Aeroelastic Simulation and Experimental Validation of a 3D-Printed Passive Morphing Airfoil
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Abstract:
To predict the deformation and aerodynamic performance of a passive morphing airfoil with a novel compliant structure, aeroelastic simulation methods were developed. The static aeroelastic problem was solved by loosely coupling a finite-element-method solver and a hierarchical Cartesian grid-based flow solver. The viscous effect was investigated by comparing the results of using the Euler and Reynolds-averaged Navier–Stokes (RANS) equations in the aerodynamic simulations. The accuracies of the structural and aerodynamic solvers were validated through structural and wind-tunnel experiments, respectively. The deformation predicted by the RANS-based aeroelastic simulation was in accordance with the experimental results, while the Euler-based aeroelastic simulation predicted a larger deformation. The lift slope of the morphing airfoil improved more than that of the rigid airfoil, showing consistency with the experimental results. The comparative study showed that the viscous flow condition leads to a smaller aerodynamic load and deformation of the morphing airfoil.Keywords:
Aeroelasticity
Morphing
NACA airfoil
因为它的优点， Morphing 翅膀在电梯在飞机技术开发吸引了许多研究注意和努力起草比率和飞行性能。Morphing 翅膀技术联合电梯，控制出现进一个无缝的翅膀并且和内部控制系统集成主要结构。它使用气动弹性变形的变丑由控制表面导致了通过空气动力学的力量的理想的再分配获得直接力量控制的翅膀。然而，控制系统和综合结构的复杂性的一些未知机械参数为 morphing 翅膀的动态建模成为主要挑战。解决这个问题，基于的形式的敏感分析被介绍由评估未知参数并且识别当模特儿的边界改进 morphing 翅膀 FE 模型的测试数据的一个方法调节。有与一个灵活的走边控制系统综合的结构的一个创新无缝的 morphing 翅膀为调查被介绍。一台伺服马达为 morphing 翅膀驾驶的使活动系统的一个试验性的模型被设计并且建立。由执行颤动测试和建议形式的敏感分析，伺服马达的未知扭力的僵硬和使活动机制模型的边界条件被识别并且评估。与测试数据作比较，改进 FE 模型的开始的四形式的频率的平均错误显著地被归结为不到 4% 。为了推进，调查当模特儿的 morphing 翅膀，包括皮肤的一个翅膀盒子然后一个整个 morphing 翅膀模型并且与后面的边使活动系统综合被建立并且测试。由使用建议方法， FE 模型被放松在皮肤和使活动机制之间的限制改进。结果证明改进 FE 模型的开始的三形式的频率的平均错误被归结为不到 6% 。研究结果证明与灵活的走边控制表面综合的介绍无缝的 morphing 翅膀能改进空气动力学的特征。由使用测试数据，基于的形式的敏感分析方法，未知参数和边界使活动模型调节能决心改进 FE 模型。在为一个 morphing 翅膀的高精确性的动态建模的问题能以一种有效方式被解决。
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Fluid-structure interaction problems (FSI) are too complex to solve analytically. Therefore, wind tunnel tests or computational methods are used to evaluate the integrity of aerospace structures. Performing wind tunnel tests for many design parameters in early stage of the design is very expensive. So, computational solid mechanics (CSM) and computational fluid dynamics (CFD) solvers which works coupled can be used to determine aeroelastic characteristics of the structure to reduce number of tests. In this study, flutter analyses of AGARD 445.6 wing are carried out using FSI method with commercially available CSM and CFD solvers. The procedure developed with the solvers is validated with the experimental data conducted by AGARD 445.6 standard aeroelastic configuration for dynamic response at subsonic and transonic free stream Mach numbers.
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Machine learning and artificial intelligence algorithms typically require large amount of data for training. This means that for nonlinear aeroelastic applications, where small training budgets are driven by the high computational burden associated with generating data, usability of such methods has been limited to highly simplified aeroelastic systems. This paper presents a novel approach for the identification of optimized sparse higher-order polynomial-based aeroelastic reduced order models (ROM) to significantly reduce the amount of training data needed without sacrificing fidelity. Several sparsity promoting algorithms are considered, including; rigid sparsity, LASSO regression, and Orthogonal Matching Pursuit (OMP). The study demonstrates that through OMP, it is possible to efficiently identify optimized s-sparse nonlinear aerodynamic ROMs using only aerodynamic response information. This approach is exemplified in a three-dimensional aeroelastic stabilator model experiencing high amplitude freeplay-induced limit cycles. The comparison shows excellent agreement between the ROM and the full-order aeroelastic response, including the ability to generalize to new freeplay and velocity index values, with online computational savings of several orders of magnitude. The development of an Optimally Sparse ROM (OS-ROM) extends previous higher-order polynomial-based ROM approaches for feasible application to complex three-dimensional nonlinear aeroelastic problems, without incurring significant computational burdens or loss of accuracy.
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This report gives a collection of several computations13; made on NACA 0012 and NPL 9615 airfoils using a two- dimensional viscous transonic flow analysis based on Bavitz code. The comparisons with experimental results of NPL and NAL indicate that the computer program can be used as a reliable method to compute two-dimensional viscous transonic flows, except in those cases involving strong shock/extensive flow separation.
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Abstract A review of the state of the art of transonic nonlinear aeroelasticity is presented. The discussion begins with a description of the generic nonlinear aeroelastic behavior that may occur followed by a summary of lessons learned from flight experience. Physical sources of nonlinear behavior are identified in both the aerodynamic fluid flow and the structure. Methods for the efficient computation of unsteady aerodynamic forces are summarized and then the chapter concludes with a discussion of correlation of theory and experiment for flutter boundaries in transonic flow and limit cycle oscillations (LCOs) arising from a variety of physical sources for several distinct aeroelastic configurations.
Aeroelasticity
Flutter
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NASA technical memorandum summarizes results of computations of viscous, transonic flow reported at Viscous Transonic Airfoil Workshop. Results reexamined and analyzed with special emphasis on drag. Compared with each other and with data from experiments. Test cases include attached and separated transonic flows about NACA 0012 airfoil.
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