Hydrodynamic forces between vessels and safe maneuvering under wind-effect in confined waters

It is well known that the ship maneuvering motion is greatly affected by hydrodynamic forces and moments acting between two ships passing too close to each other in confined waters, such as in a harbor or narrow channel. This hydrodynamic forces and moments can be assumed to be the functions of the longitudinal and transverse distance along with their speeds. The aim of the present research is to develop a guideline of ship velocity and safe distance between ships to avoid the influence of the hydrodynamic forces and moments and to navigate ships safely in confined waters. From the perspective of marine safety, considering the interaction and wind effect as a parameter, an overtaking and overtaken vessel navigating too close to each other under the condition of wind direction from 80 degrees to 150 degrees should be cautioned with high alert, regardless of ship types. Also, regardless of the ship-velocity ratio and ship types, an overtaking and overtaken vessel can be maneuvered safely without deviating from the original course under the following conditions; the transverse distance between two vessels is approximately kept at 1.0 times of ship length and 5 through 10 degrees of range in maximum rudder angle.