Numerical and Experimental characterization of a CP propeller unsteady cavitation at different pitch settings

Paper presents results obtained in a study dedicated to the experimental and numerical investigation of the steady and unsteady hydrodynamic characteristics of a modern CP propeller including off-design operating conditions, i.e. with the blade oriented at a pitch rather far from the design value. The extensive experimental campaign has offered the opportunity to validate the accuracy of two different CFD methods: a first order unsteady panel method with some non linearities (in the Kutta condition and flow adapted wake); and a state of the art RANSE solver, Also the unsteady conditions of the CP propeller are investigated at two very different pitch settings, The comparison of numerical predictions with experimental results shows a very good agreement of both the numerical methods with the experiments at design pitch, also with regards to cavitation predictions. On the contrary, results at highly reduced pitch show the limits of the conventional panel method, based on potential flow solution, for which the usual viscous corrections are not any more sufficient to cope with separated viscous flow of some blade sections, which are satisfactorily modeled by the RANSE solver, instead. From a careful comparison of the flow characteristics predicted by the two different numerical methods, some hypothesis for future enhancement of the panel method are formulated in the conclusions.