Safety range in bridge areas based on the influence of cross flow on ship navigation

The obstructive effect of bridge piers on water flow forms a cross flow, which threatens the navigation of ships. The objective of this study is to contribute to the quantitative study of navigation safety in restricted waters. For this purpose, a hydrodynamic numerical simulation that takes into account ship motion characteristics is combined with navigation safety analysis. Firstly, the cross flow characteristics around tandem double circular piers and their influence on ships are revealed, and the yaw moment is employed to verify the influence. Then, the influence of cross flow on ship navigation is quantified by analyzing the turbulent width under different bridge pier spacings and Reynolds numbers. Finally, the safety range of ship navigation in bridge areas is partitioned. The results demonstrate that when the ship-pier spacing ratio is between 0 and 2.5, there are obvious peak points of the ship's yaw moment near the pier. When the ratio is between 2.5 and 3.0, there is only a negative peak point at the pier body, and the peak value is reduced by 43%, resulting in decreased risk; The qualitative trend of turbulent width is consistent under both single-pier and two-pier conditions. With an increase in Reynolds number, the cross flow velocity in the recirculation region is greater, the stable period of the turbulent width is shorter, and the variation is more noticeable at the downstream pier body; The critical ship-pier spacing ratio for partitioning the high-risk range and the low-risk range is 2.5, and the variation of the ship's yaw moment is consistent with the partition of the safety range by the turbulent width. The research results provide a reference for refined early warning of navigation management.