Fluid-Dynamic and Mechanical Design of a Screw Propeller for an Electric Catamaran

This thesis project presents a methodology to design and numerically validate screw propellers for maritime applications. The method was designed and used during the 2022/2023 season of the UniBoAT project. The theoretical approach applied is Blade Element Momentum Theory (BEMT). A MATLAB code was developed to implement the BEMT method. Moreover, an optimization algorithm was implemented in the program to optimize the blade’s pitch and chord distributions. Then, CFD and FEA simulations with Ansys Workbench were carried out to compare analytical and numerical results. While a good correlation between BEMT and CFD has been achieved (particularly for the propeller’s thrust and efficiency), analytical methods to compute blade stress have seemed to be not reliable in maximum stress predictions because the blade’s root rounding geometry is usually not taken into account in the computation. Finally, the propellers were manufactured through 3D printing technology and tested on the boat. The propeller’s real performance was compared with the previous design and, although the tests weren’t comprehensive, the objective of obtaining a bigger thrust from the propeller has been achieved but with bigger power absorption than was expected. Further investigations and improvements in the simulations set-up will be needed to improve the correlation between BEMT and real tests.