Abstract
Wingsails as a classical means for wind-assisted ship propulsion is booming today. Crescent-shaped wingsails have shown great potential considering their aerodynamics in thrust generation. However, there have been few studies on its structural responses exposed to unsteady aerodynamic loads. In this study, a crescent-shaped wingsail at a \(1:100\) scale is investigated by using wind tunnel tests. The wingsail with aspect ratios of \(0.19\) and \(0.33\), which are derived from practical wingsail design, are measured at the angle of attack (\(\alpha\)) from \(0^\circ\) to \(90^\circ\), and at the wind speed from \(20 m/s\) to \(40 m/s\). The wind loads, pressure distribution, and wingsail tip displacements are measured and discussed. A study of the Reynolds number sensitivity indicates that the trends of the force coefficients and critical \(\alpha\) are changed when the Reynolds number (\(Re\)) is above \(3.1\times {10}^{5}\). Besides, at \(Re=3.1\times {10}^{5}\) a lift crisis is found for \(\alpha\) below \(10^\circ\), and a drag crisis happens for \(\alpha =0^\circ\) at \(Re=3.6\times {10}^{5}\). Structural response analysis is conducted based on the wingsail tip displacement in the direction perpendicular to the chord line. The fundamental eigenfrequency of the structure, instead of the flow-induced frequencies, is found to dominate the fluid-structure interaction measured in the tests. Furthermore, the aerodynamic performance of a three-wingsail system is analyzed based on experiments. Notable interactions are found among the three wingsails.