Artykuły w czasopismach: „Aerodynamic excitation”

1

Liu, Jian, Wei-Yang Qiao i Wen-Hua Duan. "Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine". International Journal of Rotating Machinery 2019 (21.05.2019): 1–13. http://dx.doi.org/10.1155/2019/4396546.

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To investigate the aerodynamic excitations in variable geometry turbines, the full three-dimensional viscous unsteady numerical simulations were performed by solving N-S equations based on SAS SST method. The aerodynamic excitations at varied expansion ratios with six different vane stagger angles that cause the unsteady pressure fluctuation on the rotor blade surface are phenomenologically identified and quantitatively analyzed. The blade pressure fluctuation levels for turbines with different vane stagger angles in the time and frequency domain are analyzed. As the results suggest, the blade excitation mechanisms are directly dependent on the operating conditions of the stage in terms of vane exit Mach numbers for all test cases. At subsonic vane exit Mach numbers the blade pressure fluctuations are simply related to the potential filed and wake propagation; at transonic conditions, the vane trailing edge shock causes additional disturbance and is the dominating excitation source on the rotor blade, and the pressure fluctuation level is three times of the subsonic conditions. The pressure fluctuation energy at subsonic condition concentrates on the first vane passing period; pressure fluctuation energy at higher harmonics is more prominent at transonic conditions. The variation of the aerodynamic excitations on the rotor blade at different vane stagger angles is caused by the varied expansion with stator and rotor passage. The aerodynamic excitation behaviors on the rotor blade surface for the VGT are significantly different at varied vane stagger angle. Spanwise variation of the pressure fluctuation patterns on is also observed, and the mechanism of the excitations at different spans is not uniform.

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Kirk, R. G. "Evaluation of Aerodynamic Instability Mechanisms for Centrifugal Compressors—Part I: Current Theory". Journal of Vibration and Acoustics 110, nr 2 (1.04.1988): 201–6. http://dx.doi.org/10.1115/1.3269499.

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Current theories of calculating levels of aerodynamic excitation are reviewed and methods of applying these results to actual compressor designs are discussed in detail. Comparison of compressor stability for approximate modal aerodynamic excitation influence to published equations for static labyrinth seal cross-coupled stiffness is made to illustrate the influence of system damping on compressor stability. The results of analysis for six operating machines are presented to give further justification for the selection of the aerodynamic excitation model.

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3

Stamatellou, Antiopi-Malvina, i Anestis I. Kalfas. "On the Efficiency of a Piezoelectric Energy Harvester under Combined Aeroelastic and Base Excitation". Micromachines 12, nr 8 (14.08.2021): 962. http://dx.doi.org/10.3390/mi12080962.

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A flutter-type, nonlinear piezoelectric energy harvester was tested in various combinations of aerodynamic and harmonic base excitation to study its power output and efficiency. The commercial polyvinylidene fluoride film transducer LDT1-028K was used in 33 excitation mode. The aerodynamic excitation was created by a centrifugal fan and the base excitation by a cone speaker. The excitations were produced by varying independently the mean airflow velocity and the frequency of base vibration. A capacitive load was used to store the harvested energy. A line laser was employed along with long exposure photography and high-speed video, for the visualization of the piezo film’s mode shapes and the measurement of maximum tip deflection. The harvested power was mapped along with the maximum tip deflection of the piezo-film, and a process of optimally combining the two excitation sources for maximum power harvesting is demonstrated. The energy conversion efficiency is defined by means of electrical power output divided by the elastic strain energy rate of change during oscillations. The efficiency was mapped and correlated with resonance conditions and results from other studies. It was observed that the conversion efficiency is related to the phase difference between excitation and response and tends to decrease as the excitation frequency rises.

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Peng, Meng, i Hans A. DeSmidt. "Stability Analysis of a Flutter Panel with Axial Excitations". Advances in Acoustics and Vibration 2016 (31.07.2016): 1–7. http://dx.doi.org/10.1155/2016/7194764.

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This paper investigates the parametric instability of a panel (beam) under high speed air flows and axial excitations. The idea is to affect out-of-plane vibrations and aerodynamic loads by in-plane excitations. The periodic axial excitation introduces time-varying items into the panel system. The numerical method based on Floquet theory and the perturbation method are utilized to solve the Mathieu-Hill equations. The system stability with respect to air/panel density ratio, dynamic pressure ratio, and excitation frequency are explored. The results indicate that panel flutter can be suppressed by the axial excitations with proper parameter combinations.

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Zhang, Xiaojie, Yanrong Wang i Xianghua Jiang. "An Efficient Approach for Predicting Resonant Response with the Utilization of the Time Transformation Method and the Harmonic Forced Response Method". Aerospace 8, nr 11 (20.10.2021): 312. http://dx.doi.org/10.3390/aerospace8110312.

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Resonant response of turbomachinery blades can lead to high cycle fatigue (HCF) if the vibration amplitudes are significant. Therefore, the dangerousness assessment of the resonance crossing is important. It requires accurate predictions of the aerodynamic excitation, damping, and response, which will consume immense computational costs. The novel aspect of this study is the development of an efficient approach, which incorporates the time transformation (TT) method to predict the aerodynamic excitations and the harmonic forced response method to obtain the response levels. The efficiency and accuracy of this method were evaluated by comparing with traditional methods for the resonance crossing excited by upstream wake in a 1.5 multistage compressor. For the aerodynamic excitation, discrepancies of ±2% at the mean pressure and ±25% at the harmonic pressure in most areas expect for the blade root were observed, but the calculation time required by the TT method was only 5% of that by the time-marching method. Moreover, response levels with the same aerodynamic forces were compared between the harmonic forced-response and transient dynamic methods. Small differences in the displacement and stress variables were observed; the relative deviation was smaller than 2% with only 1% computing time compared with the transient method, indicating the high accuracy and efficiency of the efficient approach.

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Young, T. H., T. C. Tseng i L. S. Song. "Dynamic Stability of Fluttered Systems Subjected to Parametric Random Excitations". Journal of Vibration and Control 8, nr 3 (marzec 2002): 291–310. http://dx.doi.org/10.1177/107754602023684.

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A general solution for dynamic stability of the fluttered mode of damped, fluttered systems subjected to parametric random excitations is presented in this paper. First, the system equations are pairwisely uncoupled by a modal analysis based on normal modes of the system at the onset of fluttering. The stochastic averaging method is then applied to obtain Ito's equation governing the amplitude of the fluttered mode. Finally, the Lyapunov exponent of the fluttered mode is derived, from which the criterion for asymptotic sample stability of the mode is determined. A cantilevered beam acted upon by a static follower force and a white noise parametric excitation at the free end, and a skew panel subjected to an aerodynamic force in the chordwise direction and a white noise excitation in the spanwise direction are demonstrated as examples. Numerical results show that, although the static follower force or the aerodynamic force exceeds the flutter load, the fluttered mode of the beam or the panel may remain stable in the sense of asymptotic sample stability due to the presence of the white noise excitation.

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7

Pust, Ladislav, i Ludek Pesek. "Blades Forced Vibration Under Aero-Elastic Excitation Modeled by Van der Pol". International Journal of Bifurcation and Chaos 27, nr 11 (październik 2017): 1750166. http://dx.doi.org/10.1142/s0218127417501668.

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This paper employs a new analytical approach to model the influence of aerodynamic excitation on the dynamics of a bladed cascade at the flutter state. The flutter is an aero-elastic phenomenon that is linked to the interaction of the flow and the traveling deformation wave in the cascade when only the damping of the cascade changes. As a case study the dynamic properties of the five-blade-bunch excited by the running harmonic external forces and aerodynamic self-excited forces are investigated. This blade-bunch is linked in the shroud by means of the viscous-elastic damping elements. The external running excitation depends on the ratio of stator and rotor blade numbers and corresponds to the real type of excitation in the steam turbine. The aerodynamic self-excited forces are modeled by two types of Van der Pol nonlinear models. The influence of the interaction of both types of self-excitation with the external running excitation is investigated on the response curves.

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Li, Jianxiong, Xiaodong Yang, Anping Hou, Yingxiu Chen i Manlu Li. "Aerodynamic Damping Prediction for Turbomachinery Based on Fluid-Structure Interaction with Modal Excitation". Applied Sciences 9, nr 20 (18.10.2019): 4411. http://dx.doi.org/10.3390/app9204411.

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Aerodynamic damping predictions are critical when analyzing aeroelastic stability. A novel method has been developed to predict aerodynamic damping by employing two single time-domain simulations, specifically, one with the blade impulsed naturally in a vacuum and one with the blade impulsed in flow. The focus is on the aerodynamic damping prediction using modal excitation and the logarithmic decrement theory. The method is demonstrated by considering the first two bending modes with an inter-blade phase angle (IBPA) of 0° on a transonic compressor. The results show that the flutter boundary prediction is basically consistent with the experiment. The aerodynamic damping prediction with an IBPA of 180° is also performed, demonstrating that the method is suitable for different traveling wave mode representations. Furthermore, the influence of the amplitude of modal excitation and mechanical damping using the Rayleigh damping model for aerodynamic damping was also investigated by employing fluid-structure coupled simulations.

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9

Zahn, R., i C. Breitsamter. "Airfoil buffet aerodynamics at plunge and pitch excitation based on long short-term memory neural network prediction". CEAS Aeronautical Journal 13, nr 1 (18.10.2021): 45–55. http://dx.doi.org/10.1007/s13272-021-00550-6.

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AbstractIn the present study, a nonlinear system identification approach based on a long short-term memory (LSTM) neural network is applied for the prediction of transonic buffet aerodynamics. The identification approach is applied as a reduced-order modeling (ROM) technique for an efficient computation of time-varying integral quantities such as aerodynamic force and moment coefficients. Therefore, the nonlinear identification procedure as well as the generalization of the ROM are presented. The training data set for the LSTM–ROM is provided by performing forced-motion unsteady Reynolds-averaged Navier–Stokes simulations. Subsequent to the training process, the ROM is applied for the computation of the aerodynamic integral quantities associated with transonic buffet. The performance of the trained ROM is demonstrated by computing the aerodynamic loads of the NACA0012 airfoil investigated at transonic freestream conditions. In contrast to previous studies considering only a pitching excitation, both the pitch and plunge degrees of freedom of the airfoil are individually and simultaneously excited by means of an user-defined training signal. Therefore, strong nonlinear effects are considered for the training of the ROM. By comparing the results with a full-order computational fluid dynamics solution, a good prediction capability of the presented ROM method is indicated. However, compared to the results of previous studies including only the airfoil pitching excitation, a slightly reduced prediction performance is shown.

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10

Chiang, Hsiao-Wei D., i R. E. Kielb. "An Analysis System for Blade Forced Response". Journal of Turbomachinery 115, nr 4 (1.10.1993): 762–70. http://dx.doi.org/10.1115/1.2929314.

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A frequent cause of turbomachinery blade failure is excessive resonant response. The most common excitation source is the nonuniform flow field generated by inlet distortion, wakes and/or pressure disturbances from adjacent blade rows. The standard method for dealing with this problem is to avoid resonant conditions using a Campbell diagram. Unfortunately, it is impossible to avoid all resonant conditions. Therefore, judgments based on past experience are used to determine the acceptability of the blade design. A new analysis system has been developed to predict blade forced response. The system provides a design tool, over and above the standard Campbell diagram approach, for predicting potential forced response problems. The incoming excitation sources are modeled using a semi-empirical rotor wake/vortex model for wake excitation, measured data for inlet distortion, and a quasi-three-dimensional Euler code for pressure disturbances. Using these aerodynamic stimuli, and the blade’s natural frequencies and mode shapes from a finite element model, the unsteady aerodynamic modal forces and the aerodynamic damping are calculated. A modal response solution is then performed. This system has been applied to current engine designs. A recent investigation involved fan blade response due to inlet distortion. An aero mechanical test had been run with two different distortion screens. The resulting distortion entering the fan was measured. With this as input data, the predicted response agreed almost exactly with the measured response. In another application, the response of the LPT blades of a counterrotating supersonic turbine was determined. In this case the blades were excited by both a wake and a shock wave. The shock response was predicted to be three times larger than that of the wake. Thus, the system identified a new forcing function mechanism for supersonic turbines. This paper provides a basic description of the system, which includes: (1) models for the wake excitation, inlet distortion, and pressure disturbance; (2) a kernel function solution technique for unsteady aerodynamics; and (3) a modal aeroelastic solution using strip theory. Also, results of the two applications are presented.

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Niita, Shusaku, Taichi Sato, Hiroki Ota i Katsuaki Nagahashi. "TuC-2-4 AERODYNAMIC EXCITATION FORCE GENERATED BY ROTATING FAN AND ITS REACTION FORCES". Proceedings of JSME-IIP/ASME-ISPS Joint Conference on Micromechatronics for Information and Precision Equipment : IIP/ISPS joint MIPE 2015 (2015): _TuC—2–4–1—_TuC—2–4–3. http://dx.doi.org/10.1299/jsmemipe.2015._tuc-2-4-1.

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12

Cai, Chun S., i Pedro Albrecht. "Flutter derivatives based random parametric excitation aerodynamic analysis". Computers & Structures 75, nr 5 (maj 2000): 463–77. http://dx.doi.org/10.1016/s0045-7949(99)00107-8.

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Bauer, Hans-Jörg, Achmed Schulz i Martin Schwitzke. "Aerodynamic excitation of blade vibrations in radial turbines". MTZ worldwide 74, nr 6 (29.04.2013): 48–54. http://dx.doi.org/10.1007/s38313-013-0065-9.

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Liu, Yan, i Wensai Ma. "Nonlinear Oscillations of a Composite Stepped Piezoelectric Cantilever Plate with Aerodynamic Force and External Excitation". Mathematics 11, nr 13 (7.07.2023): 3034. http://dx.doi.org/10.3390/math11133034.

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Axially moving wing aircraft can better adapt to the flight environment, improve flight performance, reduce flight resistance, and improve flight distance. This paper simplifies the fully unfolded axially moving wing into a stepped cantilever plate model, analyzes the structural nonlinearity of the system, and studies the influence of aerodynamic nonlinearity on system vibration. The model is affected by aerodynamic forces, piezoelectric excitation, and in-plane excitation. Due to Hamilton’s principle of least action, the mathematical model is established based on Reddy’s higher-order shear deformation theory, and using Galerkin’s method, the governing dimensionless partial differential equations of the system are simplified to two nonlinear ordinary differential equations, and then a study of the influence of the various engineering parameters on the nonlinear oscillations and frequency responses of this model is conducted by the method of multiple scales. It was found that the different values of a5, a6, b6 and b8 can change the shape of the amplitude–frequency response curve and size of the plate, while different symbols a7 and b7 can change the rigidity of the model. The excitations greatly impact the nonlinear dynamic responses of the plate.

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15

Ewing, Mark S. "Response of a tactical missile to convected aerodynamic excitation". Journal of Spacecraft and Rockets 33, nr 3 (maj 1996): 360–65. http://dx.doi.org/10.2514/3.26768.

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HIROAKI, Keiichi, Daiki KATOU i Masahiro WATANABE. "Forced vibration of a sheet under periodic aerodynamic excitation". Transactions of the JSME (in Japanese) 86, nr 882 (2020): 19–00258. http://dx.doi.org/10.1299/transjsme.19-00258.

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Golebiowska, Irena, i Kazimierz Peszynski. "Cable vibration caused by wind". EPJ Web of Conferences 180 (2018): 02031. http://dx.doi.org/10.1051/epjconf/201818002031.

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The paper briefly presents selected basic kinds of excitation of cable vibration caused by dynamic effect of wind. It describes the aerodynamic phenomena such as vortex excitation, wind-rain excitation, galloping and buffeting. Cables are structures which are characterised by low internal damping, low rigidity and low weight, so they are not capable of total excitation energy dissipation, hence they can reach large amplitudes of vibration. Large amplitude of vibration causes excessive stress, thereby lowering the safety of the structure.

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18

Fan, Xiaoyu, Wenchao Liang, Jin Zeng, Yang Yang, Hui Ma, Chenguang Fan i Shunguo Fu. "Dynamic Characteristics of a Rotating Blade with a Dovetail Fixture". Machines 11, nr 6 (12.06.2023): 643. http://dx.doi.org/10.3390/machines11060643.

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Considering rotation-induced centrifugal stiffening, spin softening, and Coriolis effects, the reduced dynamic model of a rotating blade with a dovetail fixture is established in the ANSYS environment via the fixed-interface method for higher computational efficiency and lower memory consumption. Then some parameters such as rotating speed, friction factor, and stator blade number affecting the nonlinear vibration responses of the system under the combined actions of aerodynamic force, centrifugal force, and gravity are elaborately discussed. The results show that: (1) the contact-induced nonlinearity between the tenon and the mortise mainly results in the frequency multiplications of the aerodynamic excitation frequency; (2) a larger friction factor results in a lower magnitude of contact pressure and a higher resonance frequency, while a larger stator blade number results in a lower magnitude of the uniform and continuous contact pressure distribution; (3) the excitation of the resonant mode caused by the aerodynamic force is primarily characterized by the first-order bending mode of the system.

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Hui, Zheng, Xingjun Hu, Peng Guo, Zewei Wang i Jingyu Wang. "Separation Flow Control of a Generic Ground Vehicle Using an SDBD Plasma Actuator". Energies 12, nr 20 (9.10.2019): 3805. http://dx.doi.org/10.3390/en12203805.

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Quiescent flow and wind tunnel tests were performed to gain additional physical insights into flow control for automotive aerodynamics using surface dielectric barrier discharge plasma actuators. First, the aerodynamic characteristics of ionic wind were studied, and a maximum induced velocity of 3.3 m/s was achieved at an excitation voltage of 17 kV. Then, the optimal installation position of the actuator and the influence of the excitation voltage on flow control at different wind speeds were studied. The conclusions drawn are as follows. The effect of flow control is better when the upper electrode of the actuator is placed at the end of the top surface, increasing the likelihood of the plasma generation region approaching the natural separation location. The pressure on top of the slanted surface is primarily affected by airflow acceleration at a low excitation voltage and by the decrease of the separation zone at a high excitation voltage. The maximum drag reduction can be realized when the maximum velocity of ionic wind reaches 1.71 m/s at a wind speed of 10 m/s and 2.54 m/s at a wind speed of 15 m/s. Moreover, effective drag reduction can be achieved only by continuing to optimize the actuator to generate considerable thrust at a high wind speed.

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Zhang, Bo, Yang Wei Liu i Bao Jie Liu. "Numerical Simulation of Low Engine Order Excitation in a Transonic Compressor". Advanced Materials Research 546-547 (lipiec 2012): 206–11. http://dx.doi.org/10.4028/www.scientific.net/amr.546-547.206.

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A full-annulus unsteady quasi-3D simulation for a transonic compressor was conducted to investigate the low engine order excitation sources. A special inlet total pressure distortion was used in the simulation to account for the effect of non-axisymmetric tip clearance. The unsteady aerodynamic forces were obtained by integrating the static pressure along the blade surface. Furthermore, the effect of downstream rotor detached shock on upstream stator was analyzed. It was shown that the unsteady aerodynamic excitation of the rotor was subjected to the first two harmonic frequencies of the inlet distortion, and the adjacent stators’ basic frequency and lower harmonics. It was found that the detached shock had a significant impact on the surface static pressure distribution of the upstream stators.

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Bhattacharya, Satadru, i SujitKumar Dalui. "Effect of Aerodynamic Modification on ‘V’ plan Shaped Tall Building Under Wind Excitation". Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, nr 1 (19.12.2022): 1479–85. http://dx.doi.org/10.38208/acp.v1.679.

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Advanced high-rise buildings with peculiar cross-sectional plan is the major challenging concern to all structural engineers as well as researchers due to variation in dynamic wind response. Irregular shaped tall buildings are vulnerable to wind force due to height and nonuniformity of the structure. In the present study, the principal objective is to investigate the significant role of the aerodynamic modification of the building model to reduce the aerodynamic effect of wind force on ‘V’ plan shaped high-rise building and to modify aerodynamic design criteria accordingly. Various cases have been made by considering different local modification like corner chamfered and corner rounded of ‘V’ plan shaped building model. The angle between the limbs is 90° which remain unchanged. The percentage is gradually increased from 5% to 20% of the total plan area with 5% regular increment for both chamfered and rounded corner. Wind incident angle is increased from 0° to 90° with 30° regular interval for each case. Computational Fluid Dynamics (CFD) is the basis of method to perform the numerical simulation of ‘V’ plan shaped building with local modifications such as corner chamfered, corner rounded which is similar wind environment as in urban terrain. Grid convergence study is performed to improve the accuracy of result by adopting very finer meshing of Computational Domain. Pressure coefficient of each face, force coefficient, velocity variation, pressure variation on each face is obtained by numerical analysis. Further, a comparison has been made with basic ‘V’ plan shaped tall building model without any modification to study the effectiveness of aerodynamic modification on wind-induced response of ‘V’ plan shaped building exposed to different wind incidence angle and observations have been made on the suitability of aerodynamic modification based on the numerical result.

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Chen, Kun, Chen-Yao Wei i Zhi-Wei Shi. "Effect of NS-DBD Actuator Parameters on the Aerodynamic Performance of a Flap Lifting Device". Applied Sciences 9, nr 23 (30.11.2019): 5213. http://dx.doi.org/10.3390/app9235213.

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The flap lift device is an important part of the conventional configuration of aircrafts and has an important impact on the aerodynamic performance. In this paper, a high-efficiency, simple, and energy-saving nanosecond dielectric barrier discharge (DBD) plasma actuator is placed in the vicinity of the flap lift device to improve the aerodynamic performance of the flap by controlling the flow field. The two-dimensional airfoil GAW-1 and its 29% flap were selected as the research objects, and the nanosecond (NS) DBD actuators were fixed at different locations near the deflection angle of the 10°flap. The excitation frequency, pulse width, and energy density parameters of the pulse discharge were adjusted, and then, the effects of parameter changes on aerodynamic characteristics of the airfoil were studied by numerical simulation. The simulation results show that adjusting the excitation frequency on the aerodynamic drag is weak and that the effect on the aerodynamic lift is obvious. The increase of the discharge pulse width will have a more significant effect on the flow field, i.e., a proper increase of the discharge pulse width can achieve better drag reduction, and increase lift after a stall at a high angle of attack. Although the increase of discharge energy density can strengthen the pulse perturbation effect on the flow field, it also contributes to some adverse effects and has no obvious optimization effect on the control efficiency of lift increase and drag reduction.

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Pan, Lei, Mingyang Yang, Shota Murae, Wataru Sato, Tomoki Kawakubo, Akihiro Yamagata i Kangyao Deng. "Study on aerodynamic excitation of radial turbine blades with vaneless volute at low excitation order". Journal of Fluids and Structures 107 (listopad 2021): 103408. http://dx.doi.org/10.1016/j.jfluidstructs.2021.103408.

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Jing, Zhiwei, i Chu Tang. "Dynamic Response Analysis of the Aircraft Exposed to the Lateral Travelling Gust". Journal of Physics: Conference Series 2364, nr 1 (1.11.2022): 012024. http://dx.doi.org/10.1088/1742-6596/2364/1/012024.

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Abstract The travelling gust from detonation is an interesting and severe excitation for a flying aircraft, and it is characterized by high emanating speed and takes strong energy. Previous investigations on the dynamic response characteristics of the aircraft in the tail-on or head-on travelling gust have been carried out. This paper focuses on the lateral travelling gust and its influence on the dynamic response of the aircraft. Based on conventional flight dynamics equations, the dynamics modelling and simulation technique of the rigid aircraft exposed to the lateral travelling gust is established. By employing the static pressure distributions, one quasi-steady aerodynamics computation method is presented to determine the aerodynamic force and moment on the aircraft in the travelling gust. Simulation results show that the approach presented in this paper is effective and can deal with the engineering requirement. Results also indicate that the enveloping process of the travelling gust increases the aerodynamic moment of the x-axis significantly and subsequently influences the dynamic responses along the x-axis.

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IWAI, Yoshinobu, Hiroshi AOKI, Hiroyuki ABE, Yoshihiro KIKUSHIMA i Eizi KATO. "118 Improvement of Aerodynamic Characteristics for Airfoil by Acoustic Excitation". Proceedings of the Symposium on Environmental Engineering 2007.17 (2007): 85–88. http://dx.doi.org/10.1299/jsmeenv.2007.17.85.

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HIROAKI, Keiichi, Hiroki UBANO i Masahiro WATANABE. "Vibration Response of a Web Partially Subjected to Aerodynamic Excitation". Proceedings of Mechanical Engineering Congress, Japan 2018 (2018): J1020301. http://dx.doi.org/10.1299/jsmemecj.2018.j1020301.

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Li, Tian, Qingshan Yang i Takeshi Ishihara. "Unsteady aerodynamic characteristics of long-span roofs under forced excitation". Journal of Wind Engineering and Industrial Aerodynamics 181 (październik 2018): 46–60. http://dx.doi.org/10.1016/j.jweia.2018.08.005.

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Jasinski, Christopher, i Thomas Corke. "Acoustic excitation impact on aerodynamic drag measured in aeroacoustic liners". Journal of the Acoustical Society of America 142, nr 4 (październik 2017): 2514–15. http://dx.doi.org/10.1121/1.5014185.

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Ma, Jiaobin, Zhufeng Liu, Yunzhu Li i Yonghui Xie. "Prediction Method of Unsteady Flow Load of Compressor Stator under Working Condition Disturbance". Applied Sciences 12, nr 22 (14.11.2022): 11566. http://dx.doi.org/10.3390/app122211566.

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Due to the complexity of the compressor operating conditions and the existence of various disturbances and unsteady effects in the flow field, the analysis of compressor stator vibration characteristics becomes particularly critical. The convolutional neural network model combined with a transient CFD method was introduced to solve the difficulty of analyzing the flow load of the compressor stator blade. This paper mainly focuses on two key points: the complex change of the aerodynamic load and the accurate prediction of the blade excitation. Considering the stator–rotor interference, the unsteady effects, and the variable working condition characteristics, the random disturbance analysis model of the flow field boundary was generated to simulate the unsteady flow excitation of the stator under complex working conditions. By establishing the neural network of boundary disturbance and flow excitation characteristics, the prediction model was trained and generated under the support of large-scale data. The most important role of the model was to establish the end-to-end data mapping between the disturbance condition and the aerodynamic load of the stator blade. The conclusions demonstrate that the introduction of an airflow disturbance is helpful to obtain the excitation characteristics of the stator under complex working conditions. The model established in this paper based on 1000 groups of disturbed working condition data can effectively predict the aerodynamic load of the blades under complex working conditions. In addition, the construction of the model is beneficial for saving a lot of computing resources, and the prediction accuracy also reaches a good level. The method presented in this paper provides a reference for the vibration analysis of the compressor stator.

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Zhang, Di, Ma Jiao-Bin i Qi Jing. "Numerical study of unsteady flow and exciting force for swept turbomachinery blades". Thermal Science 20, suppl. 3 (2016): 669–76. http://dx.doi.org/10.2298/tsci160205199z.

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The aerodynamic performance of blade affects the vibration characteristics and stable operation of turbomachinery closely. The aerodynamic performance of turbine stage can be improved by using swept blade. In this paper, the RANS method and the RNG k-? turbulence mode were adopted to investigate the unsteady flow characteristics and excitation force of swept blade stage. According to the results, for the swept blade, the fluid of boundary layer shifts in radial direction due to the influence of geometric construction. It is observed that there is similar wake development for several kinds of stators, and the wake has a notable effect on the boundary layer of the rotor blades. When compared with straight blade, pressure fluctuation of forward-swept blade is decreased while the pressure fluctuation of backward-swept blade is increased. The axial and tangential fundamental frequency excitation force factors of 15?forward-swept blade are 0.139 and 0.052 respectively, which are the least, and all excitation force factors are in the normal range. The excitation factor of the forward-swept blade is decreased compared with straight blade, and the decreasing percentage is closely related to the swept angle. As for backward-swept blades, the situation is the other way around. Additionally, the change of axial excitation factor is more obvious. So the vibration reduction performance of forward-swept blade is better.

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Srinivasan, A. V., i D. G. Cutts. "Aerodynamically Excited Vibrations of a Part-Span Shrouded Fan". Journal of Engineering for Gas Turbines and Power 107, nr 2 (1.04.1985): 399–407. http://dx.doi.org/10.1115/1.3239740.

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The structural response of a part-span shrouded fan due to an aerodynamic excitation was measured using strain gages. The excitation was provided by means of a 4-lobed distortion screen mounted upstream of the rotor. Vibration measurements made with tuned and mistuned conditions at integral order speeds have been analyzed to determine the aeromechanical response charcteristics of the assembly. The results from the experimental investigation are presented and discussed.

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32

Nusser, Katrin, i Stefan Becker. "Numerical investigation of the fluid structure acoustics interaction on a simplified car model". Acta Acustica 5 (2021): 22. http://dx.doi.org/10.1051/aacus/2021014.

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Part of vehicle interior noise is caused by the complex turbulent flow field behind the a-pillar and side mirror. It excites the structure of the side window, which radiates noise into the interior. Both aerodynamic pressure excitation and acoustic sound sources in the flow play an important role. In this work, the influence of both excitation mechanisms is investigated numerically in a hybrid simulation on a simplified car geometry. The generic model allows for an exact definition of boundary conditions and good reproducibility of simulation results. An incompressible Large-Eddy-Simulation (LES) of the flow is conducted, from which acoustic source terms within the flow field and transient fluid forces acting on the surface of the side window are extracted. This data is used in a coupled vibroacoustic and aeroacoustic simulation of the structure and passenger cabin of the vehicle. A finite element (FE) approach is used for the simulations and detailed modeling of the structure and the influence of interior absorption properties is emphasized. The computed excitation on the side window and the interior noise levels are successfully validated by using experimental data. The importance and contribution of both aerodynamic and acoustic pressure excitation to the interior sound level are determined.

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33

Darling, J., i P. M. Staden. "A Study of caravan unsteady aerodynamics". Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 217, nr 7 (1.07.2003): 551–60. http://dx.doi.org/10.1243/095440703322114933.

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The high speed stability and handling characteristics of car-trailer combinations are affected by both road and aerodynamic forces. While the tyre-to-road interaction is well understood the action of gusts, passing large vehicles and even small steering inputs will disturb the symmetry of flow and generate aerodynamic forces and moments which are suffcient to affect the handling of the system. Although accidents caused by high speed instability are relatively uncommon a better understanding of these aerodynamic effects will improve safety. In this paper a series of wind tunnel investigations using scale models are presented. Steady state investigations were used to measure the aerodynamic properties of the car-caravan pair while a novel technique was developed to measure the aerodynamic damping derivatives in yaw and side force for a caravan model. These damping derivatives were shown to be destabilizing in most cases of sideslip and stabilizing in yaw although it was demonstrated that high damping derivatives were attained at certain frequencies of excitation.

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34

Mailach, Ronald, Lutz Mu¨ller i Konrad Vogeler. "Rotor-Stator Interactions in a Four-Stage Low-Speed Axial Compressor—Part II: Unsteady Aerodynamic Forces of Rotor and Stator Blades". Journal of Turbomachinery 126, nr 4 (1.10.2004): 519–26. http://dx.doi.org/10.1115/1.1791642.

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This two-part paper presents detailed experimental investigations of unsteady aerodynamic blade row interactions in the four-stage low-speed research compressor of Dresden. In Part I of the paper the unsteady profile pressure distributions for the nominal setup of the compressor are discussed. Furthermore the effect of blade row clocking on the unsteady profile pressures is investigated. Part II deals with the unsteady aerodynamic blade forces, which are determined from the measured profile pressure distributions. A method to calculate the aerodynamic blade forces on the basis of the experimental data is presented. The resulting aerodynamic blade forces are discussed for the rotor and stator blade rows of the first stage and the third stage of the compressor. Different operating points between design point and stability limit of the compressor were chosen to investigate the influence of loading on the aerodynamic force excitation. The time traces and the frequency contents of the unsteady aerodynamic blade force are discussed. Strong periodic influences of the incoming wakes and of potential effects of downstream blade rows can be observed. The amplitude and shape of the unsteady aerodynamic blade force depend on the interaction of the superimposed influences of the blade rows.

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35

Karakozova, Anastasia, i Vladimir Mondrus. "RESONANT VORTEX EXCITATION OF HIGH-RISE STRUCTURES". International Journal for Computational Civil and Structural Engineering 19, nr 2 (27.06.2023): 60–70. http://dx.doi.org/10.22337/2587-9618-2023-19-2-60-70.

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Subject of the research: Today, the design of flexible, extended in length and height structures of transport, industry, communication is one of the important directions of construction development. Such structures include continuous extended metal constructions such as chimneys, poles, billboards, monuments, bridges, pipelines. Besides ensuring the limit states for strength and deformability, there is another important condition for the durable operation of metal structures which is the absence of aerodynamic instability phenomena (mainly wind resonance) during the whole service life. Objectives: Review of the background, analysis of accidents that have occurred, proposals to avoid such situations at the design stage and in the occurrence of emergency conditions at existing facilities. Materials and methods: Review and analysis of existing data and proposals for further improvement of calculation and design methods. Results: The paper analyzes the mechanisms of the main types of aerodynamic instability (wind resonance, flutter, galloping, oscillations in the airfoil) on different types of structures, presents particular cases of the history of famous unique constructions and the authors' calculation practice, describes the ways to avoid this type of phenomena in the design of new buildings or in emergency situations on existing structures. Conclusions: The phenomena described in the article are applicable to an extremely narrow area of construction and are often ignored in calculation and design. This article is intended to draw special attention to these phenomena not only for designers, but also for research engineers in order to create new mechanisms for their analysis.

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36

Tang, D. M., i E. H. Dowell. "Theoretical and Experimental Study on Nonlinear Response of a Rotor Blade to a Gust". Applied Mechanics Reviews 46, nr 11S (1.11.1993): S3—S11. http://dx.doi.org/10.1115/1.3122655.

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A rotating slotted cylinder (RSC) gust generator installed in the Duke University low speed wind tunnel was used to generate a gust excitation field and the nonlinear response of a flexible rotor blade to gust excitations was studied theoretically and experimentally. The quantitative agreement between theory and experiment indicates that the assumption of an uniform chordwise gust angle of attack and an approximate solution procedure of the nonlinear equations proposed are allowable for the parameter range considered in this study. For a periodic gust flow field, the effects of geometric structural nonlinearity and aerodynamic nonlinearity on dynamic aeroelastic behavior are significant and lead to aperiodic or chaotic motion when stall occurs.

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37

Chen, J., i Q. S. Li. "Analysis of Flutter and Nonlinear Dynamics of a Composite Laminated Plate". International Journal of Structural Stability and Dynamics 16, nr 06 (czerwiec 2016): 1550019. http://dx.doi.org/10.1142/s0219455415500194.

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This paper presents the analysis of flutter and nonlinear dynamics of an orthotropic composite laminated rectangular plate subjected to aerodynamic pressures and transverse excitation. The first-order linear piston theory is employed to model the air pressures. Based on Reddy’s third-order shear deformation plate theory and von Karman-type equation for the geometric nonlinearity, the nonlinear governing equations of motion are derived for the composite laminated rectangular plate by applying the Hamilton’s principle. The Galerkin method is utilized to discretize the partial differential governing equations to a set of nonlinear ordinary differential equations. The critical Mach number for occurrence of the flutter of the composite laminated plate is investigated by solving the eigenvalues problem. The relationship between the limit cycle oscillation and the critical Mach number is analyzed based on the nonlinear equations. The numerical simulation is conducted to study the influences of the transverse excitation on the nonlinear dynamics of the composited laminated plate. The numerical results, which include bifurcation diagram, phase plots and waveforms, demonstrate that there exist the bifurcation and chaotic motions of the composited laminated plate subjected to the aerodynamic pressures and the transverse excitation.

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38

Fu, Xi, Chao Ma, Jiewei Lin i Junhong Zhang. "Numerical Study on Vibration Response and Fatigue Damage of Axial Compressor Blade Considering Aerodynamic Excitation". Metals 11, nr 11 (15.11.2021): 1835. http://dx.doi.org/10.3390/met11111835.

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Axial compressor blades with a deformed initial torsion angle caused by aerodynamic excitation resonated at the working speed and changed the rule of fatigue damage accumulation. The fatigue life of a blade has a prediction error, even causing serious flight accidents if the effect of torque causing damage deterioration of the blade fatigue life is neglected. Therefore, in this paper, a uniaxial non-linear fatigue damage model was modified using the equivalent stress with torsional shear stress, and the proposed fatigue model including the torsional moment was used to study the compressor blade fatigue life. Then, the blade numerical simulation model was established to calculate the vibration characteristics under complex loads of airflow excitation and a rotating centrifugal force. Finally, the blade fatigue life under actual working conditions was predicted using the modified fatigue model. The results show that the interaction between centrifugal and aerodynamic loads affects the natural frequency, as the frequencies in modes dominated by bending deformation decreased whereas those dominated by torsional deformation increased. Furthermore, the blade root of the suction surface showed stress concentration, but there is an obvious difference of stress distribution and amplitude between the normal stress and the equivalent stress including torsional shear stress. The additional consideration of the torsional shear stress decreased the predicted fatigue life by 4.5%. The damage accumulation rate changes with the loading cycle, and it accelerates fast for the last 25% of the cycle, when the blade fracture may occur at any time. Thus, the aerodynamic excitation increased the safety factor of blade fatigue life prediction.

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39

Guo, Xiangying, Pan Jiang i Dongxing Cao. "Influence of Piezoelectric Performance on Nonlinear Dynamic Characteristics of MFC Shells". Complexity 2019 (9.10.2019): 1–15. http://dx.doi.org/10.1155/2019/1970248.

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Based on the structures of unmanned aerial vehicle (UAV) wings, nonlinear dynamic analysis of macrofiber composite (MFC) laminated shells is presented in this paper. The effects of piezoelectric properties and aerodynamic forces on the dynamic stability of the MFC laminated shell are studied. Firstly, under the flow condition of ideal incompressible fluid, the thin airfoil theory is employed to calculate the effects of the mean camber line to obtain the circulation distribution of the wings in subsonic air flow. The steady aerodynamic lift on UAV wings is derived by using the Kutta–Joukowski lift theory. Then, considering the geometric nonlinearity and piezoelectric properties of the MFC material, the nonlinear dynamic model of the MFC laminated shell is established with Hamilton’s principles and the Galerkin method. Next, the effects of electric field, external excitation force, and nonlinear parameters on the stability of the system are studied under 1 : 1 internal resonance and the effects of material parameters on the natural frequency of the structure are also analyzed. Furthermore, the influence of the aerodynamic forces and electric field on the nonlinear dynamic responses of MFC laminated shells is discussed by numerical simulation. The results indicate that the electric field and external excitation have great influence on the structural dynamic responses.

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40

Liu, Ying, Xiaobo Zhang i Fei Zhang. "Simulation of flutter suppression for a transonic fan blade based on plasma excitation". MATEC Web of Conferences 355 (2022): 01018. http://dx.doi.org/10.1051/matecconf/202235501018.

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Along with the development of advanced high-performance aero-engines to the higher thrust-weight ratio, further improvement of stage load, the adoption of new materials and new lightweight structures, the aeroelasticity of blade structure is becoming more and more prominent. The high cycle fatigue failure of blades significantly reduces the structural reliability during the process of development and using. At the same time, a large number of failure forms of aero-engine experimental and server can be attributed to aeroelastic problems. Therefore, it is urgent to improve the aeroelastic stability of the blade. One of the most important factors is to suppress the airflow separation, but its mechanism is still unclear. Based on this, this paper combines the aerodynamic damping analysis of energy method with the plasma excitation simulation and references low-speed wind tunnel plasma expansion test to consider the effects of different exciter distributions and intensities on flutter. The results show that stall flutter is related to the flow separation, but the flow separation is not a key factor that determinates whether the flutters occurs or not. Flutter suppression is strongly correlated with the shock wave intensity, amplitude of first harmonic aerodynamic force, low-speed separation and aerodynamic work density. In addition, the relative distribution of the excitation field and the positive work zone also has a direct effect on the suppression of flutter.

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41

Peil, Udo, i Matthias Behrens. "Aerodynamic admittance models for buffeting excitation of high and slender structures". Journal of Wind Engineering and Industrial Aerodynamics 95, nr 2 (luty 2007): 73–90. http://dx.doi.org/10.1016/j.jweia.2006.05.007.

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42

Ota, H., Y. Shimizu i T. Sato. "Direct measurement of aerodynamic excitation force generated by rotating-blade fan". Noise Control Engineering Journal 57, nr 4 (2009): 310. http://dx.doi.org/10.3397/1.3151962.

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43

SHIMIZU, Yohei, Hiroki OTA i Taichi SATO. "2101 Vibration of Structure Induced by Aerodynamic Excitation Force of Fan". Proceedings of the Conference on Information, Intelligence and Precision Equipment : IIP 2007 (2007): 140–45. http://dx.doi.org/10.1299/jsmeiip.2007.140.

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44

Liu, Xiaohui, Haobo Liang, Guangyun Min, Chuan Wu i Mengqi Cai. "Investigation on the Nonlinear Vibration Characteristics of Current-Carrying Crescent Iced Conductors under Aerodynamic Forces, Ampere’s Forces, and Forced Excitation Conditions". Discrete Dynamics in Nature and Society 2021 (12.10.2021): 1–22. http://dx.doi.org/10.1155/2021/5009209.

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Aiming at the problem of nonlinear vibration of current-carrying iced conductors, the aerodynamic forces are introduced into the previous vibration equation of current-carrying conductors that only considered Ampere’s forces. At the same time, on this basis, a forced excitation load is further introduced to study the influence of dynamic wind on the nonlinear vibration characteristics of current-carrying iced conductors, and a new current-carrying iced conductors system under the combined action of Ampere’s forces, forced excitation, and aerodynamic forces has been established, and the improved theoretical modeling of current-carrying iced transmission lines made the model more in line with practical engineering. Firstly, the model of current-carrying iced conductors was established, and then the vibration equation of the model was derived. And the vibration equation was transformed into a finite dimensional ordinary differential equation by using the Galerkin method. The amplitude-frequency response functions of the nonlinear forced primary resonances and super-harmonic and subharmonic resonances of the system are derived by using the multiscale method. Through numerical calculation, the influence of current-carrying, spacing, wind velocity, tension, and excitation amplitude on the response amplitude when the primary resonance of the system appears is analyzed, and the difference between the two working conditions (considering the aerodynamic forces and without considering aerodynamic forces) is compared. The influence of the variation of current-carrying i on the response amplitude of super-harmonic and subharmonic resonances and the stability of the steady-state solution of forced primary resonance was analyzed. The results show that the response amplitude and the nonlinearilty of system under the action of aerodynamic forces are smaller and weaker than without the action of aerodynamic forces; the variation of line parameters has a certain influence on the response amplitude of conductor and the nonlinearity of system; the response amplitudes of the primary resonance, super-harmonic resonance, and subharmonic resonance increase with the increase in the excitation amplitudes, and the resonance peak is offset towards the negative value of the tuning parameter σ, showing the characteristics of soft spring, and the response amplitudes are accompanied by complex nonlinear dynamic behaviors such as the multivalue and jump phenomenon. The change of current-carrying i has an obvious effect on the nonlinearity of the system. The nonlinear and response amplitudes of the system are also enhanced with the increase in wind velocity. The stability of the system is judged when the primary resonance occurs, and it is found that the response amplitude shows synchronization and the out-of-step phenomenon with the change of tuning parameters. The research results obtained in this paper would help to further improve the theoretical modeling about current-carrying iced lines, and the research of line parameters can give a certain reference value to practical engineering, and it will have a positive effect on the safe operation of high-voltage transmission lines.

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45

Wang, Binwen, i Xueling Fan. "Ground Flutter Simulation Test Based on Reduced Order Modeling of Aerodynamics by CFD/CSD Coupling Method". International Journal of Applied Mechanics 11, nr 01 (styczeń 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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46

Vacula, Jiří, i Pavel Novotný. "Identification of Aerodynamic Tonal Noise Sources of a Centrifugal Compressor of a Turbocharger for Large Stationary Engines". Applied Sciences 13, nr 10 (12.05.2023): 5964. http://dx.doi.org/10.3390/app13105964.

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The aerodynamics of centrifugal compressors is a topical issue, as the vibrations and noise reduce the comfort of people who are in proximity to the compressor. The current trend in rotating machinery research is therefore not only concerned with performance parameters but also increasingly with the effect on humans. An analysis of aerodynamic noise based on external acoustic field measurements may be a way to assess the nature of aerodynamic excitation. In this research, the experimental measurements at 20 operating points covered the entire characteristic operating range of the selected centrifugal compressor. The dominant noise arising at blade-passing frequency (BPF) was identified at all the operational points, and the dominant effect of the buzz-saw noise was identified at the maximum rotor speed. The determination of the total sound pressure level LPA showed a trend towards an increasingly higher rotor speed and compressor surge line. In the amplitude-frequency characteristics, the sound pressure was found to be dependent on the rotor speed for BPF. On the other hand, non-monotonicity was detected between the operational points at given speed lines, confirming the complexity of the aerodynamics of rotating machines. The metric chosen to identify prominent tones determined by the tonality of individual tones in the frequency spectrum showed a clear effect of integer multiples of the rotational frequency on the overall noise. Thus, the results presented here confirm the dominant influence of BPF in terms of the psychoacoustic impact on humans.

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47

Yang, Li, i Yu Xin Hao. "Analysis of Aerodynamics Behavior of FGM Cylindrical Panel". Applied Mechanics and Materials 364 (sierpień 2013): 118–23. http://dx.doi.org/10.4028/www.scientific.net/amm.364.118.

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An analysis on the aerodynamics behavior of a FGM cylindrical panel in air flow subjected to an external excitation is presented in this paper. Material properties of the constituents are assumed to be temperature-independent and the effective properties of FGM panel are graded according to a simple power law function in terms of the volume fractions in thickness direction. Based on von Karman hypothesis and Hamilton’s principle, the nonlinear governing equations of motion are derived. Galerkin’s method is then utilized to obtain a two-degree-of-freedom nonlinear system including the quadratic and cubic nonlinear terms. A third-order piston theory is applied for the aerodynamic load. The bifurcations are presented for FGM panel by numerical simulation to show the influences of in-plane load on the nonlinear dynamics.

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48

HAYASAKA, Kohei, Keiichi HIROAKI i Masahiro WATANABE. "Aerodynamic Excitation Response of a Flat Plate with Elastic Support and Measurement of Excitation Fluid Force Distribution". Proceedings of Mechanical Engineering Congress, Japan 2018 (2018): J1020303. http://dx.doi.org/10.1299/jsmemecj.2018.j1020303.

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49

Zheng, Xin-qian, Xiao-bo Zhou i Sheng Zhou. "Investigation on a Type of Flow Control to Weaken Unsteady Separated Flows by Unsteady Excitation in Axial Flow Compressors". Journal of Turbomachinery 127, nr 3 (1.03.2004): 489–96. http://dx.doi.org/10.1115/1.1860572.

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By solving unsteady Reynolds-averaged Navier-Stokes equations discretized by a high-order scheme, the results showed that the disordered unsteady separated flow could be effectively controlled by periodic suction and blowing in a wide range of incidences, resulting in enhancement of time-averaged aerodynamic performances of an axial compressor cascade. The effects of unsteady excitation frequency, amplitude, and excitation location were investigated in detail. The effective excitation frequency spans a wide spectrum, and there is an optimal excitation frequency that is nearly equal to the characteristic frequency of vortex shedding. Excitation amplitude exhibits a threshold value (nearly 10% in terms of the ratio of maximum velocity of periodic suction and blowing to the velocity of free flow) and an optimal value (nearly 35%). The optimal excitation location is just upstream of the separation point. We also explored feasible unsteady actuators by utilizing the upstream wake for constraining unsteady separation in axial flow compressors.

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50

Mailach, Ronald, i Konrad Vogeler. "Unsteady Aerodynamic Blade Excitation at the Stability Limit and During Rotating Stall in an Axial Compressor". Journal of Turbomachinery 129, nr 3 (25.07.2006): 503–11. http://dx.doi.org/10.1115/1.2720486.

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The stable operating range of axial compressors is limited by the onset of rotating stall and surge. These flow conditions endanger the reliability of operation and definitely have to be avoided in compressors of gas turbines. However, there is still a need to improve the physical understanding of these flow phenomena to prevent them while utilizing the maximum available working potential of the compressor. This paper discusses detailed experimental investigations of the rotating stall onset with the main emphasis on the aerodynamic blade excitation in the Dresden four-stage low-speed research compressor. The stall inception, which is triggered by modal waves, as well as the main flow features during rotating stall operation are discussed. To investigate the unsteady pressure distributions, both the rotor and the stator blades of the first stage were equipped with piezoresistive pressure transducers. Based on these measurements the unsteady blade pressure forces are calculated. Time-resolved results at the stability limit as well as during rotating stall are presented. For all operating conditions rotor–stator interactions play an important role on the blade force excitation. Furthermore the role of the inertia driven momentum exchange at the stall cell boundaries on the aerodynamic blade force excitation is pointed out.

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