Numerical Assessment of a BEM-based Approach for the Analysis of Ducted Propulsors

The present paper proposes a Boundary Element Method-based formulation to address hydrodynamic analysis of ducted propellers. The methodology is in the framework of preliminary design and optimization-oriented numerical tools, and is the object of a long-term research activity at INSEAN for the development of a hybrid RANSE/BEM approach to analyse hull/propulsor interaction for open screw and ducted propellers. The theoretical and computational BEM approach proposed here is valid for inviscid flows around three-dimensional bodies in arbitrary motion. A formulation for open screw propellers is extended to ducted propulsors. In fact, the inclusion of the duct into the BEM simulations is very relevant, especially at low values of the advance coefficient, due to its impact on propeller performance. In order to investigate the capabilities of a purely inviscid flow solver to address ducted propellers performance in their typical working conditions (low advance coefficient) and to avoid the uncertainties related to semiempirical models, no gap flow semi-empirical modelling will be included in the analysis. Numerical results of the BEM code will be assessed and discussed against available experimental data. Finally, sheet cavitation modelling for ducted propellers will be addressed based on the extension of previous works by the authors.