scholarly journals Vibration Mitigation of Wind Turbine Towers Using Negative Stiffness Absorbers

2021 ◽  
Vol 10 (3) ◽  
pp. 123-139
Author(s):  
Konstantinos A. Kapasakalis ◽  
Ioannis A. Antoniadis ◽  
Evangelos J. Sapountzakis ◽  
Andreas E. Kampitsis
Keyword(s):  
Wind Turbine ◽  
Seismic Isolation ◽  
Dynamic Performance ◽  
Dynamic Responses ◽  
Negative Stiffness ◽  
Vibration Absorbers ◽  
Additional Mass ◽  
Vibration Mitigation ◽  
Vibration Absorption ◽  
Wind Turbine Towers

The application of dynamic vibration absorbers (DVA) to Wind Turbine (WT) towers has the potential to significantly improve the damping of the tower and the nacelle dynamic responses, increasing thus the reliability of WTs. The Tuned Mass Damper (TMD) is limited by the requirement of large masses, in association to its installation location. In this study, two alternative concepts are considered. First, the nacelle is released from the WT tower, using a low stiffness connection. This option is based on the seismic isolation concept. Additionally, a novel passive vibration absorption configuration is implemented, based on the KDamper concept. The KDamper is essentially an extension of the TMD, introducing negative stiffness (NS) elements. Instead of increasing the additional mass, the vibration absorption capability of the KDamper can be increased by increasing the value of the NS element. Therefore, the KDamper always indicates better isolation properties than a TMD with the same additional mass.  For the nonlinear dynamic response of the WT a build-in house software is developed. The dynamic performance of the proposed vibration mitigation concepts is numerically examined. All methods present superior dynamic behaviour as compared to the uncontrolled structure, however only the KDamper-based designs significantly increase the effective damping of the WT tower, retaining the additional masses in reasonable ranges.

Effects of Fish Nets on the Nonlinear Dynamic Performance of a Floating Offshore Wind Turbine Integrated with a Steel Fish Farming Cage

2020 ◽  
Vol 20 (03) ◽  
pp. 2050042 ◽  
Author(s):  
Y. Lei ◽  
S. X. Zhao ◽  
X. Y. Zheng ◽  
W. Li
Keyword(s):  
Wind Turbine ◽  
Nonlinear Dynamic ◽  
Dynamic Performance ◽  
Fish Farming ◽  
Ocean Waves ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Offshore Wind Turbine ◽  
Wind Sea

This paper aims to study the effects of fish nets on the nonlinear dynamic performance of a floating offshore wind turbine integrated with a steel fish farming cage (FOWT-SFFC). Fully coupled aero-hydro-servo-elastic numerical models of FOWT-SFFC, with and without nets, are constructed to probe the nonlinear time-domain stochastic response. The first-order potential flow model with quadratic drag forces is employed to calculate the hydrodynamic loading on the foundation. The effects of nets on the damping ratios of 6 degree-of-freedom motions and on their displacement response amplitude operators (RAOs) are respectively investigated in numerical decay tests and monochromatic regular waves. The results show that the nets help to increase the damping level for the whole system and reduce motion RAOs when wave periods are around the natural periods of motions, while nets play insignificant role in motions when wave periods are far away from motion natural periods. The dynamic performances of FOWT-SFFC with and without nets under random ocean waves, the combined random wind and random waves as well as current are comprehensively compared and discussed. The simulation results indicate that in wind-sea dominated conditions, the nets tend to slightly increase the dynamic responses of FOWT-SFFC, especially the components corresponding to natural periods. Nonetheless, under sea states that comprise both wind-sea waves and swell, nets help to reduce the dynamic responses of FOWT-SFFC by introducing additional damping.

scholarly journals Influence of Mooring Tension on Dynamic Performance of Semi-submersible Wind Turbine under Typhoon Condition

2021 ◽  
Vol 2087 (1) ◽  
pp. 012030
Author(s):  
Liwei Zhang ◽  
Zhi Sun ◽  
Boyuan Qiu ◽  
Yilie Hou ◽  
Xin Li
Keyword(s):  
Wind Turbine ◽  
Dynamic Performance ◽  
Low Frequency ◽  
Internal Force ◽  
Dynamic Responses ◽  
Wave Frequency ◽  
Wave Load ◽  
Element Analysis ◽  
Internal Forces ◽  
Cfd Method

Abstract A numerical model of a 5 MW semi-submersible wind turbine is established based on the reference wind turbine of American national renewable energy laboratory (NREL). The nominal diameter of the mooring chains was determined after the static wind load and wave load of the turbine under the action of typhoon being calculated by CFD method and Morison method. Finally, the dynamic responses of the turbine and the internal forces of the chains are obtained by the dynamic finite element analysis for three cases. The results show that when pretension chains are used, the turbine motion frequency is consistent with wave frequency, the surge is small, the pitch is reciprocally symmetrical, and the peak internal force of the chains is quite high. When mooring chains without pretension are adopted, the motion of the turbine consists of low-frequency drift and forced motion in sync with the wave frequency, the pitch is asymmetrical, and the internal tension force of the chains is relatively low.

STIFF vertical seismic absorbers

2021 ◽  
pp. 107754632110016
Author(s):  
Konstantinos A Kapasakalis ◽  
Ioannis A Antoniadis ◽  
Evangelos J Sapountzakis
Keyword(s):  
Seismic Isolation ◽  
Ground Motions ◽  
Dynamic Performance ◽  
Negative Stiffness ◽  
Seismic Load ◽  
Building Structures ◽  
Industrial Facilities ◽  
Effective Technology ◽  
Real Earthquake ◽  
Isolation Systems

Seismic isolation is proven to be an effective technology for seismic protection of building structures, equipment, and industrial facilities. The majority of the existing isolation systems and techniques are related to horizontal ground motions, whereas there are only a few vertical isolation systems. The main reason is because of the conflict concerning the demand for isolation stiffness. More specifically, a vertical isolated system must have sufficient vertical rigidity to sustain the weight of the isolated object/system and retain the static vertical deflection in reasonable limits. On the other hand, the isolated system must also have enough flexibility to isolate the accelerations. In order to overcome this difficulty, a novel vertical seismic absorber system is proposed, that combines negative stiffness-driven absorbers with inerters. The inerter manages to reduce the frequency of the system, without weakening the structure or increasing the seismic load. At the same time, the effective damping is significantly increased with the KDamper. This way, the dynamic behavior of the system is improved, in terms of absolute accelerations, and simultaneously, the static settlements are retained at any desired level. The design of the vertical seismic absorber is based on engineering criteria, and the excitation input is selected according to the seismic design codes. The dynamic performance of the vertical seismic absorber is also evaluated with real earthquake records, using a realistic displacement-dependent configuration for the realization of the negative stiffness element. Finally, the detuning phenomena are observed and discussed via sensitivity analysis.

scholarly journals Vibration Mitigation of the Barge-Type Offshore Wind Turbine with a Tuned Mass Damper on Floating Platform

2018 ◽  
Vol 36 (2) ◽  
pp. 238-245 ◽  
Author(s):  
Jiajia Yang ◽  
Erming He ◽  
Yaqi Hu
Keyword(s):  
Wind Turbine ◽  
Tuned Mass Damper ◽  
Equal Mass ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Vibration Mitigation ◽  
Floating Wind Turbine ◽  
Mass Damper

This paper evaluates the application of a passive control technique with a tuned mass damper on platform for the barge-type offshore wind turbine. First of all, the three degrees of freedom mathematical model for the floating wind turbine is established based on Lagrange's equations, and the Levenberg-Marquardt algorithm is adopted to estimate the parameters of the wind turbine. Then, the method of frequency tuning which is utilized in engineering projects and genetic algorithm are employed respectively to simulate the optimum parameters of the tuned mass damper. The vibration mechanism about the phase-angle difference between tuned mass damper and floating platform is analyzed. Finally, the dynamic responses of floating wind turbine with/without tuned mass damper are calculated under five typical wind and wave load cases, and the vibration mitigation effects are researched in marine environment. Partial ballast is substituted by the equal mass of tuned mass damper due to the mass of floating platform with tuned mass damper would increase obviously, which would change the design of the wind turbine, and the vibration mitigation is also simulated in five typical load cases. The results show that the suppression rate of standard deviation of platform pitch is up to 47.95%, after substituting the partial mass of ballast, the suppression rate is 50%. Therefore, the dynamic responses of the barge-type floating wind turbine would be reduced significantly when the ballast is replaced by the equal mass of the tuned mass damper on floating platform.

scholarly journals COMPARISON OF ALTERNATIVE DYNAMIC VIBRATION MITIGATION APPROACHES FOR WIND TURBINE TOWERS

2020 ◽  
Author(s):  
Konstantinos A. Kapasakalis ◽  
Pyros-Orfeas N. Bollano ◽  
Evangelos J. Sapountzakis ◽  
Ioannis A. Antoniadis
Keyword(s):  
Wind Turbine ◽  
Vibration Mitigation ◽  
Dynamic Vibration ◽  
Wind Turbine Towers

Model Test of a Novel Floating Vertical-Axis Wind Turbine Under Wind and Wave Joint Loads

2021 ◽  
Author(s):  
Hua-Dong Zheng ◽  
Xiang Yuan Zheng ◽  
Yu Lei
Keyword(s):  
Wind Turbine ◽  
Wind Wave ◽  
Dynamic Performance ◽  
Low Frequency ◽  
Vertical Axis ◽  
Ocean Basin ◽  
Physical Models ◽  
Dynamic Responses ◽  
Vertical Axis Wind Turbine ◽  
Joint Loads

Abstract Recently a floating vertical-axis wind turbine (VAWT) concept that integrates a VAWT with a steel fishing cage has been developed by leading authors. In order to fathom the kinetic characteristics and performance of this floater under wind and wave joint loads, a series of model tests have been carried out in the ocean basin located at Tsinghua Shenzhen International Graduate School. The wind generation system of this facility allows turbulent wind to be produced such that examination of wind-wave joint actions can be extended to a number of stochastic scenarios. With a scale of 1/40th, the physical models of the floating VAWT and the platform of a steel fishing cage are introduced first. Details are also given to instrumentations and measurement methods. Then, thrust-wind speed tests, free-decay tests, and basin wind-wave tests are respectively carried out to probe the primary dynamic performance of the floating system. The second-order hydrodynamic effects are observed in tests, but they play a secondary role in the response of VAWTs as compared to aerodynamic effects. The aerodynamic loads can induce the obvious low-frequency response at surge and pitch eigen-frequencies, while for heave motion response its contribution is smaller. Additionally, test results reveal that third-per-revolution (3P) effects are insignificant in the platform’s surge, pitch and heave dynamic responses.

scholarly journals Metastructure plate with periodically embedded nonlinear vibration absorbers for nonlinear aeroelastic suppression

2021 ◽  
Author(s):  
Wei Tian ◽  
Tian Zhao ◽  
Zhichun Yang
Keyword(s):  
Energy Transfer ◽  
Nonlinear Vibration ◽  
Passive Control ◽  
Dynamic Pressure ◽  
Functionally Graded ◽  
Dynamic Responses ◽  
Energy Transfer Mechanism ◽  
Vibration Absorbers ◽  
Vibration Absorption ◽  
Graded Material

Abstract A metastructure plate featuring periodically embedded nonlinear vibration absorbers (NVAs) is proposed for the passive suppression of nonlinear aeroelastic responses under supersonic flow conditions. Using the von Karman large deformation theory and supersonic piston theory, the motion equations of a supersonic functionally graded material plate coupled with NVAs are derived from the Hamilton principle. Linear flutter analysis shows that the multiple-NVA design can significantly enhance the aerothermoelastic stability of the metastructure plate. Subsequently, the nonlinear aeroelastic behaviors of the plate and the energy transfer mechanism between it and the NVAs are examined using an energy-based analysis approach. The comparison of bifurcation diagrams indicates that the attachment of periodic NVAs realizes a superior suppression of vibration absorption than a single NVA. Numerical results show that the nonlinear dynamic responses of the plate can be substantially reduced via the targeted energy transfer of NVAs in the post-flutter regime. In particular, the passive control performance of the periodic NVAs does not degrade under an increase in the dynamic pressure. Furthermore, a significant reduction of more than 95% in the response amplitude of the plate can be realized by properly tuning the NVA parameters. The present work demonstrates that the metastructure design, based on periodically distributed NVAs, is effective at enhancing the flutter stability and mitigating nonlinear aeroelastic responses.

Comparison on General Track Spectrum for Chinese Main Railway Lines and Track Spectrum of American Railway Lines

2011 ◽  
Vol 250-253 ◽  
pp. 3822-3826 ◽  
Author(s):  
Xian Mai Chen ◽  
Xia Xin Tao ◽  
Gao Hang Cui ◽  
Fu Tong Wang
Keyword(s):  
Dynamic Performance ◽  
Dynamic Responses ◽  
Wave Band ◽  
Wheel Load ◽  
Railway Line ◽  
Acceleration Rate ◽  
Time Histories ◽  
Railway System ◽  
Dynamic Performances ◽  
Track Irregularity

The general track spectrum of Chinese main railway lines (ChinaRLS) and the track spectrum of American railway lines (AmericaRLS) are compared in terms of character of frequency domain, statistical property of time domain samples and dynamic performance. That the wavelength range of the ChinaRLS, which is characterized by the three levels according to the class of railway line, is less than AmericaRLS at common wave band of 1~50m is calculated. Simultaneously, the mean square values of two kinds of track spectra are provided at the detrimental wave bands of 5~10m, 10~20m, and so on. The time-histories of ChinaRLS and AmericaRLS are simulated according to the trigonometric method, and the digital statistical nature of simulated time samples is analyzed. With inputting the two kinds of time-histories into the vehicle-railway system, the comparative analysis of the two kinds of dynamic performances for ChinaRLS and AmericaRLS is done in terms of car body acceleration, rate of wheel load reduction, wheel/rail force, and the dynamic responses of track structure. The result shows that ChinaRLS can characterize the feature of the Chinese track irregularity better than AmericaRLS, the track irregularity with the ChinaRLS of 200km/h is superior to the AmericaRLS, and the track irregularity with the ChinaRLS of 160km/h corresponds to with the sixth of AmericaRLS.

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