Analysis of the Influence of Damage on Flutter Speed in CFRP Structures

2021 ◽  
pp. 114931
Author(s):  
Paulo Victor Meneguite Mendes ◽  
Guilherme Ferreira Gomes
Keyword(s):  
Flutter Speed

ROM-Based Uncertainties Quantification of Flutter Speed Prediction of the BSCW Wing

2022 ◽  
Author(s):  
Marcello Righi ◽  
Sven Düzel ◽  
David Anderegg ◽  
Andrea Da Ronch ◽  
David Massegur Sampietro ◽  
...  
Keyword(s):  
Flutter Speed ◽  
Speed Prediction

scholarly journals Flutter speed prediction by using deep learning

2021 ◽  
Vol 13 (11) ◽  
pp. 168781402110622
Author(s):  
Yi-Ren Wang ◽  
Yi-Jyun Wang
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
Short Term Memory ◽  
Learning Technology ◽  
Memory Space ◽  
Flutter Speed ◽  
Aeroelastic Flutter ◽  
Speed Prediction ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Method

Deep learning technology has been widely used in various field in recent years. This study intends to use deep learning algorithms to analyze the aeroelastic phenomenon and compare the differences between Deep Neural Network (DNN) and Long Short-term Memory (LSTM) applied on the flutter speed prediction. In this present work, DNN and LSTM are used to address complex aeroelastic systems by superimposing multi-layer Artificial Neural Network. Under such an architecture, the neurons in neural network can extract features from various flight data. Instead of time-consuming high-fidelity computational fluid dynamics (CFD) method, this study uses the K method to build the aeroelastic flutter speed big data for different flight conditions. The flutter speeds for various flight conditions are predicted by the deep learning methods and verified by the K method. The detailed physical meaning of aerodynamics and aeroelasticity of the prediction results are studied. The LSTM model has a cyclic architecture, which enables it to store information and update it with the latest information at the same time. Although the training of the model is more time-consuming than DNN, this method can increase the memory space. The results of this work show that the LSTM model established in this study can provide more accurate flutter speed prediction than the DNN algorithm.

scholarly journals Full-Span Flying Wing Wind Tunnel Test: A Body Freedom Flutter Study

Fluids ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 34
Author(s):  
Pengtao Shi ◽  
Jihai Liu ◽  
Yingsong Gu ◽  
Zhichun Yang ◽  
Pier Marzocca
Keyword(s):  
Wind Tunnel ◽  
Theoretical Analysis ◽  
Mass Balance ◽  
Degrees Of Freedom ◽  
Wind Tunnel Test ◽  
Suspension System ◽  
The Body ◽  
Structural Dynamic ◽  
Flutter Speed ◽  
Theoretical Results

Aiming at the experimental test of the body freedom flutter for modern high aspect ratio flexible flying wing, this paper conducts a body freedom flutter wind tunnel test on a full-span flying wing flutter model. The research content is summarized as follows: (1) The full-span finite element model and aeroelastic model of an unmanned aerial vehicle for body freedom flutter wind tunnel test are established, and the structural dynamics and flutter characteristics of this vehicle are obtained through theoretical analysis. (2) Based on the preliminary theoretical analysis results, the design and manufacturing of this vehicle are completed, and the structural dynamic characteristics of the vehicle are identified through ground vibration test. Finally, the theoretical analysis model is updated and the corresponding flutter characteristics are obtained. (3) A novel quasi-free flying suspension system capable of releasing pitch, plunge and yaw degrees of freedom is designed and implemented in the wind tunnel flutter test. The influence of the nose mass balance on the flutter results is explored. The study shows that: (1) The test vehicle can exhibit body freedom flutter at low airspeeds, and the obtained flutter speed and damping characteristics are favorable for conducting the body freedom flutter wind tunnel test. (2) The designed suspension system can effectively release the degrees of freedom of pitch, plunge, and yaw. The flutter speed measured in the wind tunnel test is 9.72 m/s, and the flutter frequency is 2.18 Hz, which agree well with the theoretical results (with flutter speed of 9.49 m/s and flutter frequency of 2.03 Hz). (3) With the increasing of the mass balance at the nose, critical speed of body freedom flutter rises up and the flutter frequency gradually decreases, which also agree well with corresponding theoretical results.

On the Instability Mechanisms of a Disk Rotating Close to a Rigid Surface

1995 ◽  
Vol 62 (3) ◽  
pp. 764-771 ◽  
Author(s):  
F. Y. Huang ◽  
C. D. Mote
Keyword(s):  
Rotation Speed ◽  
Maximum Speed ◽  
Film System ◽  
Rigid Surface ◽  
Flow Component ◽  
Flutter Speed ◽  
Disk Rotation ◽  
Viscous Shear ◽  
Air Film ◽  
Disk Rotation Speed

The instability mechanisms of a rotating disk, coupled to a rigid surface through a viscous fluid film at the interface, are investigated analytically. The fluid in the film is driven circumferentially by the viscous shear, and it flows outwards radially under centrifugal forces. The circumferential flow component creates an equivalent viscous damping rotating at one half the disk rotation speed. This film damping dissipates all backward traveling waves where the undamped wave speeds are greater than one half the disk rotation speed. The radial flow component creates a nonsymmetric stiffness in the disk-film system that energizes any wave mode at rotation speeds above its flutter speed. Instabilities in the disk-film system are of two types. A rotating damping instability is caused by the rotating film damping at rotation speeds above a critical value that is less than the flutter speed. A combination instability is caused by the combined effect of the film stiffness and damping at rotation speeds above a threshold that is greater than the flutter speed. The maximum rotation speed of stable disk vibration is bounded above by the lowest onset speed of rotating damping instability. This speed limit is predicted for two wall enclosure designs. The maximum stable rotation speed of a 5.25-inch diameter flexible, memory disk, separated from a rigid surface by a viscous air film, is shown to be more than 15 times greater than the maximum speed of the disk without the air film.

scholarly journals Fuzzy uncertainty analysis and reliability assessment of aeroelastic aircraft wings

2020 ◽  
Vol 124 (1275) ◽  
pp. 786-811
Author(s):  
M. Rezaei ◽  
S.A. Fazelzadeh ◽  
A. Mazidi ◽  
M.I. Friswell ◽  
H.H. Khodaparast
Keyword(s):  
Structural Parameters ◽  
Low Cost ◽  
Fuzzy Variable ◽  
Fuzzy Uncertainty ◽  
Aircraft Wings ◽  
Wing Flutter ◽  
Flutter Speed ◽  
Wing Model ◽  
Safe Region ◽  
Air Speed

ABSTRACTIn the present study, fuzzy uncertainty and reliability analysis of aeroelastic aircraft wings are investigated. The uncertain air speed and structural parameters are represented by fuzzy triangular membership functions. These uncertainties are propagated through the wing model using a fuzzy interval approach, and the uncertain flutter speed is obtained as a fuzzy variable. Further, the reliability of the wing flutter is based on the interference area in the pyramid shape defined by the fuzzy flutter speed and air speed. The ratio between the safe region volume and the total volume of the pyramid gives the reliability value. Two different examples are considered—a typical wing section, and a clean wing—and the results are given for various wind speed conditions. The results show that the approach considered is a low-cost but suitable method to estimate the reliability of the wing flutter speed in the presence of uncertainties.

Upper Bound Flutter Speed Estimation Using the mu-k Method

2005 ◽  
Vol 42 (2) ◽  
pp. 555-557 ◽  
Author(s):  
Dan Borglund
Keyword(s):  
Upper Bound ◽  
Speed Estimation ◽  
Flutter Speed

Leading-edge vortex effect on the flutter speed

1977 ◽  
Vol 14 (9) ◽  
pp. 921-922 ◽  
Author(s):  
Valter J. E. Stark
Keyword(s):  
Leading Edge ◽  
Leading Edge Vortex ◽  
Vortex Effect ◽  
Flutter Speed ◽  
Edge Vortex
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