• 풍력에너지저널
• /
• 제14권4호
• /
• pp.57-67
• /
• 2023

This study aimed to investigate differences in turbulence intensity and turbine loads among onshore wind farms located in various types of terrain. To achieve this, simulations were conducted for two onshore wind farms with identical wind turbines and capacity but situated on complex and flat terrains. The simulations used meteorological data gathered over a 10-year period from automatic weather stations nearest to the wind farms. WindSim and WindPRO software tools were employed for wind field and load analysis, respectively. The simulation results revealed that wind farm A, situated on complex terrain, exhibited significantly higher effective turbulence intensity than wind farm B on flat terrain, as expected. Consequently, the load indices of several wind turbines exceeded 100 % in wind farm A, indicating that the turbines could not reach their design lifespan. From the simulation study, aimed at reducing both the effective turbulence intensity and turbine loads, it became evident that while increasing turbine spacing could decrease effective turbulence intensity to some extent, it couldn't completely resolve the issue due to the inherently high ambient turbulence intensity on complex terrain. The problem with wind turbine loads could only be completely resolved by using wind turbines with a turbine class of A+, corresponding to a reference turbulence intensity of 0.18.

• 한국공간구조학회논문집
• /
• 제21권1호
• /
• pp.51-59
• /
• 2021

In this paper, the effect of the turbulence intensity in across-wind direction on the wind load in CFD(Computational fluid dynamics) simulation was analyzed. 'Ansys fluent' software was used for CFD simulation. And the fluctuating wind speed applied to the simulation was generated according to Korean Design Standard and Von Karman wind turbulence model. The turbulence intensity in across-wind direction for simulation was applied from 0 to 100% of the turbulence intensity in along-wind direction. The analysis results showed that the turbulence intensity in across-wind direction had a particularly great effect on the wind load in across-wind direction.

• Wind and Structures
• /
• 제18권6호
• /
• pp.599-618
• /
• 2014

In this study, a square rectangular tall building is considered to investigate the effects of turbulence integral length scale and turbulence intensity on the along-wind responses, across-wind responses and torsional responses of the tall building by Large Eddy Simulation (LES). A recently proposed inflow turbulence generator called the discretizing and synthesizing random flow generation (DSRFG) approach is applied to simulate turbulent flow fields. It has been proved that the approach is able to generate a fluctuating turbulent flow field satisfying any given spectrum, desired turbulence intensity and wind speed profiles. Five profiles of turbulence integral length scale and turbulence intensity are respectively generated for the inflow fields by the DSRFG approach for investigating the effects of turbulence integral length scale and turbulence intensity on the wind-induced responses of the tall building. The computational results indicate that turbulence integral length scale does not have significant effect on the along-wind (displacement, velocity and acceleration) responses, across-wind displacement and velocity responses, while the across-wind acceleration and torsional responses vary without a clear rule with the parameter. On the other hand, the along-wind, across-wind and torsional responses increase with the growth of turbulence intensity.

• 한국태양에너지학회 논문집
• /
• 제33권6호
• /
• pp.1-11
• /
• 2013

The investigation on wind farm design using CFD technique was carried out to reduce turbulence intensity in a wind farm. A potential wind farm in Gasiri of Jeju Island was selected for the design and the commercial S/W of Meteodyn WT was used for applying CFD technique. The initial layout of wind turbines was derived using WindPRO which is mainly used for wind farm design in Korea. Then, the distribution of turbulence intensity on complex terrain was calculated and visible by Meteodyn WT. Based on the distribution, wind turbines were positioned properly. As a result, wind turbines could be deployed at positions with minimum turbulence intensity as well as maximum Annual Energy Production, AEP, using Meteodyn WT. It is necessary to take into account turbulence intensity in wind farm design to avoid wind turbine failure.

• 한국태양에너지학회 논문집
• /
• 제30권6호
• /
• pp.59-65
• /
• 2010

Analysis on turbulence intensity profile depending on wind speed is an important process to set up design condition of wind turbine in terms of fatigue load. This paper tests goodness of fit of turbulence intensity empirical equations suggested by the IEC 61400 Standards with Jejudo Gimnyeong met-tower measurement, which is erected at a seashore. Therefore sea breeze and land breeze coexist. Sea breeze case showed apparent increasing trend of turbulence intensity in a high wind speed regime due to increase of sea surface roughness. However, neither inland wind turbine standard IEC 61400-1 nor offshore wind turbine standard IEC 61400-3 fit such a trend adequately. On the other hand, the modified empirical equation of turbulence intensity of IEC 61400-3 derived from Germany FINO1 application study by considering turbulence intensity behavior in a high wind speed regime showed good agreement with the measurement. Therefore, we can reconfirm and conclude that IEC 61400-3 Ed.1 legislated in 2009 needs to be modified.

• 한국태양에너지학회 논문집
• /
• 제32권4호
• /
• pp.17-23
• /
• 2012

The installed capacity of wind turbines in Korea are growing and enlarging by the central government's supporting program. But the majority area having the abundant wind energy resources is composed of mountainous and complex district, thus the turbulence intensity of there is so high and belongs to the turbulence characteristic A category of IEC design requirement. This paper presents the effect of the turbulence intensity on the power performance of a wind turbine system. Particularly, the effect of the power curve of the wind turbine system due to the turbulence intensity has analyzed. As a result, the power curve has a high turbulence characteristic shows the lower value than normal one in high wind speed regime and the AEP will be reduced at the relatively high turbulence area.

• Wind and Structures
• /
• 제25권1호
• /
• pp.39-61
• /
• 2017

Buffeting induced resonance (BIR) of hangers on long-suspension bridges is briefly reviewed, including mechanism and experimental verification. Taken the Xihoumen suspension bridge as a numerical example, sensitivities of the BIR of hangers to wind properties are investigated, including types of wind spectrum, turbulence intensity, and spacial coherence of wind fluctuations. Numerical simulations indicate that the BIR of hangers occur to both cases of different wind spectra, showing that it is insensitive to types of wind spectrum. On the other hand, it is found that the turbulence intensity affects buffeting of main cables almost in a linear manner, and so it does to the BIR of the hangers; however, the resonance factors, namely the ratio of the response of the hanger to that of the main cable, are little affected by the turbulence intensity. The spacial coherence of the wind fluctuations, although plays an important role on the buffeting responses of the main structure, has no substantial effects on the BIR of the hangers. Finally, replacement of steel strand with CFRP material has been verified as a very effective countermeasure against the BIR of hangers.

• Wind and Structures
• /
• 제22권2호
• /
• pp.185-209
• /
• 2016

Across-wind aerodynamic damping ratios are identified from the wind-induced acceleration responses of 15 aeroelastic models of rectangular super-high-rise buildings in various simulated wind conditions by using the random decrement technique. The influences of amplitude-dependent structural damping ratio and natural frequency on the estimation of the aerodynamic damping ratio are discussed and the identifying method for aerodynamic damping is improved at first. Based on these works, effects of turbulence intensity $I_u$, aspect ratio H/B, and side ratio B/D on the across-wind aerodynamic damping ratio are investigated. The results indicate that turbulence intensity and side ratio are the most important factors that affect across-wind aerodynamic damping ratio, whereas aspect ratio indirectly affects the aerodynamic damping ratio by changing the response amplitude. Furthermore, empirical aerodynamic damping functions are proposed to estimate aerodynamic damping ratios at low and high reduced speeds for rectangular super-high-rise buildings with an aspect ratio in the range of 5 to 10, a side ratio of 1/3 to 3, and turbulence intensity varying from 1.7% to 25%.

• 신재생에너지
• /
• 제18권1호
• /
• pp.1-16
• /
• 2022

Climatic characteristics were described using the LiDAR (Light Detection and Ranging) and the met-mast on Dongbok·Bukchon region. The influences of meteorological conditions on the power performance of wind turbines were presented using the data of Supervisory Control And Data Acquisition (SCADA) and met-mast of the Dongbok·Bukchon Wind Farm (DBWF) located in Jeju Island. The stability was categorized into three parameters (Richardson number, Turbulence intensity, and Wind shear exponent). DBWF was dominant in unstable atmospheric conditions. At wind speeds of 14 m/s or more, the proportion of slightly unstable conditions accounted for more than 50%. A clear difference in the power output of the wind turbine was exhibited in the category of atmospheric stability and turbulence intensity (TI). Particularly, a more sensitive difference in power performance was showed in the rated wind speeds of the wind turbine and wind regime with high TI. When the flow had a high turbulence at low wind speeds and a low turbulence at rated wind speeds, a higher wind energy potential was produced than that in other conditions. Finally, the high-efficiency of the wind farm was confirmed in the slightly unstable atmospheric stability. However, when the unstable state become stronger, the wind farm efficiency was lower than that in the stable state.

• Wind and Structures
• /
• 제29권4호
• /
• pp.247-270
• /
• 2019

Wind-resistant design of existing cooling tower structures overlooks the impacts of rainfall. However, rainstorm will influence aerodynamic force on the tower surface directly. Under this circumstance, the structural response of the super-large cooling tower (SLCT) will become more complicated, and then the stability and safety of SLCT will receive significant impact. In this paper, surrounding wind fields of the world highest (210 m) cooling tower in Northwest China underthree typical wind velocities were simulated based on the wind-rain two-way coupling algorithm. Next, wind-rain coupling synchronous iteration calculations were conducted under 9 different wind speed-rainfall intensity combinations by adding the discrete phase model (DPM). On this basis, the influencing laws of different wind speed-rainfall intensity combinations on wind-driving rain, adhesive force of rain drops and rain pressure coefficients were discussed. The acting mechanisms of speed line, turbulence energy strength as well as running speed and trajectory of rain drops on structural surface in the wind-rain coupling field were disclosed. Moreover, the fitting formula of wind-rain coupling equivalent pressure coefficient of the cooling tower was proposed. A systematic contrast analysis on its 3D distribution pattern was carried out. Finally, coupling model of SLCT under different working conditions was constructed by combining the finite element method. Structural response, buckling stability and local stability of SLCT under different wind velocities and wind speed-rainfall intensity combinations were compared and analyzed. Major research conclusions can provide references to determine loads of similar SLCT accurately under extremely complicated working conditions.