Trailing Edge Camber Research Articles

Effect of leading-edge and trailing-edge camber morphing on gust load for an elastic wing

This paper investigates the influence of the spanwise-distributed trailing-edge camber morphing on the dynamic stall characteristics of a finite-span wing at Re = 2 × 105. The mathematical model of the spanwise-distributed trailing-edge camber morphing is established based on Chebyshev polynomials, and the deformed wing surface is modeled by a spline surface according to the rib’s morphing in the chordwise direction. The Computational Fluid Dynamics (CFD) method is adopted to obtain flow-field results and aerodynamic forces. The SST-γ model is introduced and the overset mesh technique is adopted. The numerical results show that the spanwise-distributed trailing-edge morphing obviously changes the aerodynamic and energy transfer characteristics of the dynamic stall. Especially when the phase difference between the trailing-edge motion and the wing pitch is −π/2, the interaction between the three-dimensional (3-D) Leading-Edge Vortex (LEV) and Trailing-Edge Vortex (TEV) is strengthened, and the work done by the aerodynamic force turns negative. This indicates that the trailing-edge deformation has the potential to suppress the oscillation amplitude of stall flutter. We also found that as the trailing-edge camber morphing varies more complexly along the spanwise direction, the suppression effect decreases accordingly.

Effect of spanwise distributed camber morphing on dynamic stall characteristics of a finite-span wing

This paper investigates the influence of the spanwise-distributed trailing edge camber morphing on the dynamic stall characteristics of a finite-span wing at Re = 2 × 105. The mathematical model of the spanwise-distributed trailing-edge camber morphing is established based on Chebyshev polynomials, and the deformed wing surface is modeled by a spline surface according to rib's morphing in the chordwise direction. The computational fluid dynamics method is adopted to obtain flow-field results and aerodynamic forces. The shear-stress transportv-γ model is introduced and the overset mesh technique is adopted. The numerical results show that the spanwise distributed trailing edge morphing obviously changes the aerodynamic and energy transfer characteristics of the dynamic stall. Especially when the phase difference between the trailing edge motion and the wing pitch is −π/2, the interaction between the three-dimensional leading-edge vortex and trailing-edge vortex is strengthened, and the work done by the aerodynamic force turns negative. This indicates that the trailing edge deformation has the potential to suppress the oscillation amplitude of stall flutter. We also found that as the trailing-edge camber morphing varies more complex along the spanwise, and the suppression effect decreases accordingly.

Hybrid Models for Situational Awareness of an Aerial Vehicle from Multimodal Sensing

An integrated sensing system is presented for flight state awareness of fixed-wing aircraft. The hardware of the system consists of a lightweight and nonobtrusive sensor network that houses a multitude of piezoelectric and strain transducers in a distributed, large areal coverage setting. The sensor network is embedded onto the surface of a model morphing unmanned aerial vehicle wing with variable trailing edge camber. The data collected by the sensor network form the input of a set of physics and machine learning models that work in tandem to infer several state variables of flight in near real-time. Capabilities of the system are characterized via controlled wind tunnel experiments and presented through a custom interface that provides a side-by-side comparison of the ground truth, as captured by commercial sensors and video cameras, and predictions of the trained models. It is demonstrated that the system identifies safety-critical flight conditions with very high accuracy, paving the way for a novel aircraft instrumentation method that is lighter weight and more capable and reliable in certain aspects.

Relying on Dynamically Morphing Blades to Increase the Efficiency of a Cycloidal Rotor

The configuration of the airfoil has a significant impact on its aerodynamic performance. This paper aims to improve the aerodynamic efficiency of the cycloidal rotor system by using dynamically morphing blades. Three different camber morphing concepts (leading edge deflection, trailing edge deformation and cambered NACA profile) have been applied to a baseline 2-bladed system with rotating and pitching NACA0015 aerofoils. Then, based on these camber concepts, 2D URANS numerical simulations were conducted for blades with different morphing degrees using OpenFOAM. The simulation results verified that the flow field condition could be optimized and significantly higher thrust and efficiency could be achieved by properly tuning the morphing control. Especially, in the case of 10% trailing edge camber and 16% NACA camber, compared with baseline case, 28.1% and 43.5% higher figure of merit values were obtained, respectively. The simulation files and the results for the last rotor revolution of each case presented in this paper are available in the following dataset: https://doi.org/10.18419/darus-2191.

In-situ boundary layer transition detection on multi-segmental (a)synchronous morphing wings

This paper presents an experimental method to detect in-situ the location of transition on a multi-segmental trailing edge camber morphing wing during synchronous and asynchronous morphing. The wing consists of six independently morphing segments with two of the segments instrumented with eight embedded piezoelectric sensors distributed uniformly along the chord. Using suitable data processing, each of the sensors gives a signal that can be used to determine the state of the boundary layer (laminar, transitional, turbulent) at the location of that sensor. The results showed that synchronous morphing can substantially shift the location of transition, up to 20% of the chord length for angles of attack below 9°. Differences in the location of transition up to 5% are found between the near-root and near-tip segment. Using a dedicated data processing approach, the location of transition could be reconstructed in case of complex asynchronous morphing involving one to five segments. The results show a shift in the location of transition when morphing neighboring segments, but also show that non-neighboring segments have a minimal effect. This sensing method holds significant promise for online advanced morphing control to delay transition and thereby reducing skin friction drag.

Parametric Airfoil Design and Sensitivity Analysis for Turbulent Boundary-Layer Trailing-Edge Noise Reduction

This paper presents the investigation of airfoil turbulent boundary-layer trailing-edge noise reduction using a parametric airfoil design. The airfoil design tool performs a parametric design starting from a baseline airfoil and then morphing it with a number of design parameters, which include camber, camber crest position, thickness, thickness crest position, leading-edge radius, trailing-edge camber, and boat-tail angle. A predictive method that combines an empirical wall-pressure spectrum model and an acoustic diffraction model is used to predict airfoil turbulent boundary-layer trailing-edge noise. In this study, a NACA 0012 airfoil and a NACA 64-618 airfoil are used to analyze the effects of the design parameters on airfoil aerodynamic performance and trailing-edge noise. The sensitivity of different parameters is performed with Morris’s method in order to further assess their relative influences. Overall, it is found that thickness, trailing-edge camber, and boat-tail angle have a significant influence on noise levels.

Modeling of integrated shape memory alloy and Macro-Fiber Composite actuated trailing edge

Owing to their high energy densities, smart materials like shape memory alloys (SMAs), Macro-Fiber Composites (MFCs) and, electroactive polymers (EAPs) have massive potential as actuators in wing morphing applications. In this article, a detailed numerical model is developed for the shape prediction of an elastic base that is actuated by a combination of a shape memory alloy (SMA) wire and a Macro-Fiber Composite (MFC) bimorph. It has been demonstrated using the model that it is possible to achieve large deflections at low frequencies by virtue of the phase transformations in the SMA wire and rapid actuation with small deflections due to the MFC bimorph. In the developed scheme, the elastic base is modeled using non-linear Euler-Bernoulli beam theory. The influence of the non-linear hysteresis in the SMA wire and the linear actuation characteristics of the MFC is studied by incorporating thermo-mechanical and electro-mechanical constitutive behavior into the non-linear beam theory. The system of coupled equations hence obtained, is solved iteratively to obtain the deflected shape of the elastic base. The results from the developed numerical scheme are validated against the previously available studies in the literature and experiments. Additionally, the synergistic advantage of using the two actuators together has been shown through experiments. As an illustration, a smart trailing edge camber morphing concept is developed by integrating the flexible elastic structure along with the two smart actuators to a NACA 0012 airfoil as the trailing edge.

The morphing trailing-edge wing optimization design of the civil aircraft

The research on the aerodynamic optimization design of applying the continuous trailing-edge variable camber wing to the civil aircraft is presented, and the necessity of considering pitch moment trimming in the optimization design is explored. The free-form deform (FFD) technique is used to accomplish the parameterization of the wing shape, the trailing-edge camber and the rotation of the horizontal tail. The discrete adjoint technique based on RANS (Reynolds Averaged Navier-Stokes) equations is used to solve the gradients of aerodynamic coefficients with regard to design variables, and the sequential quadratic programming is used to carry the gradient-based optimization design. Based on the common research model (CRM), a single target optimization with constraints is carried to reduce the aerodynamic drag, and the feasibility of the optimization system is confirmed. Then, in different cruise lift coefficients, the trailing-edge variable camber wing optimizations are carried with and without moment trimming respectively. The optimization results show that by trailing-edge morphing, the spanwise lift coefficient distribution is improved and the wave strength is reduced; in order to achieve the optimized design result, it is a necessity to consider the moment trimming constraint.

Stall Recovery of a Morphing Wing via Extended Nonlinear Lifting-Line Theory

Aircraft morphing provides advantages to traditional flight including drag reduction and maneuverability. Previous research indicates that smooth spanwise transitions in trailing-edge camber, representative of a biological analog, provide aerodynamic benefits at small angles of attack by eliminating vortices at geometric discontinuities but lack nonlinear aerodynamic investigations. This work aims to analyze the adaptability of a spanwise morphing wing concept with respect to nonlinear aerodynamics using an optimized nonlinear extended lifting-line model. In this novel approach, it is shown that adaptation, including stall recovery, can be achieved solely through geometric tailoring as opposed to attitude correction for a range of flight conditions while reducing the drag penalty associated with operating at the unadapted condition. The range of conditions for which the wing can recover are restricted by the limited trailing-edge deflections and the inability of the actuators to substantially shift the stall angle of the section lift curve. These results provide insight into improving morphing wing designs, indicating that, by adding another degree of freedom to the chordwise deformation such as a morphing hinge capable of larger actuation and reflex camber, stall recovery via geometric tailoring may be feasible for an even larger range of conditions.

Stiffness requirement of flexible skin for variable trailing-edge camber wing

The method for analyzing the deformation of flexible skin under the air loads was developed based on the panel method and finite element method. The deformation of flexible skin under air pressures and effects of the local deformation on the aerodynamic characteristics were discussed. Numerical results show that the flexible skin on the upper surface of trailing-edge will bubble under the air loads and the bubble has a powerful effect on the aerodynamic pressure near the surface of local deformation. Then the stiffness requirements for flexible skin of variable trailing-edge were given by using the Jacobs rule, i.e., the maximum displacement of skin is not greater than 0.1% of wing chord. Results show that the in-plane stiffness can be reduced by increasing the ratio of bending stiffness to in-plane stiffness. Although the deformation of flexible skin increases with the in-plane stiffness decreasing, it depends on the bending stiffness. When the bending stiffness exceeds critical value, the deformation of flexible skin only depends on the bending stiffness and has nothing to do with the in-plane stiffness. The conclusions can be used for the structural design of flexible skin.

Drag optimization for transport aircraft Mission Adaptive Wing

A direct optimization study was performed to produce a preliminary evaluation of the potential benefits of a mission adaptive wing employing variable camber technology in typical jet transport aircraft missions, in terms of fuel efficiency increase directly obtainable from airfoil viscous drag reduction alone. A 2-D airfoil analysis approach was adopted, associated with an idealized variable camber mechanism based on elastic deformation and surface extension. Using a direct function optimization program coupled to a viscous-inviscid airfoil analysis routine, optimized variable camber configurations were obtained for several weight conditions of a typical transport aircraft along a sub-critical cruise mission leg. Independent runs were executed considering only trailing and both leading and trailing-edge camber variation and, for each of them, an integrated range parameter has been obtained, proportional to the maximum possible aircraft range. Results indicate that the range increases up to 7.03% over the base airfoil that could be reached with camber variation in the trailing edge region only, and up to 24.6% when leading edge adaptation was considered simultaneously. However, pressure distribution results indicate that the high leading-edge curvatures required for that would probably decrease cruise critical Mach. On other hand, the trailing-edge only approach may offer better conditions for supercritical cruise.