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Добірка наукової літератури з теми "Wake-oscillator model"

Автор: Grafiati

Опубліковано: 10 березня 2023

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Статті в журналах з теми "Wake-oscillator model"

Hagiwara, Tsuyoshi. "A Comparison between Wake Oscillator Model and Fluids Force Coefficients." Proceedings of the Fluids engineering conference 2000 (2000): 76. http://dx.doi.org/10.1299/jsmefed.2000.76.

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M, Muthaiah, Ragul Senthilkumar, and Varunkumar S. "Numerical investigation of thermo-acoustic instability in a model afterburner with a simplified model for observed lock-in Phenomena." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 265, no. 3 (February 1, 2023): 4088–99. http://dx.doi.org/10.3397/in_2022_0585.

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Thermoacoustic oscillations in a gas turbine afterburner are numerically investigated using CFD. A simplified 2-dimensional axisymmetric afterburner with bluff-body stabilized flame is considered in the investigation. Occurrences of both low and high-frequency thermo-acoustic oscillations in the afterburner chamber are observed at specific fuel flow rates. The flow field from the CFD shows the bluff-body vortex shedding frequency to lock-in with the acoustics of the chamber during the thermo-acoustic oscillations. The synchronization and lock-in of bluff-body wake with chamber acoustics happen with increase in fuel injection rates resulting in thermoacoustic coupling. The Proper Orthogonal Decomposition of the flow field revealed the presence of chamber acoustics in the pressure field confirming the coupling. Then a simplified mathematical model based on the van-der Pol oscillator is attempted to reproduce the observed lock-in behavior of the bluff-body wake. The chamber acoustic field is considered as the forcing term for the simplified oscillator. The oscillator model qualitatively captures the synchronization of the flame-holder wake oscillations with the chamber acoustics. This model could be extended to combustors with bluff-body wake in predicting the thermo-acoustic oscillations.

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Kurushina, Victoria, and Ekaterina Pavlovskaia. "Fluid nonlinearities effect on wake oscillator model performance." MATEC Web of Conferences 148 (2018): 04002. http://dx.doi.org/10.1051/matecconf/201814804002.

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Vortex-induced vibrations (VIV) need to be accounted for in the design of marine structures such as risers and umbilicals. If a resonance state of the slender structure develops due to its interaction with the surrounding fluid flow, the consequences can be severe resulting in the accelerated fatigue and structural damage. Wake oscillator models allow to estimate the fluid force acting on the structure without complex and time consuming CFD analysis of the fluid domain. However, contemporary models contain a number of empirical coeffcients which are required to be tuned using experimental data. This is often left for the future work with the opened question on how to calibrate a model for a wide range of cases and find out what is working and is not. The current research is focused on the problem of the best choice of the fluid nonlinearities for the base wake oscillator model [1] in order to improve the accuracy of prediction for the cases with mass ratios around 6.0. The paper investigates six nonlinear damping types for two fluid equations of the base model. The calibration is conducted using the data by Stappenbelt and Lalji [2] for 2 degrees-of-freedom rigid structure for mass ratio 6.54. The conducted analysis shows that predicted in-line and cross-flow displacements are more accurate if modelled separately using different damping types than using only one version of the model. The borders of application for each found option in terms of mass ratio are discussed in this work, and appropriate recommendations are provided.

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Poore, Aubrey B., Eusebius J. Doedel, and Jack E. Cermak. "Dynamics of the Iwan-Blevins wake oscillator model." International Journal of Non-Linear Mechanics 21, no. 4 (January 1986): 291–302. http://dx.doi.org/10.1016/0020-7462(86)90036-3.

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Zhang, Xiulin, Xu Zhang, Shuni Zhou, Wenzha Yang, Liangbin Xu, Lina Yi, Gengqing Tian, Yong Ma, Yuheng Hao, and Wenchi Ni. "A Modified Wake Oscillator Model for the Cross-Flow Vortex-Induced Vibration of Rigid Cylinders with Low Mass and Damping Ratios." Journal of Marine Science and Engineering 11, no. 2 (January 17, 2023): 235. http://dx.doi.org/10.3390/jmse11020235.

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The classical wake oscillator model is capable of predicting the vortex-induced vibration response of a cylinder at high mass-damping ratios, but it fails to perform satisfactorily at low mass-damping ratios. A modified wake oscillator model is presented in this paper. The modification method involves analyzing the variation law of the add mass coefficient of the cylinder versus reduced velocity and expressing the reference lift coefficient CL0 as a function of the add mass coefficient. The modified wake oscillator model has been demonstrated to have better accuracy in capturing maximum amplitudes and flow velocity at low mass-damping ratios. However, the modified model at present form is unable to accurately predict the vortex-induced vibration response at high damping ratios. The purpose of this paper is to propose a new modification idea. In order to achieve better results when applying this modification idea to particular objects, it may be necessary to first understand the response law of these kinds of objects.

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Kurushina, Victoria, Andrey Postnikov, Guilherme Franzini, and Ekaterina Pavlovskaia. "Optimization of the Wake Oscillator for Transversal VIV." Journal of Marine Science and Engineering 10, no. 2 (February 20, 2022): 293. http://dx.doi.org/10.3390/jmse10020293.

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Vibrations of slender structures associated with the external flow present a design challenge for the energy production systems placed in the marine environment. The current study explores the accuracy of the semi-empirical wake oscillator models for vortex-induced vibrations (VIV) based on the optimization of (a) the damping term and (b) empirical coefficients in the fluid equation. This work investigates the effect of ten fluid damping variations, from the classic van der Pol to more sophisticated fifth-order terms, and prediction of the simplified case of the VIV of transversally oscillating rigid structures provides an opportunity for an extended, comprehensive comparison of the performance of tuned models. A constrained nonlinear minimization algorithm in MATLAB is applied to calibrate considered models using the published experimental data, and the weighted objective function is formulated for three different mass ratios. Comparison with several sources of published experimental data for cross-flow oscillations confirms the model accuracy in the mass ratio range. The study indicates the advantageous performance of the models tuned with the medium mass ratio data and highlights some advantages of the Krenk–Nielsen wake oscillator.

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KIKITSU, Hitomitsu, Yasuo OKUDA, and Jun KANDA. "NUMERICAL EVALUATION OF INTERACTION PHENOMENON BY USING WAKE OSCILLATOR MODEL." Journal of Structural and Construction Engineering (Transactions of AIJ) 73, no. 624 (2008): 211–18. http://dx.doi.org/10.3130/aijs.73.211.

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Postnikov, Andrey, Ekaterina Pavlovskaia, and Marian Wiercigroch. "2DOF CFD calibrated wake oscillator model to investigate vortex-induced vibrations." International Journal of Mechanical Sciences 127 (July 2017): 176–90. http://dx.doi.org/10.1016/j.ijmecsci.2016.05.019.

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Alon Tzezana, Gali, and Kenneth S. Breuer. "Thrust, drag and wake structure in flapping compliant membrane wings." Journal of Fluid Mechanics 862 (January 15, 2019): 871–88. http://dx.doi.org/10.1017/jfm.2018.966.

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We present a theoretical framework to characterize the steady and unsteady aeroelastic behaviour of compliant membrane wings under different conditions. We develop an analytic model based on thin airfoil theory coupled with a membrane equation. Adopting a numerical solution to the model equations, we study the effects of wing compliance, inertia and flapping kinematics on aerodynamic performance. The effects of added mass and fluid damping on a flapping membrane are quantified using a simple damped oscillator model. As the flapping frequency is increased, membranes go through a transition from thrust to drag around the resonant frequency, and this transition is earlier for more compliant membranes. The wake also undergoes a transition from a reverse von Kármán wake to a traditional von Kármán wake. The wake transition frequency is predicted to be higher than the thrust–drag transition frequency for highly compliant wings.

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Hussin, W. N. W., F. N. Harun, M. H. Mohd, and M. A. A. Rahman. "Analytical modelling prediction by using wake oscillator model for vortex-induced vibrations." JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES 11, no. 4 (December 30, 2017): 3116–28. http://dx.doi.org/10.15282/jmes.11.4.2017.14.0280.

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Більше джерел

Дисертації з теми "Wake-oscillator model"

Metka, Matthew. "Application of Fluidic Oscillator Separation Control to a Square-back Vehicle Model." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1439205355.

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Kurishina, Victoria. "Fluid nonlinearities for calibrated VIV wake oscillator models." Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=237154.

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Анотація:

Onshore and offshore structures are subject of strict safety regulations, and acceptable design implies requirements for accurate models of potentially dangerous phenomena. The phenomenon of Vortex-Induced Vibrations (VIVs) develops when a slender structure interacts with a fluid flow. Vortices grow in the disturbed boundary layer and spread behind the structure, resulting in fluctuations of the fluid forces acting on the body. Slender structures are present almost everywhere in the form of tall buildings and skyscrapers, cranes, antennas, power lines, suspension bridges, umbilicals, risers and free spans of pipelines which deliver water, oil and gas. The deeper in the water and higher in the sky these structures are, more likely they can experience VIVs and the lock-in state due to the exposure to various flow profiles. The wake oscillator method allows to model fluid variables during VIV lock-in using self-excited and self-limited oscillators of Van der Pol or Rayleigh type. In this research, the capabilities of alternative nonlinear oscillators as fluid equations are considered for modelling elastically supported rigid structures with one and two degrees-of-freedom in uniform flow. For modelling two-dimensional flexible structures in uniform and sheared flows, new wake oscillator models are developed in this work and applied with alternative damping terms. The dynamics of the uniform flow model of flexible structure is investigated in detail with the focus on coexisting solutions of the displacement amplitudes. Empirical coefficients for wake oscillator models are calibrated in this study using constrained nonlinear minimization and experimental data available in the literature. The validation performed confirms the most successful results for the suite of models of 2DOF rigid structure for low mass ratio, where agreement with both in-line and cross-flow displacement records was obtained.

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Chen, Cong. "Unsteady Galloping of Bridge Decks during the Launching Phase." Doctoral thesis, 2021. http://hdl.handle.net/2158/1253903.

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The present work deals with the unsteady galloping instability, which arises at low reduced flow velocities, for steel-concrete composite bridge decks during the incremental launching phase. In this particular situation, the light weight and bluff shape of the steel box, which is normally first launched, imply a high proneness to the risk of unsteady galloping. The main goal of this thesis is to understand the unsteady galloping with respect to these special cross sections, which have not been investigated in depth before, and to develop an analytical approach for the modeling of unsteady galloping as a basis for design of bridges.

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Частини книг з теми "Wake-oscillator model"

Mondal, Rik, Chandan Bose, and Sirshendu Mondal. "Synchronization Study on Vortex-Induced Vibrations Using Wake Oscillator Model." In NODYCON Conference Proceedings Series, 65–74. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-81162-4_6.

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Fehér, Rafael, and Juan Pablo Julca Avila. "VORTEX-INDUCED VIBRATIONS MODEL WITH 2 DEGREES OF FREEDOM OF RIGID CYLINDERS NEAR A FIXED WALL BASED ON WAKE OSCILLATOR." In Coleção desafios das engenharias: Engenharia mecânica, 56–66. Atena Editora, 2021. http://dx.doi.org/10.22533/at.ed.5902121076.

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Тези доповідей конференцій з теми "Wake-oscillator model"

Guerra Bernadá, Gabriel Mario, and Fernando Rochinha. "Bayesian calibration of wake-oscillator model for fluid structure interaction." In DINAME2019. ABCM, 2019. http://dx.doi.org/10.26678/abcm.diname2019.din2019-0092.

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Akhtar, Imran, Osama Marzouk, and Ali Nayfeh. "Higher-Order Wake-Oscillator Model of Aerodynamic Forces on Canonical Structures." In 46th AIAA Aerospace Sciences Meeting and Exhibit. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2008. http://dx.doi.org/10.2514/6.2008-679.

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Fontoura, Diener V. R., Raphael I. Tsukada, and Denis A. Shiguemoto. "Numerical Simulation of a Submersible Buoy Using a Wake Oscillator Model Calibrated for VIM." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-42268.

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New discoveries of petroleum reservoirs in ultra deep-water depths, like Pre-salt fields in Santos Basin, are demanding new riser systems concepts. In this scenario, the Free-Standing Hybrid Riser (FSHR) system is a viable choice. A submersible buoy connected by rigid and flexible risers constitutes this riser system. The sea current can cause the Vortex-Induced Motion (VIM) of the buoy, which can increase significantly the riser fatigue damage. Although the VIM phenomenon is similar to Vortex-Induced Vibration (VIV), it generally occurs in rigid bodies with low aspect ratio, where end effects causes tridimensional flow behavior. Therefore, the vortex wake characteristics and the hydrodynamics coefficients found for VIV is no longer valid for VIM. In this context, wake oscillator models used for VIV prediction in actual form is not adequate for the VIM prediction of the buoys. In this paper, a VIV wake oscillator model is calibrated for VIM, through hydrodynamic coefficients found in the technical literature. In order to verify accuracy, the VIM calibrated wake oscillator model is used to reproduce some FSHR reduced model tests. The results of amplitude and frequency of oscillation against the reduced velocity obtained from the numerical simulation are compared with the experimental results. The numerical results presented the same trend with some differences in amplitude. The amplitude deviation could be related to the hydrodynamics coefficients used in the calibration of the wake oscillator model.

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Pavlovskaia, Ekaterina. "Calibrated Wake Oscillator Model of Horizontal Flexible Structure Moving in Uniform Flow." In DINAME2019. ABCM, 2019. http://dx.doi.org/10.26678/abcm.diname2019.din2019-0138.

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Lim, HyeongUk, Lance Manuel, Ying Min Low, and Narakorn Srinil. "Uncertainty Quantification of Riser Fatigue Damage due to VIV Using a Distributed Wake Oscillator Model." In ASME 2017 36th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/omae2017-62143.

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This study explores the use of polynomial chaos expansion (PCE) to quantify the uncertainty in accumulated fatigue damage in a top-tensioned riser (TTR) due to vortex-induced vibration (VIV). Time-domain simulations of the response of the selected riser are carried out using a distributed wake oscillator model and fatigue damage is computed using rainflow cycle-counting. The uncertainty in damage prediction that results from variability in parameters involved in the wake oscillator model is the focus of this study. The efficiency and accuracy resulting from use of the PCE model is demonstrated by comparison against Monte Carlo simulations (MCS). Specifically, starting with the use of two random variables (the cylinder maximum amplitude and a ratio of the vortex-shedding frequency to the natural frequency) and then by introducing one other random variable (the current velocity), the propagation of uncertainty from the wake oscillator model inputs to fatigue damage is studied. Numerical studies demonstrate the versatility of the PCE-based approach in such uncertainty quantification applications.

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Modarres-Sadeghi, Yahya, Franz S. Hover, and Michael S. Triantafyllou. "Fatigue Calculation of Risers Using a Van Der Pol Wake Oscillator Model With Random Parameters." In ASME 2008 27th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2008. http://dx.doi.org/10.1115/omae2008-57455.

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Vortex induced vibrations of long distributed structures (risers and mooring cables) is an inherently complicated phenomenon in which due to the riser multi-mode excitations, various combinations of traveling and standing wave patterns along the length is observed. These observations are made based on a series of model scale experiments conducted on a riser for both uniform and linearly sheared flow cases. In these model scale experiments, strain and acceleration measurements are conducted at selected points along the riser. The contour plots of amplitudes of oscillations in these experiments show a mainly traveling wave behavior for linearly sheared flow cases and a mainly standing wave one for the uniform flow cases. In order to model the vortex induced vibrations of the riser used in these experiments, a wake oscillator model is used. In this model, the riser is assumed to be a tensioned string and the wake dynamics is represented by a Van der Pol oscillator whose driving force is in parallel with the riser acceleration. Randomness in the current, added mass and lift coefficients is taken into account by considering random parameters for the wake oscillator model. By using the proper parameters in this wake oscillator model, its results can be compared with the experimental ones. The comparison is made in terms of dynamical behavior (traveling waves versus standing waves, amplitudes and frequencies of oscillations) as well as the fatigue life calculations. The statistics of fatigue life calculations based on the experimental reconstruction compares well with those of the model results showing that the theoretical model can predict fatigue damage of the riser fairly well.

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Chen, Wein-min, Liwu Zhang, and Min Li. "Prediction of Vortex-Induced Vibration of Flexible Riser Using an Improved Wake-Oscillator Model." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79336.

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Анотація:

Based on improving the wake-oscillator model, an analytical model for vortex-induced vibration (VIV) of flexible riser under non-uniform current is presented, in which the variation of added mass at lock-in and the nonlinear relationship between amplitude of response and reduced velocity are considered. By means of empirical formula combining iteration computation, the improved analytical model can be conveniently programmed into computer code with simpler and faster computation process than CFD so as to be suitable to application of practical engineering. This model is validated by comparing with experimental result and numerical simulation. Our results show that the improved model can predict VIV response and lock-in region more accurately. At last, illustrative examples are given in which the amplitude of response of flexible riser experiencing VIV under action of non-uniform current is calculated and effects of riser tension and flow distribution along span of riser are explored. It is demonstrated that with the variation of tension and flow distribution, lock-in region of mode behaves in different way, and thus the final response is a synthesis of response of locked modes.

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Ogink, R. H. M. "A Double Birkhoff Wake Oscillator for the Modeling of Vortex-Induced Vibration." In ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2011. http://dx.doi.org/10.1115/omae2011-49435.

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A double Birkhoff wake oscillator for the modeling of vortex-induced vibration is presented in which the oscillating variables are assumed to be associated with the boundary layer/near wake and the far wake. The fluid forces are assumed to consist of a potential added mass force and a force due to vortex shedding. In the limit of vanishing incoming flow velocity, the model equations reduce to a form similar to the Morison equation. The results of the double wake oscillator have been compared with forced vibration measurements and free vibration measurements over a range of mass and damping ratios. The model is capable of describing the most important trends in both the forced and free vibration experiments. Specifically, the double wake oscillator is able to model both the upper and lower branch of free vibration.

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Qu, Y., and A. V. Metrikine. "A Wake Oscillator Model With Nonlinear Coupling for the VIV of Rigid Cylinder Constrained to Vibrate in the Cross-Flow Direction." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54511.

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Анотація:

In this paper a new wake oscillator model with nonlinear coupling term is proposed to model the vortex-induced vibration of an elastically supported rigid cylinder constrained to vibrate in the cross-flow direction. The superiority of this new model lies in its ability to satisfy at the same time both free and forced vibration experiments. The new wake oscillator model is based on an existing van der Pol wake oscillator model and nonlinear coupling terms are added to improve its performance in the modelling of forced vibration. The tuning of this new model to the forced vibration shows good agreement with experiments in terms of the added damping but failed to capture the negative added mass at high reduced velocities. To eliminate this discrepancy the model is further enhanced by relaxing the assumption of constant potential added mass. Using the parameters obtained from the forced vibration experiments, the free vibration simulation is conducted and results are compared with the experiments. Comparison indicates good agreement between simulation and experiments, and the main features of VIV are captured.

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da Silveira, Lauro M. Y., Clo´vis de A. Martins, Leandro D. Cunha, and Celso P. Pesce. "An Investigation on the Effect of Tension Variation on VIV of Risers." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29247.

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This paper aims at investigating the effect of vertical motion (or equivalently the effect of variable tensioning) of the floating unit on the vortex-induced vibrations of vertical risers. This is done using a numerical procedure, based on modeling assumptions, which, though simple, succeeded in describing some expected dynamic behaviors. The model simulates the riser dynamics using a finite element model coupled to a wake-oscillator model, of the van der Pol type, used to emulate the fluid dynamics. Vertical motion (or dynamic tension) is directly imposed to the top. The transverse amplitudes at each section feed the wake-oscillator, which responds with a transverse force that is applied to the riser. The rigidity matrix is updated at each time integration step. The analysis is also carried out with a commercial simulation code dedicated to riser analysis, with a similar wake-oscillator VIV module. Amplitude envelopes are extracted from the time series, showing response mode jumps. The application of the Hilbert-Huang spectral analysis technique helps distinguishing mode jumps by tracking frequency responses in time. The results of the two different dynamic models are compared with very good agreement.

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Звіти організацій з теми "Wake-oscillator model"

Ng, Leslie, Richard H. Rand, Timothy Wei, and William L. Keith. An Examination of Wake Oscillator Models for Vortex-Induced Vibrations. Fort Belvoir, VA: Defense Technical Information Center, August 2001. http://dx.doi.org/10.21236/ada390553.

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