The droop-nose leading-edge morphing wing offers promising potential for reducing aerodynamic drag and noise during take-off and landing, thereby helping to lower aircraft fuel consumption and align with greener aviation goals outlined in Flightpath 2050 by the EU and ICAO declarations. Despite technological challenges and current technology readiness levels (TRL), droop-nose leading-edge (DNLE) wings are primarily tested and evaluated in unmanned aerial systems to reduce costs and risks. The literature proposes various optimisation methods for airfoil skin and morphing mechanisms; however, additional research contributions are needed to develop an effective design methodology. High actuator forces required for morphing, the trade-off between skin flexibility and load-bearing capacity, and the difficulty of obtaining smooth and continuous airfoil deformations are still under investigation. The present research introduces an optimisation methodology tailored for DNLE composite laminate skin and morphing mechanism structures. Its application to the UAS-S45 unmanned vehicle is utilised as a case study. Applying this design and optimisation methodology can lead to an 88% reduction in actuator mechanism force for a DNLE optimised for 6 degrees angle-of-attack, considering an airfoil. This approach significantly enhances airfoil shape smoothness across sections and spanwise direction during morphing conditions. The proposed approach reduces the computational effort, as non-linear finite element method (FEM) analyses are not required within the optimisation loop, except at selected verification stages. A mechanism prototype was constructed to validate the FEM analyses and understand the limits of the simulation. Further investigations are required to achieve a morphing shape closer to aerodynamically optimised shapes.

The adjoint method is efficient for computing derivatives, enabling gradient-based optimization to manage systems with many design variables. Therefore, this paper aims to investigate the aerodynamic optimization design of morphing wings with different leading-edge shapes. The wing shapes include a clean UAS-S45 wing and different tubercle-based wing shapes. This study emphasizes optimizing the various shapes in the leading edge to delay stall and increase the aerodynamic performance of the wing. Firstly, baseline wing design studies were carried out, followed by experimental wind tunnel validation to ensure accuracy and methodology validation. After establishing the baseline, optimization was conducted using a multidisciplinary design optimization (MDO) approach with DAFoam, a Reynolds-averaged Navier-Stokes solver. The optimization process employs a Free Form Deformation approach to produce different variants of the leading-edge shapes. Numerical investigations of flow characteristics, performed using computational fluid dynamics (CFD) computations, validate the numerical scheme against experimental data. The optimization strategy combines the Interior Point OPTimizer (IPOPT) within the adjoint solver framework with ICEM to generate high-quality numerical meshes. The experimental and numerical results showed the advantages of tubercles in maintaining aerodynamic effectiveness, particularly at high angles of attack. The study confirms that tubercle-profiled leading edges improve post-stall aerodynamic behavior by mitigating abrupt flow separation and facilitating smoother transitions during stall. For optimized tubercle-based leading edges, the peaks and valleys generate alternating regions of high and low vorticity, forming counter-rotating vortices that enhance mixing, improving aerodynamic performance. The peak configuration, in particular, exhibits smooth airflow acceleration over the crest of the tubercle, creating higher velocity regions along the leading edge and downstream, demonstrating enhanced flow attachment. While conventional bio-inspired designs already offer significant performance benefits at high angles of attack, further optimization of tubercle shapes for morphing leading edges has demonstrated additional improvements in aerodynamic efficiency at low angles of attack. However, achieving convergence during optimization remains challenging due to mesh deformation and movement complexities in these geometries. Future work will aim to expand the dataset, refine the optimization process, and enable more detailed analyses to unlock the full potential of tubercle-based designs.

This study introduces a novel “twist morphing aileron and winglet” design for the Unmanned Aircraft System UAS-S45. Improving rolling efficiency through twist morphing ailerons and reducing induced drag through twist morphing winglets are the two main objectives of this study. A novel wing design is introduced, and a high-fidelity gradient-based aerodynamic shape optimization is performed for twist morphing ailerons and twist morphing winglets, separately, with specified objective functions. The twist morphing aileron is then compared to the conventional hinged aileron configuration in terms of rolling efficiency and other aerodynamic properties, in particular aircraft maneuverability. The results for twist morphing ailerons show that the novel morphing design increases the aileron efficiency by 34% compared to the conventional design and reduces induced drag by 61%. Next, twist morphing winglets are studied regarding the induced drag in cruise and climb flight conditions. The results for twist morphing winglets indicate that the novel design reduces induced drag by 25.7% in cruise flight and up to 16.51% in climb; it also decreases the total drag by up to 7.5% and increases aerodynamic efficiency by up to 9%.

The seamless trailing edge morphing flap is investigated using a high-fidelity steady-state aerodynamic shape optimization to determine its optimum configuration for different flight conditions, including climb, cruise, and gliding descent. A comparative study is also conducted between a wing equipped with morphing flap and a wing with conventional hinged flap. The optimization is performed by specifying a certain objective function and the flight performance goal for each flight condition. Increasing the climb rate, extending the flight range and endurance in cruise, and decreasing the descend rate, are the flight performance goals covered in this study. Various optimum configurations were found for the morphing wing by determining the optimum morphing flap deflection for each flight condition, based on its objective function, each of which performed better than that of the baseline wing. It was shown that by using optimum configuration for the morphing wing in climb condition, the required power could be reduced by up to 3.8% and climb rate increases by 6.13%. The comparative study also revealed that the morphing wing enhances aerodynamic efficiency by up to 17.8% and extends the laminar flow. Finally, the optimum configuration for the gliding descent brought about a 43% reduction in the descent rate.

An integrated approach to active flow control is proposed by finding both the drooping leading edge and the morphing trailing edge for flow management. This strategy aims to manage flow separation control by utilizing the synergistic effects of both control mechanisms, which we call the combined morphing leading edge and trailing edge (CoMpLETE) technique. This design is inspired by a bionic porpoise nose and the flap movements of the cetacean species. The motion of this mechanism achieves a continuous, wave-like, variable airfoil camber. The dynamic motion of the airfoil’s upper and lower surface coordinates in response to unsteady conditions is achieved by combining the thickness-to-chord (t/c) distribution with the time-dependent camber line equation. A parameterization model was constructed to mimic the motion around the morphing airfoil at various deflection amplitudes at the stall angle of attack and morphing actuation start times. The mean properties and qualitative trends of the flow phenomena are captured by the transition SST (shear stress transport) model. The effectiveness of the dynamically morphing airfoil as a flow control approach is evaluated by obtaining flow field data, such as velocity streamlines, vorticity contours, and aerodynamic forces. Different cases are investigated for the CoMpLETE morphing airfoil, which evaluates the airfoil’s parameters, such as its morphing location, deflection amplitude, and morphing starting time. The morphing airfoil’s performance is analyzed to provide further insights into the dynamic lift and drag force variations at pre-defined deflection frequencies of 0.5 Hz, 1 Hz, and 2 Hz. The findings demonstrate that adjusting the airfoil camber reduces streamwise adverse pressure gradients, thus preventing significant flow separation. Although the trailing-edge deflection and its location along the chord influence the generation and separation of the leading-edge vortex (LEV), these results show that the combined effect of the morphing leading edge and trailing edge has the potential to mitigate flow separation. The morphing airfoil successfully contributes to the flow reattachment and significantly increases the maximum lift coefficient (cl,max)). This work also broadens its focus to investigate the aerodynamic effects of a dynamically morphing leading and trailing edge, which seamlessly transitions along the side edges. The aerodynamic performance analysis is investigated across varying morphing frequencies, amplitudes, and actuation times.

This paper aims to present a new methodology to model the aerodynamic coefficients and predict the flow structure and the behavior of dynamic stall vortices surrounding a pitching CRJ-700 airfoil. This new methodology, called the Combined Morphing Leading Edge and Trailing Edge (CoMpLETE), aimed to manage dynamic stall control using the effects of leading and trailing edge morphing mechanisms. A framework for unsteady parametrization was created to simulate the transient leading edge and trailing edge motions. The parabolic airfoil parametrization approach was used to obtain its morphing motion, and it was coupled with Laplace Diffusion dynamic mesh techniques. Precise and reliable simulations validated the geometry deflection and mesh deformation schemes because the mesh quality criteria were respected throughout the deformation process. The gamma - Re-theta turbulence model adequately captured the flow structures of dynamic airfoils associated with leading-edge vortex formations for a wide range of Reynolds numbers. The numerical results have shown that the new radius of curvature of the CRJ-700 morphing airfoil can minimize the streamwise adverse pressure gradient and further prevent significant flow separation by delaying the occurrence of Dynamic Stall Vortex (DSV). Results with the pitching-oscillation motion of the CRJ-700 airfoil and its parameters, such as the droop nose amplitude and the time at which the leading-edge morphing starts, revealed better aerodynamic performance. The CoMpLETE airfoil successfully contributes to the flow reattachment and significantly increases the maximum lift coefficient (c(l,max)).

This study investigates the design and optimization of a flexible Droop Nose Leading Edge (DNLE) based on the composite laminate skin for the UAS-S45. The concept of a morphing DNLE airfoil has excellent potential for drag and airframe noise reduction. The essential part of this DNLE airfoil type is the easiness of its mechanism deformation while maintaining the wing's structural integrity. The morphing DNLE must change the baseline shape under the influence of the aerodynamic loads to obtain its desired optimized target shape. This study proposes an optimization method to evaluate the skin design's feasibility and check the composite's failure index when the morphing DNLE changes shape. The approach yielded the desired aerodynamics shape of flexible droop nose leading edge. Wing leading edge topology depends on composite wing properties, such as ply-orientation, ply-thickness, and other composite wing parameters. This paper presents a design methodology of stiffness coefficients and lamination parameters for the stacking sequence optimization during the DNLE morphing deformation. In addition to increasing the deformation accuracy of the final airfoil shape made of composite skin, the use of stiffness coefficients and lamination parameters also effectively and efficiently defines the sequence of the composite lay-up. The deformed airfoil shapes between the optimized lay-ups and their modified shapes are compared to confirm their abilities to morph and aerodynamically optimize their shapes. The numerical results of the droop nose morphing with composite materials proved structure morphing capacity and showed feasibility of wing leading edge design mechanism and show the ability and accuracy of the methodology to obtain their morphing wing shapes.

Every aerodynamic optimization is proceeded by a parameterization of the studied aerial object, and due to its influence on the final optimization process, careful attention should be made in choosing the appropriate parameterization method. An aerodynamic optimization of a morphing trailing edge is performed using a free-form deformation parameterization technique with the purpose of examining the influence of the initial conditions of the parameterization on the optimization results, namely on the number of control points. High-fidelity gradient-based optimization using the discrete adjoint method is established by the coupling of OpenFOAM and Python within the DAFoam optimization framework. The results indicate that the number of control points has a considerable effect on the optimization process, in particular on the convergence, objective function value, and on the deformation feasibility.

Increasing fuel costs have necessitated the need for highly fuel-efficient aircraft. Industry and academic researchers are continually looking for ways to increase aircraft performance. One way is to reduce total aircraft drag, thereby improving aerodynamic efficiency without compromising structural integrity. The increase in efficiency directly benefits airlines by allowing for more frequent flights with less fuel consumption, resulting in economic benefits. Wingtip devices are already available in various shapes and sizes, and they all serve to minimize drag by recovering tip vortex energy, thereby improving fuel efficiency. Several methods have been proposed in this study for achieving the required morphing wing adaptability, resulting in considerable performance improvements over conventional wing design, such as a camber morphing wing flap.

The primary goal of this research is to investigate flow separation phenomena using various turbulence models. Also investigated are the effects of free-stream turbulence intensity on the flow over a NACA 0018 airfoil. The flow field around a NACA 0018 airfoil has been numerically simulated using RANS at Reynolds numbers ranging from 100,000 to 200,000 and angles of attack (AoA) ranging from 0 degrees to 18 degrees with various inflow conditions. A parametric study is conducted over a range of chord Reynolds numbers for free-stream turbulence intensities from 0.1 % to 0.5 % to understand the effects of each parameter on the suction side laminar separation bubble. The results showed that increasing the free-stream turbulence intensity reduces the length of the separation bubble formed over the suction side of the airfoil, as well as the flow prediction accuracy of each model. These models were used to compare the modeling accuracy and processing time improvements. The K-SST performs well in this simulation for estimating lift coefficients, with only small deviations at larger angles of attack. However, a stall was not predicted by the transition k-kl-omega. When predicting the location of flow reattachment over the airfoil, the transition k-klomega model also made some over-predictions. The Cp plots showed that the model generated results more in line with the experimental findings.

Conventional chord increase in airfoil trailing edge flaps is typically done by attaching multiple separated fowler flaps in the airfoil trailing edge, however, the airflow is prone to be turbulent near the discontinuities between the junctions of fowler flaps. The novel chord-wise extendable morphing trailing edge design for Unmanned Aerial System UAS-S45 is investigated using the gradient-based optimization approach. The purpose of this study is to investigate the advantages of synthetic trailing edge (vertical deflection) and chord elongation morphing (horizontal deflection) in comparison to conventional UAS-S45 airfoil, and to find the optimum range of deflection of the proposed morphing design for different flight conditions. The results indicate that by increasing the angle of attack, the influence of chord elongation on aerodynamic efficiency becomes considerable and the optimum angle of attack is found at near-zero values. The synthetic morphing of trailing edge and chord elongation conduct to an aerodynamic efficiency increase of up to 25.8%.

The purpose of this study is to design a variable camber morphing winglet with a composite laminate structure for the UAS-S45. The camber morphing winglet will be designed using a honeybee-inspired abdomen structure for the deformation mechanism. It was found that the morphing winglet could improve wing aerodynamic efficiency compared to its reference geometry. The leading edge and trailing edge deflections of the proposed morphing winglet design were generated by the bending and flexing motion mechanism represented by a honeybee abdomen and a flexible wing skin. The controlled winglet deformation was achieved by linear servos that stretched and retracted the flexible mechanism. The morphing winglet was controlled by three servos. The kinematic working mechanism will be presented in the study. The stress analysis is also performed on composite laminates winglet under various loads, used as pre-analysis data. A laminate with a stacking sequence of [0/90/±45/90/0] s was calculated in detail using the Classical Lamination Theory (CLT). The analysis consisted in the comparison of two materials, carbon epoxy and Glass Fibre Reinforced Plastics (GFRP). Ansys ACP was used to model the geometry, while Ansys Mechanical was utilized to model the loading cases and to perform the stress analysis to confirm the results. A demonstrative mechanism for morphing winglet was manufactured of thermoplastic polylactic acid (PLA), and its deformations were measured. The structural optimization analysis results will be presented, and investigated, therefore the optimization will result in a better orientation of composite lay-up and will minimize the morphing winglet weight.

This study uses a multi-objective Non-Dominated Sorting Genetic Algorithm to optimise the aerodynamics of a well-known UAV, the UAS-S45. The optimization algorithm is combined with updated Class Shape Transformation (CST) parameterization to improve aerodynamic performance by increasing lift-to-drag ratio and aerodynamic endurance at various angles of attack. The reference airfoil is parameterized using the CST to give local shape changes and skin flexibility for optimum morphing airfoil combinations. The optimization scheme was carried out with an in-house MATLAB code and this procedure is based on a multi-objective Non-Dominated Sorting Genetic Algorithm coupled to XFoil solver, and validation is done using the SST-K Omega model. The results of the optimizations carried out using different operating conditions are presented; starting from the optimal Pareto fronts, several solutions are selected and compared in terms of airfoil shapes and performance. The results show that the morphing improves the UAS-S45 airfoil's aerodynamic efficiency. The improved airfoils have shown a high improvement in overall aerodynamic performance by up to 65.3% in lift to drag ratio at 8 degrees angle of attack compared to the reference airfoil, and an increase in C_L^(3/2)/C_D of up to 98.8% at 8 degrees for the UAS-S45 optimized airfoil configurations. The optimization increases the overall aerodynamic performance of the configuration and the stall angle from 12º to at least 16º. The method used in this work can be employed as a valuable tool for replacing the traditional slats and flaps at the leading edge and the trailing edge of the airfoil. The pareto optimization analysis will be presented with the optimization results and numerical analysis using high fidelity CFD.

This paper investigates the effect of the Dynamically Morphing Leading Edge (DMLE) on the flow structure and the behavior of dynamic stall vortices around a pitching UAS-S45 airfoil with the objective of controlling the dynamic stall. An unsteady parametrization framework was developed to model the time-varying motion of the leading edge. This scheme was then integrated within the Ansys-Fluent numerical solver by developing a User-Defined-Function (UDF), with the aim to dynamically deflect the airfoil boundaries, and to control the dynamic mesh used to morph and to further adapt it. The dynamic and sliding mesh techniques were used to simulate the unsteady flow around the sinusoidally pitching UAS-S45 airfoil. While the γ-Reθ turbulence model adequately captured the flow structures of dynamic airfoils associated with leading-edge vortex formations for a wide range of Reynolds numbers, two broader studies are here considered. Firstly, (i) an oscillating airfoil with the DMLE is investigated; the pitching-oscillation motion of an airfoil and its parameters are defined, such as the droop nose amplitude (AD) and the pitch angle at which the leading-edge morphing starts (MST). The effects of the AD and the MST on the aerodynamic performance was studied, and three different amplitude cases are considered. Secondly, (ii) the DMLE of an airfoil motion at stall angles of attack was investigated. In this case, the airfoil was set at stall angles of attack rather than oscillating it. This study will provide the transient lift and drag at different deflection frequencies of 0.5 Hz, 1 Hz, 2 Hz, 5 Hz, and 10 Hz. The results showed that the lift coefficient for the airfoil increased by 20.15%, while a 16.58% delay in the dynamic stall angle was obtained for an oscillating airfoil with DMLE with AD = 0.01 and MST = 14.75°, as compared to the reference airfoil. Similarly, the lift coefficients for two other cases, where AD = 0.05 and AD = 0.0075, increased by 10.67% and 11.46%, respectively, compared to the reference airfoil. Furthermore, it was shown that the downward deflection of the leading edge increased the stall angle of attack and the nose-down pitching moment. Finally, it was concluded that the new radius of curvature of the DMLE airfoil minimized the streamwise adverse pressure gradient and prevented significant flow separation by delaying the Dynamic Stall Vortex (DSV) occurrence.

This chapter presents an aerodynamic optimization for a Morphing Leading Edge (MLE) winglet of a well-known UAV, the UAS-S45. The optimization algorithm is integrated with the modified Class Shape Transformation (CST) parameterization method and had the aim to enhance aerodynamic performance by minimizing drag and maximizing aerodynamic endurance at the cruise flight condition. The optimization scheme was carried out with in-house MATLAB code and by employing the Vortex Lattice Method (VLM) to calculate the aerodynamic properties of the morphing leading-edge winglet. This study presents the optimization technique and compares winglet geometries results by demonstrating that changing the winglet geometry in flight can enhance aircraft performance while lowering drag, therefore the fuel consumption. The optimized airfoils have shown a significant improvement in the overall aerodynamic performance by up to 8.55

In the Free-Form Deformation (FFD) parametrization technique, the choice of number of control points is case-dependent, and its optimum number should be found through trade-off to find its adequate value. In this study, a comparative analysis is performed to show the dependence of the final optimization results to the chosen number of control points. It is shown that there is no considerable difference in the ultimate value of objective function; however, by having 20 control points, the value of objective function and the accuracy of the optimization by considering the feasibility and optimality criteria is deteriorated. Therefore, there should be a trade-off study in the number of control points for free-form deformation block before starting the optimization process.

The unsteady flow characteristics and responses of the UAS-S45 airfoil with a morphing trailing edge shape at high angles of attack undergoing deflections are investigated at a Reynolds number of 2.4 × 106. The flexible trailing edge was simulated using a computational fluid dynamics approach using a dynamic mesh and user-defined functions. The goal was to achieve a dynamically deflected trailing edge in an unsymmetrical airfoil and assess the influence of unsteady morphing trailing edge deflection on transient forces and flow field unsteadiness. The steady aerodynamic characteristics of the morphing deflection and the conventional deflection was initially studied. Then, the unsteady aerodynamic characteristics of the morphing wing was investigated as the trailing edge deflects at different rates. The dynamic flow responses to downward deflections are studied using the turbulence model. The time histories of the lift and drag coefficient responses exhibit a proportional relationship between the morphing frequency and the slope of response at which these parameters evolve. Coefficients of lift, drag, and moment of the deflected trailing edge airfoils were compared to those of the reference airfoils for various angles of attack. The numerical results show that the transient lift coefficient in the deflection process was higher than that of the static case at different angles of attack. The transient lift coefficient were higher as the deflection frequency increased. It was also revealed that the trailing edge deflection did not favor the flow reattachment. In addition, the dynamic mesh strategy, cell quality, and the proposed method of deforming the morphing trailing-edge was presented. increased. It was also revealed that the trailing edge deflection did not favor the flow reattachment. In addition, the dynamic mesh strategy, cell quality, and the proposed method of deforming the morphing trailing-edge was presented.

This work presents an aerodynamic and structural optimization for a Droop Nose Leading Edge Morphing airfoil as a high lift device for the UAS-S45. The results were obtained using three optimization algorithms: coupled Particle Swarm Optimization-Pattern Search, Genetic Algorithm, and Black Widow Optimization algorithm. The lift-to-drag ratio was used as the fitness function, and the impact of the choice of optimization algorithm selection on the fitness function was evaluated. The optimization was carried out at various Mach numbers of 0.08, 0.1, and 0.15, respectively, and at the cruise and take-off flight conditions. All these optimization algorithms obtained effectively comparable lift-to-drag ratio results with differences of less than 0.03% and similar airfoil geometries and pressure distributions. In addition, an unsteady analysis of a Variable Morphing Leading Edge airfoil with a dynamic meshing scheme was carried out to study its flow behaviour at different angles of attack and the feasibility of leading-edge downward deflection as a stall control mechanism. The numerical results showed that the variable morphing leading edge reduces the flow separation areas over an airfoil and increases the stall angle of attack. Furthermore, a preliminary investigation was conducted into the design and sensitivity analysis of a morphing leading-edge structure of the UAS-S45 wing integrated with an internal actuation mechanism. The correlation and determination matrices were computed for the composite wing geometry for sensitivity analysis to obtain the parameters with the highest correlation coefficients. The parameters include the composite material qualities, thickness, ply angles, and the ply stacking sequence. These findings can be utilized to design the flexible skin optimization framework, obtain the target droop nose deflections for the morphing leading edge, and design an improved model.

View Video Presentation: https://doi.org/10.2514/6.2022-2575.vid While the conventional control surface-based morphing method is well-developed and widely used on modern aircraft, it is insufficiently effective across the flight envelope. Specifically, aircraft such as UAVs may be expected to perform well at a wide range of flight conditions due to multi-mission flight envelopes. Morphing systems could be a solution to this problem because they allow the aircraft to modify its shape to offer the best aerodynamic performance in any given flight condition. The present study describes a continuous camber morphing airfoil design optimization for the UAS-45 wing using the Modified Akima piecewise cubic Hermite interpolation (Makima) parameterization technique. The design technique is simple and effectively controls the geometry in terms of morphing shape flexibility. Out of the optimization algorithms tested, the BWO is used in this study due to its best performance. The optimizations are performed to maximize the lift-to-drag ratio for cruise and climb flight conditions, respectively and determine the impact of different applied constraints on the accuracy of the optimization. Computational fluid dynamics simulation is used to validate the aerodynamic performance of the camber morphing airfoil. The results show that the optimized configurations outperform the baseline airfoil designs, increasing the lift-to-drag ratio from 48.53 to 86.52 for optimized airfoil relative to a baseline airfoil at cruise flight conditions. It also shows that the lift-to-drag ratio improves at climb flight conditions. Flow field analysis reveals that the continuous morphing method can delay flow separation in some situations.