Free running computations of KCS with different propulsion models

Computations of the self-propulsion free running KCS model with 2DOF (heave and pitch) using four different propulsion models are presented. Computations are performed with HUST-Ship, in house URANS CFD code developed for ship hydrodynamics. PI speed controller is used to find the propeller rotational speed that could balance the thrust and resistance. Single-phase level-set approach is used for free surface simulation. Propulsion models include discretized propeller, the descriptive body force based on open water curve and simple Hough and Ordway approach, OUM (Osaka University Method) based on simplified quasi-steady two-dimensional BEMT (blade element momentum theory) and modified OUM based on BEMT considering three-dimensional viscous effects. Compared with OUM, modified OUM obtained the C-L and C-D from discretize propeller model open water characteristic CFD computation results so that the method could be more similar to the discretize propeller model. The computation conditions are same as the model test and the computational results show good match with model test data. The results show that considering the three-dimensional viscous effect of propellers can improve the simulation accuracy of propulsion model. The CFD computation results of open water characteristics show the modified OUM has less than 2% difference compared with the discretized propeller models and higher prediction accuracy than OUM. The self-propulsion free running computational results of thrust, velocity distribution, free-surface cuts and self-propulsion parameters using modified OUM model have been compared with EFD and discretized propeller model.