Search Results (46)

As wind energy development continues to expand toward nearshore and deep-sea regions, enhancing the aerodynamic efficiency of vertical axis wind turbines (VAWTs) in complex marine environments has become a critical challenge. To address this, a composite flow control strategy combining leading-edge suction and trailing-edge gurney flap is proposed. A two-dimensional unsteady numerical simulation framework is established based on CFD and the four-equation Transition SST (TSST) transition model. The key control parameters, including the suction slot position and width as well as the gurney flap height and width, are systematically optimized through orthogonal experimental design. The aerodynamic performance under single (suction or gurney flap) and composite control schemes is comprehensively evaluated. Results show that leading-edge suction effectively delays flow separation, while the gurney flap improves aerodynamic characteristics in the downwind region. Their synergistic effect significantly suppresses blade load fluctuations and enhances the wake structure, thereby improving wind energy capture. Compared to all other configurations, including suction-only and gurney flap-only blades, the composite control blade achieves the most significant increase in power coefficient across the entire tip speed ratio range, with an average improvement of 67.24%, demonstrating superior aerodynamic stability and strong potential for offshore applications. Full article

Numerical simulations were performed using the RANS (Reynolds-averaged Navier–Stokes) approach to analyze the flow field around an aircraft during the landing rollout phase with thrust reversers deployed. The objective was to characterize the flow structure modifications induced by the reversed jet flow and to assess its impact on the aerodynamic performance of various control surfaces. The results demonstrate that the reverse jet flow introduces significant disturbances to the flow field, substantially altering the aerodynamic load distribution over the airframe and causing a marked reduction in overall lift. High-lift devices are particularly susceptible to these effects: the pressure distributions on both the leading-edge slats and trailing-edge flaps are severely disrupted, resulting in a notable degradation of their lift augmentation capabilities. The rudder retains a generally linear response characteristic, though a slight reduction in effectiveness is observed. In contrast, the elevator exhibits a pronounced asymmetry in control effectiveness, with significantly greater degradation under positive deflection compared to negative deflection. This study elucidates the complex interference mechanisms associated with thrust reverser-induced flows and provides valuable insights for the optimization of thrust reverser system design and the enhancement of flight control strategies during the landing phase. It further delivers the first quantitative evaluation of elevator response asymmetry and accompanying lift degradation caused by reverse jet plumes, supplying design-ready metrics for reverser integration. Full article

This encyclopedia entry provides an updated appreciation of the evolution of morphing aircraft wings, organized as follows: first, lift concepts are briefly examined; second, patents related to lift enhancement are discussed, showcasing existing technology and its evolution; finally, several technologies for morphing wings and the role of UAVs as testbeds for many innovative concepts are highlighted. The background of morphing wings is presented through a recap of lift concepts and the presentation of representative patents that describe the evolution of leading-edge and trailing-edge devices, such as flaps, slats, spoilers, and control surfaces. Although these topics are not usually detailed in reviews of morphing wings, they are deemed relevant for this encyclopedia entry. Full article

An active rotor with trailing edge flaps (TEFs) is an effective method for helicopter vibration elimination. The nonlinear hysteresis of piezoelectric actuators used to drive TEFs can adversely affect helicopter vibration control performance. In this paper, a hysteresis modeling and compensation study is performed for piezoelectric actuators used in TEFs. Firstly, the hysteresis characteristics of a rhombic frame actuator with input voltages at different frequencies are investigated by bench-top tests. Subsequently, the Bouc–Wen model is adopted to establish the hysteresis model of the piezoelectric actuator, with its parameters identified through the particle swarm optimization (PSO) algorithm. Experimental results demonstrate that the proposed model is capable of accurately capturing the hysteresis phenomenon of the piezoelectric actuator within the frequency range of 10–60 Hz. Finally, a compound control regime is established by integrating inverse Bouc–Wen model control with fuzzy PID feedback control. The experimental results indicate that the developed compound control regime can significantly suppress the piezoelectric actuator hysteresis of TEFs within the frequency bandwidth of 10–60 Hz, which lays the foundation for improving the vibration control performance of the active rotor with TEFs in the future. Full article

This study was performed based on the previous work of this research group to promote the practical engineering application of trailing edge flaps. Specifically, the established “intelligent blade” simulation platform was used for simulation calculations, bringing about the achievement of a significant load reduction effect in which the standard deviation of the blade root pitching moment decreased by 12.4% under the influence of the trailing edge flap. Then, the dynamic conditions of the wind turbine and trailing edge flap under active control, obtained from the “intelligent blade” simulation platform, were input into CFD for further high-fidelity simulations. Additionally, a simulation method that allows for the real-time observation of the flow field was optimized with CFD as a flow field visualizer. This approach assisted in analyzing how the trailing edge flap affects the flow characteristics around the blade. The results reveal that the deflection of the trailing edge flap generated new vortex structures. These new vortex structures interacted with the pre-existing vortex structures. Moreover, the vortex structures produced by flap deflection supplemented the energy dissipation caused by flow separation on the leeward surface of the blade, contributing to the weakening of flow separation on the leeward side of the blade, affecting the pressure exerted by the fluid on the blade surface, and ultimately lowering the blade’s load. Full article

In aerospace, flow control techniques have improved the separation flow characteristics around airfoils by various means. In this paper, the delayed detached eddy simulation (DDES) technique is used to simulate the detailed flow field around the NACA0021 airfoil with two different flow control methods (Gurney flaps and leading- and trailing-edge flaps) applied at an angle of attack of 20°. The aerodynamic characteristics around the airfoil under these two flow control methods are investigated, and the results show that both flow control methods lead to a significant increase in the pressure on the suction surface of the airfoil, which contributes to an increase in lift. The aeroacoustic characteristics of the original airfoil, the Gurney flapped airfoil and the airfoil with leading-edge and trailing-edge flaps are then analyzed using a combination of DDES and FW-H acoustic analog equations. The results show that the total sound pressure level of the Gurney flap airfoil and the leading-edge and trailing-edge flap airfoil are improved in most azimuthal angles of the acoustic pointing distribution, among which the degree of improvement of the leading-edge and trailing-edge flap airfoil is greater than that of the Gurney flap airfoil near the trailing edge, and the total sound pressure level of the band leading- and trailing-edge flap airfoil decreases in the azimuthal angles near the leading edge. Compared with the original airfoil, the noise value is thus reduced by up to 4.13 dB. The results of pressure pulsation cloud map, sound pressure level cloud map on the airfoil surface and vortex cloud map distribution show that the two flow controls increase the pressure pulsation near the trailing edge, the range and peak value of sound emission on the airfoil surface increase, and the trailing vortex becomes more finely grained, which leads to an increase in noise. Full article

Following the promising performance of the seamless morphing trailing edge (SMTE) flap and its internal actuation system, the elephant trunk mechanism (ETM), investigated through aerodynamic and structural analyses, this study presents an experimental analysis of the SMTE flap equipped with an elephant trunk actuation mechanism. The morphing wing model was prototyped using a 3D printer. Four elephant trunk morphing ribs were embedded inside the flap section, all covered with a flexible skin. The control system for flap actuation was installed in the wing box corresponding to four elephant trunk mechanisms using an appropriate graphical interface to control the SMTE flap deflections. The completed model was further tested in a subsonic wind tunnel to validate the numerical aerodynamic results, as well as the functionality of the elephant trunk mechanism in real conditions. The results confirm the reliability and practicability of the proposed elephant trunk mechanism for actuation, and a very good agreement was obtained between the numerical aerodynamic data and wind tunnel test results. Full article

The blades of wind turbines constitute key components for converting wind energy into electrical energy, and modifications to blade airfoil geometry can effectively enhance aerodynamic performance of wind turbine. The trailing edge flap enables load control on the blades through adjustments of its motion and geometric parameters, thereby overcoming limitations inherent in conventional pitch control systems. However, current research primarily emphasizes isolated parametric effects on airfoil performance, with limited exploration of interactions between multiple design variables. This study adopts a numerical simulation approach based on the FFA-W3-241 airfoil of the DTU 10 MW. Geometric deformations are achieved by manipulating flap parameters, and the influence on airfoil aerodynamic performance is analyzed using computational fluid dynamics methods. Investigations are conducted into the effects of flap lengths and deflection angles on airfoil aerodynamic characteristics. The results show the existence of an optimal flap length and deflection angle combination. Specifically, when the flap length is 0.1$c$ and the deflection angle is 10°, the lift-to-drag ratio demonstrates significant improvement under defined operational conditions. These findings offer practical guidance for optimizing wind turbine airfoil designs. Full article

This paper presents an innovative active monitoring strategy to manage asymmetry in aircraft flaps. Complex mechanical systems like high-lift devices may undergo a wide range of faults, such as a broken transmission torsion bar or wear and tear on control surface actuators just to name a few. These faults can alter the surface symmetry between the two sides of the wing, potentially leading to dangerous conditions. The proposed relative dynamic position control technique provides a more effective monitoring method to detect and identify flap asymmetry. Once the faulty side has been identified, the system activates the wingtip brakes to halt the uncontrolled flap. The remaining functional flap is then moved to match the braking point of the failed flap, reducing the asymmetry. This approach effectively manages the unwanted roll moment caused by flap asymmetry, thereby partially restoring the aircraft’s maneuverability post-failure. The proposed monitoring technique has been subjected to extensive testing under various operational and failure conditions with the use of a mathematical model, with both new and worn actuators, and considering a wide range of possible failure scenarios. Full article

This work focuses on the design and optimization of a morphing-compliant system developed within the project HERWINGT (Clean Aviation) and aimed at generating high lift during take-off and landing. The device was conceived to replace a conventional flap of a regional aircraft and work in synergy with a droop nose and a flow control system. The architecture is based on a compliant layout, specifically selected to obtain a final morphed shape of the trailing edge of the wing efficient for high-lift purposes and adequately smooth even in cruise clean configuration. At first, the requirements at aircraft level were critically examined and then elaborated to produce the specifications of the morphing device. A layout was then sketched, considering on its potential in approaching the target morphed shape and on its intrinsic criticalities. Starting from this scheme, a simplified FE model was introduced. The scope was to have an efficient predictive tool suited for optimization processes. After having identified the most relevant design parameters (skin thickness distribution, topology of the structure, and actuator interface parameters), the cost function, and the constraints of the problem (structural integrity and stability), a genetic optimization was implemented. Repeating the genetic process starting from different initial populations, some optimized configurations were identified. A trade-off was thus organized on different criteria, such as the lightness of the structure, the load-bearing capability, the force, and the stroke needed by the actuator. The best compromise was finally taken as baseline for the realization of an advanced FE model used to validate the numerical outcomes obtained during the optimization process and as starting point for the next steps planned in the project. The achieved design is characterized by an enhanced aerodynamic performance with the absence of steps and gaps and external track fairings, reduced weight of both the structure and the actuator, reduced maintenance costs due to a simple layout, and smaller take-off and landing distances owing to the high-lift capability and the intrinsic lightness. Full article

For a special bilaterally symmetric airfoil (BSA), this paper designs an active flow control scheme based on the Co-Flow Jet (CFJ) and adaptive morphing technology, and establishes a numerical simulation method which is suitable for simulating aerodynamic characteristics. The accuracy and effectiveness of the numerical method has been verified through benchmark cases. This study investigates the effects of jet intensity, suction slot position and angle, and deflection angles of the leading and TE flap on the aerodynamic performance parameters and flow field structure of the bilaterally symmetric airfoil. The results show that the adaptive morphing technology can significantly improve the equivalent lift coefficient and equivalent lift-to-drag ratio of the bilaterally symmetric airfoil, without obviously increasing the CFJ power consumption coefficient. Selecting an appropriate CFJ intensity can achieve a relatively high equivalent lift-to-drag ratio with a low compressor power requirement. Moving the suction slot rearward can increase the lift coefficient, and placing it on the trailing edge (TE) flap can more efficiently delay flow separation, reduce power consumption, and increase the equivalent lift-to-drag ratio. The suction slot angle has little effect on the lift coefficient, but a larger suction slot angle can enhance the equivalent lift-to-drag ratio. Increasing the TE flap deflection angle enhances both the lift coefficient and drag coefficient, as well as the power consumption coefficient at high angles of attack. But it has little effect on the maximum equivalent lift-to-drag ratio. Increasing the leading edge flap deflection angle can improve the maximum equivalent lift-to-drag ratio while increasing the angle of attack corresponding to it. Overall, choosing a CFJ and adaptive morphing parameters by considering different factors can enhance the aerodynamic performance of the bilaterally symmetric airfoil. Full article

This paper studies aeroelastic control for a two-dimensional airfoil–flap system with unknown gust disturbances and model uncertainties. Open loop limit cycle oscillation (LCO) happens at the post-flutter speed. The structural stiffness and quasi-steady and unsteady aerodynamic loads of the aeroelastic system are represented by nonlinear models. To robustly suppress aeroelastic vibration within a finite time, a backstepping terminal sliding-mode control (BTSMC) is proposed. In addition, a learning rate (LR) is incorporated into the BTSMC to adjust how fast the aeroelastic response converges to zero. In order to overcome the fact that the BTSMC design is dependent on prior knowledge, a nonlinear disturbance observer (DO) is designed to estimate the variable observable disturbances. The closed-loop aeroelastic control system has proven to be globally asymptotically stable and converges within a finite time using Lyapunov theory. Simulation results of an aeroelastic two-dimensional airfoil with both trailing-edge (TE) and leading-edge (LE) control surfaces show that the proposed DO-BTSMC is effective for flutter suppression, even when subjected to gusts and parameter uncertainties. Full article

Conventional methods for solving Navier–Stokes (NS) equations to analyze flow fields and aerodynamic forces of airfoils with trailing edge flaps (TEFs) are known for their significant time cost. This study presents a Multi-Task Swin Transformer (MT-Swin-T) deep learning framework tailored for swift prediction of velocity fields and aerodynamic coefficients of TEF-equipped airfoils. The proposed model combines a Swin Transformer (Swin-T) for flow field prediction with a multi-layer perceptron (MLP) dedicated to lift coefficient prediction. Both networks undergo gradient updates through the shared encoder component of the Swin Transformer. Such a trained network model for computational fluid dynamics simulations is both effective and robust, significantly improving the efficiency of complex aerodynamic shape design optimization and flow control. The study further investigates the impact of integrating multi-task learning loss functions, skip connections, and the network’s structural design on prediction accuracy. Additionally, the effectiveness of deep learning in improving the aerodynamic simulation efficiency of airfoils with TEF is examined. Results demonstrate that the multi-task deep learning approach provides accurate predictions for TEF airfoil flow fields and lift coefficients. The strategic combination of these tasks during network training, along with the optimal selection of loss functions, significantly enhances prediction accuracy compared with the single-task network. In a specific case study, the MT-Swin-T model demonstrated a prediction time that was 1/7214 of the time necessitated by CFD simulation. Full article

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 ($c_{l,max}$)). 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. Full article

An electrically controlled rotor (ECR), also known as a swashplateless rotor, eliminates the swashplate system to implement the primary control via the trailing-edge flaps (TEFs), which can result in enhancements in rotor performance, as well as substantial reductions in weight, drag, and cost. In this paper, the unsteady aerodynamic characteristics of the airfoil with TEF of a sample ECR under unsteady freestream condition are investigated. The CFD results are obtained with sliding and overset grid techniques that simulate the airfoil pitching and flap deflection. Comparative analysis of the aerodynamic characteristics under steady and unsteady freestream conditions at different advance ratios is conducted. At various advance ratios, the lift and drag coefficients are higher at a small angle of attack under unsteady freestream condition; however, it is the opposite at a large angle of attack. The peak values of the lift and drag coefficients show an increased trend with the increase in the advance ratio. On the contrary, the pitch moment and flap hinge moment coefficients demonstrate minor variation under unsteady freestream condition. Furthermore, the aerodynamic characteristics of airfoils become more unsteady with variation in the freestream. Therefore, the lift and drag coefficients of the ECR airfoil with TEF show significant differences between steady and unsteady freestream conditions; however, the pitch moment and the flap hinge moment coefficients show little difference. Full article