Aircraft Wing Design Research Articles

Structural Optimization of Platelike Aircraft Wings Under Flutter and Divergence Constraints

Minimum-weight aircraft wing design, with an emphasis on avoiding aeroelastic instability, has been studied since the 1960s. The majority of works to date were posed as sizing problems; only a handful of researchers have employed a topology optimization approach. The aim of this study is to use the level set method for this purpose. The problem is formulated as one of plate thickness distribution, which takes on one of two prescribed values at every point on the wing planform. This is combined with constraints implemented on the eigenvalues of the flutter equation; such an approach is shown to be robust and versatile. Optimization results for rectangular plate wings at a range of sweep configurations studied previously are included to validate the present methods. Delta, high-aspect-ratio, and typical swept transport wing planforms are then optimized. All solutions demonstrate the ability to significantly reduce wing mass while maintaining flutter and divergence speed above a specified limit, which can be higher than that of the reference, maximum-thickness design. The proposed method can be used to provide insights into optimal aeroelastic wing structures and is particularly useful for developing unconventional aircraft structural configurations.

A surrogate-based multi-disciplinary design optimization framework modeling wing–propeller interaction

This paper presents a multi-disciplinary design optimization (MDO) framework for design of a general aviation aircraft wing considering the effects of tractor propellers on the wing aerodynamic characteristics. In pursuit of this objective, a wing–propeller full-interaction aerodynamic routine was developed and integrated with structural and performance models. A substantive contribution of the work is the approach for effectively modeling wing effects on propeller slipstream development while still leveraging traditional propeller and wing analysis tools. Several optimizations were carried out, starting from an existing aircraft design, to test different local and global surrogate-based optimization frameworks and to allow for the assessment of the resulting solutions and corresponding computational performance metrics. Examination of the total function calls and run times showed that the use of surrogate models improves overall optimization performance, provided that suitable surrogate modeling techniques are chosen.

Adaptive Information Granulation in Fitness Estimation for Evolutionary Optimization

Evolutionary algorithms ordinarily need to conduct lots of fitness evaluations, requiring big computational overhead particularly in complex optimization problems. This paper proposes an adaptive information granulation approach which inspired from on the granule computing, and then reduces the expensive original fitness evaluation by the aid of the fitness inheritance strategy based on the proposed adaptive information granulation approach. The proposed algorithm is compared with few fitness inheritance assisted evolutionary algorithm on both traditional benchmark problems with four different dimensions, the CEC 2013 functions and the CEC 2014 expensive optimization test problems with 30 dimensions. Experimental results show both high effectiveness and efficiency with better solutions than those compared algorithm within different finite budget of computation for different benchmark problems. Its advantages are further verified by a real-world light aircraft wing design problem.

Multiobjective optimization of an aircraft wing design with respect to structural and aeroelastic characteristics using neural network metamodel

The multidisciplinary design optimization (MDO) is an important concept that focuses on bringing together disciplines involved with machine design. It is possible to use MDO in any stage of an aircraft design, that is in the conceptual, preliminary, or detailed design, as long as the numerical models are fitted to each of these stages. This work describes the development of a multidisciplinary design optimization applied to flexible aircraft wings, with respect to structural and aeroelastic characteristics. As tools for the aircraft designer, the numerical models must be fairly accurate and fast. Therefore, metamodels for the critical flutter speed prediction of aircraft wings were considered, thereby reducing significantly the computational cost of the optimization. For this purpose, artificial neural networks (NN) metamodeling is evaluated, based on their inherent properties in dealing with complex mappings. The NN metamodel is prepared using an aeroelastic code based on finite-element model coupled with linear potential aerodynamics. Results of the metamodel performance are presented, from where one can note that the NN is well suited for flutter prediction. Multiobjective optimization (MOO) using the genetic algorithm (GA) based on non-dominance approach is considered. The objectives were the maximization of critical flutter speed and minimization of structural mass. One case study is presented to evaluate the performance of the MOO, revealing that overall optimization process actually achieves the search for the Pareto frontier.

Aircraft wing design at low speeds using Taguchi method

PurposeThe purpose of this paper is to determine the impact level of parameters affecting wing design at low speeds using Taguchi method.Design/methodology/approachUsing brain storming approach airfoil shape, wing angle of attack and Reynolds number are determined as important wing design parameters. Most important parameters over these parameters are determined using Taguchi method. The lift-to-drag ratio (CL/CD ratio) is chosen as the performance criterion and L8 orthogonal index is chosen as experimental study scheme for this study.FindingsExperimental results are examined using Taguchi method. After making experiments and also analyses, Reynolds number is found as the most important and identifier parameter for aircraft wing design.Practical implicationsTaguchi method makes the experimental design for experimental studies. This method reduces the number of experiments substantially using orthogonal indices while keeping effects of uncontrolled parameters to a minimum. Reduction in number of experiments helps save time and also cost.Originality/valueIn this study, with less number of experiments, the most important parameter for aircraft wing design is determined. Moreover, with less number of experiments, not only is time saved but the design stage is also made faster.

New biomimetic approach to the aircraft wing structural design based on aeroelastic analysis

Abstract This paper presents a new biomimetic approach to the structural design. For the purpose of aircraft wing design the numerical environment combining simultaneous structural size, shape, and topology optimization based on aeroelastic analysis was developed. For the design of aircraft elements the optimization process must be treated as a multi-load case task, because during the fluid structure interaction analysis each step represents a different structural load case. Also, considering different angles of attack, during the CFD computation each result is considered. The method-specific features (such as domain independence, functional configurations during the process of optimization, and multiple load case solution implemented in the optimization scenario) enable the optimal structural form. To illustrate the algorithm functionality, the problem of determining the optimal internal wing structure was presented. The optimal internal wing structure resulting from aeroelastic computation with different angles of attack has been presented.

Proportional fuzzy feed-forward architecture control validation by wind tunnel tests of a morphing wing

In aircraft wing design, engineers aim to provide the best possible aerodynamic performance under cruise flight conditions in terms of lift-to-drag ratio. Conventional control surfaces such as flaps, ailerons, variable wing sweep and spoilers are used to trim the aircraft for other flight conditions. The appearance of the morphing wing concept launched a new challenge in the area of overall wing and aircraft performance improvement during different flight segments by locally altering the flow over the aircraft’s wings. This paper describes the development and application of a control system for an actuation mechanism integrated in a new morphing wing structure. The controlled actuation system includes four similar miniature electromechanical actuators disposed in two parallel actuation lines. The experimental model of the morphing wing is based on a full-scale portion of an aircraft wing, which is equipped with an aileron. The upper surface of the wing is a flexible one, being closed to the wing tip; the flexible skin is made of light composite materials. The four actuators are controlled in unison to change the flexible upper surface to improve the flow quality on the upper surface by delaying or advancing the transition point from laminar to turbulent regime. The actuators transform the torque into vertical forces. Their bases are fixed on the wing ribs and their top link arms are attached to supporting plates fixed onto the flexible skin with screws. The actuators push or pull the flexible skin using the necessary torque until the desired vertical displacement of each actuator is achieved. The four vertical displacements of the actuators, correlated with the new shape of the wing, are provided by a database obtained through a preliminary aerodynamic optimization for specific flight conditions. The control system is designed to control the positions of the actuators in real time in order to obtain and to maintain the desired shape of the wing for a specified flight condition. The feasibility and effectiveness of the developed control system by use of a proportional fuzzy feed-forward methodology are demonstrated experimentally through bench and wind tunnel tests of the morphing wing model.

Morphing elastically lofted transition for active camber control surfaces

This paper introduces a compliant morphing flap transition that seeks to address a long-standing source of noise and drag in the design of aircraft wings – the gap present at the spanwise ends of the control surfaces. These gaps create large discontinuities in the flow and allow for pressure leakage from the lower to upper wing surface, generating significant amounts of vorticity, noise, and drag. The concept introduced here seals this gap with a smooth, three-dimensional morphing transition section that elastically lofts between the rigid wing and moving control surface in a passive and continuous manner. Previous transition concepts are first discussed, followed by establishment of an initial desired transition shape. Computational fluid dynamics analysis of the desired transition shape indicates both an increase in lift and a decrease in drag. The morphing, elastically lofted transition concept proposed here will then be introduced. In this concept, the complex three-dimensional shape change required is created with a novel structural architecture that combines material and geometric compliance with geometric bend-twist coupling. The concept design and operating principles will be introduced, relevant geometric parameters will be derived, and an initial prototype demonstrator capable of large deflections and smooth transition surfaces will be shown.

An evaluation of constraint aggregation strategies for wing box mass minimization

Constraint aggregation makes it feasible to solve large-scale stress-constrained mass minimization problems efficiently using gradient-based optimization where the gradients are computed using adjoint methods. However, it is not always clear which constraint aggregation method is more effective, and which values to use for the aggregation parameters. In this work, the accuracy and efficiency of several aggregation methods are compared for an aircraft wing design problem. The effect of the type of aggregation function, the number of constraints, and the value of the aggregation parameter are studied. Recommendations are provided for selecting a constraint aggregation scheme that balances computational effort with the accuracy of the computed optimal design. Using the recommended aggregation method and associated parameters, a mass of within 0.5 % of the true optimal design was obtained.

GEOMETRY OPTIMIZATION OF PORTABLE HIGH-ALTITUDE AIRCRAFT WING

Atmospheric conditions at high-altitudes challenges aircraft wing design. High altitude operations require high-performance solutions in air vehicle aerodynamics such as wing configuration, drag reduction, high value of lift coefficient. High-altitude aircraft developed at the moment have significant size due to those requirements. Overall goal is to overcome the storage and transportation limitations of high altitude aircraft and implement portability options. Therefore a portable high altitude aircraft wing was developed. It is necessary for the UAV to have a high value of aerodynamic quality Kmax, for maximum achievable altitude. High value of aerodynamic quality requires large wing aspect ratio λ, which is determined by the wing area and wing length. Two computational 3D model of UAV wing were made and analyzed for lift distribution over the span. To eliminate possible errors, flow calculation around the wings are executed by various aerodynamic computational methods which are panel-vortex method and finite element method. For wing profile R-III-A-15 airfoil was selected. Both wing have identical geometry parameters except the tip of second wing has an angle of -5°. Result of analyzes shows that lift distribution over the span is not optimal. Therefore further optimizations were made. Three different wing geometry designed for improving the first version of the portable high UAV wing. These are straight wing, combined wing with straight center section and trapezoid console, straight wing with elliptical tip. Those wings were compared for value of Сумах and Kмах and lift distribution over the span. Results clearly demonstrate advantages of straight wing with elliptical tip section, which allows for a continual flow of finite wings to a much greater extent than other reviewed options, which makes it possible to ensure effective control by the roll at supercritical flight conditions such as stall and tail spin. However, other important characteristics, especially Сумах and K мах have not significantly reduced compared.

Component allocation and supporting frame topology optimization using global search algorithm and morphing mesh

This paper proposes a stepwise structural design methodology where the component layout and the supporting frame structure is sequentially found using global search algorithm and topology optimization. In the component layout design step, the genetic algorithm is used to handle system level multiobjective problem where the optimal locations of multiple components are searched. Based on the layout design searched, a new Topology Optimization method based on Morphing Mesh technique (TOMM) is applied to obtain the frame structure topology while adjusting the component locations simultaneously. TOMM is based on the SIMP method with morphable FE mesh, and component relocation and frame design is simultaneously done using two kinds of design variables: topology design variables and morphing design variables. Two examples are studied in this paper. First, TOMM method is applied to a simple cantilever beam problem to validate the proposed design methodology and justify inclusion of morphing design variables. Then the stepwise design methodology is applied to the commercial Boeing 757 aircraft wing design problem for the optimal placement of multiple components (subsystems) and the optimal supporting frame structure around them. Additional constraint on the weight balance is included and the corresponding design sensitivity is formulated. The benefit of using the global search algorithm (genetic algorithm) is discussed in terms of finding the global optimum and independency of initial design guess. It has been proved that the proposed stepwise method can provide innovative design insight for complex modern engineering systems with multi-component structures.

High-Fidelity Hydrodynamic Shape Optimization of a 3-D Hydrofoil

With recent advances in high-performance computing, computational fluid dynamics (CFD) modeling has become an integral part in the engineering analysis and even in the design process of marine vessels and propulsors. In aircraft wing design, CFD has been integrated with numerical optimization and adjoint methods to enable high-fidelity aerodynamic shape optimization with respect to large numbers of design variables. There is a potential to use some of these techniques for maritime applications, but there are new challenges that need to be addressed to realize that potential. This work presents a solution to some of those challenges by developing a CFD-based hydrodynamic shape optimization tool that considers cavitation and a wide range of operating conditions. A previously developed three-dimensional compressible Reynolds-averaged Navier‐Stokes (RANS) solver is extended to solve for nearly incompressible flows, using a low-speed preconditioner. An efficient gradient-based optimizer and the adjoint method are used to carry out the optimization. The modified CFD solver is validated and verified for a tapered NACA 0009 hydrofoil. The need for a large number of design variables is demonstrated by comparing the optimized solution obtained using different number of shape design variables. The results showed that at least 200 design variables are needed to get a converged optimal solution for the hydrofoil considered. The need for a high-fidelity hydrodynamic optimization tool is also demonstrated by comparing RANS-based optimization with Euler-based optimization. The results show that at high lift coefficient (C L) values, the Euler-based optimization leads to a geometry that cannot meet the required lift at the same angle of attack as the original foil due to inability of the Euler solver to predict viscous effects. Single-point optimization studies are conducted for various target C L values and compared with the geometry and performance of the original NACA 0009 hydrofoil, as well as with the results from a multipoint optimization study. A total of 210 design variables are used in the optimization studies. The optimized foil is found to have a much lower negative suction peak, and hence delayed cavitation inception, in addition to higher efficiency, compared to the original foil at the design C L value. The results show significantly different optimal geometry for each C L, which means an active morphing capability was needed to achieve the best possible performance for all conditions. For the single-point optimization, using the highest C L as the design point, the optimized foil yielded the best performance at the design point, but the performance degraded at the off-design C L points compared to the multipoint design. In particular, the foil optimized for the highest C L showed inferior performance even compared to the original foil at the lowest C L condition. On the other hand, the multipoint optimized hydrofoil was found to perform better than the original NACA 0009 hydrofoil over the entire operation profile, where the overall efficiency weighted by the probability of operation at each C L, is improved by 14.4%. For the multipoint optimized foil, the geometry remains fixed throughout the operation profile and the overall efficiency was only 1.5% lower than the hypothetical actively morphed foil with the optimal geometry at each C L. The new methodology presented herein has the potential to improve the design of hydrodynamic lifting surfaces such as propulsors, hydrofoils, and hulls.

High-Fidelity Hydrodynamic Shape Optimization of a 3-D Hydrofoil

With recent advances in high-performance computing, computational fluid dynamics (CFD) modeling has become an integral part in the engineering analysis and even in the design process of marine vessels and propulsors. In aircraft wing design, CFD has been integrated with numerical optimization and adjoint methods to enable high fidelity aerodynamic shape optimization with respect to large numbers of design variables. There is a potential to use some of these techniques for maritime applications, but there are new challenges that need to be addressed to realize that potential. This work presents a solution to some of those challenges by developing a CFD-based hydrodynamic shape optimization tool that considers cavitation and a wide range of operating conditions. A previously developed three-dimensional compressible Reynold saveraged Navier-Stokes (RANS) solver is extended to solve for nearly incompressible flows, using a low-speed preconditioner. An efficient gradient-based optimizer and the adjoint method are used to carry out the optimization. The modified CFD solver is validated and verified for a tapered NACA 0009 hydrofoil. The need for a large number of design variables is demonstrated by comparing the optimized solution obtained using different number of shape design variables. The results showed that at least 200 design variables are needed to get a converged optimal solution for the hydrofoil considered. The need for a high-fidelity hydrodynamic optimization tool is also demonstrated by comparing RANS-based optimization with Euler-based optimization. The results show that at high lift coefficient (CL) values, the Euler-based optimization leads to a geometry that cannot meet the required lift at the same angle of attack as the original foil due to inability of the Euler solver to predict viscous effects. Single-point optimization studies are conducted for various target CL values and compared with the geometry and performance of the original NACA 0009 hydrofoil, as well as with the results from a multipoint optimization study. A total of 210 design variables are used in the optimization studies. The optimized foil is found to have a much lower negative suction peak, and hence delayed cavitation inception, in addition to higher efficiency, compared to the original foil at the design CL value. The results show significantly different optimal geometry for each CL, which means an active morphing capability was needed to achieve the best possible performance for all conditions. For the single-point optimization, using the highest CL as the design point, the optimized foil yielded the best performance at the design point, but the performance degraded at the off-design CL points compared to the multipoint design. In particular, the foil optimized for the highest CL showed inferior performance even compared to the original foil at the lowest CL condition. On the other hand, the multipoint optimized hydrofoil was found to perform better than the original NACA 0009 hydrofoil over the entire operation profile, where the overall efficiency weighted by the probability of operation at each CL, is improved by 14.4%. For the multipoint optimized foil, the geometry remains fixed throughout the operation profile and the overall efficiency was only 1.5% lower than the hypothetical actively morphed foil with the optimal geometry at each CL. The new methodology presented herein has the potential to improve the design of hydrodynamic lifting surfaces such as propulsors, hydrofoils, and hulls.

AIRCRAFT WING AND AERODYNAMIC ANALYSIS USING INTEGRATED MATLAB AND STAAD.Pro MODELS

Aircrafts have evolved significantly throughout the years, in large part to advances in technology. As technology grows, analytical models of aircrafts have become more accurate and play a more significant role in the design process. This paper examines the integration of commonly used mathematical and structural analysis software to conduct parametric studies on aircraft wing design and aerodynamics analysis for class project. The forces considered in this study include engine, fuel, and lift forces. The engine force is evaluated as a constant point load throughout the duration of the flight, while the fuel weight is changed throughout the flight as it was being consumed. The MATLAB algorithm is set up to analyze one fuel force input which is distributed evenly over the wing at a location where the fuel tank is located. The lift force is estimated using the Schrenk Approximation and the MATLAB algorithm is then used to distribute the lift force over the area of the wing. The methodology developed in this paper shows the potential of efficiently use non-aerodynamic software to produce a detailed preliminary structural analysis of an aircraft wing and the ability to use it in classroom projects.

A matrix-free augmented lagrangian algorithm with application to large-scale structural design optimization

In many large engineering design problems, it is not computationally feasible or realistic to store Jacobians or Hessians explicitly. Matrix-free implementations of standard optimization methods—implementations that do not explicitly form Jacobians and Hessians, and possibly use quasi-Newton approximations—circumvent those restrictions, but such implementations are virtually non-existent. We develop a matrix-free augmented-Lagrangian algorithm for nonconvex problems with both equality and inequality constraints. Our implementation is developed in the Python language, is available as an open-source package, and allows for approximating Hessian and Jacobian information.We show that our approach solves problems from the CUTEr and COPS test sets in a comparable number of iterations to state-of-the-art solvers. We report numerical results on a structural design problem that is typical in aircraft wing design optimization. The matrix-free approach makes solving problems with thousands of design variables and constraints tractable, even when function and gradient evaluations are costly.

Optimization of Aircraft Lifting Surfaces Using a Cellular Division Method

The development of a biologically inspired methodology for topology, shape, sizing, and control surface optimization of aircraft lifting surfaces is presented. The methodology is based on the map L-systems modeling of cellular division to generate the substructure topology. This is combined with variables for aerodynamic shape, structural sizing, and control surfaces (number, size, location, and aeroelastic trimmed settings) and constraints on stiffness, strength, local skin panel buckling, static aeroelastic response (roll performance, pitch rate, trimmed angle of attack), and flutter requirements. A dual-objective function is formulated with weight and and is solved with a bilevel optimization algorithm. The map -system rules that develop the topology are evolved using a genetic algorithm in the outer optimization loop on and weight, which obtains the optimal parameter settings for topology, shape, and control surfaces, whereas the inner loop performs weight minimization with the structural sizing variables. The methodology is demonstrated on the design of a generic fighter aircraft wing.

Flutter Analysis of an Aircraft Wing Using Computational Fluid Dynamics

In today’s aviation world, the design of aircraft wing becomes a challenging one for aeronautical engineers, in order to meet the aero elastic phenomenon such as flutter, wing divergence in both aerodynamics and structural aspects. There are so many FEM packages available for both flow and structural analysis such as ANSYS, NASTRAN, ALGOR, NISA, ADINA, COSMOS, etc. The paper presents the application of computational aero-elasticity (CA) methods to analyze the wing in both aerodynamic and structural aspects, using ANSYS-FLOTRAN; 2-D typical aerofoil sections were analyzed and validated with experimental results. Also the vibration behavior of wing section is analyzed under MODAL, HARMONIC, TRANSIENT and SPECTRUM analysis under the aerodynamic lift force and moments. The support reaction forces and moments at the fuselage-wing intersection are developed in this research.

Supercritical natural laminar flow airfoil optimization for regional aircraft wing design

An optimization design method of supercritical natural laminar flow airfoil based on Genetic Algorithm and Computational Fluid Dynamics is tested in this paper. Class Shape Transformation method is adopted as geometry parameterization method. Constraints on pressure distribution are applied to gain appropriate flow field in addition to the L/D performance. A fixed transition computation method is used in the optimization process to save computation time while giving the reasonable friction drag estimation and predicting the influence of the laminar boundary layer on airfoil performances. Specified favorable pressure gradient constraints are used to guarantee the expected laminar length. Objective of optimization is set to weaken the shock wave and minimize the pressure drag. Such a simplified NLF optimization process is verified by natural transition computation. The optimal setting of the favorable pressure gradient constraint, which is important for the trade-off between drag reduction and laminar stability, is then studied via numerical investigation. Results show that the airfoil optimized by constraining a favorable pressure gradient larger than 0.2 is good for both cruise efficiency and robustness. A natural laminar wing is then designed based on the optimized airfoil. Numerical verifications show that the wing has good natural laminar performance and low speed behavior.

Aircraft wing structural design optimization based on automated finite element modelling and ground structure approach

An optimization procedure combining an automated finite element modelling (AFEM) technique with a ground structure approach (GSA) is proposed for structural layout and sizing design of aircraft wings. The AFEM technique, based on CATIA VBA scripting and PCL programming, is used to generate models automatically considering the arrangement of inner systems. GSA is used for local structural topology optimization. The design procedure is applied to a high-aspect-ratio wing. The arrangement of the integral fuel tank, landing gear and control surfaces is considered. For the landing gear region, a non-conventional initial structural layout is adopted. The positions of components, the number of ribs and local topology in the wing box and landing gear region are optimized to obtain a minimum structural weight. Constraints include tank volume, strength, buckling and aeroelastic parameters. The results show that the combined approach leads to a greater weight saving, i.e. 26.5%, compared with three additional optimizations based on individual design approaches.

Improved Reliability-Based Optimization with Support Vector Machines and Its Application in Aircraft Wing Design

A new reliability-based design optimization (RBDO) method based on support vector machines (SVM) and the Most Probable Point (MPP) is proposed in this work. SVM is used to create a surrogate model of the limit-state function at the MPP with the gradient information in the reliability analysis. This guarantees that the surrogate model not only passes through the MPP but also is tangent to the limit-state function at the MPP. Then, importance sampling (IS) is used to calculate the probability of failure based on the surrogate model. This treatment significantly improves the accuracy of reliability analysis. For RBDO, the Sequential Optimization and Reliability Assessment (SORA) is employed as well, which decouples deterministic optimization from the reliability analysis. The improved SVM-based reliability analysis is used to amend the error from linear approximation for limit-state function in SORA. A mathematical example and a simplified aircraft wing design demonstrate that the improved SVM-based reliability analysis is more accurate than FORM and needs less training points than the Monte Carlo simulation and that the proposed optimization strategy is efficient.