Methodological proposal for the selection and analysis of the performance of rigid sails considering pre-stall and post-stall aerodynamic conditions

The shipping industry is increasingly considering the issues of green shipping and zero-emission shipping, which are closely related to reducing the consumption of fossil fuels to mitigate its environmental impact. In this way, the use of renewable energies is increasingly perceived as part of the energy mix, with the use of rigid sails being one of the tested alternatives as auxiliary propulsion systems. This work studied the analysis of the performance of rigid sails considering pre-stall and post-stall aerodynamic conditions. A methodology was developed to obtain the aerodynamic coefficients of the rigid sail for any position of the sail with respect to the wind depending on the tested airfoil. Once the aerodynamic coefficients were modelled for several angles of attack, the thrust and overturning components generated by the sail force on the boat were computed from before and after airfoil stalling predictive models of the aerodynamic coefficients. From the obtained results, the following two main conclusions can be stated. i) The use of the sail in post-stall conditions for higher angles of incidence (> 90 degrees) substantially improved the thrust generated on the boat. For the case of small incidence angles, it is recommended to set the sail at an angle of attack less than the airfoil stall. ii) Within the symmetrical four-digit NACA series, the symmetrical NACA 0015 airfoil turned out to be the best choice for geometrically defining the rigid sail cross section.

Automated summary

The shipping industry is increasingly focusing on green and zero-emission shipping, aiming to reduce fossil fuel consumption and mitigate environmental impact. The use of renewable energies, including rigid sails as auxiliary propulsion systems, is being explored. This study analyzed the performance of rigid sails under pre-stall and post-stall aerodynamic conditions. A methodology was developed to obtain the aerodynamic coefficients of the rigid sail for any position relative to the wind using different tested airfoils. The results showed that post-stall conditions significantly improved the thrust generated by the sail, especially at higher angles of incidence (> 90 degrees). The symmetrical NACA 0015 airfoil was found to be the most suitable choice for defining the cross-section of the rigid sail.