To see the other types of publications on this topic, follow the link: Aerodynamic flutter.
Journal articles on the topic 'Aerodynamic flutter'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 journal articles for your research on the topic 'Aerodynamic flutter.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse journal articles on a wide variety of disciplines and organise your bibliography correctly.
1
Berci, Marco. "On Aerodynamic Models for Flutter Analysis: A Systematic Overview and Comparative Assessment." Applied Mechanics 2, no. 3 (July 29, 2021): 516–41. http://dx.doi.org/10.3390/applmech2030029.
Full textAbstract:
This work reviews different analytical formulations for the time-dependent aerodynamic load of a thin aerofoil and clarifies numerical flutter results available in the literature for the typical section of a flexible wing; inviscid, two-dimensional, incompressible, potential flow is considered in all test cases. The latter are investigated using the exact theory for small airflow perturbations, which involves both circulatory and non-circulatory effects of different nature, complemented by the p-k flutter analysis. Starting from unsteady aerodynamics and ending with steady aerodynamics, quasi-unsteady and quasi-steady aerodynamic models are systematically derived by successive simplifications within a unified approach. The influence of the aerodynamic approximations on the aeroelastic stability boundary is then rigorously assessed from both physical and mathematical perspectives. All aerodynamic models are critically discussed and compared in the light of the numerical results as well, within a comprehensive theoretical framework in practice. In all cases, results accuracy depends on the aero-structural arrangement of the flexible wing; however, simplified unsteady and simplified quasi-unsteady aerodynamic approximations are suggested for robust flutter analysis whenever the wing’s elastic axis lies ahead of the aerofoil’s control point.
2
Schäfer, Dominik. "T-tail flutter simulations with regard to quadratic mode shape components." CEAS Aeronautical Journal 12, no. 3 (June 18, 2021): 621–32. http://dx.doi.org/10.1007/s13272-021-00524-8.
Full textAbstract:
AbstractIt is known that the dynamic aeroelastic stability of T-tails is dependent on the steady aerodynamic forces at aircraft trim condition. Accounting for this dependency in the flutter solution process involves correction methods for doublet lattice method (DLM) unsteady aerodynamics, enhanced DLM algorithms, unsteady vortex lattice methods (UVLM), or the use of CFD. However, the aerodynamic improvements along with a commonly applied modal approach with linear displacements results in spurious stiffness terms, which distort the flutter velocity prediction. Hence, a higher order structural approach with quadratic mode shape components is required for accurate flutter velocity prediction of T-tails. For the study of the effects of quadratic mode shape components on T-tail flutter, a generic tail configuration without sweep and taper is used. Euler based CFD simulations are applied involving a linearized frequency domain (LFD) approach to determine the generalized aerodynamic forces. These forces are obtained based on steady CFD computations at varying horizontal tail plane (HTP) incidence angles. The quadratic mode shape components of the fundamental structural modes for the vertical tail plane (VTP), i.e., out-of-plane bending and torsion, are received from nonlinear as well as linear finite element analyses. Modal coupling resulting solely from the extended modal representation of the structure and its influence on T-tail flutter is studied. The g-method is applied to solve for the flutter velocities and corresponding flutter mode shapes. The impact of the quadratic mode shape components is visualized in terms of flutter velocities in dependency of the HTP incidence angle and the static aerodynamic HTP loading.
3
Xie, Dan, Min Xu, Honghua Dai, and Tao Chen. "New Look at Nonlinear Aerodynamics in Analysis of Hypersonic Panel Flutter." Mathematical Problems in Engineering 2017 (2017): 1–13. http://dx.doi.org/10.1155/2017/6707092.
Full textAbstract:
A simply supported plate fluttering in hypersonic flow is investigated considering both the airflow and structural nonlinearities. Third-order piston theory is used for nonlinear aerodynamic loading, and von Karman plate theory is used for modeling the nonlinear strain-displacement relation. The Galerkin method is applied to project the partial differential governing equations (PDEs) into a set of ordinary differential equations (ODEs) in time, which is then solved by numerical integration method. In observation of limit cycle oscillations (LCO) and evolution of dynamic behaviors, nonlinear aerodynamic loading produces a smaller positive deflection peak and more complex bifurcation diagrams compared with linear aerodynamics. Moreover, a LCO obtained with the linear aerodynamics is mostly a nonsimple harmonic motion but when the aerodynamic nonlinearity is considered more complex motions are obtained, which is important in the evaluation of fatigue life. The parameters of Mach number, dynamic pressure, and in-plane thermal stresses all affect the aerodynamic nonlinearity. For a specific Mach number, there is a critical dynamic pressure beyond which the aerodynamic nonlinearity has to be considered. For a higher temperature, a lower critical dynamic pressure is required. Each nonlinear aerodynamic term in the full third-order piston theory is evaluated, based on which the nonlinear aerodynamic formulation has been simplified.
4
Dai, Yuting, and Chao Yang. "Smolyak-Grid-Based Flutter Analysis with the Stochastic Aerodynamic Uncertainty." Discrete Dynamics in Nature and Society 2014 (2014): 1–8. http://dx.doi.org/10.1155/2014/174927.
Full textAbstract:
How to estimate the stochastic aerodynamic parametric uncertainty on aeroelastic stability is studied in this current work. The aerodynamic uncertainty is more complicated than the structural one, and it takes more significant effect on the flutter boundary. First, the nominal unsteady aerodynamic influence coefficients were calculated with the doublet lattice method. Based on this nominal model, the stochastic uncertainty model for unsteady aerodynamic pressure coefficients was constructed with physical meaning. Afterwards, the methodology for flutter uncertainty quantification due to aerodynamic perturbation was developed, based on the nonintrusive polynomial chaos expansion theory. In order to enhance the computational efficiency, the integration algorithm, namely, Smolyak sparse grids, was employed to calculate the coefficients of the stochastic polynomial basis. Finally, the flutter uncertainty analysis methodology was applied to an aircraft's wing model. The influence of uncertainty with uniform distribution for aerodynamic pressure coefficients on flutter boundary was quantified. The numerical results indicate that, the influence of unsteady aerodynamic pressure due to the motion of coupling modes takes significant effect on flutter boundary. It is validated that the flutter uncertainty analysis based on Smolyak sparse grids integration is efficient and accurate for quantifying input uncertainty with high dimensions.
5
Wang, Binwen, and Xueling Fan. "Ground Flutter Simulation Test Based on Reduced Order Modeling of Aerodynamics by CFD/CSD Coupling Method." International Journal of Applied Mechanics 11, no. 01 (January 2019): 1950008. http://dx.doi.org/10.1142/s175882511950008x.
Full textAbstract:
Flutter is an aeroelastic phenomenon that may cause severe damage to aircraft. Traditional flutter evaluation methods have many disadvantages (e.g., complex, costly and time-consuming) which could be overcome by ground flutter test technique. In this study, an unsteady aerodynamic model is obtained using computational fluid dynamics (CFD) code according to the procedure of frequency domain aerodynamic calculation. Then, the genetic algorithm (GA) method is adopted to optimize interpolation points for both excitation and response. Furthermore, the minimum-state method is utilized for rational fitting so as to establish an aerodynamic model in time domain. The aerodynamic force is simulated through exciters and the precision of simulation is guaranteed by multi-input and multi-output robust controller. Finally, ground flutter simulation test system is employed to acquire the flutter boundary through response under a range of air speeds. A good agreement is observed for both velocity and frequency of flutter between the test and modeling results.
6
Kobayashi, H. "Annular Cascade Study of Low Back-Pressure Supersonic Fan Blade Flutter." Journal of Turbomachinery 112, no. 4 (October 1, 1990): 768–77. http://dx.doi.org/10.1115/1.2927720.
Full textAbstract:
Low back-pressure supersonic fan blade flutter in the torsional mode was examined using a controlled-oscillating annular cascade test facility. Precise data of unsteady aerodynamic forces generated by shock wave movement, due to blade oscillation, and the previously measured data of chordwise distributions of unsteady aerodynamic forces acting on an oscillating blade, were joined and, then, the nature of cascade flutter was evaluated. These unsteady aerodynamic forces were measured by direct and indirect pressure measuring methods. Our experiments covered a range of reduced frequencies based on a semichord from 0.0375 to 0.547, six interblade phase angles, and inlet flow velocities from subsonic to supersonic flow. The occurrence of unstalled cascade flutter in relation to reduced frequency, interblade phase angle, and inlet flow velocity was clarified, including the role of unsteady aerodynamic blade surface forces on flutter. Reduced frequency of the flutter boundary increased greatly when the blade suction surface flow became transonic flow. Interblade phase angles that caused flutter were in the range from 40 to 160 deg for flow fields ranging from high subsonic to supersonic. Shock wave movement due to blade oscillation generated markedly large unsteady aerodynamic forces which stimulated blade oscillation.
7
Dowell, Earl H., Kenneth C. Hall, and Michael C. Romanowski. "Eigenmode Analysis in Unsteady Aerodynamics: Reduced Order Models." Applied Mechanics Reviews 50, no. 6 (June 1, 1997): 371–86. http://dx.doi.org/10.1115/1.3101718.
Full textAbstract:
In this article, we review the status of reduced order modeling of unsteady aerodynamic systems. Reduced order modeling is a conceptually novel and computationally efficient technique for computing unsteady flow about isolated airfoils, wings, and turbomachinery cascades. Starting with either a time domain or frequency domain computational fluid dynamics (CFD) analysis of unsteady aerodynamic or aeroacoustic flows, a large, sparse eigenvalue problem is solved using the Lanczos algorithm. Then, using just a few of the resulting eigenmodes, a Reduced Order Model of the unsteady flow is constructed. With this model, one can rapidly and accurately predict the unsteady aerodynamic response of the system over a wide range of reduced frequencies. Moreover, the eigenmode information provides important insights into the physics of unsteady flows. Finally, the method is particularly well suited for use in the active control of aeroelastic and aeroacoustic phenomena as well as in standard aeroelastic analysis for flutter or gust response. Numerical results presented include: 1) comparison of the reduced order model to classical unsteady incompressible aerodynamic theory, 2) reduced order calculations of compressible unsteady aerodynamics based on the full potential equation, 3) reduced order calculations of unsteady flow about an isolated airfoil based on the Euler equations, and 4) reduced order calculations of unsteady viscous flows associated with cascade stall flutter, 5) flutter analysis using the Reduced Order Model. This review article includes 25 references.
8
Yang, Lei, Fei Shao, Qian Xu, and Ke-bin Jiang. "Flutter Performance of the Emergency Bridge with New-Type Cable-Girder." Mathematical Problems in Engineering 2019 (March 17, 2019): 1–14. http://dx.doi.org/10.1155/2019/1013025.
Full textAbstract:
Based on the proposed emergency bridge scheme, the flutter performance of the emergency bridge with the new-type cable-girder has been investigated through wind tunnel tests and numerical simulation analyses. Four aerodynamic optimization schemes have been developed in consideration of structure characteristics of the emergency bridge. The flutter performances of the aerodynamic optimization schemes have been investigated. The flutter derivatives of four aerodynamic optimization schemes have been analyzed. According to the results, the optimal scheme has been determined. Based on flutter theory of bridge, the differential equations of flutter of the emergency bridge with new-type cable-girder have been established. Iterative method has been used for solving the differential equations. The flutter analysis program has been compiled using the APDL language in ANSYS, and the bridge flutter critical wind speed of the optimal scheme has been determined by the program. The flutter analysis program has also been used to determine the bridge flutter critical wind speed of different wind-resistance cable schemes. The results indicate that the bridge flutter critical wind speed of the original emergency bridge scheme is lower than the flutter checking wind speed. The aerodynamic combined measurements of central-slotted and wind fairing are the optimal scheme, with the safety coefficients larger than 1.2 at the wind attack angles of −3°, 0°, and +3°. The bridge flutter critical wind speed of the optimal scheme has been determined using the flutter analysis program, and the numerical results agree well with the wind tunnel test results. The wind-resistance cable scheme of 90° is the optimal wind cable scheme, and the bridge flutter critical wind speed increased 31.4%. However, in consideration of the convenience in construction and the effectiveness in erection, the scheme of wind-resistance cable in the horizontal direction has been selected to be used in the emergency bridge with new-type cable-girder.
9
Zhong, Jize, and Zili Xu. "An energy method for flutter analysis of wing using one-way fluid structure coupling." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 231, no. 14 (September 14, 2016): 2560–69. http://dx.doi.org/10.1177/0954410016667146.
Full textAbstract:
In this paper, an energy method for flutter analysis of wing using one-way fluid structure coupling was developed. To consider the effect of wing vibration, Reynolds-averaged Navier–Stokes equations based on the arbitrary Lagrangian Eulerian coordinates were employed to model the flow. The flow mesh was updated using a fast dynamic mesh technology proposed by our research group. The pressure was calculated by solving the Reynolds-averaged Navier–Stokes equations through the SIMPLE algorithm with the updated flow mesh. The aerodynamic force for the wing was computed using the pressure on the wing surface. Then the aerodynamic damping of the wing vibration was computed. Finally, the flutter stability for the wing was decided according to whether the aerodynamic damping was positive or not. Considering the first four modes, the aerodynamic damping for wing 445.6 was calculated using the present method. The results show that the aerodynamic damping of the first mode is lower than the aerodynamic damping of higher order modes. The aerodynamic damping increases with the increase of the mode order. The flutter boundary for wing 445.6 was computed using the aerodynamic damping of the first mode in this paper. The calculated flutter boundary is consistent well with the experimental data.
10
Chen, Xingyu, Ruijie Hu, Haojun Tang, Yongle Li, Enbo Yu, and Lei Wang. "Flutter Stability of a Long-Span Suspension Bridge During Erection in Mountainous Areas." International Journal of Structural Stability and Dynamics 20, no. 09 (August 2020): 2050102. http://dx.doi.org/10.1142/s0219455420501023.
Full textAbstract:
In mountainous areas, more challenges are expected for the construction of long-span bridges. The flutter instability during erection is an outstanding issue due to flexible structural characteristics and strong winds with large angles of attack. Taking the suspension bridge as an example, the flutter stability of the bridge with different suspending sequences was investigated. First, the dynamic characteristics of the bridge during erection were computed by the finite element software ANSYS, along with the effects on flutter stability discussed. Then, different aerodynamic shapes of the bridge girder during erection were considered. The aerodynamic coefficients and the critical flutter state were determined by wind tunnel tests. Based on the above analysis, some structural measures are proposed for improving the flutter stability of the bridge during erection. The results show that the flutter stability of the bridge during erection is related to the suspending sequence and the aerodynamic shape of the girder. Owing to the structural dynamic characteristics, the bridge has better flutter stability when the girder segments are suspended symmetrically from the two towers to the mid-span. Considering the construction requirement that the bridge deck should be laid without intervals, this structural superiority is seriously weakened by the unfavorable aerodynamic shape of the girder. In order to improve the flutter stability of the bridge during erection, an effective way is to adopt some temporary structural strengthening measures.
11
Sudha, U. P. V., G. S. Deodhare, and K. Venkatraman. "A comparative assessment of flutter prediction techniques." Aeronautical Journal 124, no. 1282 (October 27, 2020): 1945–78. http://dx.doi.org/10.1017/aer.2020.84.
Full textAbstract:
ABSTRACTTo establish flutter onset boundaries on the flight envelope, it is required to determine the flutter onset dynamic pressure. Proper selection of a flight flutter prediction technique is vital to flutter onset speed prediction. Several methods are available in literature, starting with those based on velocity damping, envelope functions, flutter margin, discrete-time Autoregressive Moving Average (ARMA) modelling, flutterometer and the Houbolt–Rainey algorithm. Each approach has its capabilities and limitations. To choose a robust and efficient flutter prediction technique from among the velocity damping, envelope function, Houbolt–Rainey, flutter margin and auto-regressive techniques, an example problem is chosen for their evaluation. Hence, in this paper, a three-degree-of-freedom model representing the aerodynamics, stiffness and inertia of a typical wing section is used(1). The aerodynamic, stiffness and inertia properties in the example problem are kept the same when each of the above techniques is used to predict the flutter speed of this aeroelastic system. This three-degree-of-freedom model is used to generate data at speeds before initiation of flutter, during flutter and after occurrence of flutter. Using these data, the above-mentioned flutter prediction methods are evaluated and the results are presented.
12
Li, Wenjie, and Shujin Laima. "Experimental Investigations on Nonlinear Flutter Behaviors of a Bridge Deck with Different Leading and Trailing Edges." Applied Sciences 10, no. 21 (November 3, 2020): 7781. http://dx.doi.org/10.3390/app10217781.
Full textAbstract:
Recently, the nonlinear flutter behavior of long-span suspension bridges has attracted attention. Unlike the classical theory of bridge flutter, the stable limit cycle oscillations (LCO) have occurred for some bluff aerodynamic configurations when the inflow velocity exceeded a specific critical value. To explore the influence of aerodynamic configurations on flutter behaviors a series of flutter tests for spring-suspended sectional models were conducted. When the leading edges and trailing edges with various shapes were installed at the sectional models, different flutter types occurred. In the test, the self-excited forces and flutter responses were measured. Then, the characteristics of coupling vibration and aerodynamic hysteresis of the two kinds of flutter were analyzed and compared. Finally, the role of the phase difference between self-excited forces and displacements was discussed in the mechanism difference of the classical flutter and the postflutter LCO. As the leading edge became the bluffer, the results showed that the type of flutter gradually transformed from classical divergent flutter to postcritical LCO and the torsional mode played a more important role in the flutter than in the vertical mode. For the postflutter LCO, there was a negative feedback pattern, i.e., as the vibration amplitude increased, the phase difference gradually decreased, and the energy input to the dynamic system did not grow rapidly, which limited the further vibration divergence and resulted in a stable LCO.
13
Yun, J. M., and J. H. Han. "Development of ground vibration test based flutter emulation technique." Aeronautical Journal 124, no. 1279 (May 4, 2020): 1436–61. http://dx.doi.org/10.1017/aer.2020.36.
Full textAbstract:
ABSTRACTIn demand of simpler and alternative ground flutter test, a new technique that emulates flutter on the ground has recently emerged. In this paper, an improvement of the test technique is made and verified through the experimental work. The technique utilizes general ground vibration test (GVT) devices. The key idea is to emulate the distributed unsteady aerodynamic force by using a few concentrated actuator forces; referred to as emulated flutter test (EFT) technique. The EFT module contains two main logics; namely, real-time aerodynamic equivalent force calculator and multi-input-multi-output (MIMO) force controller. The module is developed to emulate the subsonic, linear flutter on a specified target structure, which is a thin aluminum clamped-plate with aspect ratio (AR) of 2.25. In this study, doublet hybrid method (DHM) was applied to model the subsonic aerodynamic force, which restricts the application to a 2-dimensional structure. Given that, correlation of several experimental works, such as wind-tunnel flutter test, EFT using laser displacement sensor (LDS), and EFT using accelerometer, on the target structure are investigated to verify the technique. In addition to the flutter boundary, flutter mode shape and trend of aerodynamic damping effect are also presented in this work. Together with these various kinds of test results, application of more compact actuator and an accelerometer as a sensor, makes the current technique the most advanced ground flutter emulation test method.
14
LEE, SEUNG JUN, DONG-KYUN IM, IN LEE, and JANG-HYUK KWON. "THE WING-BODY AEROELASTIC ANALYSES USING THE INVERSE DESIGN METHOD." Modern Physics Letters B 24, no. 13 (May 30, 2010): 1479–82. http://dx.doi.org/10.1142/s0217984910023918.
Full textAbstract:
Flutter phenomenon is one of the most dangerous problems in aeroelasticity. When it occurs, the aircraft structure can fail in a few second. In recent aeroelastic research, computational fluid dynamics (CFD) techniques become important means to predict the aeroelastic unstable responses accurately. Among various flow equations like Navier-Stokes, Euler, full potential and so forth, the transonic small disturbance (TSD) theory is widely recognized as one of the most efficient theories. However, the small disturbance assumption limits the applicable range of the TSD theory to the thin wings. For a missile which usually has small aspect ratio wings, the influence of body aerodynamics on the wing surface may be significant. Thus, the flutter stability including the body effect should be verified. In this research an inverse design method is used to complement the aerodynamic deficiency derived from the fuselage. MGM (modified Garabedian-McFadden) inverse design method is used to optimize the aerodynamic field of a full aircraft model. Furthermore, the present TSD aeroelastic analyses do not require the grid regeneration process. The MGM inverse design method converges faster than other conventional aerodynamic theories. Consequently, the inverse designed aeroelastic analyses show that the flutter stability has been lowered by the body effect.
15
Gennaretti, M., and L. Greco. "Whirl flutter analysis of prop-rotors using unsteady aerodynamics reduced-order models." Aeronautical Journal 112, no. 1131 (May 2008): 261–70. http://dx.doi.org/10.1017/s0001924000002207.
Full textAbstract:
Abstract The prediction of this aeroelastic phenomenon is an urgent need of the designer and requires devoted numerical tools. This work examines the influence of the accuracy of the aerodynamic modelling on whirl flutter analysis, with particular attention to those models that can conveniently be applied to preliminary design and control purposes. Considering a simple pylon/prop-rotor structure, the aeroelastic instability boundaries are identified by 2D quasi-steady and 2D unsteady aerodynamics theories, along with a 3D unsteady, potential flow BEM solver. A methodology for deriving reduced-order models from unsteady aerodynamic solutions is used. The numerical investigation highlights that the accuracy of the aerodynamic solver included in the analysis may be of crucial importance. The use of 2D aerodynamic models does not always guarantee conservative stability predictions, and this is particularly true for three-bladed rotors where a fully 3D unsteady solver coupled with a wake alignment algorithm seems to be necessary.
16
Eskandary, Keivan, Morteza Dardel, Mohammad Hadi Pashaei, and Abdol Majid Kani. "Effects of Aeroelastic Nonlinearity on Flutter and Limit Cycle Oscillations of High-Aspect-Ratio Wings." Applied Mechanics and Materials 110-116 (October 2011): 4297–306. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.4297.
Full textAbstract:
In this study aeroelastic characteristics of long high aspect ratio wing models with structural nonlinearities in quasi-steady aerodynamics flows are investigated. The studied wing model is a cantilever wing with double bending and torsional vibrations and with large deflection ability in according to Dowell-Hodges wing model. This wing model is valid for long, straight and thin homogeneous isotropic beams. Aerodynamics model is based on quasi-steady aerodynamic which is valid for aerodynamic flows in low velocity and without wake, viscosity and compressibility effects. The effect of different parameters such as mass ratios and stiffness ratios on flutter and divergence velocities and limit cycle oscillation amplitudes are carefully studied.
17
Simpson, A. "On flexure-torsion flutter criteria." Aeronautical Journal 103, no. 1028 (October 1999): 457–74. http://dx.doi.org/10.1017/s0001924000064411.
Full textAbstract:
Abstract The classical criteria of the 1920s for the avoidance of flexure-torsion flutter were based on parameters such as stiffness ratio and the position across the typical chord of the aerodynamic, elastic and mass centres. In more recent times, and in the context of aeroelastic tailoring of lifting surfaces constructed with composite materials, a new terminology has emerged — as evident from technical papers produced in the USA over the past decade. The prevention of flexure-torsion flutter, or the raising of the critical speed, is now achieved by providing more wash-in or less wash-out , where these terms do not have their established aeronautical meanings — and for this reason (and other, non-semantic ones) are to be deprecated. By recourse to a typical section model (with quasi-steady and unsteady compressible aerodynamics), the writer argues that, for conventionally constructed wings, the new criteria are ‘fuzzy’ and incomplete versions of the earlier criteria in respect of the positioning of the various ‘centres’ (i.e., elastic, mass and aerodynamic) across the typical chord, and therefore that the new terminology is redundant in this context. For laminated composite wing structures, even when the construction is uniform and the fiexural axis straight, it is established that the inclination of this axis with respect to the CG and aerodynamic axes may be so large that the fiexural and shear centres at the tip could be several chords forward or aft of the mid-chord axis; the criteria of the 1920s are then irrelevant. The wash-in/wash-out criteria may then be said to ‘come into their own’, albeit that it is shown herein that they remain fuzzy and incomplete — even for quasisteady binary problems. A crude modal binary model of a rudimentary laminated composite wing is included to illustrate this and other features. By recourse to a higher-order flutter formulation, the writer demonstrates that the wash-in/wash-out criteria are, in certain respects, unreliable.
18
Matsumoto, Masaru, and Fumitaka Yoshizumi. "Aerodynamic Active Control of Flutter Instability." Wind Engineers, JAWE 1996, no. 68 (1996): 90–94. http://dx.doi.org/10.5359/jawe.1996.68_90.
Full text
19
RIKIZEN, Shota, Keiichi HIROAKI, and Masahiro WATANABE. "Aerodynamic Coupled Flutter of Multiple Sheets." Proceedings of the Dynamics & Design Conference 2020 (August 25, 2020): 608. http://dx.doi.org/10.1299/jsmedmc.2020.608.
Full text
20
Bai, Hua, Wei Guo, Wei Li, and Yu Li. "Research on the Influence of the Aerodynamic Measure on the Flutter Derivative of the Steel Truss Suspension Bridge." Advanced Materials Research 532-533 (June 2012): 252–56. http://dx.doi.org/10.4028/www.scientific.net/amr.532-533.252.
Full textAbstract:
Flutter derivative is a significant index of the structure flutter stability. Identifying flutter derivative precisely contributes to the bridge flutter stability analyzing. In this paper, we take a research on the Liujiaxia Bridge in Gansu Province, China. Different flutter derivatives, which were got via segment model vibration tests with different aerodynamic measures, were classified, and made comparison in order to get the law of how different aerodynamic measures effect on the flutter derivative. The results show that, setting central stabilized plate, Build-in deflector, flange plate all affect flutter derivative significantly, which leads to changes in the flutter critical wind velocity of the structure. Setting central stabilized plate above the deck contributes to identify the flutter derivative of the 0° and positive attack angle, while setting central stabilized plate will contribute to flutter derivative identification at negative angles. It will make it difficult to identify the flutter derivative at 0° and -3° if the built-in deflector was set. Wind plate contributes to the identification of the flutter derivative at +3°, however, it will make it harder to identify the flutter derivative at 0° and -3°.
21
Liu, Zhanhe, Jinlou Quan, Jingyuan Yang, Dan Su, and Weiwei Zhang. "A High Efficient Fluid-Structure Interaction Method for Flutter Analysis of Mistuned." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 36, no. 5 (October 2018): 856–64. http://dx.doi.org/10.1051/jnwpu/20183650856.
Full textAbstract:
The time cost is very high by direct fluid-structure interaction method for mistuned bladed disk structures, so aerodynamic loads generally are ignored or treated as small perturbations in traditional flutter analysis. In order to analyze the flutter characteristics of mistuned blade rapidly and accurately, this paper presents an efficient fluid-structure interaction method based on aerodynamic reduced order model. system identification technology and two basic assumptions are used to build the unsteady aerodynamic reduced order model. Coupled the structural equations and the aerodynamic model in the state space, the flutter stability of mistuned bladed disk can be obtained by changing the structural parameters. For the STCF 4 example, the response calculated by this method agrees well with the results obtained by the direct CFD, but the computational efficiency is improved by nearly two orders of magnitude. This method is used to study the stiffness mistuned cascade system, and the stability characteristics of the system are obtained by calculating the eigenvalues of the aeroelastic matrix. The results show that the stiffness mistuning can significantly improve the flutter stability of the system, and also lead to the localization of the mode. The mistuning mode, mistuning amplitude and fluid structure interaction can influence the flutter stability obviously.
22
Abdul Majid, Dayang Laila Abang, Shahnor Basri, Renuganth Varatharajoo, and A. H. Attaran. "Flutter Analysis of a Hybrid Plate-Like Fiber-Reinforced Composite Wing." Key Engineering Materials 471-472 (February 2011): 1107–12. http://dx.doi.org/10.4028/www.scientific.net/kem.471-472.1107.
Full textAbstract:
The aeroelastic flutter of a laminated hybrid composite wing was investigated. The composite wing was modelled as composite plates and the aeroelastic analysis has been carried out in the frequency-domain. Pre-determined fiber orientation of a 3-layers carbon/epoxy and glass/epoxy laminated plate has been employed with various aspect ratios. The modal approach and the Doublet-lattice Method (DLM) have been used herein to calculate the normal modes and the unsteady aerodynamics of the plate. The structural and aerodynamic models were connected using surface splines and the flutter speed has been calculated using the p-k method that provides the eigenvalues at different air densities and airstream velocities. The study showed that it is imperative that the carbon/epoxy should be employed in the outermost layers in order to improve the flutter speed and flutter frequency.
23
Zhu, Ledong, Xiao Tan, Zhenshan Guo, and Quanshun Ding. "Effects of central stabilizing barriers on flutter performances of a suspension bridge with a truss-stiffened deck under skew winds." Advances in Structural Engineering 22, no. 1 (May 19, 2018): 17–29. http://dx.doi.org/10.1177/1369433218774144.
Full textAbstract:
To improve the flutter performance of a suspension bridge with a 1088-m-span truss-stiffened deck, the aerodynamic measures of upper and lower central stabilizing barriers were investigated at first via wind tunnel tests of sectional model under the normal wind condition. The yaw wind effect on the flutter performance of the bridge with the above aerodynamic measures was then examined via a series of wind tunnel tests of oblique sectional models. The test results show that the effect of the lower central stabilizing barrier on the flutter critical wind speed is remarkably different from that of the upper central stabilizing barrier for both the normal and skew wind cases. The inclination angle +3° is the most unfavorable inclination angle to the flutter performance of the truss-stiffened suspension bridge no matter whether the aerodynamic control measures are adopted or not. Furthermore, for most cases, the lowest flutter critical wind speed occurs when the incident wind deviates from the normal direction of the bridge span by a small yaw angle between 5° and 10°.
24
Kumar Sinha, Anjani, Eriki Ananda Kumar, and A. Johnrajan. "Flutter Analysis of an Aircraft Wing Using Computational Fluid Dynamics." Applied Mechanics and Materials 754-755 (April 2015): 817–27. http://dx.doi.org/10.4028/www.scientific.net/amm.754-755.817.
Full textAbstract:
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.
25
Smith, T. E., and J. R. Kadambi. "The Effect of Steady Aerodynamic Loading on the Flutter Stability of Turbomachinery Blading." Journal of Turbomachinery 115, no. 1 (January 1, 1993): 167–74. http://dx.doi.org/10.1115/1.2929201.
Full textAbstract:
An aeroelastic analysis is presented that accounts for the effect of steady aerodynamic loading on the aeroelastic stability of a cascade of compressor blades. The aeroelastic model is a two-degree-of-freedom model having bending and torsional displacements. A linearized unsteady potential flow theory is used to determine the unsteady aerodynamic response coefficients for the aeroelastic analysis. The steady aerodynamic loading was caused by the addition of (1) airfoil thickness and camber and (2) steady flow incidence. The importance of steady loading on the airfoil unsteady pressure distribution is demonstrated. Additionally, the effect of the steady loading on the tuned flutter behavior and flutter boundaries indicates that neglecting either airfoil thickness, camber, or incidence could result in nonconservative estimates of flutter behavior.
26
Rogólski, Robert, and Aleksander Olejnik. "Structural model with controls of a very light airplane for numerical flutter calculations." Aircraft Engineering and Aerospace Technology 92, no. 3 (October 18, 2018): 304–17. http://dx.doi.org/10.1108/aeat-01-2018-0059.
Full textAbstract:
Purpose The finite element model developed for a new-designed aircraft was used to solve some problems of structural dynamics. The key purpose of the task was to estimate the critical flutter velocities of the light airplane by performing numerical analysis with application of MSC Software. Design/methodology/approach Flutter analyses processed by Nastran require application of some complex aeroelastic model integrating two separate components – structural model and aerodynamic model. These sub-models are necessary for determining stiffness, mass and aerodynamic matrices, which are involved in the flutter equation. The aircraft structural model with its non-structural masses was developed in Patran. To determine the aerodynamic coefficient matrix, some simplified aerodynamic body-panel geometries were developed. The flutter equation was solved with the PK method. Findings The verified aircraft model was used to determine its normal modes in the range of 0-30 Hz. Then, some critical velocities of flutter were calculated within the range of operational velocities. As there is no certainty that the computed modes are in accordance with the natural ones, some parametric calculations are recommended. Modal frequencies depend on structural parameters that are quite difficult to identify. Adopting their values from the reasonable range, it is possible to assign the range of possible frequencies. The frequencies of rudder or elevator modes are dependent on their mass moments of inertia and rigidity of controls. The critical speeds of tail flutter were calculated for various combinations of stiffness or mass values. Practical implications The task described here is a preliminary calculational study of normal modes and flutter vibrations. It is necessary to prove the new airplane is free from flutter to fulfil the requirement considered in the type certification process. Originality/value The described approach takes into account the uncertainty of results caused by the indeterminacy of selected constructional parameters.
27
Rahi, Abbas, Mortaza Shahravi, and Darvish Ahmadi. "The Effects of Airfoil Camber on Flutter Suppression Regarding Timoshenko Beam Theory." Applied Mechanics and Materials 110-116 (October 2011): 1531–38. http://dx.doi.org/10.4028/www.scientific.net/amm.110-116.1531.
Full textAbstract:
The application of Timoshenko beam theory is presented, thereby the effects of airfoil camber can be investigated analytically and numerically by considering rotary inertia and shear deformation in addition to moment of inertia, aerodynamic loading and bending/torsion coupling. Regarding a tuned blisk, the analysis is simplified to a single blade with plunge and pitch DOF. Pressure distribution of the airfoil surfaces and the resulting aerodynamic forces are calculated with ‘ANSYS/FLOTRAN’ during one-cycle time marching at several reduced frequencies. A parametric relation is then achieved by Roger’s approximation including quasi-inertia, quasi-damping, quasi-elastic and lag terms. The final aeroelastic equations are established by bending-torsion and aerodynamics-structure coupling which is solved by state space approach. This procedure is repeated at several free stream velocities until the real component of an eigenvalue equals zero. The latest velocity is the flutter speed. Following this procedure, flutter characteristics of two similar aeroleastic cases are determined considering only one difference in blade configuration; one with cambered and the other with uncambered airfoil. Comparison of these two cases shows the considerable suppression effect of airfoil camber on flutter.
28
Mohamad, El Katt, Shaker Raafat, and Kassem Younis. "Optimum Control System for Seismic and Aerodynamic Flutter Response of Cable-Stayed Bridge Using Magnetorheological Dampers." Advanced Materials Research 163-167 (December 2010): 4269–79. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.4269.
Full textAbstract:
Control of cable-stayed bridge flutter for earthquake and aerodynamic hazard mitigation represents a relatively new area of research. This paper proposes a new optimized smart control system to mitigate the cable-stayed bridge flutter due to seismic and aerodynamic vibration. A Magnetorheological (MR) fluid damper, which belongs to the class of controllable fluid dampers, is proposed for use in a control strategy for mitigating its effect on the cable-stayed bridge. Genetic algorithm is adopted to determine the flutter acceleration levels, and corresponding forces of MR dampers. The optimized forces values from MR dampers are studied under the effect of five strong earthquakes recorded, known as El-Centro, Mexico City, San Fernando, Ker Country, and Northridge earthquakes. The time delay between the monitoring system and the actuator response is also studied. The simulation and optimization results shows that the proposed control strategy using MR dampers is the promising one of the applicable control methods to reduce the seismic and aerodynamic flutter vibration of the stayed bridge.
29
Ouyang, Ke Jian, Yi Long, and Bi Cao Peng. "Aerodynamic Forces of Stay Cables Incorporating in Flutier Analysis." Applied Mechanics and Materials 438-439 (October 2013): 894–900. http://dx.doi.org/10.4028/www.scientific.net/amm.438-439.894.
Full textAbstract:
With the length of stay cables close to 580m, only inclusion in aerodynamic forces of main deck cannot reflect the actual situation during wind-resistant design. The aerodynamic forces of stay cables should be considered in the three-dimensional flutter analysis of cable-stayed bridges. In this paper, mathematic expressions of unsteady aerodynamic force of stay cable were then derived in terms of aerodynamic damping and stiffness matrices. The above procedure is implemented into NACS by an independent module. As an example, the multimode flutter analysis of Sutong Bridge was conducted by using NACS. Fair agreement is achieved between the present numerical simulation and wind tunnel test results.
30
Wang, Wei, Zhou Zhou, and Xiao Ping Zhu. "Solar Array Mounting Effects on Flutter Characteristics of Solar-Powered UAV." Advanced Materials Research 940 (June 2014): 410–14. http://dx.doi.org/10.4028/www.scientific.net/amr.940.410.
Full textAbstract:
Solar powered UAV has the characteristics of high aspect ratio, low structural surface density, high structural flexibility and low flutter speed. Different solar array mountings will affect the flutter characteristics of the structure. The mechanical properties of solar arrays packaged and unpackaged are measured in this paper and the solar powered UAV structural finite element model based on Patran/Nastran was also established in the paper. Two solar array mounting ways are researched: embedded solar arrays and patching solar arrays. To investigate the flutter characteristics under the two solar array mounting ways, the Doublet lattice method (DLM) aerodynamic model is used to model the unsteady aerodynamic loads. Finally, flutter speed of the structure was determined by using the P-K method and the analysis result indicate that patching solar arrays is more conductive to improve the flutter characteristics of the structure.
31
Tang, D., and E. H. Dowell. "Flutter/LCO suppression for high-aspect ratio wings." Aeronautical Journal 113, no. 1144 (June 2009): 409–16. http://dx.doi.org/10.1017/s0001924000003079.
Full textAbstract:
Abstract An experimental high-aspect ratio wing aeroelastic model with a device to provide a controllable slender body tip mass distribution has been constructed and the model response due to flutter and limit cycle oscillations has been measured in a wind tunnel test. A theoretical model has also been developed and calculations made to correlate with the experimental data. Structural equations of motion based on nonlinear beam theory are combined with the ONERA aerodynamic stall model (an empirical extension of Theodorsen aerodynamic theory that accounts for flow separation). A dynamic perturbation analysis about a nonlinear static equilibrium is used to determine the small perturbation flutter boundary which is compared to the experimentally determined flutter velocity and flutter frequency. Time simulation is used to compute the limit cycle oscillations response when the flutter/LCO control system is ON or OFF. Theory and experiment are in good agreement for predicting the flutter/LCO suppression that can be achieved with the control device.
32
Kobayashi, H. "Unsteady Aerodynamic Damping Measurement of Annular Turbine Cascade With High Deflection in Transonic Flow." Journal of Turbomachinery 112, no. 4 (October 1, 1990): 732–40. http://dx.doi.org/10.1115/1.2927716.
Full textAbstract:
Unsteady aerodynamic forces acting on oscillating blades of a transonic annular turbine cascade were investigated in both aerodynamic stable and unstable domains, using a Freon gas annular cascade test facility. In the facility, whole blades composing the cascade were oscillated in the torsional mode by a high-speed mechanical drive system. In the experiment, the reduced frequency K was changed from 0.056 to 0.915 with a range of outlet Mach number M2 from 0.68 to 1.39, and at a constant interblade phase angle. Unsteady aerodynamic moments obtained by two measuring methods agreed well. Through the moment data the phenomenon of unstalled transonic cascade flutter was clarified as well as the significance of K and M2 for the flutter. The variation of flutter occurrence with outlet flow velocity in the experiments showed a very good agreement with theoretical analysis.
33
Hoyniak, D., and S. Fleeter. "Aerodynamic Detuning Analysis of an Unstalled Supersonic Turbofan Cascade." Journal of Engineering for Gas Turbines and Power 108, no. 1 (January 1, 1986): 60–67. http://dx.doi.org/10.1115/1.3239886.
Full textAbstract:
A new, and as yet unexplored, approach to passive flutter control is aerodynamic detuning, defined as designed passage-to-passage differences in the unsteady aerodynamic flow field of a rotor blade row. Thus, aerodynamic detuning directly affects the fundamental driving mechanism for flutter, i.e., the unsteady aerodynamic forces and moments acting on individual rotor blades. In this paper, a model to demonstrate the enhanced supersonic unstalled aeroelastic stability associated with aerodynamic detuning is developed. The stability of an aerodynamically detuned cascade operating in a supersonic inlet flow field with a subsonic leading edge locus is analyzed, with the aerodynamic detuning accomplished by means of nonuniform circumferential spacing of adjacent rotor blades. The unsteady aerodynamic forces and moments on the blading are defined in terms of influence coefficients in a manner that permits the stability of both a conventional uniformly spaced rotor configuration as well as the detuned nonuniform circumferentially spaced rotor to be determined. With Verdon’s uniformly spaced Cascade B as a baseline, this analysis is then utilized to demonstrate the potential enhanced aeroelastic stability associated with this particular type of aerodynamic detuning.
34
Borglund, Dan, and Ulrik Nilsson. "Robust Wing Flutter Suppression Considering Aerodynamic Uncertainty." Journal of Aircraft 41, no. 2 (March 2004): 331–34. http://dx.doi.org/10.2514/1.9328.
Full text
35
Mannini, C., and G. Bartoli. "Aerodynamic uncertainty propagation in bridge flutter analysis." Structural Safety 52 (January 2015): 29–39. http://dx.doi.org/10.1016/j.strusafe.2014.07.005.
Full text
36
Matsumoto, M., Y. Kobayashi, and H. Shirato. "The influence of aerodynamic derivatives on flutter." Journal of Wind Engineering and Industrial Aerodynamics 60 (April 1996): 227–39. http://dx.doi.org/10.1016/0167-6105(96)00036-0.
Full text
37
Ajaj, Rafic M., Farag K. Omar, Tariq T. Darabseh, and Jonathan Cooper. "Flutter of Telescopic Span Morphing Wings." International Journal of Structural Stability and Dynamics 19, no. 06 (June 2019): 1950061. http://dx.doi.org/10.1142/s0219455419500615.
Full textAbstract:
This paper studies the aeroelastic behavior of telescopic, multi-segment, span morphing wings. The wing is modeled as a linear, multi-segment, stepped, cantilever Euler–Bernoulli beam. It consists of three segments along the axis and each segment has different geometric, mechanical, and inertial properties. The aeroelastic analysis takes into account spanwise out-of-plane bending and torsion only, for which the corresponding shape functions are derived and validated. The use of shape functions allows representing the wing as an equivalent aerofoil whose generalized coordinates are defined at the wingtip according to the Rayleigh–Ritz method. Theodorsen’s unsteady aerodynamic theory is used to estimate the aerodynamic loads. A representative Padé approximation for the Theodorsen’s transfer function is utilized to model the aerodynamic behaviors in state-space form allowing time-domain simulation and analysis. The effect of the segments’ mechanical, geometric, and inertial properties on the aeroelastic behavior of the wing is assessed. Finally, the viability of span morphing as a flutter suppression device is studied.
38
Alsaif, Khalid A., Mosaad A. Foda, and Hachimi Fellouah. "Analytical and Experimental Aeroelastic Wing Flutter Analysis and Suppression." International Journal of Structural Stability and Dynamics 15, no. 06 (June 17, 2015): 1450084. http://dx.doi.org/10.1142/s0219455414500849.
Full textAbstract:
Aeroelastic response and control of airfoil-flap wing exposed to unsteady aerodynamic loads is addressed. The aim is to suppress flutter and to maintain stability of the system. The analytical aerodynamic model is featuring plunging–pitching–flapping coupled motion. Both linear and nonlinear models are developed. Linear quadratic regulator theory is used to design a full state feedback controller in state-space. The control law is implemented through the flap torque to suppress flutter instability and enhance the aeroelastic response. The system response is investigated when it is flying beyond the flutter speed and the control is delayed by a few seconds. The effects of aircraft propeller excitation and the variation of the aspect ratio on the intitiation of flutter are investigated. Numerical simulations are complemented by experimental measurements in a wind tunnel for NACA0012 airfoil.
39
Peng, Zhi Ling. "The Research on Aeroelasticity of the Vehicle Wing Surface." Advanced Materials Research 284-286 (July 2011): 2456–60. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.2456.
Full textAbstract:
By taking high aspect ratio straight wing as the research object, static aerodynamic force and dynamic aerodynamic force are detailed analysed and researched. The flutter speed of panel derived from Unsteady Theory and Theory.
40
Simpson, A. "Real actuator effects and the aerodynamic energy method." Aeronautical Journal 92, no. 912 (February 1988): 77–83. http://dx.doi.org/10.1017/s0001924000021916.
Full textAbstract:
Summary The aerodynamic energy method provides a means of flutter-suppression control-law design based wholly on oscillatory aerodynamic forces on a notional structure with notional normal vibration modes. The method has been proposed as a means of flutter suppression regardless of structural considerations, other than those mentioned. As originally conceived, the method is based upon the assumption of totally irreversible active controls. In this paper, the effects of finite impedance of actuators on the implementation of the method are investigated analytically. The conclusions do not augur well for the method.
41
Yang, Yongxin, Yaojun Ge, Rui Zhou, Shiguo Chen, and Lihai Zhang. "Aerodynamic Countermeasure Schemes of Super Long-Span Suspension Bridges with Various Aspect Ratios." International Journal of Structural Stability and Dynamics 20, no. 05 (May 2020): 2050061. http://dx.doi.org/10.1142/s0219455420500613.
Full textAbstract:
The purpose of this study is to investigate the flutter control scheme of super long-span bridges with various aspect ratios (e.g. width to height (B/H)) using passive aerodynamic countermeasures. Through a series of wind tunnel testing and theoretical analysis, three types of passive aerodynamic countermeasures, i.e. vertical central stabilizer (VCS), wind barrier and inspection rail, were investigated for five typical aspect ratios of a closed-box girder bridge. The results show that both the aspect ratio and flutter critical wind speed generally increase with the decrease of the ratio of torsional and vertical frequencies of the bridge. In the case of an aspect ratio of 8.9, a downward VCS (DVCS) has a much better flutter performance than that of an upward VCS (UVCS) because aerodynamic damping of Part A and Part D could produce a higher heaving degree of freedom (DOF) participation level. Furthermore, the position variation of wind barriers is superior to their shape variation for the bridge with an aspect ratio of 8.3, and the flutter performance of the girder with a combination of the wind barrier (WB3P3) and UDVCS with 0.3[Formula: see text]h/H DVCS appears to be better than that without countermeasures. In addition, the installation of an inspection rail near the bottom point of an inclined-web (IR3) has the best flutter control effect among four positions of inspection rails.
42
Yu, Mei, Hai Li Liao, Ming Shui Li, Cun Ming Ma, and Ming Liu. "Analysis of Flutter Stability of the Xihoumen Bridge in the Completed Stage." Advanced Materials Research 243-249 (May 2011): 1629–33. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.1629.
Full textAbstract:
Aerodynamic stability is an issue in the wind-resistant design of long-span bridges, flutter is an aerodynamic instability phenomenon that occurs due to interactions between wind and structural motion. The Xihoumen Bridge is the second long suspension bridge in the world, the aeroelastic performance of the Xihoumen Bridge is investigated by wind tunnel testing and an analytical approach. In the case, wind-tunnel testing was performed using an aeroelastic full model of the bridge, and two section models of the bridge. Flutter derivatives of bridge decks are routinely extracted from wind tunnel section model experiments for the assessment of performance against wind loading, the analytical method used here were a two-dimensional flutter analysis and a multi-mode analysis in the frequency domain. The analytical results were compared with the wind tunnel test data; it showed that the flutter analysis results were good agreement with the wind-tunnel test data.
43
Wang, Feng, Chuan Xiong, Zijian Wang, Congmin Guo, Hua Bai, and Jiawu Li. "A Quick Assessment and Optimization Method for a Flutter Aerodynamic Measure of a Typical Flat Box Girder." Shock and Vibration 2020 (August 12, 2020): 1–11. http://dx.doi.org/10.1155/2020/8823921.
Full textAbstract:
Flutter is one of the most serious wind-induced vibration phenomena for long-span bridges and may cause the collapse of a bridge (e.g., the Old Tacoma Bridge, 1940). The selection and optimization of flutter aerodynamic measures are difficult in wind tunnel tests. It usually takes a long time and consumes more experimental materials. This paper presents a quick assessment and design optimization method for the flutter stability of a typical flat box girder of the long-span bridges. Numerical analysis could provide a reference for wind tunnel tests and improve the efficiency of the test process. Based on the modal energy exchange in the flutter microvibration process, the global energy input and local energy input are analyzed to investigate the vibration suppression mechanism of a flat steel box girder with an upper central stabilizer. Based on the comparison between the experimental and numerical data, a quick assessment method for the optimization work is proposed. It is practical to predict the effects of flutter suppression measures by numerical analysis. Thus, a wind tunnel test procedure for flutter aerodynamic measures is proposed which could save time and experimental materials.
44
Chi, R. M., and A. V. Srinivasan. "Some Recent Advances in the Understanding and Prediction of Turbomachine Subsonic Stall Flutter." Journal of Engineering for Gas Turbines and Power 107, no. 2 (April 1, 1985): 408–17. http://dx.doi.org/10.1115/1.3239741.
Full textAbstract:
In this paper, some recent advances in the understanding and prediction of subsonic flutter of jet engine fan rotor blades are reviewed. Among the topics discussed are (i) the experimental evidence of mistuning in flutter responses, (ii) new and promising unsteady aerodynamic models for subsonic stall flutter prediction, (iii) an overview of flutter prediction methodologies, and (iv) a new research effort directed toward understanding the mistuning effect on subsonic stall flutter of shrouded fans. A particular shrouded fan of advanced design is examined in the detailed technical discussion.
45
Zhou, Jian, Minglong Xu, and Wei Xia. "Passive Suppression of Panel Flutter Using a Nonlinear Energy Sink." International Journal of Aerospace Engineering 2020 (July 11, 2020): 1–14. http://dx.doi.org/10.1155/2020/8896744.
Full textAbstract:
A nonlinear energy sink (NES) is used to suppress panel flutter. A nonlinear aeroelastic model for a two-dimensional flat panel with an NES in supersonic flow is established using the Galerkin method. First-order piston aerodynamic theory is adopted to build the aerodynamic load. The effects of NES parameters on flutter boundaries of the panel are investigated using Lyapunov’s indirect method. The mechanism of the NES suppression of panel flutter is studied through energy analysis. Effects of NES parameters on aeroelastic responses of the panel are obtained, and a design technique is adopted to find a suitable combination of parameter values of the NES that suppresses the panel flutter effectively. Results show that the NES can increase or reduce the onset dynamic pressure of the panel flutter and it can reduce the aeroelastic response amplitude effectively within a certain range of dynamic pressure behind the onset dynamic pressure. The installation position of the NES depends on the direction of the airflow. The robust characteristics should be considered to find the suitable combination of parameter values of the NES.
46
Majidi-Mozafari, Kazem, Reza Bahaadini, Ramin Bahaadini, Faramarz Abbasi, and Hanif Maghzi. "Static and Dynamic Analyses of Nanocomposite Plates in Mechanical and Aerodynamic Loading." International Journal of Applied Mechanics 12, no. 03 (April 2020): 2050034. http://dx.doi.org/10.1142/s1758825120500349.
Full textAbstract:
In this paper, flutter and divergence instabilities of functionally graded porous plate strip reinforced with graphene nanoplatelets in supersonic flow and subjected to an axial loading are studied. The graphene nanoplatelets are distributed in the matrix either uniformly or non-uniformly along the thickness direction. Four graphene nanoplatelets distribution patterns namely, Patterns A through D are considered. Based on the modified Halpin–Tsai micromechanics model and the rule of mixture, the effective material properties of functionally graded plate strip reinforced with graphene nanoplatelets are obtained. The aerodynamic pressure is considered in accordance with the quasi-steady supersonic piston theory. To transform the governing equations of motion to a general eigenvalue problem, the Galerkin method is employed. The flutter aerodynamic pressure and stability boundaries are determined by solving standard complex eigenvalue problem. The effects of graphene nanoplatelets distributions, graphene nanoplatelets weight fraction, geometry of graphene nanoplatelets, porosity coefficient and porosity distributions on the flutter and divergence instabilities of the system are studied. The results show that the plate strip with symmetric distribution pattern (stiffness in the surface areas) and GPLs pattern A predict the highest stable area. The flutter and divergence regions decrease as the porosity coefficient increases. Besides, the critical aerodynamic loads increase by adding a small amount of GPL to the matrix.
47
F., Promio Charles, Raja Samikkannu, Niranjan K. Sura, and Shanwaz Mulla. "System identification-based aeroelastic modelling for wing flutter." Aircraft Engineering and Aerospace Technology 90, no. 2 (March 5, 2018): 261–69. http://dx.doi.org/10.1108/aeat-08-2016-0122.
Full textAbstract:
Purpose Ground vibration testing (GVT) results can be used as system parameters for predicting flutter, which is essential for aeroelastic clearance. This paper aims to compute GVT-based flutter in time domain, using unsteady air loads by matrix polynomial approximations. Design/methodology/approach The experimental parameters, namely, frequencies and mode shapes are interpolated to build an equivalent finite element model. The unsteady aerodynamic forces extracted from MSC NASTRAN are approximated using matrix polynomial approximations. The system matrices are condensed to the required shaker location points to build an aeroelastic reduced order state space model in SIMULINK. Findings The computed aerodynamic forces are successfully reduced to few input locations (optimal) for flutter simulation on unknown structural system (where stiffness and mass are not known) through a case study. It is demonstrated that GVT data and the computed unsteady aerodynamic forces of a system are adequate to represent its aeroelastic behaviour. Practical implications Airforce of every nation continuously upgrades its fleet with advanced weapon systems (stores), which demands aeroelastic flutter clearance. As the original equipment manufacturers does not provide the design data (stiffness and mass) to its customers, a new methodology to build an aeroelastic system of unknown aircraft is devised. Originality/value A hybrid approach is proposed, involving GVT data to build an aeroelastic state space system, using rationally approximated air loads (matrix polynomial approximations) computed on a virtual FE model for ground flutter simulation.
48
Shiau, L. C., and S. Y. Kuo. "Nonlinear Panel Flutter of Composite Sandwich Plates with Thermal Effect." Journal of Mechanics 24, no. 2 (June 2008): 179–88. http://dx.doi.org/10.1017/s1727719100002215.
Full textAbstract:
ABSTRACTBy considering the total transverse displacement of a sandwich plate as the sum of the displacement due to bending of the plate and that due to shear deformation of the core, a high precision higher order triangular plate element is developed for the nonlinear panel flutter analysis of thermally buckled sandwich plates. Von Karman large deformation assumptions and quasi-steady aerodynamic theory are employed for the analysis. Newmark numerical time integration method is applied to solve the nonlinear governing equations in time domain. Results show that temperature will increase both the maximum displacement and motion speed of the plate. But the maximum displacement and velocity of the plate will not vary much with the aerodynamic pressure. Buckle pattern change phenomenon occurred in some specific case will increase the flutter boundary and change the flutter motion type of the plate. Temperature gradient increases the overall stiffness of the plate, which in turn stabilizes the sandwich panel and increases the flutter boundary of the plate.
49
Makihara, Kanjuro, and Shigeru Shimose. "Supersonic Flutter Utilization for Effective Energy-Harvesting Based on Piezoelectric Switching Control." Smart Materials Research 2012 (May 14, 2012): 1–10. http://dx.doi.org/10.1155/2012/181645.
Full textAbstract:
The harvesting of electrical energy generated from the flutter phenomenon of a plate wing is studied using the quasi-steady aerodynamic theory and the finite element method. The example of supersonic flutter structure comes from sounding rockets’ wings. Electrical energy is harvested from supersonic flutter by using piezoelectric patches and switching devices. In order to evaluate the harvesting performance, we simulate flutter dynamics of the plate wing to which piezoelectric patches are attached. We demonstrate that our harvesting system can generate much more electrical energy from wing flutter than conventional harvesting systems can. This flutter utilization changes our perception to a useful one in various fruitful applications from a destructive phenomenon.
50
Iyas, Mahzan Muhammad, Muhamad Sallehuddin, Mat Ali Mohamed Sukri, and Mansor Mohd Shuhaimi. "Wind Tunnel Testing of Composite Wing Flutter Speed due to Control Surface Excitation." Applied Mechanics and Materials 315 (April 2013): 359–63. http://dx.doi.org/10.4028/www.scientific.net/amm.315.359.
Full textAbstract:
Flutter is a dynamic instability problem represents the interaction among aerodynamic forces and structural stiffness during flight. The study was conducted to investigate whether deflecting the control surface will affect the flutter speed and the flutter frequency. A wind tunnel test was performed using a flat plate wing made of composite material. It was found that by deflecting the control surface at 45°, the wing entered flutter state at wind speed of 28.1 m/s instead of 33.4 m/s. In addition, the flutter frequency also reduced from 224.52 Hz to 198.96 Hz. It was concluded that by deflecting the control surface, the wing experienced flutter at lower speed and frequency.