Numerical Investigation of Oblique Currents' Effects on the Hydrodynamic Characteristics of Ships in Restricted Waters

The influence of oblique currents in narrow and shallow channels causes the fluid flow around ships to become complex. To analyze the hydrodynamic characteristics of a ship in such channels, it is essential to examine the influence of oblique currents on the ship's hydrodynamic characteristics. In this study, current direction, ship speed, current speed, and water depth were identified as determinants affecting the hydrodynamic characteristics of a ship. Numerical simulations were conducted on a large oil tanker to investigate the effects of these factors on the ship's hydrodynamic characteristics. The viscous fluid flow was modeled using the unsteady Reynolds-averaged Navier-Stokes (URANS) equations in conjunction with the k-epsilon turbulence model. The URANS equations were discretized using the finite volume method. The numerical results indicate substantial differences in the hydrodynamic characteristics of ships under oblique current conditions compared to still-water conditions. At a current direction of beta = -45 degrees, the direction of the sway force is consistent with that of still water's sway force, which is an attractive force. The yaw moment at beta = -45 degrees changes from a bow-out moment under still-water conditions to a bow-in moment. Conversely, at a current direction of beta = 45 degrees, the sway force shifts from an attractive force under still-water conditions to a repulsive force. The yaw moment acts as a bow-out moment, which is consistent with that observed in still-water conditions. Furthermore, the influence of hydrodynamic characteristics on a ship varies significantly with changes in ship speed, current speed, and water depth. To ensure the safe navigation of ships, it is essential to develop and apply comprehensive strategies and countermeasures that account for practical conditions.