In harbours & coastal areas the manoeuvring and course keeping of ships will be affected by the interaction between ships. The forces and moments due to pressure variation around the hull can be attractive or repulsive depending on the stagger distance, and the magnitudes are influenced by their size, water depth, underwater form, transverse separation distance between the ships, speed of the ships and their relative direction on movement (Encounter). These forces and moment can drastically influence the path of both the vessels, where it can collide each other or with other vessels and/or structures in their vicinity. The hydrodynamic interaction between ships increases in shallow waters compared to that in deep water condition.

The present study focuses on numerically simulating the horizontal planar motion mechanism in varying water depths by solving the Unsteady Reynolds Averaged Navier Stokes Equations. Effect of water depth on hydrodynamic derivatives are studied and compared with the empirical relations. From the results, a new regression expression for hydrodynamic derivatives of an Inland barge for varying water depth is proposed. Similarly, the instantaneous hydrodynamic interaction forces and moments between two container ships in the encounter case were found numerically. New regression for peak values of interaction forces and moments are proposed based on the obtained results. Finally, the vessel trajectory during encounter manoeuver is simulated using the estimated hydrodynamic coefficients.