Numerical and Experimental Study of Propeller Ventilation

The primary objective of the numerical and experimental study of propeller ventilation is to obtain knowledge about the forces acting on thrusters in heavy seas. To address this problem, a joint European project,PropSeas, has been established. One aspect of the project"s activities is toinvestigate the forces acting on the propeller during ventilation events, and how the occurrence of ventilation depends on different operational parameters, like submergence and propeller loading.Thispaper is largely based on the comparison between the model test conducted by MARINTEK and calculations performed by TUHH. The comparison contains two main tasks: a comparison between blade forces and moments during non-ventilating and ventilating phases; as well as a comparison between flow visualization using high-speed video (experiments) and CFD simulation.The comparisons aim at indentifying the degree of correlation, and reasons for deviations are discussed. It is found that while the agreement for non-ventilating conditions is very good, CFD generally overpredicts the propeller forces in ventilating conditions. Also, the variation of thruston a single blade over a revolution is larger in CFD than in the model tests. It is believed that this is caused by the inability to resolvethin ventilating vortices in the RANS Volume of Fluid type CFD calculations.