In this work, we present the results of a ship propeller design optimization campaign
carried out in the framework of the research project PRELICA, funded by the Friuli Venezia Giulia
regional government. The main idea of this work is to operate on a multidisciplinary
level to identify propeller shapes that lead to reduced tip vortex-induced pressure and increased
efficiency without altering the thrust. First, a specific tool for the bottom-up construction of
parameterized propeller blade geometries has been developed. The algorithm proposed operates with
a user defined number of arbitrary shaped or NACA airfoil sections, and employs arbitrary degree
NURBS to represent the chord, pitch, skew and rake distribution as a function of the blade radial
coordinate. The control points of such curves have been modified to generate, in a fully automated
way, a family of blade geometries depending on as many as 20 shape parameters. Such geometries have
then been used to carry out potential flow simulations with the Boundary Element Method based
software PROCAL. Given the high number of parameters considered, such a preliminary stage allowed
for a fast evaluation of the performance of several hundreds of shapes. In addition, the data
obtained from the potential flow simulation allowed for the appli- cation of a parameter space
reduction methodology based on active subspaces (AS) property, which suggested that the main
propeller performance indices are, at a first but rather accurate approximation, only depending on
a single parameter which is a linear combination of all the original geometric ones. AS analysis
has also been used to carry out a constrained optimization exploiting response surface method in
the reduced parameter space, and a sensitivity analysis based on such surrogate model. The few
selected shapes were finally used to set up high fidelity
RANS simulations and select an optimal shape.
