Correction notice The CL in the title of Fig. 7(b) was corrected from 0.4 in the original version to CL=1.0. (a) Climb local lift spanwise distribution at CL=1 0 0.2 0.4 0.6 0.8 1 0 5 10 10-3 0 0.2 0.4 0.6 0.8 1 0 5 10 10-3 (b) Solid line (suction side)-dashed line (pressure side) Fig. 7 Local lift coefficient distribution with a selected friction coefficient of one section.

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This study investigates the aerodynamic benefits of integrating trailing edge camber morphing on the strut of a regional strut-braced wing aircraft designed to cruise at Mach number of 0.5. Strut-braced wings are recognized for their weight advantages in high aspect ratio designs compared to the equivalent cantilever wings since the strut decreases the main wing’s bending moment. Hence, the induced drag component can be reduced due to the high aspect ratio without increasing the weight of the main wing. However, the strut increases the parasite drag component highlighting the need for innovative methods to improve the strut-braced wing overall aerodynamic efficiency. Recent studies have shown the significance of strut shape in the overall drag reduction and the necessity of maintaining high aerodynamic efficiency in off-design conditions. In this work, a genetic algorithm was utilized in conjunction with a mid-fidelity aerodynamic model to optimize the morphing strut trailing edge geometry across a range of climb and cruise conditions. The optimization objective was the minimization of drag and the design variables were the equivalent trailing edge deflection angles in seven sections of the strut. The results demonstrate a drag reduction of 0.5% to 3% both in climb and cruise. For lift coefficients below 0.8, the drag reduction is mainly attributed to the redistribution of the loading and the induced drag component reduction. In contrast, at lift coefficients above 0.8, the parasite drag component decreases due to the increased region of laminar flow over the upper wing surface.@en

High aspect ratio strut-braced wing aircraft can significantly reduce the induced drag while limiting the weight penalty of increasing the wingspan. As part of the Hybrid Electric Regional Wing Integration Novel Green Technologies (HERWINGT) project, a multifunctional morphing strut is being investigated. In this study, an optimization framework is proposed to define the thickness distribution of the morphing trailing edge of the strut to achieve the desired operational shapes while considering laminate manufacturing guidelines and material allowables. The optimizer finds designs capable of achieving the objective shapes and provides load and mass estimations that can be used to make design decisions.

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This paper presents an experimental investigation into the aeroelastic behavior of an innovative wind turbine design featuring a downwind two-blade rotor with a teetering hub mounted on a tower with adjustable tilt. The rotor model incorporates two sets of elastic blades—stiff and flexible—for scaling purposes, each instrumented with strain gauges and accelerometers. Ground and wind tunnel tests were conducted to analyze the aeroelastic response. Static tests exhibited discrepancies between measured and numerically predicted displacements, with maximum displacements near the tip exceeding numerical predictions by 14% and 31% for flexible and stiff blades respectively. Frequency differences between measured and numerically simulated elastic modes ranged from 0.5% to 18% for both blade sets, as determined by ground vibration tests. Wind tunnel tests revealed the dominance of rotational speed harmonics, particularly the second harmonic, in the blades’ periodic response. A sensitivity analysis was also carried out with respect to tower tilt angle, rotational speed and blade pitch angle, for both blade sets at a range of tip-speed ratio values. The static response of the system, as captured by the generated power and thrust, was primarily sensitive to tower tilt angle variation and to a lesser extent blade pitch angle. Conversely, the tip-speed ratio in conjunction with rotational speed were found to dictate the dynamic response, influencing the azimuthal position and magnitude of the maximum bending moment at the blade root. Finally, no dynamic aeroelastic instability was observed during wind tunnel tests.

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