Enhanced body-force propeller model for non-uniform inflow flow and application to turning circle test of KCS in calm water

Abstract

An enhanced body-force propeller model is developed to consider propulsion effects without solving the actual propeller geometry in ship maneuvering problems. Application to the KCS turning circle test in calm water (starting at the self-propulsion point) is conducted using the computational fluid dynamics solver, snuMHLFoam, which was developed on OpenFOAM-plus. Based on the original Hough and Ordway model, the non-uniform advance velocity of the propeller is considered using the local velocity on the inflow plane, to compute the local advance coefficient for different parts of the propeller disk when the propeller works behind a hull. The original overset algorithm is revised by introducing more flexible hole-patch definitions for the hole-cutting procedure and an iterative procedure for the donor-searching procedure to remove invalid donors. The motion decomposition of ship and rudder motions with the revised overset is implemented in order to handle body motions effectively. Self-propulsion and turning circle tests for KCS ships are successfully conducted in calm water. The predicted results, including the PI control results, turning trajectory and parameters, ship motions and velocities, forces and moments, and flow and vortical structures are illustrated and compared with the benchmark experimental data, as well as the numerical results obtained using the Maneuvering Modeling Group (MMG) model. The results indicate that the developed body-force propeller model can provide more reasonable predictions of the propulsive performance when the propeller works behind a hull. The snuMHLFoam solver, which is coupled with motion decomposition using the revised overset grid methodology, is validated to be effective and reliable.