Wind loads on moored ships are an important factor in determining the loads on the mooring lines. Present methods of calculating wind loads largely depend on the wind coefficients obtained from past experimental data for scaled models of various ships in a wind tunnel. However, this leads to erroneous calculations in the built environment such as a port surrounded by buildings. The present methodology uses CFD simulations to accurately calculate forces on the ship and thereafter providing corrected wind coefficients that can be widely used to further calculate the forces on moored lines.
Firstly, a wind assessment is performed and CFD simulations were carried out for 4 prevalent wind directions with all the buildings and structures near the port but without the ship. This gives a good general insight into the flow at the docking locations and gives a general understanding of how the buildings and structures effect the flow and whether it leads to localized increase or decrease of velocities. Therefore, this can be highly valuable information to avoid a localized increase in wind velocities at the docking locations.
Secondly, force coefficients are calculated from full scale CFD simulations that include the effect of the wind profile and the nearby structures on the wind loads on ships. When comparing the wind forces from CFD to the conventional approach, it is found that both the wind profile and the nearby structures have a significant effect on the force in the lateral direction (perpendicular to the ship length) which is not captured by the conventional calculations. The moment on the ship along the vertical axis seem to be significantly affected by the nearby structures as well. However, the full scale CFD results are only valid for the present port and a Panamax ship. Therefore, it is advised that to estimate forces on ships at docking locations with nearby buildings and structures, full scale CFD is desirable. Use of wind coefficients, such as estimated using conventional wind coefficient methods can lead to over prediction of loads.
Digital wind tunnel and zoomed view of the port model with ship and nearby buildings
Wind factor contours and streamlines for the wind direction perpendicular to the docked ship
Moment coefficients along the vertical axis and force coefficients in the longitudinal and lateral directions for different wind directions