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<p>Backfilling for hydraulic structures like subsea pipelines is essential for coastal engineering safety and marine ecosystem protection.To investigate and accurately predict the material loss during subsea pipeline backfilling, this study develops an idealized coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model. The model was validated against theoretical solutions with a maximum discrepancy of 6.55%. Using this model, the combined effects of varying cross-flow velocities (0.1–1.2&#xa0;m/s) and backfill particle sizes (D = 0.04&#xa0;m, 0.2&#xa0;m, 0.4&#xa0;m) on the Material Loss Rate (MLR) were systematically investigated. The results reveal a non-linear increase in MLR with flow velocity and identify distinct critical velocity thresholds. For instance, significant loss for small (0.04&#xa0;m) particles began above 0.2&#xa0;m/s, whereas large (0.4&#xa0;m) particles remained stable up to 0.9&#xa0;m/s. Particle size is the dominant factor: at a 1.0&#xa0;m/s cross-flow, the MLR for 0.04&#xa0;m particles (47.8%) is approximately 38 times that of 0.4&#xa0;m particles (1.24%). The underlying mechanism is the competition between a particle’s vertical settling time and its horizontal drift distance; larger particles possess higher terminal velocities and thus shorter residence times in the water column, effectively suppressing current-induced drift. Based on these findings, a semi-empirical predictive model is proposed, grounded in fundamental hydrodynamic principles, which establishes a cubic polynomial relationship between material loss and cross-flow velocity above a critical threshold. This model provides a rapid engineering tool for optimizing backfill design, estimating material quantities, and defining operational weather windows, thereby enhancing the economic and environmental sustainability of subsea pipeline projects.</p>

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An idealized CFD-DEM study of the effects of cross-flow and particle size on backfill material loss in subsea pipeline backfilling

  • 期刊论文

  • 发表日期：

    2025年11月25日

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  • Boshuai Zhang,
  • Guomin Sun,
  • Chunhong Hu,
  • Kunming Ma,
  • Li Li

摘要

Backfilling for hydraulic structures like subsea pipelines is essential for coastal engineering safety and marine ecosystem protection.To investigate and accurately predict the material loss during subsea pipeline backfilling, this study develops an idealized coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model. The model was validated against theoretical solutions with a maximum discrepancy of 6.55%. Using this model, the combined effects of varying cross-flow velocities (0.1–1.2 m/s) and backfill particle sizes (D = 0.04 m, 0.2 m, 0.4 m) on the Material Loss Rate (MLR) were systematically investigated. The results reveal a non-linear increase in MLR with flow velocity and identify distinct critical velocity thresholds. For instance, significant loss for small (0.04 m) particles began above 0.2 m/s, whereas large (0.4 m) particles remained stable up to 0.9 m/s. Particle size is the dominant factor: at a 1.0 m/s cross-flow, the MLR for 0.04 m particles (47.8%) is approximately 38 times that of 0.4 m particles (1.24%). The underlying mechanism is the competition between a particle’s vertical settling time and its horizontal drift distance; larger particles possess higher terminal velocities and thus shorter residence times in the water column, effectively suppressing current-induced drift. Based on these findings, a semi-empirical predictive model is proposed, grounded in fundamental hydrodynamic principles, which establishes a cubic polynomial relationship between material loss and cross-flow velocity above a critical threshold. This model provides a rapid engineering tool for optimizing backfill design, estimating material quantities, and defining operational weather windows, thereby enhancing the economic and environmental sustainability of subsea pipeline projects.