Relevant bibliographies by topics / Aerodynamic flutter

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  2. Dissertations / Theses
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Academic literature on the topic 'Aerodynamic flutter'

Author: Grafiati
Published: 4 June 2021
Last updated: 15 February 2022

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Journal articles on the topic "Aerodynamic flutter"

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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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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.

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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.
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Dissertations / Theses on the topic "Aerodynamic flutter"

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PENNACHIONI, M. "ROTATING AERODYNAMIC- EXCITERS for in-flight flutter testing." International Foundation for Telemetering, 1985. http://hdl.handle.net/10150/615759.

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International Telemetering Conference Proceedings / October 28-31, 1985 / Riviera Hotel, Las Vegas, Nevada
Telemetering, as used in in-flight testing, has several advantages including that of allowing what is known as real-time utilization; and thereby, in certain specific cases, the continuation of the flight programme in terms of the results obtained therein. This feature is especially attractive during the opening of the aircraft’s flutter envelope. It then becomes a matter of experimentally determining the aircraft’s aeroelastic stability throughout its flight envelope, and specifically at high speeds. In this connection, it’s common knowledge that in excess of a certain so-called critical speed, two or more vibratory modes of the structure can become coupled via the aerodynamic forces they respectively generate; and can lead to diverging oscillation liable to cause vibration failure. It’s easy to see that such a critical speed must be well within the permitted aircraft operation envelope and that approaching it during in-flight testing should only be considered with a certain amount of prudence and subject to strict monitoring of the structure’s behaviour. The most widely used monitoring system is to measure the transfer function relating an alternating force applied to the aircraft structure in flight to the displacements it causes at different points of that structure (figure 1). Progress in the flight envelope is made in speed steps, any variations in this transfer function being monitored between steps, and usually being reflected in terms of vibration frequencies and damping. Using telemetering, as in conducting these tests, is beneficial in several respects (figure 2). First it allows instant visual monitoring of the structure’s behaviour at its most significant points (rudders, bearing surface ends) by a team conveniently arranged on the ground. Then, further to a preliminary processing operation occurring in real-time, the test can be validated by merely observing the spectrums and the coherence functions existing between the forces applied and the structure’s response; a poor quality test, either due to a mismatched excitation or to the unexpected effect of an atmospheric turbulence, can be rerun without waiting for the aircraft to land. Finally, if adequate computing facilities are available, a comprehensive utilization of the values measured and their identification with a theoretical model lets the structure’s general behaviour be compared with the estimated figures, and thereby lets the aircraft resume the same test sequence at a higher speed or Mach number. The accuracy of the result and the speed at which it is obtained, so essential to the safe resumption of the flight, primarily depend on the extent and on the adequacy of the available information on the artificially applied forces. The design of “exciters” capable of creating controlled and measurable forces of an adequate level is thus the most vital constraint of the flutter testing facility.
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Saini, Manjinder. "Experimental and computational study of airfoil load alteration using oscillating fence actuator." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663059971&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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Al-Assaf, Adel. "Flutter analysis of open-truss stiffened suspension bridges using synthesized aerodynamic derivatives." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/Al_Assaf_122306.pdf.

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Wang, Zhida. "Experimental and CFD Investigations of the Megane Multi-box Bridge Deck Aerodynamic Characteristics." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32209.

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The shape of bridge deck sections used for long-span suspension bridges has evolved through the years, from the compact box deck girders, to twin box and multi-box decks sections, which proved to have better aerodynamic behaviour, and to bring economic advantages on the construction material usage side. This thesis presents a study of a new type of multi-box bridge deck for the Megane Bridge, consisting of two side decks for traffic lanes, and two middle decks for railway traffic, connected using stabilizing beams. Aerodynamic static force coefficient measurements were performed on a section model with a scale of 1:80, for Reynolds numbers up to 5.1 × 105 under angles of attack from -10° to 10°. Also there-dimensional CFD simulations were performed by employing a Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for Re = 9.3 × 107 and angles of attack 𝛼= -4°, -2°, 0°, 2° and 4°. The experimental and numerical results were compared with respect to accuracy, sensitivity, and practical suitability. Furthermore, the aerodynamic character for each individual decks including static coefficients, wind flow pattern and pressure distribution were studied through CFD simulation. ILS (Iterative Least Squares) method was applied to extract the flutter derivatives of Megane section model based on the results obtained from free vibration tests for evaluating the flutter stability. A comparison of the flutter derivatives was carried out between bridges with different deck configurations and the results are included in this thesis.
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Thake, Michael P. "Effect of mistuning on bending-torsion flutter using a compressible time-domain aerodynamic theory." Connect to resource, 2009. http://hdl.handle.net/1811/38781.

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Karadal, Fatih Mutlu. "Active Flutter Suppression Of A Smart Fin." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609830/index.pdf.

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This study presents the theoretical analysis of an active flutter suppression methodology applied to a smart fin. The smart fin consists of a cantilever aluminum plate-like structure with surface bonded piezoelectric (PZT, Lead- Zirconate-Titanate) patches. A thermal analogy method for the purpose of modeling of piezoelectric actuators in MSC®
/NASTRAN based on the analogy between thermal strains and piezoelectric strains was presented. The results obtained by the thermal analogy were compared with the reference results and very good agreement was observed. The unsteady aerodynamic loads acting on the structure were calculated by using a linear two-dimensional Doublet-Lattice Method available in MSC®
/NASTRAN. These aerodynamic loads were approximated as rational functions of the Laplace variable by using one of the aerodynamic approximation schemes, Roger&
#8217
s approximation, with least-squares method. These approximated aerodynamic loads together with the structural matrices obtained by the finite element method were used to develop the aeroelastic equations of motion of the smart fin in state-space form. The Hinf robust controllers were then designed for the state-space aeroelastic model of the smart fin by considering both SISO (Single-Input Single-Output) and MIMO (Multi-Input Multi-Output) system models. The verification studies of the controllers showed satisfactory flutter suppression performance around the flutter point and a significant improvement in the flutter speed of the smart fin was also observed.
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Monaco, Lucio. "PARAMETRIC STUDY OF THE EFFECT OF BLADE SHAPE ON THE PERFORMANCE OF TURBOMACHINERY CASCADES : PART III A: AERODYNAMIC DAMPING BEHAVIOUR – COMPRESSOR PROFILES." Thesis, KTH, Kraft- och värmeteknologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-131210.

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McHugh, Garrett R. "An Experimental Investigation in the Mitigation of Flutter Oscillation Using Shape Memory Alloys." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1479119992818089.

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Stasolla, Vincenzo. "Numerical analysis of aerodynamic damping in a transonic compressor." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-264359.

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Aeromechanics is one of the main limitations for more efficient, lighter, cheaper and reliable turbomachines, such as steam or gas turbines, as well as compressors and fans. In fact, aircraft engines designed in the last few years feature more slender, thinner and more highly loaded blades, but this trend gives rise to increased sensitivity for vibrations induced by the fluid and result in increasing challenges regarding structural integrity of the engine. Forced vibration as well as flutter failures need to be carefully avoided and an important parameter predicting instabilities in both cases is the aerodynamic damping. The aim of the present project is to numerically investigate aerodynamic damping in the first rotor of a transonic compressor (VINK6). The transonic flow field leads to a bow shock at each blade leading edge, which propagates to the suction side of the adjacent blade. This, along with the fact that the rotating blade row vibrates in different mode shapes and this induces unsteady pressure fluctuations, suggests to evaluate unsteady flow field solutions for different cases. In particular, the work focuses on the unsteady aerodynamic damping prediction for the first six mode shapes. The aerodynamic coupling between the blades of this rotor is estimated by employing a transient blade row model set in blade flutter case. The commercial CFD code used for these investigations is ANSYS CFX. Aerodynamic damping is evaluated on the basis of the Energy Method, which allows to calculate the logarithmic decrement employed as a stability parameter in this study. The least logarithmic decrement values for each mode shape are better investigated by finding the unsteady pressure distribution at different span locations, indication of the generalized force of the blade surface and the local work distribution, useful to get insights into the coupling between displacements and consequent generated unsteady pressure. Two different transient methods (Time Integration and Harmonic Balance) are employed showing the same trend of the quantities under consideration with similar computational effort. The first mode is the only one with a flutter risk, while the higher modes feature higher reduced frequencies, out from the critical range found in literature. Unsteady pressure for all the modes is quite comparable at higher span locations, where the largest displacements are prescribed, while at mid-span less comparable values are found due to different amplitude and direction of the mode shape. SST turbulence model is analyzed, which does not influence in significant manner the predictions in this case, with respect to the k-epsilon model employed for the whole work. Unsteady pressure predictions based on the Fourier transformation are validated with MATLAB codes making use of Fast Fourier Transform in order to ensure the goodness of CFX computations. Convergence level and discrepancy in aerodamping values are stated for each result and this allows to estimate the computational effort for every simulation and the permanent presence of numerical propagation errors.
Aeromekanik är en av huvudbegränsningarna för mer effektiva, lättare, billigare och mer pålitliga turbomaskiner, som ångturbiner, gasturbiner, samt kompressorer och fläktar. I själva verket har flygplansmotorer som designats under de senaste åren har fått tunnare och mer belastade skovlar, men denna trend ger upphov till ökad känslighet för aeromekaniska vibrationer och resulterar i ökande utmaningar när det gäller motorns strukturella integritet. Aerodynamiskt påtvingade vibrationer såväl som fladder måste predikteras noggrant för att kunna undvikas och en viktig parameter som förutsäger instabilitet i båda fallen är den aerodynamiska dämpningen. Syftet med det aktuella projektet är att numeriskt undersöka aerodynamisk dämpning i den första rotorn hos en transonisk kompressor (VINK6). Det transoniska flödesfältet leder till en bågformad stötvåg vid bladets främre kant, som sprider sig till sugsidan på det intilliggande bladet. I och med detta, tillsammans med det faktum att den roterande bladraden vibrerar i olika modformer och detta inducerar instationära tryckfluktuationer, syftar detta arbete på att utvärdera flödesfältslösningar för olika fal. I synnerhet fokuserar arbetet på prediktering av den instationära aerodynamiska dämpningen för de första sex modformen. Den aerodynamiska kopplingen mellan bladen hos denna rotor uppskattas genom att använda en transient bladradmodell uppsatt för fladderberäkningen. Den kommersiella CFD-koden som används för denna utredning är ANSYS CFX. Aerodynamisk dämpning utvärderas med hjälp av energimetoden, som gör det möjligt att beräkna den logaritmiska minskningen som används som en stabilitetsparameter i denna studie. De minsta logaritmiska dekrementvärdena för varje modform undersöks bättre genom att hitta den ostadiga tryckfördelningen på olika spannpositioner, som är en indikering av den lokala arbetsfördelningen, användbar för att få insikt i kopplingen mellan förskjutningar och därmed genererat ostabilt tryck. Två olika transienta metoder används som visar samma trend för de kvantiteter som beaktas med liknande beräkningsinsatser. Den första modformen är den enda med en fladderrisk, medan de högre modformerna har högre reducerade frekvenser, och ligger utanför det kritiska intervallet som finns i litteraturen. Instationärt tryck för alla moder är ganska jämförbart på de högre spannpositioner, där de största förskjutningarna föreskrivs, medan runt midspannet finns mindre jämförbara värden på grund av olika amplitud och riktning för modformen. SSTturbulensmodellen analyseras, som i detta fall inte påverkar predikteringen på ett betydande sätt. Det predikterade instationära trycket baserad på Fourier-transformationen valideras med MATLAB-koder som använder sig av Fast Fourier Transform för att säkerställa noggrannheten hos CFX-beräkningar. Konvergensnivå och skillnader i aerodämpningsvärden anges för varje resultat och detta gör det möjligt att uppskatta beräkningsinsatsen för varje simulering och uppskatta utbredningen av det numeriska felet.
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Glodic, Nenad. "Sensitivity of Aeroelastic Properties of an Oscillating LPT Cascade." Licentiate thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123504.

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Modern turbomachinery design is characterized by a tendency towards thinner, lighter and highly loaded blades, which in turn gives rise to increased sensitivity to flow induced vibration such as flutter. Flutter is a self-excited and self-sustained instability phenomenon that may lead to structural failure due to High Cycle Fatigue (HCF) or material overload. In order to be able to predict potential flutter situations, it is necessary to accurately assess the unsteady aerodynamics during flutter and to understand the physics behind its driving mechanisms. Current numerical tools used for predicting unsteady aerodynamics of vibrating turbomachinery components are capable of modeling the flow field at high level of detail, but may fail in predicting the correct unsteady aerodynamics under certain conditions. Continuous validation of numerical models against experimental data therefore plays significant role in improving the prediction accuracy and reliability of the models.   In flutter investigations, it is common to consider aerodynamically symmetric (tuned) setups. Due to manufacturing tolerances, assembly inaccuracies as well as in-service wear, the aerodynamic properties in a blade row may become asymmetric. Such asymmetries can be observed both in terms of steady as well as unsteady aerodynamic properties, and it is of great interest to understand the effects this may have on the aeroelastic stability of the system.   Under certain conditions vibratory modes of realistic blade profiles tend to be coupled i.e. the contents of a given mode of vibration include displacements perpendicular and parallel to the chord as well as torsion of the profile. Current design trends for compressor blades that are resulting in low aspect ratio blades potentially reduce the frequency spacing between certain modes (i.e. 2F & 1T). Combined modes are also likely to occur in case of the vibration of a bladed disk with a comparatively soft disk and rigid blades or due to tying blades together in sectors (e.g. in turbines).   The present investigation focuses on two areas that are of importance for improving the understanding of aeroelastic behavior of oscillating blade rows. Firstly, aeroelastic properties of combined mode shapes in an oscillating Low Pressure Turbine (LPT) cascade were studied and validity of the mode superposition principle was assessed. Secondly, the effects of aerodynamic mistuning on the aeroelastic properties of the cascade were addressed. The aerodynamic mistuning considered here is caused by blade-to-blade stagger angle variations   The work has been carried out as compound experimental and numerical investigation, where numerical results are validated against test data. On the experimental side a test facility comprising an annular sector of seven free-standing LPT blades is used. The aeroelastic response phenomena were studied in the influence coefficient domain where one of the blades is made to oscillate in three-dimensional pure or combined modes, while the unsteady blade surface pressure is acquired on the oscillating blade itself and on the non-oscillating neighbor blades. On the numerical side, a series of numerical simulations were carried out using a commercial CFD code on a full-scale time-marching 3D viscous model. In accordance with the experimental part the simulations are performed using the influence coefficient approach, with only one blade oscillating.   The results of combined modes studies suggest the validity of combining the aeroelastic properties of two modes over the investigated range of operating parameters. Quality parameters, indicating differences in mean absolute and imaginary values of the unsteady response between combined mode data and superposed data, feature values that are well below measurement accuracy of the setup.   The findings of aerodynamic mistuning investigations indicate that the effect of de-staggering a single blade on steady aerodynamics in the cascade seem to be predominantly an effect of the change in passage throat. The changes in steady aerodynamics are thereby observed on the unsteady aerodynamics where distinctive effects on flow velocity lead to changes in the local unsteady pressure coefficients. In order to assess the overall aeroelastic stability of a randomly mistuned blade row, a Reduced Order Model (ROM) model is introduced, allowing for probabilistic analyses. From the analyses, an effect of destabilization due to aero-asymmetries was observed. However the observed effect was of moderate magnitude.

QC 20130610


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Books on the topic "Aerodynamic flutter"

1

James P. Smith - undifferentiated. X-38 vehicle 131 flutter assessment. [Houston, Tex.]: National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, 1997.

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James P. Smith - undifferentiated. X-38 vehicle 131 flutter assessment. [Houston, Tex.]: Lyndon B. Johnson Space Center, 1997.

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James P. Smith - undifferentiated. X- 38 vehicle 131 flutter assessment. Washington, D.C: National Aeronautics and Space Administration, 1997.

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James P. Smith - undifferentiated. X-38 vehicle 131 flutter assessment. [Houston, Tex.]: National Aeronautics and Space Administration, Lyndon B. Johnson Space Center, 1997.

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Nissim, E. Design of control laws for flutter suppression based on the aerodynamic energy concept and comparisons with other design methods. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1990.

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Nissim, E. Effect of control surface mass unbalance on the stability of a closed-loop active control system. [Washington, DC]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1989.

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Nissim, E. Control surface spanwise placement in active flutter suppression systems. [Washington, DC]: National Aeronautics and Space Administration, Scientific and Technical Information Division, 1989.

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Scott, Robert C. A method of predicting quasi-steady aerodynamics for flutter analysis of high speed vehicles using steady CFD calculations. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1993.

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Thompson, Scott A. Surface pressure distributions on a delta wing undergoing large amplitude pitching oscillations. Notre Dame, Ind: Dept. of Aerospace and Mechanical Engineering, University of Notre Dame, 1990.

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Kehoe, M. W. Aircraft flight flutter testing at the NASA Ames-Dryden Flight Research Facility. Edwards, Calif: National Aeronautics and Space Administration, Ames Research Center, Dryden Flight Research Facility, 1988.

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Book chapters on the topic "Aerodynamic flutter"

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Kurniawan, Riccy. "Flutter Analysis of an Aerofoil Using State-Space Unsteady Aerodynamic Modeling." In Transactions on Engineering Technologies, 141–48. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-017-8832-8_11.

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Piscitelle, Louis J. "Dynamical Systems Analysis of an Aerodynamic Decelerator: Bifurcation to Divergence and Flutter." In NATO ASI Series, 161–64. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4899-1609-9_27.

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Arena, Andrew S., and Kajal K. Gupta. "Expediting time-marching supersonic flutter prediction through a combination of CFD and aerodynamic modeling techniques." In Fifteenth International Conference on Numerical Methods in Fluid Dynamics, 268–73. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/bfb0107113.

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Merrett, Craig G., and Harry H. Hilton. "Linear Aero-Thermo-Servo-Viscoelasticity, Part II: Dynamic Considerations: Lifting Surface and Panel Flutter and Aerodynamic Noise." In Encyclopedia of Thermal Stresses, 2737–44. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-007-2739-7_909.

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Smati, L., S. Aubert, P. Ferrand, and F. Massão. "Comparison of Numerical Schemes to Investigate Blade Flutter." In Unsteady Aerodynamics and Aeroelasticity of Turbomachines, 749–63. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5040-8_49.

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Clarkson, J. D., J. A. Ekaterinaris, and M. F. Platzer. "Computational Investigation of Airfoil Stall Flutter." In Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines and Propellers, 415–32. New York, NY: Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4613-9341-2_21.

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Shibata, Takanori, and Shojiro Kaji. "Role of Shock Structures in Transonic Fan Rotor Flutter." In Unsteady Aerodynamics and Aeroelasticity of Turbomachines, 733–47. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5040-8_48.

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Kaji, Shojiro. "Transonic Cascade Flutter in Combined Bending-Chordwise Translational Mode." In Unsteady Aerodynamics and Aeroelasticity of Turbomachines, 783–95. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5040-8_51.

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Chiang, Hsiao-Wei D., and Sanford Fleeter. "Splitter Blades for Passive Turbomachine Flutter Control." In Unsteady Aerodynamics, Aeroacoustics, and Aeroelasticity of Turbomachines and Propellers, 807–28. New York, NY: Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4613-9341-2_41.

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Sayma, A. I., M. Vahdati, J. S. Green, and M. Imregun. "Whole-Assembly Flutter Analysis of a Low Pressure Turbine Blade." In Unsteady Aerodynamics and Aeroelasticity of Turbomachines, 347–59. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5040-8_23.

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Conference papers on the topic "Aerodynamic flutter"

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Borgueta, Samuel J., Nicholas R. Bach, Jared J. Correia, Brendan G. J. Egan, Joshua S. Horton, James E. Lipsett, and Raymond N. Laoulache. "Aerodynamic Flutter of Turbine Brush Seals." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-73500.

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With global energy demands continually growing and environmental impacts a major concern in power production, maximizing the efficiencies of power plants is of top priority. EthosEnergy2 has sponsored a project at the University of Massachusetts Dartmouth to study and analyze the brush seals in steam turbines in pursuit of increasing steam turbine thermodynamic efficiency. Brush seals are incorporated circumferentially around the turbine blades in their housing. The brush seals provide a very minimal clearance height that compensates for start-up rotor deviation and minimizes high-pressure steam blow-by around the edges of the blades. Brush seals minimize the clearance height between the blades and housing, which allows the turbine to produce more work. However, overtime brush seals can be damaged, greatly reducing efficiency. The seals that are repeatedly showing excessive wear and damage, occur in the high-pressure sections of steam turbines with high Reynolds numbers. The bristle breakdown is attributed to high Reynolds numbers and aerodynamic flutter. The purpose of this research is to design a prototype and empirically model steam turbine conditions with air to map out the fluid-solid interaction, determine the modes of bristle failure, and ultimately reproduce and record bristle flutter. A pressure vessel and pressure system was designed to test linear strips of brush seals with air as the working fluid. The pressure vessel accommodates varying clearance heights to identify the correlation of clearance height and the effects on fluid flow. The system also incorporates a high-speed camera that can capture the phenomena of flutter, precisely identify the modes of failure, and record fluid-solid interaction and the interaction of the bristles with each other. Designing a prototype to empirically model this problem serves as a fundamental and critical step in understanding the fluid interaction with seals in high-pressure steam turbines and will identify brush seal modes of failure. The prototype’s ability to model steam turbine conditions and rapidly test various seal designs will facilitate better brush seal designs to be constructed and will ultimately increase the thermal efficiencies of steam turbines, aid in accommodating the increase in global energy demands, and reduce the detrimental environmental impacts of producing power. The system successfully produced and recorded brush-seal-bristle flutter while modeling high-pressure steam turbine conditions. Matching Reynolds and Euler numbers of the steam turbine stages provided the ability to scale the steam turbine to our prototype, with air as the working fluid. Brush seal breakdown was occurring in steam turbines at Reynolds numbers above 20,000. The prototype repeatedly produced brush seal flutter at Reynolds numbers above 25,000, validating the theory that brush seal breakdown is dependent predominantly on the Reynolds number.
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Gadsden, S. A., and S. Habibi. "Aerodynamic Flutter and Flight Surface Actuation." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41897.

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This paper proposes a novel form of impedance control in order to reduce the effects of aerodynamic flutter on a flight surface actuator. The forces generated by small amplitude flutter were studied on an electrohydrostatic actuator (EHA). The effects of flutter were modeled and analyzed. Through analysis, it was found that in EHA systems, two parameters would impact the response of flutter: damping (B) of the mechanical load, and the effective bulk modulus of the hydraulic oil (βe). These can be actively controlled as proposed here in order to provide variable impedance. The results of changing these variables are discussed and presented here.
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Larsen, Allan. "Horizontal Aerodynamic Derivatives in Bridge Flutter Analysis." In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28251.

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Inclusion of a horizontal degree of freedom along with the vertical and twisting degrees of freedom has been an active area of research in bridge flutter predictions for the past three decades. While much work has been published on theoretical aspects, limited experience as to the importance of the horizontal degree of freedom is available in the literature. Three cases of actual long span bridge designs are examined with respect to the critical wind speed for onset of classical flutter. For the tree cases examined inclusion of the horizontal modes of motion had almost negligible influence on the flutter wind speed.
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Dai, Yuting, Zhang Zhang, Chao Yang, Zhigang Wu, and Anping Hou. "Unsteady Aerodynamic Uncertainty Estimation and Robust Flutter Analysis." In 29th AIAA Applied Aerodynamics Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2011. http://dx.doi.org/10.2514/6.2011-3517.

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He, Sicheng, Eirikur Jonsson, Charles A. Mader, and Joaquim R. R. A. Martins. "Aerodynamic Shape Optimization with Time Spectral Flutter Adjoint." In AIAA Scitech 2019 Forum. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2019. http://dx.doi.org/10.2514/6.2019-0697.

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SPARA, KAREN, and SANFORD FLEETER. "Supersonic turbomachine rotor flutter control by aerodynamic detuning." In 25th Joint Propulsion Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1989. http://dx.doi.org/10.2514/6.1989-2685.

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Ekici, Kivanc, Robert Kielb, and Kenneth Hall. "The Effect of Aerodynamic Asymmetries on Turbomachinery Flutter." In 47th AIAA Aerospace Sciences Meeting including The New Horizons Forum and Aerospace Exposition. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2009. http://dx.doi.org/10.2514/6.2009-893.

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Ji, Chen, Ziqiang Liu, Nong Chen, and Li Feng. "Development of a Hypersonic Flutter Test Capability." In 32nd AIAA Aerodynamic Measurement Technology and Ground Testing Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-3820.

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Goldman, Benjamin D., and Earl Dowell. "Flutter Analysis of the Thermal Protection Layer on the NASA HIAD." In AIAA Aerodynamic Decelerator Systems (ADS) Conference. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2013. http://dx.doi.org/10.2514/6.2013-1254.

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ABBAS, JEHAD, R. IBRAHIM, and RONALD GIBSON. "Nonlinear flutter of orthotropic composite panel under aerodynamic heating." In Dynamics Specialists Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1992. http://dx.doi.org/10.2514/6.1992-2132.

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Reports on the topic "Aerodynamic flutter"

1

Striz, Alfred G. Influence of Structural and Aerodynamic Modeling on Flutter Analysis and Structural Optimization. Fort Belvoir, VA: Defense Technical Information Center, June 1991. http://dx.doi.org/10.21236/ada248487.

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