Design of contracted and tip loaded propellers by using boundary element methods and optimization algorithms

In present work, a design by optimization of contracted and tip-loaded (CLT) propellers is proposed and implemented. The design approach is based on a parametric description of the propeller blade, derived from the usual design table by using B-Spline parametric curves, and an in-house developed Panel Method/Boundary Element Method (BEM) aimed to evaluate the performance (including cavitation) of the propellers selected by a genetic optimization algorithm. The modeFRONTIER optimization environment drives the entire design process. A preliminary sensitivity study is carried out to evaluate the effect of the discretization meshes for BEM and RANSE calculations. Based on this analysis, Boundary Element Method and RANSE results over the parent propeller, in terms of both open water propeller performance, unsteady cavitation and induced pressure pulses, are compared with the available experimental measurements in order to validate the adopted design approach. Finally, to assess the reliability of the design by optimization, a set of optimized geometries, selected on the basis of the fulfillment of the design objectives, are checked by means of dedicated RANSE calculations.