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stall flutter prediction based on multi-layer GRU neural network

Chinese Journal of Aeronautics 2023年第1期36卷 75-90页

作者： Yuting DAI Haoran RONG You WU Chao YANG Yuntao XU School of Aeronautic Science and Engineering Beihang UniversityBeijing 100083China

The modeling of dynamic stall aerodynamics is essential to stall flutter, due to the flow separation in a large-amplitude pitching oscillation process. A newly neural network based Reduced Order Model(ROM) framework for predicting the aerodynamic forces of an airfoil undergoing large-amplitude pitching oscillation at various velocities is presented in this work. First, the dynamic stall aerodynamics is calculated by solving RANS equations and the transitional SST-γ model. Afterwards, the stall flutter bifurcation behavior is calculated by the above CFD solver coupled with structural dynamic equation. The critical flutter speed and limit-cycle oscillation amplitudes are consistent with those obtained by experiments. A newly multi-layer Gated Recurrent Unit(GRU) neural network based ROM is constructed to accelerate the calculation of aerodynamic forces. The training and validation process are carried out upon the unsteady aerodynamic data obtained by the proposed CFD method. The well-trained ROM is then coupled with the structure equation at a specific velocity, the Limit-Cycle Oscillation(LCO) of stall flutter under this flow condition is predicted precisely and more quickly. In order to predict both the critical flutter velocity and LCO amplitudes after bifurcation at different velocities, a new ROM with GRU neural network considering the variation of flow velocities is developed. The stall flutter results predicted by ROM agree well with the CFD ones at different velocities. Finally, a brief sensitivity analysis of two structural parameters of ROM is carried out. It infers the potential of the presented modeling method to depict the nonlinearity of dynamic stall and stall flutter phenomenon.

关键词： Deep learning Dynamic stall Limit-cycle oscillation Reduced order model stall flutter

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维普期刊数据库

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stall flutter Analysis of High-Aspect-Ratio Composite Wing

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Chinese Journal of Aeronautics 2006年第1期19卷 36-43页

作者：刘湘宁向锦武 School of Aeronautics Science and Engineering Beijing University of Aeronautics and Astronautics Beijing 100083 China

The stall flutter characters of high-aspect-ratio composite wing are investigated, and the effects of structure geometric nonlinearity and stiffness couple created by composite anisotropy on them also are discussed. Firstly, the high-aspect-ratio wing is modeled as a composite thin-walled closed section Euler beam whose displacement and rotation both could be of finite value, and the nonlinear dynamic equations is build up on it with all the effects of geometric nonlinearity, aerodynamic nonlinearity and anisotropy of material being considered. Then vibration equations are deduced through perturbing the dynamic equations at wing＇s equilibrium position, and coupled with unsteady stall aerodynamic model and ONERA model, to obtain the nonlinear stall flutter analysis equations of wing. Finally, the flutter stabilities with various wind speeds are determined by the harmonic balance method. With several exampies, the validity of the stall flutter model is proved, and the significant effects of geometric nonlinearity on the stall flutter various characters as wall as the effects of ply angle on the stall flutter speed and frequency also are discussed.

关键词： stall flutter high-aspect-ratio wing geometric nonlinearity composites thln-walled closed section beam

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维普期刊数据库

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Airfoil Aeroelastic flutter Analysis Based on Modified Leishman-Beddoes Model at Low Mach Number

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Chinese Journal of Aeronautics 2011年第5期24卷 550-557页

作者： SHAO Song ZHU Qinghua ZHANG Chenglin NI Xianping Science and Technology on Rotorcraft Aeromechanics Laboratory Nanjing University of Aeronautics and Astronautics Nanjing 210016 China

Based on modified Leishman-Beddoes （L-B） state space model at low Mach number （lower than 0.3）, the airfoil aeroelastic system is presented in this paper. The main modifications for L-B model include a new dynamic stall criterion and revisions of normal force and pitching moment coefficient. The bifurcation diagrams, the limit cycle oscillation （LCO） phase plane plots and the time domain response figures are applied to investigating the stall flutter bifurcation behavior of airfoil aeroelastic systems with symmetry or asymmetry. It is shown that the symmetric periodical oscillation happens after subcritical bifurcation caused by dynamic stall, and the asymmetric periodical oscillation, which is caused by the interaction of dynamic stall and static divergence, only happens in the airfoil aeroelastic system with asymmetry. Validations of the modified L-B model and the airfoil aeroelastic system are presented with the experimental airload data of NACA0012 and OA207 and experimental stall flutter data of NACA0012 respectively. Results demonstrate that the airfoil aeroelastic system presented in this paper is effective and accurate, which can be applied to the investigation of airfoil stall flutter at low Mach number.

关键词： low Mach number unsteady aerodynamics airfoil aeroelastic system stall flutter bifurcation

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