Aerodynamic Study of Multiple Wingsails with Co-Flow Jet Active Flow Control

Abstract

Wingsails can be used as a means of reducing fuel consumption for maritime vessels. To improve on their performance there are different methods available, one of which is flow control. This thesis investigates how the co-flow jet (CFJ) active flow control (AFC) technology can improve the aerodynamic performance of a wingsail based on a NACA 0015 airfoil. The objective is to enhance thrust with minimal energy expenditure, thereby improving the net power savings of the wingsail. The study was performed using two-dimensional CFD simulations with the Unsteady Reynolds-averaged Navier Stokes (URANS) equations and the k-ω Shear Stress Transport (SST) turbulence model. The baseline airfoil was modified to accommodate the CFJ requirements, which include injection and suction slots. A parametric study was performed on the resulting airfoil to establish an appropriate jet momentum coefficient (Cµ), together with the size and location of the slots. To make a direct comparison between a single CFJ and a baseline wingsail, a one-sail configuration was studied. Results demonstrate a substantial increase in thrust and net power savings for the CFJ wingsail. To study flow interactions between multiple wingsails, a three-sail configuration was studied, mimicking a vessel equipped with three wingsails. The study reveals that the wingsails are greatly affected by the apparent wind angle, with substantial flow interactions between the sails. In all tested conditions, the results demonstrate a significant improvement in propulsive performance. The findings also highlight the importance of a Cµ distribution strategy, together with individual adjustment of the angle of attack (AoA) of each wingsail. Overall, the CFJ technology applied to a wingsail is highly effective in preventing flow separation and improving performance over a wide range of operating conditions.