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The morphing wing can improve the flight performance during different phases. However, research has been subject to limitations in aerodynamic characteristics of the morphing wing with a flexible leading-edge. The computational fluid dynamic method and dynamic mesh were used to simulate the continuous morphing of the flexible leading-edge. After co...
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... ratio occurs, and in comparison with the baseline airfoil ( = 0°), the maximum lift-to-drag ratio of the morphing wing with = 4° and = 12°, increase by 1.6% and 10.1% respectively. Apparently, the downward deflection is conducive to improve the lift-to-drag ratio characteristics, while the upward deflection has the opposite effect. Fig. 9 is the pressure distribution of the morphing wing with different leading-edge deflection angles at α = 16°. Pressure distributions on the lower surface are nearly the same, while the pressures on the upper surface reveal obvious differences. Compared to the baseline airfoil ( = 0°), the area enclosed by pressure coefficient curves ...
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Steady airflow over the wing of an aircraft in-flight is critical to achieving maximum aerodynamic performance. However, commercial flight routes are most times characterized by fluctuations in the airflow properties. The unsteadiness in the air velocity vectors and mass flow directly affects the aerodynamic efficiency (AE) of the aircraft during f...
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... The literature presents camber-morphing airfoils in various ways. The deformation could be applied to the leading edge section [35], trailing edge section [36], or both sections of an airfoil [37,38]. The most popular is a continuous camber-morphing trailing edge, as it replaces conventional flaps and is undisturbed by the slit geometry. ...
In recent years, morphing wings have become not only a concept, but an aerodynamic solution for the aviation industry to take a step forward toward future technologies. However, continuously morphing airfoils became an interesting answer to provide green energy solutions. In this paper, the authors conducted experimental research on a continuously camber-morphing airfoil using the Particle Image Velocimetry (PIV) and Computational Fluid Dynamics (CFD) methods. The main objective of this work was to research a variety of morphing airfoils with different camber deflections. An average velocity distribution and turbulence distribution were compared and are discussed. The two-dimensional PIV results were compared to the CFD simulations to validate the numerical method’s accuracy and obtain the aerodynamic coefficient’s trends. A further comparison revealed that morphing airfoils have better aerodynamic performance than conventional airfoils for very low camber deflections and create substantial amounts of drag for significant camber deflections.
... Variable-camber continuous trailing-edge flap (VCCTEF) technology was developed for a NASA general transport aircraft to study the drag reduction effect of the morphing TE [29], thus achieving an 8.4% drag reduction. Deflection frequency and angle effects were analyzed in a morphing LE airfoil's aerodynamics under steady and unsteady conditions [30]. The impact of trailing-edge flaps (TEFs) on mitigating both the negative pitching moment and aerodynamic damping induced by a dynamic stall vortex (DSV) was examined in [31]. ...
... Another study demonstrated that the transient lift coefficient associated with leadingedge (LE) morphing during the nose-up phase had a greater magnitude than that observed in the static situation [30]. The primary objective of the TE control is to enhance the moment characteristics and mitigate the dynamic stall compared to that achieved with conventional rudder surfaces. ...
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.
... Therefore, research on the dynamic stall characteristics of a rotor airfoil to reveal the evolution process of dynamic stall has had a guiding role in improving the aerodynamic performance of rotors and improving the overall performance of helicopters. It had always been a research hotspot and cutting-edge issue in relation to the unsteady aerodynamics of helicopter rotors [5,6]. ...
The influencing characteristic for the evolution mechanism of a dynamic stall vortex structure and distributed blowing control on rotor airfoils was investigated. Based on the moving-embedded grid method, the finite volume scheme, and Roe's FDS scheme, a simulation method for the unsteady flow field of a pitch-oscillating airfoil was established. The flow field of the NACA63-218 airfoil was calculated using Reynolds-averaged Navier-Stokes equations. The evolution processes of different vortex structures during dynamic stall and the principal controlled vortex mechanism affecting aerodynamic nonlinearity were analyzed based on the pressure contours C p and Q of the flow field structure and the spatiotemporal evolution characteristics of the wall pressure distribution. The research indicated that dynamic stall vortices (DSVs) and shear layer vortices (SLVs) were the major sources of the increase in aerodynamic coefficients and the onset of nonlinear hysteresis. Building upon these findings, the concept of distributed blowing control for DSVs and shear layer vortices (SLVs) was introduced. A comparative analysis was conducted to assess the control effectiveness of dynamic stall with different blowing locations and blowing coefficients. The results indicated that distributed blowing control effectively inhibited the formation of DSVs and reduced the intensity of SLVs. This led to a significant decrease in the peak values of the drag and pitch moment coefficients and the disappearance of secondary peaks in the aerodynamic coefficients. Furthermore, an optimal blowing coefficient existed. When the suction coefficient C µ exceeded 0.03, the effectiveness of the blowing control no longer showed a significant improvement. Finally, with a specific focus on the crucial motion parameters in dynamic stall, the characteristics of dynamic stall controlled by air blowing were investigated. The results showed that distributed air blowing control significantly reduced the peak pitching moment coefficient and drag coefficient. The peak pitching moment coefficient was reduced by 72%, the peak drag coefficient was reduced by 70%, and the lift coefficient hysteresis loop area decreased by 46%. Distributed blowing jet control effectively suppressed the dynamic stall characteristics of the airfoil, making the unsteady load changes gentler.
... Variable-Camber Continuous Trailing-Edge Flap (VCCTEF) technology was developed for a NASA general transport aircraft to study the drag reduction effect of the morphing TE [29], thus achieving an 8.4% drag reduction. Deflection frequency and angle effects were analyzed in a morphing LE airfoil's aerodynamics under steady and unsteady conditions [30]. The impact of Trailing Edge Flaps (TEF) on mitigating both the negative pitching moment and aerodynamic damping induced by a Dynamic Stall Vortex (DSV) was examined in [31]. ...
... Another study demonstrated that the transient lift coefficient associated with Leading Edge (LE) morphing during the nose-up phase had a greater magnitude than that observed in the static situation [30]. The primary objective of the TE control is to enhance the moment characteristics and mitigate the dynamic stall compared to that achieved with conventional rudder surfaces. ...
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 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 the 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 (c_(l,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.
... The results showed an improvement in aerodynamic performance with the curved leading edge. The study, [7], examined the morphing wings with upward and downward deflections of the leading edge at different frequencies. The numerical results show that the deflection of the leading edge has the most significant effect on the stall characteristics and the stall angle of attack increases due to the downward deflection of the leading edge. ...
The aerodynamic performance of an aircraft mainly depends on the lift force, drag force, and the lift to drag ratio. The geometric shapes of aircraft wings are considered crucial for this aerodynamic performance. The purpose of this study is to determine the most efficient wing shape that improves the aerodynamic performance of the airfoil. For that purpose, a numerical comparative study was carried out between the rectangular and tapered wing shapes of the NACA 4412 airfoil for a wide range of angles of attack in the subsonic regime. ANSYS Fluent software, based on the finite volume method, was used for the numerical resolution of the governing equations. The Realizable k-ε model was chosen for the turbulence modeling. The numerical procedure was validated based on experimental results obtained from the literature. The results show an improvement in the lift coefficient and a reduction in the drag coefficient of the Tapered shape compared to the rectangular shape at all angles of attack. However, a gain was achieved in the lift-to-drag coefficient ratio of the Tapered shape.
... 4,5 While most of these studies are still at the conceptual level due to structural limits, ongoing research in aerodynamics and at a structural level have shown a promising future for this technology. Many morphing approaches have been examined over the past few decades from sweep, 6 twist, 7,8 winglet, 9,10 and span morphing, 11 to camber, [12][13][14][15] chord, 16 leading edge, [17][18][19] and upper surface [20][21][22][23][24][25][26][27][28][29] morphing. However, among these approaches, the trailing edge morphing 30 has received considerable attention due to its substantial influence in improving flight performance and reducing fuel consumption. ...
... where g p is the propulsive efficiency, c p weight-specific fuel consumption and W 1 and W 2 are initial and final aircraft weight, respectively. According to Eq. (19), the only aerodynamic term that impacts the flight range is the lift-to-drag ratio, thus by increasing this ratio, the range will be increased. Therefore, the objective function in terms of range improvement is the maximization of the lift-to-drag ratio. ...
... Dynamic stall control is especially significant because it occurs in all aerospace applications, such as on UAVs [31,32], helicopter rotors [33,34], wind turbines [35,36] and military aircraft [37,38]. The effects of unsteady parameters, such as the oscillation amplitude, reduced frequency, Reynolds number and aerofoil kinematics (deformation, variable thickness etc.) have been investigated by different researchers from the perspective of aerodynamic coefficients [39][40][41][42]. Numerical studies were used to investigate morphing wing aerodynamic stall and to explore adaptive morphing trailing-edge wings, 1% drag reduction on-design and 5% off-design were obtained [43]. ...
This paper investigates the effect of the optimised morphing leading edge (MLE) and the morphing trailing edge (MTE) on dynamic stall vortices (DSV) for a pitching aerofoil through numerical simulations. In the first stage of the methodology, the optimisation of the UAS-S45 aerofoil was performed using a morphing optimisation framework. The mathematical model used Bezier-Parsec parametrisation, and the particle swarm optimisation algorithm was coupled with a pattern search with the aim of designing an aerodynamically efficient UAS-45 aerofoil. The $\gamma - R{e_\theta }$ transition turbulence model was firstly applied to predict the laminar to turbulent flow transition. The morphing aerofoil increased the overall aerodynamic performances while delaying boundary layer separation. Secondly, the unsteady analysis of the UAS-S45 aerofoil and its morphing configurations was carried out and the unsteady flow field and aerodynamic forces were analysed at the Reynolds number of 2.4 × 10 ⁶ and five different reduced frequencies of k = 0.05, 0.08, 1.2, 1.6 and 2.0. The lift ( ${C_L})$ , drag ( ${C_D})$ and moment ( ${C_M})\;$ coefficients variations with the angle-of-attack of the reference and morphing aerofoils were compared. It was found that a higher reduced frequencies of 1.2 to 2 stabilised the leading-edge vortex that provided its lift variation in the dynamic stall phase. The maximum lift $\left( {{C_{L,max}}} \right)$ and drag $\left( {{C_{D,max}}} \right)\;$ coefficients and the stall angles of attack are evaluated for all studied reduced frequencies. The numerical results have shown that the new radius of curvature of the MLE aerofoil can minimise the streamwise adverse pressure gradient and prevent significant flow separation and suppress the formation of the DSV. Furthermore, it was shown that the morphing aerofoil delayed the stall angle-of-attack by 14.26% with respect to the reference aerofoil, and that the ${C_{L,max}}\;$ of the aerofoil increased from 2.49 to 3.04. However, while the MTE aerofoil was found to increase the overall lift coefficient and the ${C_{L,max}}$ , it did not control the dynamic stall. Vorticity behaviour during DSV generation and detachment has shown that the MTE can change the vortices’ evolution and increase vorticity flux from the leading-edge shear layer, thus increasing DSV circulation. The conclusion that can be drawn from this study is that the fixed drooped morphing leading edge aerofoils have the potential to control the dynamic stall. These findings contribute to a better understanding of the flow analysis of morphing aerofoils in an unsteady flow.
... Airfoil-level morphing typically involves morphing the leading edge or trailing edge of the wing to control the aerial vehicle during different phases of flight by varying the wing's camber. Recent studies have focused on this type of morphing, with Kan et al. [1] investigating the aero-dynamic characteristics of a morphing wing with a flexible leading edge to improve flight performance during different phases, while Abdessemed et al. [2] presented an unsteady flow analysis of a 3D wing with a morphing trailing edge flap to assess its ability to enhance aerodynamic efficiency. Another approach to airfoil-level morphing is the variable thickness concept, which modifies the airfoil's thickness to change the laminar-to-turbulent flow transition location, resulting in drag reduction. ...
... Regarding aerodynamic characteristics, the research has primarily focused on twodimensional morphing airfoils or three-dimensional airfoils in terms of leading edge, trailing edge, thickness, etc. [1,2,20]. However, few studies have analyzed the aerodynamic characteristics of large folding configurations like Z-shaped folding wings. ...
... Aerodynamic characteristics analysis is an essential part of the Z-shaped folding wing aircraft design process, with Computational Fluid Dynamics (CFD) being the most common method used to perform this study. For instance, Kan et al. [1] discussed the influence of the deflection frequency and deflection angle of morphing wings with flexible leading edges on the unsteady lift coefficient using CFD. Abdessemed et al. [2,20] used dynamic meshing to analyze the aerodynamic characteristics of NACA 0012 airfoils and 3D wings with morphing trailing edges. ...
Z-shaped folding wings have the potential to enhance the flight performance of an aircraft, contingent upon its mission requirements. However, the current scope of research on unmanned aerial vehicles (UAVs) with Z-shaped folding wings primarily focuses on the analysis of their folding structure and aeroelasticity-related vibrations. Computational fluid dynamics methods and dynamic meshing are employed to examine the folding process of Z-shaped folding wings. By comparing the steady aerodynamic characteristics of Z-shaped folding wings with those of conventional wings, this investigation explores the dynamic aerodynamic properties of Z-shaped folding wings at varying upward folding speeds. The numerical findings reveal that the folding of Z-shaped folding wings reduces the lift-to-drag ratio, yet simultaneously diminishes the nose-down pitching moment, thereby augmenting maneuverability. Concerning unsteady aerodynamics, the transient lift and drag coefficients of the folded wing initially increase and subsequently decrease as the folding angle increases at small angles of attack. Likewise, the nose-down pitching moment exhibits the same pattern in response to the folding angle. Additionally, the aerodynamic coefficients experience a slight decrease during the initial half of the folding process with increasing folding speed. Once the wing reaches approximately 40°~45° of folding, there is an abrupt change in the transient aerodynamic coefficients. Notably, this abrupt change is delayed with higher folding speeds, eventually converging to similar values across different folding speeds.
... In [20] Z. Kan (et al.) presented an aerodynamic calculation of an adaptive wing and compared the obtained aerodynamic characteristics with those of a conventional wing. For numerical simulation, a two-dimensional NACA 0012 airfoil with a flexible leading edge was taken. ...
... The aerodynamic characteristics of an adaptive wing were studied in [20]- [22]. ...
The article discusses methods for manufacturing power elements of an adaptive wing from composite materials, as well as various principles for changing the configuration of an adaptive wing. A comparison is made of the aerodynamic characteristics of an adaptive wing and a wing with traditional high lift devices.
... However, the strong time-varying, nonlinear dynamic characteristics, and aerodynamic interferences during morphing cause the attitude stabilization and control for morphing vehicles to become key problems and impose significant challenges. Many experts and scholars are committed to related studies and have made important progress in these areas [8][9][10]. ...
This paper investigates the attitude control problem for large-scale morphing unmanned vehicles. Considering the rapid time-varying and strong aerodynamic interference caused by large-scale morphing, a modified model-free control method utilizing only the system input and output is proposed. Firstly, a two-loop equivalent data model for the morphing unmanned vehicle is developed, which can better reflect the practical dynamics of morphing unmanned vehicles compared to the traditional compact form dynamic linearization data model. Based on the proposed data model, a modified model-free adaptive control (MMFAC) scheme is proposed, consisting of an external-loop and an inner-loop controller, so as to generate the required combined control torques. Additionally, in light of the aerodynamic uncertainties of the large-scale morphing unmanned vehicle, a rudder deflection actuator control scheme is designed by employing the model-free adaptive control approach. Finally, the boundedness of the closed-loop system and the convergence of tracking errors are guaranteed, based on the stability analysis. Additionally, numerical examples are presented to demonstrate the effectiveness and robustness of the proposed control scheme in the case of the effect of large-scale morphing.
