Effect of chord length ratio on aerodynamic performance of two-element wing sail

Abstract

This study aims to optimize the chord length ratio of a two-element wing sail in order to enhance the aerodynamic performance of a wind-powered unmanned sailboat. The viscous Navier-Stokes flow solver was used to solve for changes in the numerical aerodynamic performance with the chord length ratio and rear wing sail deflection angle of the two-element wing sail for different wind angles and angles of attack. The comparative results demonstrate that at a given angle of attack, increasing the chord length ratio between the front and rear sails leads to higher lift and thrust coefficients of the wing sail, thereby improving the sailboat's performance. Moreover, increasing the deflection angle of the rear sail at a given angle of attack results in an overall increase in the lift and thrust coefficients of the wing sail. It was also observed that a smaller chord length ratio and a larger deflection angle of the rear sail contribute to a more unstable flow field. Based on these findings, the optimum values of the chord length ratio, c1/c2, could range between 1.5 and 3. These findings have significant implications for optimizing the structures and control systems of wing sails.