URANS simulations for a free-running container ship: Part 1. Turning-circle

Abstract

The incompressible unsteady Reynolds-averaged Navier-Stokes (URANS) simulations are performed for a free-running container ship in maneuvering conditions: the starboard and portside turning circle simulations with 35 degrees rudder deflection. The validation variables include trajectory, motions, and propeller performances, and the prediction shows acceptable agreements against the experimental data. During the steady-state part of the turning, the inertial forces balancing the local forces are reported to quantitatively assess the centrifugal force which appears from the force equilibrium between the rudder, propeller, and the bare-hull. The study on the local flow focuses on finding the correlations between the propeller inflow and the propeller performance to investigate the differences in propeller performances during the portside and starboard turning. The preliminary simulations, performed with the grid triplet, comprise propeller open-water, resistance, and self-propulsion simulations, from which the validation studies and the studies for the local force and the local flow are fulfilled and applied for the main simulations. Both propeller and rudder are fully discretized and controlled, mimicking the experiment. Level-set, overset approach and Mentor's SST model are employed for the free-surface capturing, large motion prediction, and turbulence closure.