RANS investigation of the hydrodynamic interactions between two approaching ships in shallow water considering the effects of drift motion and rudder deflection

Abstract

There exists a high risk of collision between two approaching ships in the lightering operation. The investigations of the hydrodynamic interactions between such two ships are of great interest to ensure navigation safety. To this end, the RANS (Reynolds-Averaged Navier-Stokes) technique based on OpenFOAM is employed to simulate the flow around two approaching Wigleys in this work. The two Wigleys are identical. Due to the slow ship speed, the water-air flow is simplified as the double-body flow in the present consideration. The computed hydrodynamic side forces and yaw moments are compared with the available experimental data, and acceptable agreements are found. The effects of lateral distance between the two ships, water depth, rudder deflection, ship scale and drift motion on the hydrodynamic forces and moments on both ships are analyzed. This study shows that the suction forces and bow-out moments generally become larger as the water depth or lateral distance decreases, while the suction forces trends to become repulsion forces when both the water depth and lateral distance are very small. It is also found that the rudder deflection of one ship has a very little hydrodynamic disturbance on the other ship, rather than the drift motion which affects much the hydrodynamic forces and moments on the other ship especially in very shallow water.