Propeller-hull interaction beyond the propulsive factors-A case study on the performance of different propeller designs

The propulsive factors are critical for scaling of model-test data, and hence important for the final power prediction. When comparing different propulsion systems based on model-scale tests, differences in propulsive factors, and hence the propeller-hull interaction, are often not well understood. In this study the propeller-hull interaction is instead described and compared using CFD for three different propulsion systems, a tip-unloaded ice-classed propeller, an ice-classed propeller with conventional radial load distribution and a non ice-classed propeller with conventional radial load distribution. To post-process the results KT/KQ is evaluated for one blade around a revolution and complemented with radial distributions of the same measure. Both tip-unloaded blades and sharp leading edges suffer in-behind due to poor performance at low load. Open water performance dependency on Reynolds number reveals that ice-classed propellers are more negatively influenced by the low Reynolds numbers of self-propulsion tests. Further, it is noted that a more even radial load distribution favours a low thrust deduction factor. Since the propulsive factors to a large extent are influenced by scale-effects and also due to that their association to the observed hydrodynamics makes the commonly applied scaling procedure of them questionable, they are not considered representative for ship-scale power prediction.

Automated summary

Propulsive factors are critical for scaling of model-test data and final power prediction. Understanding the differences in propulsive factors and propeller-hull interaction is important when comparing different propulsion systems based on model-scale tests. This study compares three different propulsion systems using CFD and evaluates the propeller-hull interaction.