Assessment of full-scale KCS free running simulation with body-force models

Self-propulsion free running ship simulation is most closely similar to the running ship for different operating condition without any simplification of the ship hull and appendages. Accurate evaluations of self-propulsion performance are vitally important in the design of hull-propeller systems. This paper describes unsteady Reynolds-averaged Navier-Stokes (RANS) simulations to determine the self-propulsion performance of a fullscale container ship with a KP505 propeller. An inhouse code is used to solve the RANS equations with a discretized propeller, descriptive body-force, OUM (Osaka University Method) and modified OUM body-force methods selected as the propulsion models. The modified OUM body-force method couples blade element momentum theory, considering the three-dimensional viscous effects, with the RANS solver. Before the full-scale self-propulsion simulations, uncertainty analyses are performed on the full-scale hull and the propeller. The effect of roughness on the full-scale simulations is also studied. We discuss how the modified OUM body-force method can be used for full-scale self-propulsion simulations, and show that the model-scale body force can be substituted into the full-scale rough propeller in the self-propulsion simulations. The body-force results are compared with extrapolated experimental data, full-scale simulation results from the literature, and simulation results with the discretized propeller. In this paper, the modified OUM shows higher accuracy for full-scale selfpropulsion simulation than other two body forces for inhouse URANS solver. Moreover, the scale effect is discussed by comparing open-water, resistance, and self-propulsion simulations at different scales. The open-water and resistance results show that the propeller scale effect can be ignored, whereas both the wake flow and skin friction correction have large scale effects. The self-propulsion scale effect is mainly reflected in the wake factor, thrust deduction factor, and rotation speed. For the container ship considered herein, the full-scale wake fraction is smaller than the model-scale prediction, whereas the rotational speed and thrust deduction factor are greater.