Evaluation of Self-propulsion and Energy Saving Device Performance Predictions for JBC

Self-propulsion cases for the JBC hull with and without an energy saving duct are analyzed in this chapter. Test cases are set up for self-propulsion condition at the ship point. No rudder is fitted in either case. About half of the submissions employ actual propeller models in which a propeller geometry is discretized using a moving mesh and the remainder uses body force models in which propeller effects are considered as a body force computed using external potential-flow based programs. Self-propulsion simulations are carried out in two ways. The first is to follow the self-propulsion test procedure in a towing tank and a propeller revolution rate is adjusted in such a way that propeller thrust and towing force or SFC (Skin Friction Correction) for the ship point condition are balanced with ship’s resistance. The other way is to fix the propeller revolution rate equal to the experimental value and the force invariance is computed. Thrust and torque coefficients, propeller revolution and ship’s resistance components in self-propulsion condition are items to be submitted. Analysis of grid uncertainty is carried out based on the submission data with multiple grids. Average of comparison errors and the standard deviations of propeller thrust and torque together with revolution rates are estimated using the towing tank test data of 7.0 m model. Self-propulsion factors are estimated using the submitted data and compared with the measured data. Finally, model scale delivered powers are used to evaluate overall accuracy of the current CFD analysis in terms of the prediction accuracy of energy saving duct performance.