Abstrakt

This article addresses the problem of the scale effect for an Ultra Large Container Ship (ULCS) with a novel twin-crp-pod propulsion system. Twin-crp-pod steering-propulsion arrangement is an innovative solution that gains from three well-known systems: twin-propeller, contra-rotating propellers and pod propulsors. It is expected that applying the twin-crp-pod system to the analysed Ultra Large Container Ship will increase propulsion efficiency and manoeuvring safety. To prove that, a series of model tests have been carried out, including towing tank tests and free-sailing manoeuvring tests. The scope of the presented simulations included calm water resistance simulations and self-propulsion tests for the full-scale and model-scale vessels. The model-scale calculations have been performed at a scale of 1:37.416. During self-propulsion simulations, the required front and aft propeller revolutions were searched to find the optimum power balance. Calculations were performed for the ship design speed and constant front-to-aft propeller revolutions ratio. The case study vessel was a 400m Ultra Large Container Ship. CFD Simulations were performed using the unsteady RANS approach. The sliding mesh approach with a rotating region around the local coordinate system was used to model the propeller directly. The flow was turbulent with the k-ω SST turbulence model applied. The second-order implicit temporal discretisation scheme was applied. Parallel, due to the early stage of research, an extrapolation method including the wake scaling, propellers interactions and pod housing resistance is being elaborated. Later on, the model-scale CFD results will be extrapolated and compared to the results of the full-scale simulations. As for now, the comparison included the total resistance of the bare hull, wake fraction, relative rotational efficiency, thrust deduction and propeller revolution required to achieve the self-propulsion point.

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