scour, and stable scour. The maximum scour depth occurs directly below the pipeline, and the shape of the scour pits is asymmetric. (2) As the water depth decreases and the pipeline suspension height increases, the scour becomes more intense. (3) When currents go through a pipeline, a clear stagnation point is formed in front of the pipeline, and the flow velocity is positively correlated with the depth of scour. This study can provide a valuable reference for the protection of submarine pipelines in this area.
This article establishes a three‐dimensional numerical model of currents and waves–submarine pipeline–silty sandy seabed, explores the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed in the prototype environment, and analyzes the influence of the presence of pipelines on hydrodynamic features such as the surrounding flow field, shear stress, and turbulence intensity.
Highlights
Based on the renormalized group k‐ε turbulence model and Stokes fifth‐order wave theory, a three‐dimensional numerical model of currents and waves–submarine pipeline–silty sandy seabed was established for scouring.
The reliability and accuracy of the numerical model were verified against experimental data measured from a self‐built waveflow flume.
Computational and experimental investigations were conducted on the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed. The effects of different water depths, flow velocities, and pipeline suspension heights on the local scour characteristics of submarine pipelines were compared and analyzed.