Статті в журналах: "Flutter studies"

1

Gabriela, STROE, and ANDREI Irina-Carmen. "STUDIES ON FLUTTER PREDICTION." INCAS BULLETIN 4, no. 1 (March 9, 2012): 115–23. http://dx.doi.org/10.13111/2066-8201.2012.4.1.12.

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2

Khan, Abid Ali, Muhammad Arif Ashraf, Asim Shehzad, Abroon Jamal Qazi, and Imran Hayat. "Computational and experimental studies of horizontal tail flutter suppression." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 233, no. 1 (August 14, 2017): 34–43. http://dx.doi.org/10.1177/0954410017725363.

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Flutter is an extremely violent instability that may result in catastrophic failure. Thus, flutter clearance test is one of the critical phases in qualification of an aircraft’s airworthiness. During design and development process of an aircraft, flutter problems were experienced on an aerodynamic surface (horizontal tail). In order to tackle the observed problem, a number of approaches to optimize the design for flutter speed were computationally and experimentally studied and evaluated. This paper presents and discusses the outcomes of these studies. A hybrid approach based on evaluations and design change constraints has been proposed to suppress the flutter of the horizontal tail.

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3

Cosio, Francisco G., Maria Löapezgil, Antonio Goicolea, Fernando Arribas, and A. John Camm. "Electrophysiologic studies in atrial flutter." Clinical Cardiology 15, no. 9 (September 1992): 667–73. http://dx.doi.org/10.1002/clc.4960150910.

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4

Sasaki, Kenichi, Shingo Sasaki, Masaomi Kimura, Shingen Owada, Daisuke Horiuchi, Taihei Itoh, and Ken Okumura. "Electrocardiographic and Electroanatomical Studies on Flutter Waves in Typical, Counterclockwise Atrial Flutter." Journal of Arrhythmia 27, Supplement (2011): OP52_4. http://dx.doi.org/10.4020/jhrs.27.op52_4.

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5

Lobitz, Don W. "Parameter Sensitivities Affecting the Flutter Speed of a MW-Sized Blade." Journal of Solar Energy Engineering 127, no. 4 (July 12, 2005): 538–43. http://dx.doi.org/10.1115/1.2037091.

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With the current trend toward larger and larger horizontal axis wind turbines, classical flutter is becoming a more critical issue. Recent studies have indicated that for a single blade turning in still air the flutter speed for a modern 35 m blade occurs at approximately twice its operating speed (2 per rev), whereas for smaller blades (5–9 m), both modern and early designs, the flutter speeds are in the range of 3.5–6 per rev. Scaling studies demonstrate that the per rev flutter speed should not change with scale. Thus, design requirements that change with increasing blade size are producing the concurrent reduction in per rev flutter speeds. In comparison with an early small blade design (5 m blade), flutter computations indicate that the non rotating modes which combine to create the flutter mode change as the blade becomes larger (i.e., for the larger blade the second flapwise mode, as opposed to the first flapwise mode for the smaller blade, combines with the first torsional mode to produce the flutter mode). For the more modern smaller blade design (9 m blade), results show that the non rotating modes that couple are similar to those of the larger blade. For the wings of fixed-wing aircraft, it is common knowledge that judicious selection of certain design parameters can increase the airspeed associated with the onset of flutter. Two parameters, the chordwise location of the center of mass and the ratio of the flapwise natural frequency to the torsional natural frequency, are especially significant. In this paper studies are performed to determine the sensitivity of the per rev flutter speed to these parameters for a 35 m wind turbine blade. Additional studies are performed to determine which structural characteristics of the blade are most significant in explaining the previously mentioned per rev flutter speed differences. As a point of interest, flutter results are also reported for two recently designed 9 m twist/coupled blades.

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6

ILIE, Marcel, and Augustin SEMENESCU. "COMPUTATIONAL STUDIES OF AEROELASTICITY OF AIRCRAFT ENGINE TURBINE BLADE." ANNALS OF THE ACADEMY OF ROMANIAN SCIENTISTS Series on ENGINEERING SCIENCES 14, no. 2 (2022): 19–32. http://dx.doi.org/10.56082/annalsarscieng.2022.2.19.

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Transient blade loading limits the lifetime of aircraft engine turbine blades. Thus, accurate prediction of the unsteady aerodynamic loading and coupled fluid-structure interactions would improve the life the lifetime of the turbine blades. This study investigates the flutter instability of an axial turbine blade under unsteady aerodynamic loading. The viscous Navier-Stokes equations with the SST-kω turbulence model are employed. The results show that the flutter phenomenon causes unsteady oscillations of the aerodynamic coefficients lift and drag.

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7

Koch, Christopher. "Parametric whirl flutter study using different modelling approaches." CEAS Aeronautical Journal 13, no. 1 (October 6, 2021): 57–67. http://dx.doi.org/10.1007/s13272-021-00548-0.

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AbstractThis paper demonstrates the importance of assessing the whirl flutter stability of propeller configurations with a detailed aeroelastic model instead of local pylon models. Especially with the growing use of electric motors for propulsion in air taxis and commuter aircraft whirl flutter becomes an important mode of instability. These configurations often include propeller which are powered by lightweight electric motors and located at remote locations, e.g. the wing tip. This gives rise to an aeroelastic instability called whirl flutter, involving the gyroscopic whirl modes of the engine. The driving parameters for this instability are the dynamics of the mounting structure. Using a generic whirl flutter model of a propeller at the tip of a lifting surface, parameter studies on the flutter stability are carried out. The aeroelastic model consists of a dynamic MSC.Nastran beam model coupled with the unsteady ZAERO ZONA6 aerodynamic model and strip theory for the propeller aerodynamics. The parameter studies focus on the influence of different substructures (ranging from local engine mount stiffness to global aircraft dynamics) on the aeroelastic stability of the propeller. The results show a strong influence of the level of detail of the aeroelastic model on the flutter behaviour. The coupling with the lifting surface is of major importance, as it can stabilise the whirl flutter mode. Including wing unsteady aerodynamics into the analysis can also change the whirl flutter behaviour. This stresses the importance of including whirl flutter in the aeroelastic stability analysis on aircraft level.

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8

Yoshikawa, Masahiro, Kensuke Asaba, and Tomohiro Nakayama. "Causal effect of atrial fibrillation/flutter on chronic kidney disease: A bidirectional two-sample Mendelian randomization study." PLOS ONE 16, no. 12 (December 13, 2021): e0261020. http://dx.doi.org/10.1371/journal.pone.0261020.

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Chronic kidney disease (CKD) and atrial fibrillation are both major burdens on the health care system worldwide. Several observational studies have reported clinical associations between CKD and atrial fibrillation; however, causal relationships between these conditions remain to be elucidated due to possible bias by confounders and reverse causations. Here, we conducted bidirectional two-sample Mendelian randomization analyses using publicly available summary statistics of genome-wide association studies (the CKDGen consortium and the UK Biobank) to investigate causal associations between CKD and atrial fibrillation/flutter in the European population. Our study suggested a causal effect of the risk of atrial fibrillation/flutter on the decrease in serum creatinine-based estimated glomerular filtration rate (eGFR) and revealed a causal effect of the risk of atrial fibrillation/flutter on the risk of CKD (odds ratio, 9.39 per doubling odds ratio of atrial fibrillation/flutter; 95% coefficient interval, 2.39–37.0; P = 0.001), while the causal effect of the decrease in eGFR on the risk of atrial fibrillation/flutter was unlikely. However, careful interpretation and further studies are warranted, as the underlying mechanisms remain unknown. Further, our sample size was relatively small and selection bias was possible.

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9

Bandorski, Dirk, Jörn Schmitt, Claudia Kurzlechner, Damir Erkapic, Christian W. Hamm, Werner Seeger, Ardeschir Ghofrani, Reinhard Höltgen, and Henning Gall. "Electrophysiological Studies in Patients with Pulmonary Hypertension: A Retrospective Investigation." BioMed Research International 2014 (2014): 1–6. http://dx.doi.org/10.1155/2014/617565.

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Few studies have investigated patients with pulmonary hypertension and arrhythmias. Data on electrophysiological studies in these patients are rare. In a retrospective dual-centre design, we analysed data from patients with indications for electrophysiological study. Fifty-five patients with pulmonary hypertension were included (Dana Point Classification: group 1: 14, group 2: 23, group 3: 4, group 4: 8, group 5: 2, and 4 patients with exercised-induced pulmonary hypertension). Clinical data, 6-minute walk distance, laboratory values, and echocardiography were collected/performed. Nonsustained ventricular tachycardia was the most frequent indication (n=15) for an electrophysiological study, followed by atrial flutter (n=14). In summary 36 ablations were performed and 25 of them were successful (atrial flutter 12 of 14 and atrioventricular nodal reentrant tachycardia 4 of 4). Fluoroscopy time was 16±14.4 minutes. Electrophysiological studies in patients with pulmonary hypertension are feasible and safe. Ablation procedures are as effective in these patients as in non-PAH patients with atrial flutter and atrioventricular nodal reentrant tachycardia and should be performed likewise. The prognostic relevance of ventricular stimulations and inducible ventricular tachycardias in these patients is still unclear and requires further investigation.

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10

Georghiades, G. A., and J. R. Banerjee. "Flutter Prediction for Composite Wings Using Parametric Studies." AIAA Journal 35, no. 4 (April 1997): 746–48. http://dx.doi.org/10.2514/2.170.

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11

Calabria, Andrea, Davide Di Pasquale, Matteo Gnocchi, Paolo Alessandro Cozzi, Alessandro Orro, Gabriele Antonio Trombetti, and Luciano Milanesi. "Grid Based Genome Wide Studies on Atrial Flutter." Journal of Grid Computing 8, no. 4 (September 1, 2010): 511–27. http://dx.doi.org/10.1007/s10723-010-9163-y.

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12

Georghiades, G. A., and J. R. Banerjee. "Flutter prediction for composite wings using parametric studies." AIAA Journal 35 (January 1997): 746–48. http://dx.doi.org/10.2514/3.13577.

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13

Tsushima, Natsuki, Kenichi Saitoh, Hitoshi Arizono, and Kazuyuki Nakakita. "Structural and Aeroelastic Studies of Wing Model with Metal Additive Manufacturing for Transonic Wind Tunnel Test by NACA 0008 Example." Aerospace 8, no. 8 (July 25, 2021): 200. http://dx.doi.org/10.3390/aerospace8080200.

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Additive manufacturing (AM) technology has a potential to improve manufacturing costs and may help to achieve high-performance aerospace structures. One of the application candidates would be a wind tunnel wing model. A wing tunnel model requires sophisticated designs and precise fabrications for accurate experiments, which frequently increase manufacturing costs. A flutter wind tunnel testing, especially, requires a significant cost due to strict requirements in terms of structural and aeroelastic characteristics avoiding structural failures and producing a flutter within the wind tunnel test environment. The additive manufacturing technique may help to reduce the expensive testing cost and allows investigation of aeroelastic characteristics of new designs in aerospace structures as needed. In this paper, a metal wing model made with the additive manufacturing technique for a transonic flutter test is studied. Structural/aeroelastic characteristics of an additively manufactured wing model are evaluated numerically and experimentally. The transonic wind tunnel experiment demonstrated the feasibility of the metal AM-based wings in a transonic flutter wind tunnel testing showing the capability to provide reliable experimental data, which was consistent with numerical solutions.

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14

Zuhal, Lavi R., Eky Valentian Febrianto, and Duong Viet Dung. "Flutter Speed Determination of Two Degree of Freedom Model Using Discrete Vortex Method." Applied Mechanics and Materials 660 (October 2014): 639–43. http://dx.doi.org/10.4028/www.scientific.net/amm.660.639.

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This paper describes a fluid-structure interaction methodology to determine flutter speed of a two degree of freedom model. Fluid properties are calculated using a specially developed mesh-free computational fluid dynamics (CFD) method called Discrete Vortex Method (DVM). The acquired unsteady aerodynamic loads from DVM are used to calculate the flutter derivatives. The results are then used to predict the maximum allowable wind speed before flutter occurs. To test the methodology, a flutter instability analysis of a long span bridge with two degree of freedom (heaving and pitching) is performed. It is found that results obtained using the current methods are in good agreement with those obtained in previous studies.

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15

Yazdi, Ali Amin, and Jalil Rezaeepazhand. "Flutter of Perforated Metallic Plates Repaired with Cross-Ply Composite Patches." Key Engineering Materials 417-418 (October 2009): 709–12. http://dx.doi.org/10.4028/www.scientific.net/kem.417-418.709.

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This study investigates the application of laminated composite patches for enhancement of flutter behavior of perforated metallic plates repaired with an external composite patch. Due to material anisotropy and discontinuity in geometry involved in flutter analysis of repaired plates, closed form solutions are practically unobtainable. Numerical studies using commercial finite element software were conducted to investigate the effects of variation in lamination parameters on the flutter boundary of perforated plates repaired with cross-ply composite patches. Both ply-level and sub-laminate level configurations are investigated. Presented results illustrate that flutter boundaries of perforated plates can be changed by choosing proper stacking sequence for composite patches.

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16

Niu, Yaobin, Zhongwei Wang, and Weihua Zhang. "Nonlinear Thermal Flutter Analysis of Supersonic Composite Laminated Panels Using Differential Quadrature Method." International Journal of Structural Stability and Dynamics 14, no. 07 (July 24, 2014): 1450030. http://dx.doi.org/10.1142/s0219455414500308.

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In this paper, the differential quadrature method (DQM) was extended to deal with the nonlinear thermal flutter problem of supersonic composite laminated panel. Based on Hamilton's principle, the nonlinear thermal flutter model of composite panels was first established. The model adopted the von Karman large deflection plate theory for the geometrical nonlinearity, and the third order piston theory for the supersonic aerodynamic loads. Convergence and accuracy studies were carried out to verify the proposed approach. Finally, the nonlinear thermal flutter characteristics of a supersonic composite panel were studied. Uniform temperatures were first applied to the model in order to determine general heating effects on the stability of the composite panel. Owing to the varying structural stiffness of composite panels when subjected to thermal stresses, the thermal load reduced the frequency of composite panel, as well as the frequency interval between the first frequency and the second frequency; thereby hastening the flutter of composite panel. The nonlinear thermal flutter velocity ratio was decreased with respect to increasing temperature load for all aspect ratios. However, the influence of thermal loadings on flutter with various cross angles was different. Cases of unequal temperatures were considered. The average temperature load was kept constant which differs from the temperature gradient form of loading. The results show that the nonlinear thermal frequencies are affected in the presence of different temperature distributions. The changes in the temperature distribution have a slightly greater effect than changes in the average temperature. These effects due to temperature distribution changes do not have a substantial effect on the flutter dynamic pressure.

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17

Kunnumpurath, Anthony, and Gilbert-Roy Kamoga. "Ehrlichiosis-Induced Atrial Flutter: An Unusual Cause of Atrial Flutter." Journal of Investigative Medicine High Impact Case Reports 8 (January 2020): 232470962095012. http://dx.doi.org/10.1177/2324709620950128.

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Tick-borne illness has been increasingly on the rise, since the first human case was reported in the late 1980s. Ehrlichia chaffeensis is one of the most common reported causes of tick-borne illness, particularly in the southern states of the United States. The clinical picture presents as a paradigm to the clinician, often missing the diagnosis without an appropriate history being taken and sometimes mistreated for other conditions. With the number of cases on the rise, new manifestations and clinical presentations due to E chaffeensis continue to be reported. Our case report is one such case in a 46-year-old male from Arkansas, with known exposure to multiple tick bites who presented with classical symptoms and laboratory values of tick-borne illness leading to atrial flutter. This unusual manifestation of atrial flutter due to tick-borne illness is rare and poorly understood. Further studies on tick-borne illness due to E chaffeensis may be needed to understand the systemic causes of the bacteria. In addition, in our case report, we bring to attention the standard presentation (symptoms, signs, and laboratory values) of tick-borne illness due to E chaffeensis along with the current standard for diagnosis and treatment.

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18

Zotova, Irina V. "PROTOCOL FOR PRESCRIBING ANTICOAGULANTS FOR ATRIAL FLUTTER: ARE ALL ISSUES RESOLVED?" Medical Journal of the Russian Federation 25, no. 5-6 (December 15, 2019): 309–15. http://dx.doi.org/10.18821/0869-2106-2019-25-5-6-309-315.

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The article is devoted to the issue of prescribing long-term anticoagulant therapy for patients with atrial flutter. Currently, a unified approach to prescribing anticoagulants for atrial flutter and fibrillation is generally accepted. However, this approach does not have strong evidence. The article provides a comparative analysis of the risk of thromboembolic complications and left atrium thrombosis in atrial flutter and fibrillation, discusses possible mechanisms of these differences. The results of studies confirming and refuting the unified approach to anticoagulant therapy for these arrhythmias are discussed. The author’s clinical protocol for prescribing long-term anticoagulant therapy to patients with atrial flutter is presented. a comparative analysis of current clinical recommendations on this problem is carried out.

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19

Bai, Hua, Cheng Fang, and Yu Li. "Research on the Impact of Damping to the Flutter Derivatives of Steel Truss Suspension Bridge." Advanced Materials Research 532-533 (June 2012): 325–29. http://dx.doi.org/10.4028/www.scientific.net/amr.532-533.325.

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The flutter derivative is the important basic tache of bridge flutter stability analysis. Taking the Liujiaxia Bridge in Gansu province as the research object, this dissertation studies the impaction of damping ratio on the flutter derivatives and the critical wind speed through different series of section model vibration test. The results showed that the change of vertical bending and torsional damping ratio have no obvious regular influence on the eight flutter derivatives. But the changing of vertical bending and torsional damping ratio have the greatly impact on the critical wind speed at 0° and -3° angle of attack. When it is at 0° angle of attack ,the vertical bending damping ratio ζh is increased by 23%,the torsional damping ratio is increased by 0.63%, the flutter critical wind speed is increased by 4%;when the ζh is increased by 1.04%, the ζα is increased by 0.87% , the flutter critical wind speed is increased by 7%. When it is at -3° angle of attack, the vertical bending damping ratio remained around 0.8%, the torsional damping ratio is increased from 0.65% to 1.05%, the flutter critical wind speed is increased by 14%; when the ζα is increased from 0.65% to 2.05%, the flutter critical wind speed is increased by 24 %.When it is at +3 °angle of attack, the vertical bending and torsion damping ratio have little effect on the flutter critical wind speed.

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20

Nguyen, Xuan Tuan, The Nam Huy Nguyen, Thanh Nam Phan, Sinh Huy Nguyen, and Duc Hanh Nguyen. "Result assessment of typical atrial flutter ablation base on application of three-dimensional electroanatomy mapping at Hanoi heart hospital." Tạp chí Phẫu thuật Tim mạch và Lồng ngực Việt Nam 43 (August 28, 2023): 205–11. http://dx.doi.org/10.47972/vjcts.v43i.1029.

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Background: Atrial flutter is a rare type of arrhythmia in clinical practice, but it is a long-lasting complex arrhythmia that causes uncomfortable symptoms and serious complications. The method of ablation of atrial flutter using X-ray irradiation has many shortcomings such as prolonged irradiation time, and the success rate is only 80-85%. The method of ablation using the 3-Dimensional electrical mapping method has been widely used in typical atrial flutter ablation, but there have not been many studies evaluating its effectiveness, so we carry out this study. Objectives of the study: Assessment for electrocardiography, electrophysiology study characteristic, and ablation result of typical atrial flutter using three-dimensional electrical mapping. Research objects and methods: case series study, 17 patients diagnosed with atrial flutter were electrophysiology study and ablated from 10/2019 to 10/2022 at Hanoi Heart Hospital. Results: Regarding the effectiveness of atrial flutter ablation, 100% of patients with atrial flutter caused a seizure and successfully ablated atrial flutter by RF. In terms of procedure time, our study has an average of 103.53 ± 74.64 minutes for each procedure, of which the fastest is 20 minutes and the longest is 360 minutes. Regarding the time of X-ray irradiation, the average of our study was 10.67 ± 9.86 minutes, of which the shortest was 4 minutes and the longest was 45 minutes. Conclusion: Typical atrial flutter ablation based on 3D mapping application has had high success at Hanoi heart hospital.

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21

Alizadeh, A., Z. Ebrahimi, A. Mazidi, and S. Ahmad Fazelzadeh. "Experimental Nonlinear Flutter Analysis of a Cantilever Wing/Store." International Journal of Structural Stability and Dynamics 20, no. 07 (July 2020): 2050082. http://dx.doi.org/10.1142/s0219455420500820.

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This paper studies experimentally the nonlinear aeroelastic and flutter behavior of a cantilever plate wing with an external store. The wing model that is constructed from plexiglass sheet is designed and tested in a closed-circuit subsonic wind tunnel. To deal with the structural nonlinearities of the model, various analysis tools such as time history plots, phase-plane projections and Fast Fourier Transform (FFT) have been used for detecting the critical and post-critical behaviors of the structure. The results show that flutter takes place by the coupling between the torsional and bending modes. A good correlation between the present experiments and previous numerical results is obtained. The nonlinear aeroelastic response and flutter boundary are investigated for different sweep angles. The flutter velocity and amplitudes of limit cycle oscillations (LCOs) increase rapidly with increasing sweep angle. The nonlinear response of the wing with an external store is also investigated, with the effect of store location on the nonlinear flutter boundary evaluated.

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22

Wang, Gang, and Jinwei Shen. "Flutter instabilities of cantilevered piezoelectric pipe conveying fluid." Journal of Intelligent Material Systems and Structures 30, no. 4 (January 11, 2019): 606–17. http://dx.doi.org/10.1177/1045389x18818774.

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In this article, a nonlinear model was developed for a cantilevered piezoelectric pipe conveying fluid that included geometric nonlinearity and electromechanical coupling. The Galerkin method discretized the system in order to characterize its behavior. Critical flutter velocity and its associated unstable mode can be determined based on linear analysis. Due to the presence of piezoelectric materials, the critical flutter velocity depends on the resistive piezoelectric damping and electromechanical coupling. This added resistive piezoelectric damping tends to decrease the flutter velocity. Comprehensive simulations were also conducted to characterize the post-flutter behaviors. System parameters including amplitude, deformed pipe shape, and collected voltage in piezoelectric materials were calculated. The system will undergo limited cycle oscillation when the fluid velocity passes the flutter velocity. Parametric studies were conducted as well to investigate the system responses under different flow velocities. Physical insights can be collected from these simulation results to conduct piezoelectric pipe design and performance predictions for future pipe vibration control and energy harvesting applications.

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23

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.

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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.

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24

Barinova, K. I., A. V. Dolgopolov, O. A. Orlova, and M. A. Pronin. "The analysis of flutter characteristics based on generalized parameters of eigen modes of vibrations." PNRPU Mechanics Bulletin, no. 1 (December 15, 2021): 95–102. http://dx.doi.org/10.15593/perm.mech/2021.1.10.

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Flutter numerical analysis of a dynamically scaled model (DSM) of a high aspect ratio wing was performed using experimentally obtained generalized parameters of eigen modes of vibrations. The DSM is made of polymer composite materials and is designed for aeroelastic studies in a high-speed wind tunnel. As a result of the analysis, safe operation conditions (flutter limits) of the DSM were determined. The input data to develop the flutter mathematical model are DSM modal test results, i.e. eigen frequencies, mode shapes, modal damping coefficients, and generalized masses obtained from the experiment. The known methods to determine generalized masses have experimental errors. In this work some of the most practical methods to get generalized masses are used: mechanical loading, quadrature component addition and the complex power method. Errors of the above methods were analyzed, and the most reliable methods were selected for flutter analysis. Comparison was made between the flutter analysis using generalized parameters and a pure theoretical one based on developing the mathematical model from the DSM design specifications. According to the design specifications, the mathematical model utilizes the beam-like schematization of the wing. The analysis was performed for Mach numbers from 0.2 to 0.8 and relative air densities of 0.5, 1, 1.5. Comparison of the two methods showed the difference in critical flutter dynamic pressure no more than 6%, which indicates good prospects of the flutter analysis based on generalized parameters of eigen modes.

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25

Wang, Jiayi, and Mitao Song. "Aeroelastic Flutter of Functionally Graded Beams Reinforced with Hydrogen-Functionalized Graphene Nanoplatelets." Journal of Scientific Research and Reports 29, no. 4 (March 27, 2023): 1–10. http://dx.doi.org/10.9734/jsrr/2023/v29i41738.

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This paper studies aeroelastic flutter behaviors of hydrogen-functionalized graphene nanoplatelet-reinforced composite (HFGRC) beams. Displacements of the beams are described based on the first-order shear deformation theory (FSDT). Material properties of the HFGRCs are predicted by the micromechanics models which have been modified by machine learning (ML) assistance. Combined with Ritz trial functions, Hamilton’s principle is employed to derive the dynamic equations of the beams under supersonic airflow. The eigenvalue equation is derived and is numerically solved to get the flutter velocities. A detailed parametric study is conducted to investigate the effect of boundary conditions, GPL distribution pattern, temperature change, and hydrogenation percentage on the flutter behaviors of the beams.

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26

Frandsen, J. B. "Numerical bridge deck studies using finite elements. Part I: flutter." Journal of Fluids and Structures 19, no. 2 (February 2004): 171–91. http://dx.doi.org/10.1016/j.jfluidstructs.2003.12.005.

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27

Khudayarov, B. A. "Computational Experiments to Evaluate the Approaches to the Modeling of Viscoelastic Plates Motion Based on Various Theories." Mechanical Engineering and Computer Science, no. 9 (December 2, 2018): 15–33. http://dx.doi.org/10.24108/0918.0001412.

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Mathematical and computer modeling of the flutter of elements and units of the aircraft design is an actual scientific problem; its study is stimulated by the failure of aircraft elements, parts of space and jet engines. In view of the complexity of the flutter phenomenon of aircraft elements, simplifying assumptions are used in many studies. However, these assumptions, as a rule, turn out to be so restrictive that the mathematical model ceases to reflect the real conditions with sufficient accuracy. Therefore, results of theoretical and experimental studies are in bad agreement.At present, the problem of panel flutter is very relevant. Improvement of characteristics of military and civil aircraft inevitably requires reducing their weight, and consequently, the rigidity of paneling, which increases the possibility of a panel flutter. The concept of creating the aircraft with a variable shape, which would inevitably lead to a reduction in paneling thickness are actively discussed. Finally, the use of new materials and, in particular, composites, changes physical properties of the panels and can also lead to a flutter.The above-mentioned scientific problem gives grounds to assert that the development of adequate mathematical models, numerical methods and algorithms for solving nonlinear integral-differential equations of dynamic problems of the hereditary theory of viscoelasticity is actual.In connection with this, the development of mathematical models of individual elements of aircraft made of composite material is becoming very important.Generalized mathematical models of non-linear problems of the flutter of viscoelastic isotropic plates, streamlined by a supersonic gas flow, are constructed in the paper on the basis of integral models. To study oscillation processes in plates, a numerical algorithm is proposed for solving nonlinear integro-differential equations with singular kernels. Based on the developed computational algorithm, a package of applied programs is created. The effect of the singularity parameter in heredity kernels on the vibrations of structures with viscoelastic properties is numerically investigated. In a wide range of changes in plate parameters, critical flutter velocities are determined. Numerical solutions of the problem of viscoelastic plate flutter are compared for different models. It is shown that the most adequate theory for investigating a wide class of problems of the hereditary theory of viscoelasticity is the geometric nonlinear Kirchhoff-Love theory with consideration of elastic waves propagation. It is established that an account of viscoelastic properties of plate material leads to 40-60% decrease in the critical flutter velocity.

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28

Kim, Dong Hyun, Se Won Oh, In Lee, Jin Hwe Kweon, and Jin Ho Choi. "Weight Optimization of Composite Flat and Curved Wings Satisfying Both Flutter and Divergence Constrains." Key Engineering Materials 334-335 (March 2007): 477–80. http://dx.doi.org/10.4028/www.scientific.net/kem.334-335.477.

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Aeroelastic tailoring studies using effective computational method with genetic algorithm have been conducted to find an optimized lamination set which give minimum structural weight. The efficient and robust computational system for the flutter optimization has been developed using the coupled computational method based on the micro genetic algorithm. It is shown that the wing structural weight with both divergence and flutter constrains can be significantly reduced using composite materials with proper optimum lamination compared to the case of isotropic wing model.

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29

Vilensky, L. I. "To the atrial fibrillation and flutter clinic." Kazan medical journal 20, no. 3 (August 11, 2021): 246–57. http://dx.doi.org/10.17816/kazmj76460.

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The study of atrial fibrillation began in the 50s of the last century, thanks to the studies of Hoffa and Karl Ludwig, who first noted, in animal experiments, such a work of the heart in which individual segments of it produce frequent, small fibrillar movements and are unable to rhythmic coordinated contractions.

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30

Cosío, Francisco G. "Atrial Flutter, Typical and Atypical: A Review." Arrhythmia & Electrophysiology Review 6, no. 2 (2017): 55. http://dx.doi.org/10.15420/aer.2017.5.2.

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Clinical electrophysiology has made the traditional classification of rapid atrial rhythms into flutter and tachycardia of little clinical use. Electrophysiological studies have defined multiple mechanisms of tachycardia, both re-entrant and focal, with varying ECG morphologies and rates, authenticated by the results of catheter ablation of the focal triggers or critical isthmuses of re-entry circuits. In patients without a history of heart disease, cardiac surgery or catheter ablation, typical flutter ECG remains predictive of a right atrial re-entry circuit dependent on the inferior vena cava–tricuspid isthmus that can be very effectively treated by ablation, although late incidence of atrial fibrillation remains a problem. Secondary prevention, based on the treatment of associated atrial fibrillation risk factors, is emerging as a therapeutic option. In patients subjected to cardiac surgery or catheter ablation for the treatment of atrial fibrillation or showing atypical ECG patterns, macro-re-entrant and focal tachycardia mechanisms can be very complex and electrophysiological studies are necessary to guide ablation treatment in poorly tolerated cases.

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31

Cosío, Francisco G. "Atrial Flutter, Typical and Atypical: A Review." Arrhythmia & Electrophysiology Review 6, no. 2 (2017): 55. http://dx.doi.org/10.15420/aer.2017:5:2.

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Clinical electrophysiology has made the traditional classification of rapid atrial rhythms into flutter and tachycardia of little clinical use. Electrophysiological studies have defined multiple mechanisms of tachycardia, both re-entrant and focal, with varying ECG morphologies and rates, authenticated by the results of catheter ablation of the focal triggers or critical isthmuses of re-entry circuits. In patients without a history of heart disease, cardiac surgery or catheter ablation, typical flutter ECG remains predictive of a right atrial re-entry circuit dependent on the inferior vena cava–tricuspid isthmus that can be very effectively treated by ablation, although late incidence of atrial fibrillation remains a problem. Secondary prevention, based on the treatment of associated atrial fibrillation risk factors, is emerging as a therapeutic option. In patients subjected to cardiac surgery or catheter ablation for the treatment of atrial fibrillation or showing atypical ECG patterns, macro-re-entrant and focal tachycardia mechanisms can be very complex and electrophysiological studies are necessary to guide ablation treatment in poorly tolerated cases.

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32

Xu, Xu. "Parametric studies on relationships between flutter derivatives of slender bridge (I)." Applied Mathematics and Mechanics 30, no. 2 (February 2009): 237–45. http://dx.doi.org/10.1007/s10483-009-0211-2.

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33

Xu, Xu. "Parametric studies on relationships between flutter derivatives of slender bridge (II)." Applied Mathematics and Mechanics 30, no. 3 (March 2009): 335–41. http://dx.doi.org/10.1007/s10483-009-0307-x.

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34

Schäfer, Dominik. "Influence of Fluid Viscosity and Compressibility on Nonlinearities in Generalized Aerodynamic Forces for T-Tail Flutter." Aerospace 9, no. 5 (May 9, 2022): 256. http://dx.doi.org/10.3390/aerospace9050256.

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The numerical assessment of T-tail flutter requires a nonlinear description of the structural deformations when the unsteady aerodynamic forces comprise terms from lifting surface roll motion. For linear flutter, a linear deformation description of the vertical tail plane (VTP) out-of-plane bending results in a spurious stiffening proportional to the steady lift forces, which is corrected by incorporating second-order deformation terms in the equations of motion. While the effect of these nonlinear deformation components on the stiffness of the VTP out-of-plane bending mode shape is known from the literature, their impact on the aerodynamic coupling terms involved in T-tail flutter has not been studied so far, especially regarding amplitude-dependent characteristics. This term affects numerical results targeting common flutter analysis, as well as the study of amplitude-dependent dynamic aeroelastic stability phenomena, e.g., Limit Cycle Oscillations (LCOs). As LCOs might occur below the linear flutter boundary, fundamental knowledge about the structural and aerodynamic nonlinearities occurring in the dynamical system is essential. This paper gives an insight into the aerodynamic nonlinearities for representative structural deformations usually encountered in T-tail flutter mechanisms using a CFD approach in the time domain. It further outlines the impact of geometrically nonlinear deformations on the aerodynamic nonlinearities. For this, the horizontal tail plane (HTP) is considered in isolated form to exclude aerodynamic interference effects from the studies and subjected to rigid body roll and yaw motion as an approximation to the structural mode shapes. The complexity of the aerodynamics is increased successively from subsonic inviscid flow to transonic viscous flow. At a subsonic Mach number, a distinct aerodynamic nonlinearity in stiffness and damping in the aerodynamic coupling term HTP roll on yaw is shown. Geometric nonlinearities result in an almost entire cancellation of the stiffness nonlinearity and an increase in damping nonlinearity. The viscous forces result in a stiffness offset with respect to the inviscid results, but do not alter the observed nonlinearities, as well as the impact of geometric nonlinearities. At a transonic Mach number, the aerodynamic stiffness nonlinearity is amplified further and the damping nonlinearity is reduced considerably. Here, the geometrically nonlinear motion description reduces the aerodynamic stiffness nonlinearity as well, but does not cancel it.

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35

Burnett, E. L., J. A. Beranek, B. T. Holm-Hansen, C. J. Atkinson, and P. M. Flick. "Design and flight test of active flutter suppression on the X-56A multi-utility technology test-bed aircraft." Aeronautical Journal 120, no. 1228 (May 10, 2016): 893–909. http://dx.doi.org/10.1017/aer.2016.41.

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ABSTRACTEfforts to develop the next generation of aircraft with ever-increasing levels of performance – higher, farther, faster, cheaper – face great technical challenges. One of these technical challenges is to reduce structural weight of the aircraft. Another is to look to aircraft configurations that have been unrealizable to date. Both of these paths can lead to a rigid flex coupling phenomenon that can result in anything from poor flying qualities to the loss of an aircraft due to flutter. This has led to a need to develop an integrated flight and aeroelastic control capability where structural dynamics are included in the synthesis of flight control laws. Studies have indicated that the application of an integrated flight and aeroelastic control approach to a SensorCraft high-altitude long-endurance vehicle would provide substantial performance improvement(1,2). Better flying qualities and an expanded flight envelope through multi-flutter mode control are two areas of improvement afforded by integrated flight and aeroelastic control. By itself, multi-flutter mode control transforms the flutter barrier from a point of catastrophic structural failure to a benign region of flight. This paper discusses the history and issues associated with the development of such an integrated flight and aeroelastic control system for the X-56A aircraft.

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36

Taylor, N. V., C. B. Allen, A. L. Gaitonde, D. P. Jones, G. A. Vio, J. E. Cooper, A. M. Rampurawala, K. J. Badcock, M. A. Woodgate, and M. J. de C. Henshaw. "Aeroelastic analysis through linear and non-linear methods: a summary of flutter prediction in the PUMA DARP." Aeronautical Journal 110, no. 1107 (May 2006): 333–43. http://dx.doi.org/10.1017/s0001924000013208.

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AbstractThis paper presents a comparison of linear and non-linear methods for the analysis of aeroelastic behaviour and flutter boundary prediction. The methods in question include NASTRAN and ZAERO, based on linear aerodynamics, and the non-linear coupled CFD-CSD methods RANSMB and PMB, developed at the Universities of Bristol and Glasgow respectively. The test cases used for this comparison are the MDO and AGARD 445.6 weakened wing. In general, it was found that the non-linear methods demonstrate excellent agreement with respect to pressure distributions, deflections, dynamic behaviour, and flutter boundary locations for both cases. This is in contrast to previous studies involving similar methods, where notable differences across the MDO span were found, and is taken to imply good performance of the CFD-CSD interpolation schemes employed here. While the linear methods produce similar flutter boundaries to the coupled codes for the aerodynamically simple AGARD 445.6 wing, results for the transonic ‘rooftop’ MDO wing design did not agree as well.

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37

Ortiz, J., A. Nozaki, A. Shimizu, C. Khrestian, Y. Rudy, and A. L. Waldo. "Mechanism of interruption of atrial flutter by moricizine. Electrophysiological and multiplexing studies in the canine sterile pericarditis model of atrial flutter." Circulation 89, no. 6 (June 1994): 2860–69. http://dx.doi.org/10.1161/01.cir.89.6.2860.

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38

Prasad, Deepa, Joni Steinberg, and Christopher Snyder. "Cost-effectiveness of digoxin, pacing, and direct current cardioversion for conversion of atrial flutter in neonates." Cardiology in the Young 28, no. 5 (March 6, 2018): 725–29. http://dx.doi.org/10.1017/s104795111800029x.

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AbstractIntroductionNewborn atrial flutter can be treated by medications, pacing, or direct current cardioversion. The purpose is to compare the cost-effectiveness of digoxin, pacing, and direct current cardioversion for the treatment of atrial flutter in neonates.Materials and methodsA decision tree model was developed comparing the efficacy and cost of digoxin, pacing, and direct current cardioversion based on a meta-analysis of published studies of success rates of cardioversion of neonatal atrial flutter (age<2 months). Patients who failed initial attempt at cardioversion progressed to the next methodology until successful. Data were analysed to assess the cost-effectiveness of these methods with cost estimates obtained from 2015 Medicare reimbursement rates.ResultsThe cost analysis for cardioversion of atrial flutter found the most efficient method to be direct current cardioversion at a cost of $10 304, pacing was next at $11 086, and the least cost-effective was digoxin at $14 374. The majority of additional cost, regardless of method, was from additional neonatal ICU day either owing to digoxin loading or failure to covert. Direct current cardioversion remains the most cost-effective strategy by sensitivity analyses performed on pacing conversion rate and the cost of the neonatal ICU/day. Direct current cardioversion remains cost-effective until the assumed conversion rate is below 64.6%.ConclusionThe most cost-efficient method of cardioverting a neonate with atrial flutter is direct current cardioversion. It has the highest success rates based on the meta-analysis, shorter length of stay in the neonatal ICU owing to its success, and results in cost-savings ranging from $800 to $4000 when compared with alternative approaches.

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39

Koksal, Sertac, Erdinc Nuri Yildiz, Yigit Yazicioglu, and Gokhan Osman Ozgen. "Minimization of Ground Vibration Test Configurations for F-16 Aircraft by Subtractive Modification." Shock and Vibration 2019 (November 7, 2019): 1–19. http://dx.doi.org/10.1155/2019/9283125.

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The certification process of external loads designed for aircraft needs to satisfy various criteria where compatibility with existing systems is one of the essential requirements. Flight flutter testing is a critical part of a certification process that requires many preliminary studies. Computational flutter analysis must precede actual flutter test to determine an approximately safe flight envelope to ensure the safety of the personnel and aircraft. To be able to perform flutter analysis of an aircraft, an accurate structural model such as finite element (FE) model is required. An accurate FE model can be obtained from a coarse model using ground vibration test (GVT) which is also the primary test campaign for certification of a new external load, new aircraft design, or modification on existing aircraft. On the other hand, performing GVT for each configuration of an aircraft is both time consuming and costly. It would be more practical to determine the critical configurations for an aircraft using computational tools and perform actual GVT for those configurations. The objective of this study is to simulate GVT characteristics for downloading and fuel configurations of F-16 aircraft. A novel methodology is proposed where various loading configurations can be simulated by subtractive modification from loaded GVT data so that joint stiffnesses between stores and aircraft need not be identified. The proposed technique decreases the number of necessary physical GVT testing campaigns.

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40

Henglein, Dagmar, Bruno Cauchemez, and Gérard Bloch. "Simultaneous surgical treatment of atrial septal defect and atrial flutter using a simple modification of the atrial incision." Cardiology in the Young 9, no. 2 (March 1999): 197–99. http://dx.doi.org/10.1017/s1047951100008453.

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AbstractThe reentrant circuit of common atrial flutter is known to located in the right atrium between two anatomical barriers. Recent electrophysiologic studies have defined the tricuspid annulus as the anterior barrier, and the terminal crest and its continuation as the eustachian ridge as the posterior barrier. Construction of a bidirectional block to conduction between these two barriers by means of lesions created with radiofrequency current have been shown to be effective in ablating the flutter. We now find that surgical creation of such a block to conduction between the barriers by a simple modification of the atrial incision line is equally effective. In a 6-year-old boy, who was admitted to our hospital for closure of an atrial septal defect and treatment of sustained atrial flutter, the atriotomy was performed perpendicular to the terminal groove and extended towards the tricuspid annulus, placing some crythermal lesions between the end of the incision and the annuals. The special defect was closed using a Dacron patch. The child was free of arrhythmia both during the postoperative stay and over the initial three months of follow-up. We conclude that this simple modification of the atrial incision line provides cure of atrial flutter in children who require atriotomy for repair of congential cardiac anomalies. It may also be beneficial in preventing ‘incisional’ reentrant tachycardia.

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41

Chiarelli, Mario Rosario, and Salvatore Bonomo. "Numerical Investigation into Flutter and Flutter-Buffet Phenomena for a Swept Wing and a Curved Planform Wing." International Journal of Aerospace Engineering 2019 (February 27, 2019): 1–19. http://dx.doi.org/10.1155/2019/8210235.

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The results of numerical studies carried out on high-aspect-ratio wings with different planforms are discussed: the transonic regime is analysed for a swept wing and a curved planform wing. The wings have similar aspect ratios and similar aerodynamic profiles. The analyses were carried out by CFD and FE techniques, and the reliability of the numerical aerodynamic results was proven by a sensitivity study. Analysing the performances of the two wings demonstrated that in transonic flight conditions, a noticeable drag reduction can be obtained by adopting a curved planform wing. In addition, for such a wing, the aeroelastic instability condition, consisting in a classical flutter, is postponed compared to a conventional swept wing, for which a flutter-buffet instability occurs. In a preliminary manner, the study shows that, for a curved planform wing, the high speed buffet is not an issue and at the same time notable fuel saving can be achieved.

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42

Zhan, Hao. "Flutter Stability Studies of Long Span Suspension Bridge by CFD Numerical Simulation." IABSE Congress Report 18, no. 20 (September 19, 2012): 795–802. http://dx.doi.org/10.2749/222137912805111159.

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43

Olshansky, Brian, Ken Okumura, Richard W. Henthorn, and Albert L. Waldo. "Characterization of double potentials in human atrial flutter: Studies during transient entrainment." Journal of the American College of Cardiology 15, no. 4 (March 1990): 833–41. http://dx.doi.org/10.1016/0735-1097(90)90283-u.

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44

Cavallaro, R., R. Bombardieri, L. Demasi, and A. Iannelli. "PrandtlPlane Joined Wing: Body freedom flutter, limit cycle oscillation and freeplay studies." Journal of Fluids and Structures 59 (November 2015): 57–84. http://dx.doi.org/10.1016/j.jfluidstructs.2015.08.016.

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45

Wang, Zilong, Lin Zhao, Hanlin Chen, Genshen Fang, Ke Li, and Yaojun Ge. "Flutter Control of Active Aerodynamic Flaps Mounted on Streamlined Bridge Deck Fairing Edges: An Experimental Study." Structural Control and Health Monitoring 2023 (February 16, 2023): 1–16. http://dx.doi.org/10.1155/2023/9970603.

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Traditional aerodynamic measures with fixed geometric shapes make it difficult to relieve the wind-induced vibration issues under the continuous expansion of bridge spans. Active aerodynamic control measures would be an alternative way to improve the wind vibration performance of long-span bridges. In this study, a bridge flutter control method based on active flaps was proposed, and the main girder-active flap-suspended aeroelastic model was designed to study the control effect. A pair of active flaps was installed on both sides of the box girder near the lateral fairings, and the movement signal of the main girder was detected using internal sensors. The two flaps move relative to the deck according to the preset equations of motion. This improved the flutter stability of the system with high effectiveness compared to traditional passive aerodynamic measures. By adjusting the gain coefficient in the motion function of the flaps and the phase difference between the flaps and the deck, the changing characteristics of the critical flutter wind speed were revealed with a deeper understanding of the relationship between the phase differences and gain coefficient of the active flaps and main girder. Studies have shown that the flutter performance of the deck-flap system is significantly affected by the phase difference and gain coefficient on both sides of the aerodynamic flap. The control law of the windward flap is relatively stable, but the control effect of the leeward flap is greatly affected by the movement of the windward flap.

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46

Kim, Jung Hwan, and Ji Hwan Kim. "Flutter Analysis of Functionally Graded Panel Based on Neutral Surface." Advanced Materials Research 1125 (October 2015): 526–30. http://dx.doi.org/10.4028/www.scientific.net/amr.1125.526.

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In this work, flutter behavior of Functionally Graded Material (FGM) panel is investigated based on the physical neutral surface. The panel is made with ceramic and metal according to linear rule of mixture. The virtual work principle is applied including pressure due to aero-dynamic load. Then governing equations are derived using von Karman's strain-displacement relations. Conventionally, mid-plane is used as a reference plane for laminate structures, while this concept is not appropriate for materially asymmetry of a panel such as FGMs. For this reason, physical neutral surface is defined as the origin of coordinate system in the structure. Numerical results are discussed and compared with previous studies. Finally, flutter behavior is investigated according to the volume fractions, temperature distributions and aero-dynamic pressures.

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47

ELOY, CHRISTOPHE, ROMAIN LAGRANGE, CLAIRE SOUILLIEZ, and LIONEL SCHOUVEILER. "Aeroelastic instability of cantilevered flexible plates in uniform flow." Journal of Fluid Mechanics 611 (September 25, 2008): 97–106. http://dx.doi.org/10.1017/s002211200800284x.

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We address the flutter instability of a flexible plate immersed in an axial flow. This instability is similar to flag flutter and results from the competition between destabilizing pressure forces and stabilizing bending stiffness. In previous experimental studies, the plates have always appeared much more stable than the predictions of two-dimensional models. This discrepancy is discussed and clarified in this paper by examining experimentally and theoretically the effect of the plate aspect ratio on the instability threshold. We show that the two-dimensional limit cannot be achieved experimentally because hysteretical behaviour and three-dimensional effects appear for plates of large aspect ratio. The nature of the instability bifurcation (sub- or supercritical) is also discussed in the light of recent numerical results.

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48

Yu, Kok Hwa. "ACOUSTIC EFFECTS ON BINARY AEROELASTICITY MODEL." IIUM Engineering Journal 12, no. 2 (October 18, 2011): 123–30. http://dx.doi.org/10.31436/iiumej.v12i2.108.

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Acoustics is the science concerned with the study of sound. The effects of sound on structures attract overwhelm interests and numerous studies were carried out in this particular area. Many of the preliminary investigations show that acoustic pressure produces significant influences on structures such as thin plate, membrane and also high-impedance medium like water (and other similar fluids). Thus, it is useful to investigate the structure response with the presence of acoustics on aircraft, especially on aircraft wings, tails and control surfaces which are vulnerable to flutter phenomena. The present paper describes the modeling of structural-acoustic interactions to simulate the external acoustic effect on binary flutter model. Here, the binary flutter model which illustrated as a rectangular wing is constructed using strip theory with simplified unsteady aerodynamics involving flap and pitch degree of freedom terms. The external acoustic excitation, on the other hand, is modeled using four-node quadrilateral isoparametric element via finite element approach. Both equations then carefully coupled and solved using eigenvalue solution. The mentioned approach is implemented in MATLAB and the outcome of the simulated result are later described, analyzed and illustrated in this paper.

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49

Lanham, Theresa N., and Farah Hena Morgan. "Management of Atrial Flutter in Thyroid Storm." Journal of the Endocrine Society 5, Supplement_1 (May 1, 2021): A941. http://dx.doi.org/10.1210/jendso/bvab048.1923.

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Abstract Introduction: Thyroid storm, life-threatening hyperthyroidism, commonly presents with tachyarrhythmias. We present a case of hyperthyroid-induced atrial flutter, refractory to beta-blockade, successfully treated with electrical cardioversion (CV) while biochemically hyperthyroid. Case Description: A 49-year-old female with history of asthma and no family or personal history of thyroid disease presented with new-onset atrial flutter and heart failure. The patient endorsed weight loss, hot flashes, anxiousness, tremors, and palpitations. She denied gastrointestinal symptoms or visual changes. She was afebrile with normal mentation. Heart rate was found to be 260 beats per minute (bpm) in atrial flutter. Exam demonstrated bilateral lower extremity edema, and profound exophthalmos. Labs were remarkable for thyroid stimulating hormone (TSH) <0.01 [ref: 0.27-4.2] uIU/mL, free T4 4.5 [ref: 0.8-1.8] ng/dL, free T3 15.5 [ref: 2.0-4.4] pg/mL, thyroid stimulating immunoglobulin (TSI) of 379 [ref: <140] % and a thyroid receptor antibody (TRab) of 10.02 [ref:<=2.0] IU/L. White blood cell count and liver function tests were normal. Chest x-ray (CXR) showed bilateral pulmonary edema and ultrasound showed an enlarged heterogeneous hypervascular thyroid gland. The patient was initially started on Methimazole 30 mg daily and Metoprolol 25 mg every six hours but on day two, the patient was transitioned to Propylthiouracil (PTU) 250 mg every 6 hours given continued atrial flutter and concern for thyroid storm given Burch-Wartofsky score was 50. She was also given potassium iodide for three days. Cardioversion was deferred, as it was felt that the severity of thyrotoxicosis would limit success. On day six, TFTs were improved with a free T4 of 2.2, free T3 3.6. On day 8, because of continued tachycardia >130 bpm with limitation of beta-blockade due to hypotension, she underwent a cardioversion which was successful. On discharge, free T4 was 1.7 and she was transitioned to Methimazole 40 mg daily. Discussion: Thyroid storm has a mortality rate of 10-20%, often related to tachyarrhythmias which can be difficult to treat during a hyperthyroid state. Tachycardia should initially be treated with beta-blockade and antithyroid therapy. Amiodarone is avoided due to concern for worsening hyperthyroidism. A literature review suggests that electrical CV should not be attempted until a patient is euthyroid for four months, as a majority will spontaneously revert once thyroid levels normalize. Conversely, other studies have found that the rate of recurrence of atrial fibrillation between clinically hyperthyroid and euthyroid patients was not statistically significant, suggesting CV should not be delayed until a patient is euthyroid. This suggests that further studies need to be completed to better elucidate appropriate timing in hyperthyroid patient’s refractory to pharmacologic treatment alone.

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50

Shimizu, Akihiko, Akira Nozaki, Cecil W. Thomas, Yoram Rudy, and Albert L. Waldo. "Multiplexing studies during entrainment and interruption of atrial flutter to characterize double potentials." Journal of the American College of Cardiology 15, no. 2 (February 1990): A123. http://dx.doi.org/10.1016/0735-1097(90)92209-k.

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