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A simulation-based study on longitudinal gust response of flexible flapping wings

Acta Mechanica Sinica 2018年第6期34卷 1048-1060页

作者： Toshiyuki Nakata Ryusuke Noda Shinobu Kumagai Hao Liu Graduate School of Engineering Chiba UniversityChiba 263-8522Japan Department of Mechanical Engineering Kanto Gakuin UniversityKanagawa 263-8501Japan

Winged animals such as insects are capable of flying and surviving in an unsteady and unpredictable aerial *** generate and control aerodynamic forces by flapping their flexible *** the dynamic shape changes of their flapping wings are known to enhance the efficiency of their flight,they can also affect the stability of a flapping wing flyer under unpredictable disturbances by responding to the sudden changes of aerodynamic forces on the *** order to test the hypothesis,the gust response of flexible flapping wings is investigated numerically with a specific focus on the passive maintenance of aerodynamic forces by the wing *** computational model is based on a dynamic flight simulator that can incorporate the realistic morphology,the kinematics,the structural dynamics,the aerodynamics and the fluid-structure interactions of a hovering *** longitudinal gusts are imposed against the tethered model of a hovering hawkmoth with flexible flapping *** is found that the aerodynamic forces on the flapping wings are affected by the gust,because of the increase or decrease in relative wingtip velocity or kinematic angle of *** passive shape change of flexible wings can,however,reduce the changes in the magnitude and direction of aerodynamic forces by the gusts from various directions,except for the downward *** adaptive response of the flexible structure to stabilise the attitude can be classified into the mechanical feedback,which works passively with minimal delay,and is of great importance to the design of bio-inspired flapping wings for micro-air vehicles.

关键词： Insect flight Flapping wing Flexible wing gust response Fluid-structure interaction Mechanical feedback

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Near ground wind characteristics during typhoon Meari:Turbulence intensities, gust factors, and peak factors

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Journal of Central South University 2017年第10期24卷 2421-2430页

作者：王旭黄鹏余先锋黄超 State Key Laboratory Breeding Base of Mountain Bridge and Tunnel Engineering Chongqing Jiaotong University State Key Laboratory of Disaster Reduction in Civil Engineering Tongji University State Key Laboratory of Subtropical Building Science South China University of Technology

Wind data were collected during the 2011 typhoon Meari at heights of 10, 20, 30, and 40 m above the ground using a 40 m high anemometer tower in the coastal area near Shanghai Pudong International Airport. Wind speeds and directions, turbulence intensities, gust factors, and peaks were analyzed using the time records of wind speed. The results show that turbulence intensity components in longitudinal, lateral, and vertical directions decrease with mean wind speed, regardless of elevations, and the turbulence intensities are in a linear relationship with mean wind speeds. The ratios of three turbulence intensity components(i.e. Iu, Iv, Iw) at heights of 10, 20 and 40 m were calculated and equal to be 1:0.88:0.50, 1:0.84:0.57, and 1:0.9:0.49, respectively. In addition, the gust factors in three directions exhibit a reduction with increasing mean wind speed. The peak factors at different heights show a similar trend and slightly decrease with mean wind speed; average peak factors for all 10-min data from Typhoon Meari are 2.43, 2.48, and 2.47, respectively.

关键词： typhoon Meari wind characteristics turbulence intensity gust factor peak factor

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Aerodynamic Performance of Parafoil with Different Leading Edge Incision in the gust

Aerodynamic Performance of Parafoil with Different Leading E...

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第36届中国控制会议

作者： Wannan Wu Qinglin Sun Zengqiang Chen Mingwei Sun Shuzhen Luo College of Computer and Control Engineering Nankai University

ISBN: (纸本)9781538629185

A high precision and novel modeling method, to identify the aerodynamic parameters of the parafoil based on CFD（Computational Fluid Dynamics） is proposed. By solving the governing equations and the k-ε equations, the effects of leading edge incision of the parafoil on aerodynamic performance and stability are investigated. It is concluded that increasing the length and slope of the leading edge incision can decrease the lift coefficient and increase the drag coefficient, the stall angle of attack and lift to drag ratio are also decreased. The slope angle and the length have different effects on aerodynamic performance of the parafoil. Increasing the length affects the pressure distribution of the upper and lower wing surface. Increasing the slope leads to airflow separation at the trailing edge of the parafoil. Then, the variation of lift coefficients with time is obtained by adding different types of wind into the flow field on the basis of field velocity approach. By comparing the flow field of different models, it can be found that reducing the incision length and the slope are beneficial to enhance the stability of the parafoil.

关键词： Leading Edge Incision Aerodynamic Performance Stability gust

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Interesting Beat Phenomenon for Airfoil

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International Journal of Plant Engineering and Management 2022年第1期27卷 18-28页

作者： JING Zhiwei General Configuration and Aerodynamics Design Department Xi′an Aircraft Design InstituteXi′an 710089China

The airfoil with two degrees is simulated to get the beat *** results indicate that the occurrence of beat phenomenon is very sensitive to the equivalent frequency and damping,contributed by the structural and aerodynamic *** the equivalent damping approaches to zero and the equivalent frequency is very close to the gust frequency which the beat phenomenon occurs.

关键词： beat phenomenon aeroelasticity gust flutter airfoil

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Robust Adaptive Control Design for Rotorcraft Unmanned Aerial Vehicles Based on Sliding Mode Approach

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Transactions of Tianjin University 2014年第6期20卷 393-401页

作者：郭建川鲜斌 Tianjin Key Laboratory of Process Measurement and Control School of Electrical Engineering and AutomationTianjin University

This paper presents a nonlinear robust control design method for a generic rotorcraft unmanned aerial vehicle(RUAV). The control objective is to let the RUAV track some pre-defined time-varying position and heading trajectories. The proposed controller employs feedback linearization process to realize the dynamic decoupling control and applies adaptive sliding mode control to compensate for the parametric uncertainties and external disturbances. The global asymptotical stability is proved via stability analysis. Compared with the cascaded controller, the proposed controller demonstrates a superior tracking performance and robustness through numerical simulation in the presence of parametric uncertainties and unknown disturbances.

关键词： rotorcraft unmanned aerial vehicle (RUAV) nonlinear robust control sliding mode control parametricuncertainty wind gust disturbance

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Optimization of Aerospace Structures for Aeroelastic Response Reliability

Optimization of Aerospace Structures for Aeroelastic Respons...

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The Fourth World Congress of Structural and Multidisciplinary Optimization

作者： Chris L.Pettit Ramana V.Grandhi Air Force Research Laboratory Wright-Patterson AFB OH USA Wright State University Dayton OHUSA

＜正＞Reliability-based optimization of a generic, fighter-like wing structure is conducted for gust response and aileron effectiveness. This work is performed within a framework that integrates ASTROS for structural and loads analysis, object-oriented MATLAB tools for reliability analysis, and DOT for optimization and most probable point estimation. The reliability analysis algorithm takes advantage of adaptive nonlinear approximations to compensate for nonlinearity of the failure surfaces. The wing structure is modeled with finite elements, each of which is assumed to have random thickness of known standard deviation. Young’s modulus of the wing skin material is also assumed to be random. The mean thickness values are taken as design variables. Linear unsteady aerodynamics theory is used to estimate frequency response functions due to loads induced by harmonic variations in the vertical component of the freestream velocity. Continuous gust excitation is modeled as a stationary random process that follows the von Karman turbulence spectrum. Reliability index constraints are enforced for gust-induced bending moment and shear at the wing’s root, and also for aileron effectiveness. Redistribution of structural mass by the optimizer produces designs with improved aeroelastic performance reliability and relatively small weight penalties.

关键词： structural reliability optimization gust aileron effectiveness

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