Relevant bibliographies by topics / Aerodynamic excitation

Academic literature on the topic 'Aerodynamic excitation'

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Published: 6 September 2023
Last updated: 7 September 2023

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Journal articles on the topic "Aerodynamic excitation"

1

Liu, Jian, Wei-Yang Qiao, and Wen-Hua Duan. "Investigation of Unsteady Aerodynamic Excitation on Rotor Blade of Variable Geometry Turbine." International Journal of Rotating Machinery 2019 (May 21, 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, no. 2 (April 1, 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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Stamatellou, Antiopi-Malvina, and Anestis I. Kalfas. "On the Efficiency of a Piezoelectric Energy Harvester under Combined Aeroelastic and Base Excitation." Micromachines 12, no. 8 (August 14, 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, and Hans A. DeSmidt. "Stability Analysis of a Flutter Panel with Axial Excitations." Advances in Acoustics and Vibration 2016 (July 31, 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, and 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, no. 11 (October 20, 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, and L. S. Song. "Dynamic Stability of Fluttered Systems Subjected to Parametric Random Excitations." Journal of Vibration and Control 8, no. 3 (March 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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Pust, Ladislav, and Ludek Pesek. "Blades Forced Vibration Under Aero-Elastic Excitation Modeled by Van der Pol." International Journal of Bifurcation and Chaos 27, no. 11 (October 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, and Manlu Li. "Aerodynamic Damping Prediction for Turbomachinery Based on Fluid-Structure Interaction with Modal Excitation." Applied Sciences 9, no. 20 (October 18, 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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Zahn, R., and C. Breitsamter. "Airfoil buffet aerodynamics at plunge and pitch excitation based on long short-term memory neural network prediction." CEAS Aeronautical Journal 13, no. 1 (October 18, 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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Chiang, Hsiao-Wei D., and R. E. Kielb. "An Analysis System for Blade Forced Response." Journal of Turbomachinery 115, no. 4 (October 1, 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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Dissertations / Theses on the topic "Aerodynamic excitation"

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Laumert, Björn. "Numerical Investigation of Aerodynamic Blade Excitation Mechanisms in Transonic Turbine Stages." Doctoral thesis, KTH, Energy Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3417.

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With the present drive in turbomachine engine developmenttowards thinner and lighter bladings, closer spaced blade rowsand higher aerodynamic loads per blade row and blade, advanceddesign criteria and accurate prediction methods for vibrationalproblems such as forced response become increasingly importantin order to be able to address and avoid fatigue failures ofthe machine early in the design process. The present worksupports both the search for applicable design criteria and thedevelopment of advanced prediction methods for forced responsein transonic turbine stages. It is aimed at a betterunderstanding of the unsteady aerodynamic mechanisms thatgovern forced response in transonic turbine stages and furtherdevelopment of numerical methods for rotor stator interactionpredictions.

The investigation of the unsteady aerodynamic excitationmechanisms is based on numerical predictions of thethree-dimensional unsteady flow field in representative testturbine stages. It is conducted in three successive steps. Thefirst step is a documentation of the pressure perturbations onthe blade surface and the distortion sources in the bladepassage. This is performed in a phenomenological manner so thatthe observed pressure perturbations are related to thedistortion phenomena that are present in the blade passage. Thesecond step is the definition of applicable measures toquantify the pressure perturbation strength on the bladesurface. In the third step, the pressure perturbations areintegrated along the blade arc to obtain the dynamic bladeforce. The study comprises an investigation of operationvariations and addresses radial forcing variations. With thehelp of this bottom-up approach the basic forcing mechanisms oftransonic turbine stages are established and potential routesto control the aerodynamic forcing are presented.

For the computation of rotor stator interaction aerodynamicsfor stages with arbitrary pitch ratios a new numerical methodhas been developed, validated and demonstrated on a transonicturbine test stage. The method, which solves the unsteadythree-dimensional Euler equations, is formulated in thefour-dimensional time-space domain and the derivation of themethod is general such that both phase lagged boundaryconditions and moving grids are considered. Time-inclination isutilised to account for unequal pitchwise periodicity bydistributing time co-ordinates at grid nodes such that thephase lagged boundary conditions can be employed. The method isdemonstrated in a comparative study on a transonic turbinestage with a nominal non integer blade count ratio and anadjusted blade count ratio with a scaled rotor geometry. Thepredictions show significant differences in the blade pressureperturbation signal of the second vane passing frequency, whichwould motivate the application of the new method for rotorstator predictions with non-integer blade count ratios.

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Ilgin, Huseyin Emre. "A Study On Tall Buildings And Aerodynamic Modifications Against Wind Excitation." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607000/index.pdf.

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The purpose of this thesis is to create basic design guidance for tall buildings and their aerodynamic modifications as a resource for architects, engineers, developers, and students. It aims to make a contribution to and strengthen particularly the architect&
#8217
s understanding of tall building design, that requires a high level of interdisciplinary approach, by providing a broad overview of the tall building with its general concepts
to demonstrate the importance of human element as a critical component in the design of tall building by clarifying the wind forces and resulting movements which cause discomfort to building occupants and create serious serviceability issues
and to show the significance of aerodynamic modifications as an effective design approach in terms of mitigating wind excitation. In order to achieve these purposes, firstly, a comprehensive literature survey, which includes the definition, emergence and historical background, basic planning and design parameters, and lateral load considerations of tall buildings is presented. Following a structural classification of the tall buildings, wind excitation, its negative effects on occupant comfort and serviceabilty issues, and the methods to control wind excitation are studied. Finally, the significance of aerodynamic modifications against wind excitation, which include modifications of building&
#8217
s cross-sectional shape and its corner geometry, sculptured building tops, horizontal and vertical openings through-building, are presented from the scholarship on this topic.
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Jöcker, Markus. "Numerical Investigation of the Aerodynamic Vibration Excitation of High-Pressure Turbine Rotors." Doctoral thesis, KTH, Energy Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3416.

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The design parameters axial gap and stator count of highpressure turbine stages are evaluated numerically towards theirinfluence on the unsteady aerodynamic excitation of rotorblades. Of particular interest is if and how unsteadyaerodynamic considerations in the design could reduce the riskofhigh cycle fatigue (HCF) failures of the turbine rotor.

A well-documented 2D/Q3D non-linear unsteady code (UNSFLO)is chosen to perform the stage flow analyses. The evaluatedresults are interpreted as aerodynamic excitation mechanisms onstream sheets neglecting 3D effects. Mesh studies andvalidations against measurements and 3D computations provideconfidence in the unsteady results. Three test cases areanalysed. First, a typical aero-engine high pressure turbinestage is studied at subsonic and transonic flow conditions,with four axial gaps (37% - 52% of cax,rotor) and two statorconfigurations (43 and 70 NGV). Operating conditions areaccording to the resonant conditions of the blades used inaccompanied experiments. Second, a subsonic high pressureturbine intended to drive the turbopump of a rocket engine isinvestigated. Four axial gap variations (10% - 29% ofcax,rotor) and three stator geometry variations are analysed toextend and generalise the findings made on the first study.Third, a transonic low pressure turbine rotor, known as theInternational Standard Configuration 11, has been modelled tocompute the unsteady flow due to blade vibration and comparedto available experimental data.

Excitation mechanisms due to shock, potential waves andwakes are described and related to the work found in the openliterature. The strength of shock excitation leads to increasedpressure excitation levels by a factor 2 to 3 compared tosubsonic cases. Potential excitations are of a typical wavetype in all cases, differences in the propagation direction ofthe waves and the wave reflection pattern in the rotor passagelead to modifications in the time and space resolved unsteadypressures on the blade surface. The significant influence ofoperating conditions, axial gap and stator size on the wavepropagation is discussed on chosen cases. The wake influence onthe rotorblade unsteady pressure is small in the presentevaluations, which is explicitly demonstrated on the turbopumpturbine by a parametric study of wake and potentialexcitations. A reduction in stator size (towards R≈1)reduces the potential excitation part so that wake andpotential excitation approach in their magnitude.

Potentials to reduce the risk of HCF excitation in transonicflow are the decrease of stator exit Mach number and themodification of temporal relations between shock and potentialexcitation events. A similar temporal tuning of wake excitationto shock excitation appears not efficient because of the smallwake excitation contribution. The increase of axial gap doesnot necessarily decrease the shock excitation strength neitherdoes the decrease of vane size because the shock excitation mayremain strong even behind a smaller stator. The evaluation ofthe aerodynamic excitation towards a HCF risk reduction shouldonly be done with regard to the excited mode shape, asdemonstrated with parametric studies of the mode shapeinfluence on excitability.

Keywords:Aeroelasticity, Aerodynamics, Stator-RotorInteraction, Excitation Mechanism, Unsteady Flow Computation,Forced Response, High Cycle Fatigue, Turbomachinery,Gas-Turbine, High-Pressure Turbine, Turbopump, CFD, Design

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Elkoby, Ronen. "Acoustic excitation of wing wake flows." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/12265.

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Raubenheimer, Gert. "Vibration excitation of axial compressor rotor blades." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17987.

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Thesis (MScEng)--Stellenbosch University, 2011.
ENGLISH ABSTRACT: Turbomachines are exposed to several environmental factors which may cause failure of components. One of these factors, high cycle fatigue, is often caused by blade utter. This thesis forms part of a project of the European Seventh Framework Programme (FP7), called project Future. Project Future is doing theoretical and experimental investigation into the occurrence of utter in turbomachinery. The objective of this thesis was to evaluate the effectiveness of a gas injection system as a means of exciting vibrations on the rst stage rotor blades of a compressor. Unsteady simulations of the excitation velocity perturbations were performed in the Computational Fluid Dynamics (CFD) software, Numeca FINE/Turbo. Experimental testing on the in-house Rofanco compressor test bench, using one prototype of the 15 injector system, provided data that was used to implement boundary conditions and to verify certain aspects of the unsteady simulation results. The simulation results revealed the following: the injector bypass frequency was so dominant that the excitation frequency was hardly detectable in the majority of cases. Furthermore, several secondary frequencies were consistently present. The injector bypass frequency, as well as the secondary frequencies, occurred as a result of the convolution of Fast Fourier Transforms. While the injector bypass frequencies can theoretically be eliminated, it will not be possible to eliminate the secondary frequencies from the blade response. In conclusion, according to the CFD results, it will not be possible to excite a single excitation frequency by making use of a nite number of gas injector vibration exciters.
AFRIKAANSE OPSOMMING: Turbomasjiene word onderwerp aan verskeie omgewingsfaktore wat falings van komponente kan veroorsaak. Een van hierdie faktore, naamlik hoëfrekwensie vermoeidheid, word onder andere veroorsaak deur lem adder. Hierdie tesis is deel van 'n projek in die Sewende Europese Raamwerk Program (European Seventh Framework Programme - FP7), projek Future. Projek Future doen teoretiese en eksperimentele ondersoek na die voorkoms van lemfl adder in turbomasjienerie. Die doelwit van hierdie tesis was om die effektiwiteit van 'n gasinspuiter vibrasie-opwekkingstelsel te evalueer, deur gebruik te maak van onbestendige simulasie in die berekenings vloei-meganika sagtewarepakket, Numeca FINE/Turbo. Eksperimentele toetswerk op die plaaslike Rofanco kompressortoetsbank, met 'n prototipe van die 15 inspuiter stelsel, het inligting verskaf wat gebruik is om die inlaattoestande te spesi seer en simulasieresultate te korreleer. Die simulasieresultate het getoon dat die frekwensie waarteen 'n lem by die inspuiters verbybeweeg, so prominent is, dat dit in die meerderheid van gevalle baie meer prominent is as die opwekkingsfrekwensie. Verder was daar ook deurgaans 'n aantal sekondêre frekwensies teenwoordig. Die teenwoordigheid van die inspuiter verbybeweeg frekwensie en die sekondêre frekwensies is die resultaat van die konvolusie van Vinnige Fourier Transforme. Alhoewel dit in teorie moontlik sal wees om die inspuiter verbybeweeg frekwensie te elimineer, is dit onmoontlik om die sekondêre frekwensies uit die lem vibrasie te elimineer. Ter opsomming, volgens die berekenings vloei-meganika resultate, is dit nie moontlik om met 'n stelsel van 'n eindige aantal inspuiters, 'n enkele vibrasie frekwensie op te wek nie.
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Clifford, Christopher J. "An Investigation of Physics and Control of Flow Passing a NACA 0015 in Fully-Reversed Condition." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440156651.

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Sood, Sanjeev. "Active vibration control of flexible structures under aerodynamic excitation." Thesis, 2018. http://eprint.iitd.ac.in:80//handle/2074/7930.

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"A STUDY ON TALL BUILDINGS AND AERODYNAMIC MODIFICATIONS AGAINST WIND EXCITATION." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607000/index.pdf.

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LIU, CI-YAO, and 劉賜耀. "The influence of acoustic excitation on aerodynamic performance of three dimensional wings." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/44118131932286691071.

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Books on the topic "Aerodynamic excitation"

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Raman, Ganesh. Enhanced mixing of an axisymmetric jet by aerodynamic excitation. Cleveland, Ohio: Lewis Research Center, 1986.

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Raman, Ganesh. Enhanced mixing of an axisymmetric jet by aerodynamic excitation. Cleveland, Ohio: Lewis Research Center, 1986.

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M, Abbott John, and United States. National Aeronautics and Space Administration., eds. Control of flow separation and mixing by aerodynamic excitation. [Washington, D.C.]: NASA, 1990.

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M, Abbott John, and United States. National Aeronautics and Space Administration., eds. Control of flow separation and mixing by aerodynamic excitation. [Washington, D.C.]: NASA, 1990.

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United States. National Aeronautics and Space Administration., ed. Effect of acoustic excitation on stalled flows over an airfoil. [Washington, DC]: National Aeronautics and Space Administration, 1990.

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United States. National Aeronautics and Space Administration., ed. A steadying effect of acoustic excitation on transitory stall. [Washington, DC]: National Aeronautics and Space Administration, 1991.

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Center, Lewis Research, ed. Modal forced vibration analysis of aerodynamically excited turbosystems: Final report. Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, 1995.

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Martinez-Sanchez, Manuel. Turbine blade-tip clearance excitation forces: Final report on Contract number NAS8-35018. Cambridge, Mass: Massachusetts Institute of Technology, 1985.

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Martinez-Sanchez, Manuel. Turbine blade-tip clearance excitation forces: Final report on Contract number NAS8-35018. Cambridge, Mass: Massachusetts Institute of Technology, 1985.

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M, Greitzer Edward, George C. Marshall Space Flight Center., and Massachusetts Institute of Technology, eds. Turbine blade-tip clearance excitation forces: Final report on Contract number NAS8-35018. Cambridge, Mass: Massachusetts Institute of Technology, 1985.

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Book chapters on the topic "Aerodynamic excitation"

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Daborn, P. M., P. R. Ind, and D. J. Ewins. "Replicating Aerodynamic Excitation in the Laboratory." In Topics in Modal Analysis, Volume 7, 259–72. New York, NY: Springer New York, 2013. http://dx.doi.org/10.1007/978-1-4614-6585-0_24.

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Aubrun, Sandrine, Alain Seraudie, Daniel Biron, and Daniel Arnal. "Influence of Acoustic Excitation on 3D Boundary Layer Instabilities." In Aerodynamic Drag Reduction Technologies, 180–87. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-540-45359-8_20.

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Abegg, C., H. Bippes, A. Boiko, V. Krishnan, T. Lerche, A. Pöthke, Y. Wu, and U. Dallmann. "Transitional Flow Physics and Flow Control for Swept Wings: Experiments on Boundary-Layer Receptivity, Instability Excitation and HLF-Technology." In Aerodynamic Drag Reduction Technologies, 199–206. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-540-45359-8_22.

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Urban, Brigitte, Heinz Stetter, and Nicolas Vortmeyer. "Aerodynamic Excitation of Transonic Turbine Cascade; Description of the Experimental Method." In Notes on Numerical Fluid Mechanics (NNFM), 488–95. Wiesbaden: Vieweg+Teubner Verlag, 1999. http://dx.doi.org/10.1007/978-3-663-10901-3_63.

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Ichchou, Mohamed N., Olivier Bareille, Bernard Troclet, Bastien Hiverniau, Marie De Rochambeau, and Dimitrios Chronopoulos. "Vibroacoustics Under Aerodynamic Excitations." In Flinovia - Flow Induced Noise and Vibration Issues and Aspects, 227–47. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09713-8_11.

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Sato, W., A. Yamagata, and H. Hattori. "A study on unsteady aerodynamic excitation forces on radial turbine blade due to rotor-stator interaction." In 11th International Conference on Turbochargers and Turbocharging, 389–98. Elsevier, 2014. http://dx.doi.org/10.1533/978081000342.389.

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Conference papers on the topic "Aerodynamic excitation"

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Hauptmann, Thomas, and Joerg R. Seume. "Aerodynamic Excitation Analysis for Variable Tip Gap." In ASME Turbo Expo 2016: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/gt2016-57217.

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In jet engines, blade repair is often more economical than the replacement of damaged blades with spare parts. Besides such regeneration of turbine blades, blade rubbing and erosion lead to a deviation of the geometry in the tip region of the original blade. These geometric variations can introduce non-uniform flow conditions which in turn may lead to an excitation of the blades. An analysis of the aerodynamic excitation due to typical geometric variations of the radial tip gap, introduced through substantial wear, is numerically investigated using a fluid-structure interaction (FSI) approach. The model was previously validated against experimental data. The results of the analysis show up to 1.6 times higher excitation than in the reference case, because rotor blades are excited by the wakes of the stator vanes and are amplified by a modified tip flow in the rotor passage.
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Pourzeynali, S., and T. K. Datta. "RESPONSE OF SUSPENSION BRIDGES TO AERODYNAMIC EXCITATION." In Proceedings of the Second International Conference. WORLD SCIENTIFIC, 2002. http://dx.doi.org/10.1142/9789812776228_0040.

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Ewing, Mark. "Response of a tactical missile to aerodynamic excitation." In 36th Structures, Structural Dynamics and Materials Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 1995. http://dx.doi.org/10.2514/6.1995-1495.

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Kumar, Arun, Erik Sallstrom, Simone Sebben, and Bengt Jacobson. "Predictive Model of Driver’s Perception of Vehicle Stability under Aerodynamic Excitation." In WCX SAE World Congress Experience. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2023. http://dx.doi.org/10.4271/2023-01-0903.

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<div class="section abstract"><div class="htmlview paragraph">In vehicle development, a subjective evaluation of the vehicle’s behavior at high speeds is usually conducted by experienced drivers with the objective of assessing driving stability. To avoid late design changes, it is desirable to predict and resolve perceived instabilities early in the development phase. In this study, a mathematical model is developed from measurements during on-road tests to predict the driver’s ability to identify vehicle instabilities under excitations such as aerodynamic excitations. A vehicle is fitted with add-ons to create aerodynamic excitations and is driven by multiple drivers on a high-speed track. Drivers’ evaluation, responses, cabin motion, and crosswind conditions are recorded. The influence of yaw and roll rates, lateral acceleration, and steering angle at various frequency ranges when predicting the drivers’ evaluation of induced excitation is demonstrated. The drivers’ evaluation of vehicle behavior is influenced by driver-vehicle interactions. Excess rotational rates, defined as the part of rotational rates that are not the result of steering action, reduce the importance of steering as a predictor and improve the accuracy of the predictive model. The present model is compared with an earlier developed model derived from data from a driving simulator under preconditioned aerodynamic excitations.</div></div>
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Kielb, Robert E., John W. Barter, Jeffrey P. Thomas, and Kenneth C. Hall. "Blade Excitation by Aerodynamic Instabilities: A Compressor Blade Study." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38634.

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In this paper, we investigate non-synchronous vibrations (NSV) in turbomachinery, an aeromechanic phenomenon in which rotor blades are driven by a fluid dynamic instability. Unlike flutter, a self-excited vibration in which vibrating rotor blades and the resulting unsteady aerodynamic forces are mutually reinforcing, NSV is primarily a fluid dynamic instability that can cause large amplitude vibrations if the natural frequency of the instability is near the natural frequency of the rotor blade. In this paper, we present both experimental and computational data. Experimental data was obtained from a full size compressor rig where the instrumentation consisted of blade-mounted strain gages and case-mounted unsteady pressure transducers. The computational simulation used a three-dimensional Reynolds averaged Navier-Stokes (RANS) time accurate flow solver. The computational results suggest that the primary flow features of NSV are a coupled suction side vortex shedding and a tip flow instability. The simulation predicts a fluid dynamic instability frequency that is in reasonable agreement with the experimentally measured value.
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Li, Jianlan, Huafeng Liu, Chen Yu, and Shuhong Huang. "Catastrophe Performance Analysis of Aerodynamic Excitation for Steam Turbine." In 2012 IEEE PES Asia-Pacific Power and Energy Engineering Conference (APPEEC). IEEE, 2012. http://dx.doi.org/10.1109/appeec.2012.6307677.

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Melbourne, W. H. "Shaping Tall Buildings to Reduce Aerodynamic Excitation and Response." In Structures Congress 2000. Reston, VA: American Society of Civil Engineers, 2000. http://dx.doi.org/10.1061/40492(2000)89.

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Bibo, Amin, and Mohammed F. Daqaq. "Energy Harvesting Under Combined Aerodynamic and Base Excitations." In ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-7908.

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This paper investigates the transduction of a piezoaeroelastic energy harvester under combined base and aerodynamic loadings. The harvester consists of a typical rigid airfoil supported by hardening flexural and torsional springs. The airfoil is placed in an incompressible air flow and subjected to a harmonic base excitation in the plunge direction. Considering a nonlinear quasi-steady aerodynamic model, the response behavior and electric output of the harvester are analyzed near the flutter instability. A center manifold reduction is implemented to reduce the original five-dimensional system into one nonlinear first-order ordinary differential equation. Subsequently, the normal form of the reduced system is derived to study slow modulation of the voltage amplitude and phase. Several case studies are presented indicating a considerable improvement in the output voltage of the harvester under the combined loading even when the air speed is below the flutter velocity, i.e., even when the harvester cannot maintain steady-state periodic oscillations in the absence of the harmonic base excitation. It is also shown that, when the base-excitation amplitude is sufficiently large and its frequency is close to the frequency of the self-sustained limit-cycle oscillations emanating from the flutter instability, the periodic solution resulting from the base excitation entrains the self-sustained oscillations yielding a periodic output voltage. However, when the excitation frequency is far from the limit-cycle frequency, or the amplitude of base excitation is small, the voltage is two-period quasiperiodic.
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Kulatilaka, Waruna, Sukesh Roy, and James Gord. "Multi-Photon Fluorescence Imaging of Flame Species Using Femtosecond Excitation." In 28th Aerodynamic Measurement Technology, Ground Testing, and Flight Testing Conference. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2012. http://dx.doi.org/10.2514/6.2012-2882.

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Bibo, Amin, and Mohammed F. Daqaq. "Concurrent Energy Harvesting From Vibratory Base Excitations and Aerodynamic Flows." In ASME 2013 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/smasis2013-3115.

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This paper presents theoretical and experimental investigations into the potential of utilizing a piezoaeroelastic micropower generator to harvest energy from the combination of an external base excitation and an aerodynamic load. In particular, a harvester consisting of a rigid airfoil supported by a flexural piezoelectric beam and a torsional spring is placed in an incompressible air flow and subjected to an external harmonic base excitation in the plunge direction. Electromechanical equations describing the nonlinear system are given along with theoretical simulations. The performance of the piezoaeroelastic generator is studied experimentally below and above the flutter speed and found to exhibit qualitative agreement with the theory. Below the flutter speed, the response of the harvester is observed to be always periodic with the air flow serving to amplify the influence of the base excitation on the response by reducing the effective stiffness of the system, and hence, increasing the RMS output power. Beyond the flutter speed, the harvester’s response and its performance were observed to depend on the nearness of the excitation frequency to the frequency of the self-sustained oscillations induced by the flutter instability and the magnitude of the base excitation. When the base excitation is small and/or the excitation frequency is not close to the frequency of the self-sustained oscillations, the response of the harvester is two-period quasiperiodic with amplitude modulation due to the presence of two incommensurate frequencies. This amplitude modulation reduces the RMS output power. On the other hand, when the frequency of excitation is close to the frequency of the self-sustained oscillations and/or the amplitude of excitation is large enough to quench the quasiperiodic behavior, the response becomes periodic and the output power increases exhibiting little dependence on the base excitation.
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Reports on the topic "Aerodynamic excitation"

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Candler, Graham V. Effect of Internal Energy Excitation on Supersonic Blunt-Body Aerodynamics. Fort Belvoir, VA: Defense Technical Information Center, March 2001. http://dx.doi.org/10.21236/ada387503.

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