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The implementation of morphing wing applications in aircraft design has sparked significant interest as it enables the dimensional properties of the aircraft to be modified during flight. By allowing manipulation of the 2D and 3D parameters on the aircraft’s wings, tail surfaces, or fuselage, a variety of possibilities have arisen. Two primary schools of thought have emerged in the field of morphing wing applications: the mechanisms school and the smart surfaces approach that uses shape-memory materials and smart actuators. Among the research in this field, the Fishbone Active Camber (FishBAC) approach has emerged as a promising avenue for controlling the deflection of the wing’s trailing edge. This study revisits previous research on morphing wings and the FishBAC concept, evaluates the current state of the field, and presents an original design process flow that includes the design of a unique and innovative UAV called the Stingray within the scope of the study. A novel morphing concept developed for the Stingray UAV, Rear Spar Articulated Wing Camber (RSAWC), employs a fishbone-like morphing wing rib design with rear spar articulation in a cost-effective manner. The design process and flight tests of the RSAWC are presented and directly compared with a conventional wing. Results are evaluated based on performance, weight, cost, and complexity. Semi-empirical data from the flight testing of the concept resulted in approximately a 19% flight endurance increment. The study also presents future directions of research on the RSAWC concept to guide the researchers.

The morphing wing can adaptively adjust its aerodynamic shape according to the change of flight missions to obtain the best aerodynamic performance. In this paper, the SMA spring is used as the actuator to design a lightweight, low-energy consumption continuous variable camber wing with quick response. The structural design was verified by the finite element simulation and experimental demonstration. The results show that the deflection of the morphing trailing edge can reach 14.3°, which meets the expected demand and shows the feasibility of the proposed design.

Morphing structures can allow significant improvements in performance by optimally changing shape across varying conditions. A critical barrier to the design of morphing structures is the challenge of determining how optimal shape changes as a function of the many operating conditions that affect optimality. Traditional engineering optimization techniques are able to determine an optimal shape only for one condition or an aggregation over operating conditions (i.e., optimizing average performance). Parametric optimization is an alternative approach that can solve a family of related optimization problems simultaneously. Herein the authors analyze the design of a structurally consistent camber morphing wing for light aircraft applications using parametric optimization techniques. The approach combines rigorous consideration of structural constraints via Class/Shape Transformation (CST) equations and use of a C 1 -continuous analytical representation of wing outer mold line geometry with the Predictive Parametric Pareto Genetic Algorithm (P3GA), an algorithm for nonlinear multi-parametric optimization. The system is tuned to maximize lift-to-drag ratio, a key metric for aircraft flight range. Kriging-based interpolation is applied to P3GA output to obtain an optimal solution map determining optimal shape variable values as a function of flight conditions (airspeed, angle of attack, and altitude). Solutions obtained from iterated use of traditional optimization techniques are utilized to benchmark the more novel and efficient parametric optimization accuracy. Results show that parametric optimization is useful for optimizing morphing structures across a range of operating conditions.

This paper describes the results of a six-year project aiming at designing and constructing a flapping twin-wing robot of the size of hummingbird (Colibri in French) capable of hovering. Our prototype has a total mass of 22 g, a wing span of 21 cm and a flapping frequency of 22 Hz; it is actively stabilized in pitch and roll by changing the wing camber with a mechanism known as wing twist modulation. The proposed design of wing twist modulation effectively alters the mean lift vector with respect to the center of gravity by reorganization of the airflow. This mechanism is modulated by an onboard control board which calculates the corrective feedback control signals through a closed-loop PD controller in order to stabilize the robot. Currently, there is no control on the yaw axis which is passively stable, and the vertical position is controlled manually by tuning the flapping frequency. The paper describes the recent evolution of the various sub-systems: the wings, the flapping mechanism, the generation of control torques, the avionics and the PD control. The robot has demonstrated successful hovering flights with an on-board battery for the flight autonomy of 15–20 s.

Camber morphing is an effective way to control the lift generated by any aerofoil and potentially improve the range (as measured by the lift-to-drag ratio) and endurance (as measured by$C_l^{3/2}/C_d$). This can be especially useful for fixed-wing Unmanned Aerial Vehicles (UAVs) undergoing different flying manoeuvres and flight phases. This work investigates the aerodynamic characteristics of the NACA0012 aerofoil morphed using a Single Corrugated Variable-Camber (SCVC) morphing approach. Structural analysis and morphed shapes are obtained based on small-deformation beam theory using chain calculations and validated using finite-element software. The aerofoil is then reconstructed from the camber line using a Radial Basis Function (RBF)-based interpolation method (J.H.S. Fincham and M.I. Friswell, “Aerodynamic optimisation of a camber morphing aerofoil,” Aerosp. Sci. Technol., 2015). The aerodynamic analysis is done by employing two different finite-volume solvers (OpenFOAM and ANSYS-Fluent) and a panel method code (XFoil). Results reveal that the aerodynamic coefficients predicted by the two finite-volume solvers using a fully turbulent flow assumption are similar but differ from those predicted by XFoil. The aerodynamic efficiency and endurance factor of morphed aerofoils indicate that morphing is beneficial at moderate to high lift requirements. Further, the optimal morphing angle increases with an increase in the required lift. Finally, it is observed for a fixed angle-of-attack that an optimum morphing angle exists for which the aerodynamic efficiency becomes maximum.

Of the medals awarded during the Winter Olympics Games, most are awarded for sports involving cross-country (XC) skiing. The Double Poling (DP) technique, which is one of the sub-techniques used most frequently in XC skiing, has not yet been studied using simulations of the ski–snow contact mechanics. This work introduces a novel method for analysing how changes in the distribution of pressure on the sole of the foot (Plantar Pressure Distribution or PPD) during the DP motion affect the contact between the ski and the snow. The PPD recorded as the athlete performed DP, along with an Artificial Neural Network trained to predict the geometry of the ski (ski-camber profile), were used as input data for a solver based on the boundary element method, which models the interaction between the ski and the snow. This solver provides insights into how the area of contact and the distribution of pressure on the ski-snow interface change over time. The results reveal that variations in PPD, the type of ski, and the stiffness of the snow all have a significant impact on the contact between the ski and the snow. This information can be used to improve the Double Poling technique and make better choices of skis for specific snow conditions, ultimately leading to improved performance. Graphical Abstract

To study the influence mechanism of leading-edge variable camber (LEVC) technology on the dynamic stall of rotor in forward flight, a rotor flowfield simulation method is established based on the motion-embedded grid and URANS equation, in which the body-fitted grid of LEVC rotor is reconstructed by the RBF grid deformation method. The effectiveness of the mesh method and the numerical simulation method is verified by comparing the unsteady aerodynamic characteristics of the SMART rotor with trailing edge winglet. Subsequently, the effect of LEVC rotor on the unsteady aerodynamic phenomena of rotor is analyzed, and the influence mechanism of LEVC rotor on the dynamic stall is explained. The results demonstrate that the LEVC technology can significantly improve the load characteristics of blade under dynamic stall, which suppresses the dynamic stall vortex by reducing the inverse pressure gradient at the leading edge of airfoil, thereby increasing the lift on retreating blade of rotor, and inhibit the divergence of counter-torque.

In order to better understand the influence of camber on aerodynamic performance of airfoil, airfoil NACA0012, NACA2412, NACA4412 and NACA6412 were selected as research objects to conduct numerical simulation at 10m/s. According to lift coefficient, lift-drag ratio and airfoil pressure cloud diagram, the influence of camber on airfoil aerodynamic performance is obtained. The results show that the lift coefficient of airfoil increases with the increase of airfoil bending degree within a certain range of attack Angle. The lift-drag ratio of airfoil increases with the increase of its bending degree.

Flutter is the phenomenon where the body will experience uncontrolled motions after reaching a certain velocity known as the critical velocity. The focus of this work is on studying the influence of position of camber of an airfoil on its flutter behaviour. Four different NACA five digit airfoils were selected based on the variation in position of camber and were analyzed at different air speeds. These airfoils were studied for their pitch and plunge behaviour which are the base for understanding the flutter characteristics of any body and the flutter characteristics are derived from those results.

A low-order physics-based model to simulate the unsteady flow response to airfoils undergoing large-amplitude variations of the camber is presented in this paper. Potential-flow theory adapted for unsteady airfoils and numerical methods using discrete-vortex elements are combined to obtain rapid predictions of flow behavior and force evolution. To elude the inherent restriction of thin-airfoil theory to small flow disturbances, a time-varying chord line is proposed in this work over which to satisfy the appropriate boundary condition, enabling large deformations of the camber line to be modeled. Computational fluid dynamics simulations are performed to assess the accuracy of the low-order model for a wide range of dynamic trailing-edge flap deflections. By allowing the chord line to rotate with trailing-edge deflections, aerodynamic loads predictions are greatly enhanced as compared to the classical approach where the chord line is fixed. This is especially evident for large-amplitude deformations.