Impacts of wind and current on ship behavior in ports and waterways

Abstract

In ports and waterways, the impacts of external navigational factors may lead to serious incidents due to limited space for ship maneuvering. Using nautical traffic models, these incidents can be predicted in advance. In current studies of nautical traffic models, the impacts of wind and current on ship behavior are seldom considered when modeling the ship behavior in a port area. The numerical maneuvering models simulate the individual ship behavior under such impacts by calculating the hydrodynamic forces working on the ship's hull. However, the input, maneuvering particulars of individual ships, are not available in ports. In order to fill the knowledge gap of estimating ship behavior under external impacts without detailed ship maneuvering information, the impacts of wind and current on the observed dynamic ship behavior (speed over ground and leeway and drift angle) in ports and waterways have been investigated by analyzing Automatic Identification System data (showing ship paths over time) and the meteorological and hydrological data collected from the port of Rotterdam. The relation between unhindered speed variation and ship size is revealed. The regression analysis results on ships with similar size indicate the differences between wind and current impacts. Especially for small ships, the current impact on speed over ground outweighs the wind, while the wind influences the leeway and drift angle more than the current. Based on the quantified impact variation over ship size, the proposed impact mechanism explains the variance of speed over ground and leeway and drift angle. Some conventional sailing habits based on good seamanship, such as a series of small-angle alterations rather than direct turning at waypoints, are also revealed by the statistical analyses. Considering the variation of wind and current conditions in the study area, the analysis result provides generic quantitative insights into the wind and current impacts on the individual behavior of ships of different sizes. These mathematical formulations can be adopted in a microscopic nautical traffic model to include the impacts of external conditions.