26 / 2025-04-24 11:27:26

Scaled Prediction Method for Estimating Propeller-Induced Scour for Large Scale Applications

As vessels continue to increase in size and power, the potential for propeller-induced scour in marine environments becomes a critical concern, particularly for large commercial installation vessels. Propeller scour can cause significant erosion of the seabed, leading to structural instability in nearby marine infrastructure, such as offshore platforms, moorings, and underwater cables. This erosion is influenced by the powerful propulsive jets from modern vessels, which far exceed the velocities typically observed in smaller-scale experimental models. Given the growing need to accurately predict and mitigate scour effects in these large-scale scenarios, current prediction models, which are based on densimetric Froude numbers related to efflux velocities from scaled-down tests, face significant limitations.
The primary challenge lies in the fact that the efflux velocities of propulsion systems on large vessels surpass those produced in scaled model tests by an order of magnitude. Consequently, applying these scale-test-derived models to larger vessels often results in inaccuracies. In light of these limitations, this paper examines the validity of existing scour prediction methods for large-scale vessels and identifies key gaps in current approaches. Through a comprehensive case study involving a large commercial installation vessel, we assess the extent to which these models can predict the depth and extent of scour caused by the vessel’s propeller.
To address the shortcomings of current methodologies, this paper proposes a practical, scaled prediction method based on the schematic diagram of the scouring process published by Hong et al. (2013). Factors such as vessel size, propeller configuration and water depth are incorporated into the model, providing a more accurate framework for predicting scour in real-world conditions. Our findings show that by adopting this modified approach, the predicted scour depth and range aligns with the output of the relevant flow velocity isolines from the thruster hydrodynamic models. The case study demonstrates that the modified method significantly improves the accuracy of scour depth predictions compared to existing publicly available models.
In conclusion, this paper presents a scalable and practical approach to predict propeller-induced scour for large commercial installation vessels. By addressing the limitations of existing methods and introducing a scaled model based on the work of Hong et al. (2013).

Jian-Hao Hong, Yee-Meng Chiew, Nian-Shen Cheng (2013) Scour Caused by a Propeller Jet.