The MELD structure provides an interface between the rigid wing structures and actuated surfaces to maintain geometric continuity within the wing to reduce pressure leakage and the associated loss in the aerodynamic lift. Likewise, the FishBAC mechanism allows for a single actuated morphing wing consisting of a chordwise bending beam spine with a pre-tensioned elastomeric matrix composite skin, a tendon-driven actuation system that inhibits morphing capabilities, and a rigid non-morphing spar on which the morphing system hinges. NASA’s VCCTEF consists of a discretized spanwise trailing edge utilizing a three-hinge actuation system on the outboard swept portion of the wing that allows for the actively adaptive control of wing twisting and bending. Notable examples of the morphing wing technologies developed within the past decade include NASA’s Variable Camber Continuous Trailing-Edge Flap (VCCTEF), Fishbone Active Camber (FishBAC) with Morphing Elastically LofteD (MELD) structure, Variable Camber Compliant Wing (VCCW), and Spanwise Morphing Trailing Edge (SMTE). Currently, several developments in compliant structures and mechanisms to achieve morphing wing capabilities are underway. Development in materials and structural designs has revived the concept of utilizing conforming structures to enhance aircraft performance in all flight regimes. As aircraft continue to develop in performance and speed, the need to increase structural stiffness to avoid aeroelastic instabilities and meet loading requirements became a necessity. However, it was only with the recent advancements with the smart composite materials and structural designs that wing morphing in the modern flight speeds have become technologically viable. The wing morphing concept’s origins could be traced back to the Wright Brothers’ wing warping design to produce a rolling motion by twisting the wing in flight.
Hence, the morphing wing design may deliver superior aerodynamic performance. In contrast, modern morphing wings maintain a smooth variation along the wing surface, which removes the effects of discontinuity in the geometry. However, the discontinuity in wing geometry introduced by those mechanisms typically leads to non-uniform aerodynamic profiles and increased drag. In conventional aircraft, lift enhancing mechanisms such as the flaps and slats are incorporated into the wings to increase the aerodynamic performance. An increase in aerodynamic performance leads to higher fuel efficiency, range, and endurance than conventional in-flight actuators, such as flaps and slats currently used in commercial aircraft. The ability to modify a wing’s geometry during flight allows the aircraft to achieve optimal aerodynamic performance at every stage of its mission profile. Morphing wing actuation technology is a research area of importance due to its capability to increase aircraft performance and maneuverability by adapting the wing shape to the various flight conditions. The study demonstrates that morphing wings can achieve significant aerodynamic performance gains through active actuation of hinge point location and control deflection to suit the flight regimes encountered through a mission profile. The results also indicated that the morphing wing shape optimization should start from lower values of control deflection and hinge location as an initial design approach. The results showed that a higher Reynolds number leads to better aerodynamic performance while the control deflection and hinge location needs to be optimized for a given flight condition. The CFD simulations are performed using the three- dimensional (3D) Reynolds-Average Navier-Stokes (RANS) equations with the k – ω Shear Stress Transport (SST) turbulence model. This research was conducted numerically through Computational Fluid Dynamics (CFD) simulations. Control deflection for the trailing edge, hinge location, Reynolds number, and angle of attack were parameterized to investigate trends.
Following the authors' previous study, an elliptical curve was used as the morphing model for the spanwise trailing edge deflection. The morphing wing presented considers a NACA 0012 airfoil with a rigid portion at the leading edge and a continuously conforming trailing edge flap. In this research, the morphing wing geometries are studied parametrically to identify the aerodynamic characteristics at various flight conditions.
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