CFD Analysis of Scale Effects on Conventional and Tip-Modified Propellers

Full-scale propeller performance is traditionally predictedby scaling model-scale test results, but the traditionalscaling methods do not take into account hydrodynamicdistinctions of tip-modified propellers in full-scaleperformance. An open-water CFD analysis is made onscale effects of tip-modified and conventional propellers,which are designed for the same operating condition withidentical propeller diameter and expanded area ratio.While model-scale computations are made with atransition model, a fully turbulent flow is modeled in the full-scale computations.

The investigation on the effectsof the transition model shows that laminar and transitionalflow modeling is crucial in model-scale computations.Grid-independent solutions at model and full scale areachieved by grid verification studies. The CFD analysis of scale effects shows that theefficiency gain of the tip-modified propeller is increasedat full scale.

The difference of scale effects between thetip-modified and conventional propellers is related toalterations of tip vortex and sectional pressuredistributions by the bent tip and the higher spanwiseloading at the tip region of the tip-modified propeller.