Aerodynamic Performance of Morphing and Periodic Trailing-Edge Morphing Airfoils in Ground Effect

Applying fish bone active camber morphing to the wing-in-ground effect to improve the aerodynamic efficiency was investigated using computational fluid dynamics (CFD) at a Reynolds number of 320,000. Steady-static morphing was first carried out with Reynolds-averaged Navier–Stokes (RANS) equations in two dimensions for morphing start locations off (60%, 80%, and 90% chord), ground clearances ($h/c=0.1$, 0.2, 0.4, 1), and angles of attack (AoAs) 0°, 2°, 3°, 4°, and 12°. A morphing displacement ($w_{te}$) of 0.5% increased the efficiency by 2.8% (compared to non-morphing in the ground effect) for the 3° AoA and 90% start location, and by 62% in comparison to the baseline unmorphed airfoil in freestream. Reducing $h/c=1$ to 0.1 increased the lift between 10% and 17%; the larger gain was with the highest morphing deflection. A key finding was that morphing the airfoil reduced the distance between the trailing edge and ground, enhancing the ground effect. Also, morphing at an earlier start location in the chord direction resulted in a smaller area beneath the airfoil, reducing the total pressure, which reduced the overall lift compared to a later morphing start location. Dynamic morphing at 1 Hz using URANS K-Omega-SST showed a similar amount of lift as static morphing but a slightly higher amount of drag. Reducing the period caused an initial overshoot in drag before settling. The dynamic ground effect showed higher efficiency at low AoAs compared to dynamic morphing in freestream, which is beneficial for aircraft to fly with less pitch. Finally, periodic morphing for $h/c=0.1$ using sinusoidal motion with morphing starting at 25% along the chord and 4° AoA was investigated between 0.05% to 0.15% $w_{te}$ and 0.5 to 3.5 Strouhal number. Periodically morphing at 0.125% $w_{te}$ and Strouhal number of 0.9 using DES simulations increased the efficiency by 5.4%; however, it reduced the lift by 0.7%, the drag reduced by 5.8%, and it showed Kelvin–Helmholtz instability at 9.8 Strouhal number.

The use of UAVs is increasing in popularity for many missions, which include observation, surveys, and the delivery of supplies, including medical. The use of UAVs typically has lower aircraft and operational costs as well as allowing the craft to carry out dangerous missions without putting the crew in danger. A wing-in-ground effect (WIG) craft typically operates on water due to the large fuel consumption savings as well as allowing the craft to travel at higher speed compared to conventional marine craft. The study focused on applying morphing wings to a UAV WIG effect craft to improve the aerodynamic performance of the craft and allow further fuel efficiency savings compared to a marine craft. The improved performance of the WIG craft and applying morphing translates to improvements in flight time and increased range. Morphing wings also allow the wing to adapt to different flight conditions allowing for optimized aerodynamic performance depending on factors such as cargo weight and weather conditions.