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.

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.

Study on the Dynamic Response for Floating Foundation of Offshore Wind Turbine

2011 ◽  
Author(s):  
Yougang Tang ◽  
Jun Hu ◽  
Liqin Liu
Keyword(s):  
Wind Turbine ◽  
Wind Farm ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Load ◽  
Mooring Lines ◽  
Floating Foundation ◽  
Wind Turbine System ◽  
Sea Area

The wind resources for ocean power generation are mostly distributed in sea areas with the distance of 5–50km from coastline, whose water depth are generally over 20m. To improve ocean power output and economic benefit of offshore wind farm, it is necessary to choose floating foundation for offshore wind turbine. According to the basic data of a 600kW wind turbine with a horizontal shaft, the tower, semi-submersible foundation and mooring system are designed in the 60-meter-deep sea area. Precise finite element models of the floating wind turbine system are established, including mooring lines, floating foundation, tower and wind turbine. Dynamic responses for the floating foundation of offshore wind turbine are investigated under wave load in frequency domain.

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.

Dynamic Response Analysis of Wind Turbine Gearbox Using Simplified Local Tooth Stiffness of Internal Gear System

2015 ◽  
Vol 10 (4) ◽  
Author(s):  
J. R. Cho ◽  
K. Y. Jeong ◽  
M. H. Park ◽  
N. G. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Wind Turbine ◽  
Dynamic Models ◽  
Gear Tooth ◽  
Dynamic Responses ◽  
Response Analysis ◽  
Analysis Model ◽  
Wind Turbine Gearbox ◽  
Element Analysis

This paper presents a dynamic finite element analysis model for a wind turbine gearbox in which a number of internal gears mesh with each other in a complex pattern. Differing from the conventional dynamic models in which the detailed gear teeth are fully modeled or gears and shafts are replaced with lumped masses, the tooth contact between a pair of gears is modeled using a spring element. The equivalent spring constant is determined by computing the stiffness of a gear tooth using a finite element analysis. The numerical accuracy of the proposed dynamic model is verified through a benchmark experiment of a gearbox with simple gear transmission system. In addition, the natural frequencies and dynamic responses of a 5 MW wind turbine gearbox that are obtained by the proposed modeling technique are given to support its validity and effectiveness.

Dynamic responses of offshore wind turbine considering soil nonlinearity and wind-wave load combinations

2020 ◽  
Vol 217 ◽  
pp. 108155
Author(s):  
Guangwei Cao ◽  
Zhixiong Chen ◽  
Chenglong Wang ◽  
Xuanming Ding
Keyword(s):  
Wind Turbine ◽  
Wind Wave ◽  
Dynamic Responses ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Wave Load ◽  
Soil Nonlinearity

scholarly journals Static and Dynamic Analysis of a 6300 KN Cold Orbital Forging Machine

Processes ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 7
Author(s):  
Zhiqiang Gu ◽  
Mingzhang Chen ◽  
Chaoyang Wang ◽  
Wuhao Zhuang
Keyword(s):  
Fatigue Life ◽  
Dynamic Performance ◽  
Low Frequency ◽  
Optimization Method ◽  
Vertical Vibration ◽  
Element Analysis ◽  
Static And Dynamic Analysis ◽  
Low Frequency Vibration ◽  
Orbital Forging

In cold orbital forging (COF) processes, large stress, displacement and vertical vibration of the COF machine are bad for the quality of the part and the fatigue life of the COF machine. It is necessary to investigate the static and dynamic performance of the COF machine and provide methods for reducing the stress, displacement and vertical vibration of the COF machine. In this paper, finite element analysis, theoretical analysis, numerical simulation and experimental analysis were applied to study the static and dynamic performance of a 6300 KN COF machine. The static and dynamic analyses were verified effectively by carrying out strain and vertical vibration test experiments. In the static analysis, the large stress and displacement positions of the COF machine were mainly distributed near the working table and the junction between the working table and the column. Large stress and displacement will be bad for the quality of the part and the fatigue life of the COF machine. Structural optimizations of the COF machine include ribbed plates on the working table and beam. This structural optimization method of the COF machine obviously reduced the stress and displacement of the COF machine. When the angular velocities of the eccentric rings were 8π rad/s, the vertical vibration of the swing shaft is a low-frequency vibration. The existence of absorber obviously reduced the vertical vibration of the COF machine.

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.

Temperature effect on service performance of high-speed railway concrete bridges

2016 ◽  
Vol 20 (6) ◽  
pp. 865-883 ◽  
Author(s):  
Y Tian ◽  
N Zhang ◽  
H Xia
Keyword(s):  
Temperature Effect ◽  
High Speed ◽  
Low Frequency ◽  
Numerical Approach ◽  
Service Performance ◽  
Dynamic Responses ◽  
Temperature Fields ◽  
Coupled Analysis ◽  
Element Analysis ◽  
High Speed Railway

Non-uniform temperature fields induced by time-varying solar position and heat exchange are of great significance for the bridge safety. The accurate identifications of these changes are necessary to avoid unexpected deformations and the loss of service performance. This article presents a numerical approach to determine temperature effects on train–bridge-coupled dynamics. Heat flux density of different components of a 32-m simply supported concrete bridge on high-speed railway is calculated, in which a section segmentation method is adopted for simplifications of boundary conditions. Based on heat–stress-coupled technology, temperature fields and deformation fields of the bridge are then computed via finite element analysis. Combining track irregularities and its thermal deformation as external excitations, the train–bridge-coupled analysis is solved by an inter-system iteration method. Dynamic responses of bridge and train are compared to those obtained neglecting the temperature effect. Comparative studies illustrate that temperature effect has major impacts on the bridge displacement due to the increase in low-frequency components of excitations. For the train, lateral responses are more obvious. Maximum derail factor and lateral wheel–rail force occur when the train leaves from the bridge.

Study on Selection of the Length of Reinforced Concrete Segment for Oil and Gas Shield Tunnel with 3D Numerical Analysis

2014 ◽  
Vol 488-489 ◽  
pp. 517-520
Author(s):  
Xiao Feng Wang ◽  
Xiao Jun Zhou ◽  
Hong Yun Hu
Keyword(s):  
Reinforced Concrete ◽  
Oil And Gas ◽  
Earth Pressure ◽  
Internal Force ◽  
Segment Length ◽  
Shield Tunnel ◽  
Element Analysis ◽  
Calculated Stress ◽  
Internal Forces ◽  
Rational Length

3D finite element analysis is utilized to calculate stress and internal forces in three different lengths of reinforced concrete segment for oil and gas shield tunnel subject to water and earth pressure by means of load-structure model. The rational length of concrete segment is determined to be 1.2m long after comparing the calculated stress and internal force in concrete segment with length of 1.0m, 1.2m and 1.5m respectively. Meanwhile, the safety factor is also compared in order to determine the rational length of concrete segment. The analysis shows that segment length for oil and gas shield tunnel with small cross-section should be less than 1.2m so as to facilitate its transportation and erection on construction site.

A Simplified Procedure for Global Hull Strength Analysis of Classic Spars

2014 ◽  
Author(s):  
Xiaoqing Teng
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Frequency Response ◽  
Shear Force ◽  
Low Frequency ◽  
Bending Moment ◽  
Wave Frequency ◽  
Structural Components ◽  
Element Analysis ◽  
Wave Induced

Primary structural components of a spar hull are designed to resist lateral hydrodynamic and hydrostatic pressure and global loads. The scantlings of each primary component are usually determined based on the largest pressure it may encounter in various phases such as wet-tow, upending, and in-place operational conditions. The effect of global bending moment and shear force on the spar hull is often evaluated much later via laborious finite element analysis. This paper proposes a simple analytical tool for quickly assessing global hull strength of classic spars in the in-place condition. A spar platform undergoes steady, low-frequency, and wave-frequency motion of comparable magnitude at the same time in a storm event. The present approach separates the wave-frequency component from the steady and low-frequency response. A closed-form solution is developed for wave-induced motion and loads by taking advantage of the simple cylindrical shape of classic spar hulls. The theoretical solution is verified by comparing to numerical WAMIT results. The low-frequency response is approximated as one part of the steady response, since its dynamic effect is weak. The steady structural response is mainly a function of the heel angle. It is demonstrated that local effect of wind pressure and current load is not significant. The total response, as a summation of the wave-induced loads and the steady solution, is represented by global bending moment and shear force envelopes along the spar hull for a given sea state. Global bending and shear stresses of primary structural components can be further calculated and checked against code requirements. This procedure has been implemented through Matlab scripts. A comparison with global finite element analysis for a classic spar is made showing very good agreement. The present simple procedure allows us to evaluate primary structural components of a spar hull without resorting to expensive finite element modeling. It can help the scantling design by providing the global load. The approach can also be used to identify critical environmental conditions and structural components for detailed finite element analysis.

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