A study on PID controlled self-propulsion and turning simulations based on the URANS CFD free running approach

In this study, the proportional, integral, and differential control constants for a self-propulsion point search were investigated using free running Computational Fluid Dynamics (CFD) simulations. The experimental data obtained using a 1/100 scale model of KVLCC2 were used to verify the calculation results. A range of initial propeller rotational speeds from 30% to 140% of the self-propulsion point of the experiment was considered. The controller constants were estimated using the trial-and-error and the Ziegler-Nichols methods, and the two results were similar. As a result, a robust numerical result was obtained within a 0.01% difference of the target speed, and a 0.5% difference of the self-propulsion point of the experiment with P and I constants of 180/m and 30 RPS/m, respectively, for a straight-ahead time of 12.5 L/V. Under the straight-ahead condition, a time step of 0.005 L/V was sufficient. However, in the turning simulation, a time step of 0.0025 L/V or less was required. The key findings obtained from this study are believed to provide a practical guideline for self-propulsion and maneuvering simulation using CFD.