Search Results (6)

It is well established that increasing vehicle efficiency enables the achievement of N + 3 sustainable air travel goals. To this end, the integration of a slotted natural-laminar-flow airfoil with a transonic, truss-based commercial wing configuration is projected to significantly decrease fuel consumption demand. The slotted natural-laminar-flow airfoil is designed with two elements to extend favorable pressure gradients further aft than single-element airfoils. This two-element design increases the extent of laminar flow to approximately 90% of the airfoil surface, thus decreasing streamwise instabilities, which in turn reduces the wing profile drag. The slotted natural-laminar-flow airfoil also exhibits the dumping-velocity effect and achieves an off-surface pressure recovery, both critical to achieving laminar flow and overcoming single-element airfoil limitations. Given the potential of this novel concept, the objective of this literature review is to discuss the history of slotted natural-laminar-flow airfoils, recent research to mature the design, and future work needed for the implementation of this airfoil on a commercial aircraft. Full article

A natural laminar flow (NLF) airfoil is designed to reduce drag by expanding laminar flow areas. In-depth knowledge of transition performance is essential for its aerodynamic design. The k-ω-γ-Re_θ framework, which consists of the SST k-ω turbulence model and γ-Re_θ transition model, is employed to simulate transitional flows around an NLF wing RAE5243 airfoil. The transition performances of the RAE5243 airfoil under various values of turbulent intensity, temperature, angle of attack, and Mach number are simulated and compared. The results show that the rise of inflow turbulent intensity will promote an earlier transition on both the suction and pressure sides. The influence of wall temperature on transition is limited. The rise of angle of attack will lead to an earlier transition on the pressure side but a later transition on the suction side. With the rise of Mach number, the transition happens earlier under a zero and positive angle of attack but later under a negative angle of attack. In addition, the correlation of transition onset locations with respect to turbulent intensity, surface temperature, angle of attack, and Mach number is established based on numerical results. Full article

Aircraft winglets are well-established devices that improve aircraft fuel efficiency by enabling a higher lift over drag ratios and lower induced drag. Retrofitting winglets to existing aircraft also increases aircraft payload/range by the same order of the fuel burn savings, although the additional loads and moments imparted to the wing may impact structural interfaces, adding more weight to the wing. Winglet installation on aircraft wing influences numerous design parameters and requires a proper balance between aerodynamics and weight efficiency. Advanced dynamic aeroelastic analyses of the wing/winglet structure are also crucial for this assessment. Within the scope of the Clean Sky 2 REG IADP Airgreen 2 project, targeting novel technologies for next-generation regional aircraft, this paper deals with the integrated design of a full-scale morphing winglet for the purpose of improving aircraft aerodynamic efficiency in off-design flight conditions, lowering wing-bending moments due to maneuvers and increasing aircraft flight stability through morphing technology. A fault-tolerant morphing winglet architecture, based on two independent and asynchronous control surfaces with variable camber and differential settings, is presented. The system is designed to face different flight situations by a proper action on the movable control tabs. The potential for reducing wing and winglet loads by means of the winglet control surfaces is numerically assessed, along with the expected aerodynamic performance and the actuation systems’ integration in the winglet surface geometry. Such a device was designed by CIRA for regional aircraft installation, whereas the aerodynamic benefits and performance were estimated by ONERA on the natural laminar flow wing. An active load controller was developed by PoliMI and UniNA performed aeroelastic trade-offs and flutter calculations due to the coupling of winglet movable harmonics and aircraft wing bending and torsion. Full article

This article presents some application of the morphing technology for aerodynamic performance improvement of turboprop regional aircraft. It summarizes the results obtained in the framework of the Clean Sky 2 AIRGREEN2 program for the development and application of dedicated morphing devices for take-off and landing, and their uses in off design conditions. The wing of the reference aircraft configuration considers Natural Laminar Flow (NLF) characteristics. A deformable leading edge morphing device (“droop nose”) and a multi-functional segmented flap system have been considered. For the droop nose, the use of the deformable compliant structure was considered, as it allows a “clean” leading edge when not used, which is mandatory to keep natural laminar flow (NLF) properties at cruise. The use of a segmented flap makes it possible to avoid external flap track fairings, which will lead to performance improvement at cruise. An integrated tracking mechanism is used to set the flap at its take-off optimum setting, and, then, morphing is applied in order to obtain a high-performance level for landing. Lastly, some performance improvements can be obtained in climb conditions by using the last segment of the flap system to modify the load distribution on the wing in order to recover some extended laminar flow on the wing upper surface. Full article

Modern transport aircraft wings have reached near-peak levels of energy-efficiency and there is still margin for further relevant improvements. A promising strategy for improving aircraft efficiency is to change the shape of the aircraft wing in flight in order to maximize its aerodynamic performance under all operative conditions. In the present work, this has been developed in the framework of the Clean Sky 2 (REG-IADP) European research project, where the authors focused on the design of a multifunctional twistable trailing-edge for a Natural Laminar Flow (NLF) wing. A multifunctional wing trailing-edge is used to improve aircraft performance during climb and off-design cruise conditions in response to variations in speed, altitude and other flight parameters. The investigation domain of the novel full-scale device covers 5.15 m along the wing span and the 10% of the local wing chord. Concerning the wing trailing-edge, the preliminary structural and kinematic design process of the actuation system is completely addressed: three rotary brushless motors (placed in root, central and tip sections) are required to activate the inner mechanisms enabling different trailing-edge morphing modes. The structural layout of the thin-walled closed-section composite trailing-edge represents a promising concept, meeting both the conflicting requirements of load-carrying capability and shape adaptivity. Actuation system performances and aeroelastic deformations, considering both operative aerodynamic and limit load conditions, prove the potential of the proposed structural concept to be energy efficient and lightweight for real aircraft implementation. Finally, the performance assessment of the outer natural laminar flow (NLF) wing retrofitted with the multifunctional trailing-edge is performed by high-fidelity aerodynamic analyses. For such an NLF wing, this device can improve airplane aerodynamic efficiency during high speed climb conditions. Full article

The Energy System Transition in Aviation research project of the Aeronautics Research Center Niedersachsen (NFL) searches for potentially game-changing technologies to reduce the carbon footprint of aviation by promoting and enabling new propulsion and drag reduction technologies. The greatest potential for aerodynamic drag reduction is seen in laminar flow control by boundary layer suction. While most of the research so far has been on partial laminarization by application of Natural Laminar Flow (NLF) and Hybrid Laminar Flow Control (HLFC) to wings, complete laminarization of wings, tails and fuselages promises much higher gains. The potential drag reduction and suction requirements, including the necessary compressor power, are calculated on component level using a flow solver with viscid/inviscid coupling and a 3D Reynolds-Averaged Navier-Stokes (RANS) solver. The effect on total aircraft drag is estimated for a state-of-the-art mid-range aircraft configuration using preliminary aircraft design methods, showing that total cruise drag can be halved compared to today’s turbulent aircraft. Full article