A comparison of the forces on dome and prism for straight and tornadic wind using CFD model

Yousef, Majdi A.A.,Selvam, Panneer R.,Prakash, Jai Techno-Press 2018 Wind and Structures, An International Journal (WAS Vol.26 No.6

Tornadoes are vertical swirling air formed because of the existence of layers of air with contrasting features of temperature, wind flow, moisture, and density. Tornadoes induce completely different wind forces than a straight-line (SL) wind. A suitably designed building for an SL wind may fail when exposed to a tornado-wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. In tornado-damaged areas, dome buildings seem to have less damage. As a dome structure is naturally wind resistant, domes have been used in back yards, as single family homes, as in-law quarters, man caves, game rooms, storm shelters, etc. However, little attention has been paid to the tornadic wind interactions with dome buildings. In this work, the tornado forces on a dome are computed using Computational Fluid Dynamics (CFD) for tornadic and SL wind. Then, the interaction of a tornado with a dome and a prism building are compared and analyzed. This work describes the results of the tornado wind effect on dome and prism buildings. The conclusions drawn from this study are illustrated in visualizations. The tornado force coefficients on a dome building are larger than SL wind forces, about 120% more in x- and y-directions and 280% more in z-direction. The tornado maximum pressure coefficients are also higher than SL wind by 150%. The tornado force coefficients on the prism are larger than the forces on the dome, about 100% more in x- and y-directions, and about 180% more in z-direction. The tornado maximum pressure coefficients on prism also are greater those on dome by 150% more. Hence, a dome building has less tornadic load than a prism because of its aerodynamic shape.

Monitoring of wind effects on an instrumented low-rise building during severe tropical storm

Q.S. Li,S.Y. Hu 한국풍공학회 2015 Wind and Structures, An International Journal (WAS Vol.20 No.3

A full-scale instrumented low-rise building with gable roof was built at a coastal site with a highincidence of tropical cyclones for monitoring of wind effects on the building during windstorms. This paperpresents the field measurements of the wind velocity field around and the wind-induced pressures on thelow-rise building during the passage of severe tropical storm Soudelor. Near-ground wind characteristicssuch as wind speed, wind direction, turbulence intensity, gust factor, turbulence integral length scale andwind velocity spectra were investigated. The wind-induced pressures on the roof of the building wereanalyzed and discussed. The results revealed that the eave and ridge edges on the roof were subjected to themost severe suction pressures under quartering winds. These suction pressures showed obviousnon-Gaussian behavior. The measured results were compared with the provisions of ASCE 7-10 to assessthe suitability of the code of practice for the wind-resistant design of low-rise buildings under tropicalcyclones. The field study aims to provide useful information that can enhance our understanding of theextreme wind effects on low-rise buildings in an effort to reduce tropical cyclone wind damages toresidential buildings.

Wind-sand coupling movement induced by strong typhoon and its influences on aerodynamic force distribution of the wind turbine

Shi-Tang Ke,Yifan Dong,Rongkuan Zhu,Tongguang Wang 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.4

The strong turbulence characteristic of typhoon not only will significantly change flow field characteristics surrounding the large-scale wind turbine and aerodynamic force distribution on surface, but also may cause morphological evolution of coast dune and thereby form sand storms. A 5MW horizontal-axis wind turbine in a wind power plant of southeastern coastal areas in China was chosen to investigate the distribution law of additional loads caused by wind-sand coupling movement of coast dune at landing of strong typhoons. Firstly, a mesoscale Weather Research and Forecasting (WRF) mode was introduced in for high spatial resolution simulation of typhoon “Megi”. Wind speed profile on the boundary layer of typhoon was gained through fitting based on nonlinear least squares and then it was integrated into the user-defined function (UDF) as an entry condition of small-scaled CFD numerical simulation. On this basis, a synchronous iterative modeling of wind field and sand particle combination was carried out by using a continuous phase and discrete phase. Influencing laws of typhoon and normal wind on moving characteristics of sand particles, equivalent pressure distribution mode of structural surface and characteristics of lift resistance coefficient were compared. Results demonstrated that: Compared with normal wind, mesoscale typhoon intensifies the 3D aerodynamic distribution mode on structural surface of wind turbine significantly. Different from wind loads, sand loads mainly impact on 30° ranges at two sides of the lower windward region on the tower. The ratio between sand loads and wind load reaches 3.937% and the maximum sand pressure coefficient is 0.09. The coupling impact effect of strong typhoon and large sand particles is more significant, in which the resistance coefficient of tower is increased by 9.80% to the maximum extent. The maximum resistance coefficient in typhoon field is 13.79% higher than that in the normal wind field.

Operation Scheme for a Wind Farm to Mitigate Output Power Variation

Sung-Eun Lee,Dong-Jun Won,Il-Yop Chung 대한전기학회 2012 Journal of Electrical Engineering & Technology Vol.7 No.6

Because of the nature of wind, the output power of wind turbines fluctuates according to wind speed variation. Therefore, many countries have set up wind-turbine interconnection standards usually named as Grid-Code to regulate the output power of wind farms to improve power system reliability and power quality. This paper proposes three operation modes of wind farms such as maximum power point tracking (MPPT) mode, single wind turbine control mode and wind farm control mode to control the output power of wind turbines as well as overall wind farms. This paper also proposes an operation scheme of wind farm to alleviate power fluctuation of wind farm by choosing the appropriate control mode and coordinating multiple wind turbines in consideration of grid conditions. The performance of the proposed scheme is verified via simulation studies in PSCAD/EMTDC with doubly-fed induction generator (DFIG) based wind turbine models.

Wind Direction and Wind Speed Analysis around Hanbit Nuclear Power Plant

이윤종 (사)한국방사선산업학회 2022 방사선산업학회지 Vol.16 No.4

The Korean Peninsula is affected by westerlies and seasonal monsoons. In addition, atyphoon may generate storms with maximum wind speeds of 17 m s-1 or more. The direction and speedof the wind have the greatest influence on the distribution of radioactivity (radioactive material) leaks froma nuclear facility to the outside. In the event of such a radiation emergency, local wind direction and windspeed data are very important when preparing resident protection measures, such as the evacuation ofresidents. Among the various weather data provided by the Korea Meteorological Administration, in thisstudy, temperature, wind direction, and wind speed data measured and recorded from 2012 to August 2022at the Yeonggwang Weather Station, the location of the Hanbit Nuclear Power Plant, were provided andanalyzed. The characteristics of the wind direction and wind speed were investigated based on the annualwind speed and wind direction data in this area over a period of 10 years. The average temperature ofthe Yeonggwang area is 13.41 degrees, and the average temperature is gradually increasing. The maximumwind speed by year was counted as a gradual downward trend. In the case of wind direction, it wasfound that a northeast wind of 0~30 degrees and a north wind and northwest wind between 330~360degrees were predominant, despite the influence of the westerly and monsoon winds. Based on theHanbit Nuclear Power Plant, the location of the first aid station is mainly located in the east and south, andthe first aid station is concentrated in places where the influence of the wind direction is relatively smallin terms of the probabilistic impact of the emergency accident. Based on the nuclear power plant, thelocation of the monitoring center for radiation emergency prevention is located in the southeast, so it isexpected that the detector installed outside the plant fence can efficiently detect leakage accidents early.

Characteristics of Zonda wind in South American Andes

Loredo-Souza, Acir M.,Wittwer, Adrian R.,Castro, Hugo G.,Vallis, Matthew B. Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.24 No.6

This paper discusses some features and conditions that characterize the Zonda wind, focusing particularly on the implications for wind engineering applications. This kind of wind, typical of mountainous regions, is far from being adequately characterized for computational simulations and proper modeling in experimental facilities such as boundary layer wind tunnels. The objective of this article is to report the research works that are being developed on this kind of wind, describing the main obtained results, and also to establish some general guidelines for the proper analysis of the Zonda in the wind engineering context. A classification for the Zonda wind is indicated and different cases of structural and environmental effects are described. Available meteorological data is analyzed from the wind engineering point of view to obtain the Zonda wind gust factors, as well as basic wind speeds relevant for structural design. Some considerations and possible directions for the Zonda wind-tunnel and computational modeling are provided. Gust factor values larger than those used for open terrain were obtained, nevertheless, the basic wind speed values obtained are similar to values presented by the Argentinian Wind Code for three-second gust, principally at Mendoza airport.

Wind loads and load-effects of large scale wind turbine tower with different halt positions of blade

Ke, Shitang,Yu, Wei,Wang, Tongguang,Zhao, Lin,Ge, Yaojun Techno-Press 2016 Wind and Structures, An International Journal (WAS Vol.23 No.6

In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in $350^{\circ}$ to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in $330^{\circ}$ under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

Nonlinear response history analysis and collapse mode study of a wind turbine tower subjected to tropical cyclonic winds

Dai, Kaoshan,Sheng, Chao,Zhao, Zhi,Yi, Zhengxiang,Camara, Alfredo,Bitsuamlak, Girma Techno-Press 2017 Wind and Structures, An International Journal (WAS Vol.25 No.1

The use of wind energy resources is developing rapidly in recent decades. There is an increasing number of wind farms in high wind-velocity areas such as the Pacific Rim regions. Wind turbine towers are vulnerable to tropical cyclones and tower failures have been reported in an increasing number in these regions. Existing post-disaster failure case studies were mostly performed through forensic investigations and there are few numerical studies that address the collapse mode simulation of wind turbine towers under strong wind loads. In this paper, the wind-induced failure analysis of a conventional 65 m hub high 1.5-MW wind turbine was carried out by means of nonlinear response time-history analyses in a detailed finite element model of the structure. The wind loading was generated based on the wind field parameters adapted from the cyclone boundary layer flow. The analysis results indicate that this particular tower fails due to the formation of a full-section plastic hinge at locations that are consistent with those reported from field investigations, which suggests the validity of the proposed numerical analysis in the assessment of the performance of wind-farms under cyclonic winds. Furthermore, the numerical simulation allows to distinguish different failure stages before the dynamic collapse occurs in the proposed wind turbine tower, opening the door to future research on the control of these intermediate collapse phases.

Statistical characteristics of sustained wind environment for a long-span bridge based on long-term field measurement data

Ding, Youliang,Zhou, Guangdong,Li, Aiqun,Deng, Yang Techno-Press 2013 Wind and Structures, An International Journal (WAS Vol.17 No.1

The fluctuating wind induced vibration is one of the most important factors which has been taken into account in the design of long-span bridge due to the low stiffness and low natural frequency. Field measurement characteristics of sustained wind on structure site can provide accurate wind load parameters for wind field simulation and structural wind resistance design. As a suspension bridge with 1490 m main span, the Runyang Suspension Bridge (RSB) has high sensitivity to fluctuating wind. The simultaneous and continuously wind environment field measurement both in mid-span and on tower top is executed from 2005 up to now by the structural health monitoring system installed on this bridge. Based on the recorded data, the wind characteristic parameters, including mean wind speed, wind direction, the turbulence intensity, the gust factors, the turbulence integral length, power spectrum and spatial correlation, are analyzed in detail and the coherence functions of those parameters are evaluated using statistical method in this paper. The results indicate that, the turbulence component of sustain wind is larger than extremely strong winds although its mean wind speed is smaller; the correlation between turbulence parameters is obvious; the power spectrum is special and not accord with the Simiu spectrum and von Karman spectrum. Results obtained in this study can be used to evaluate the long term reliability of the Runyang Suspension Bridge and provide reference values for wind resistant design of other structures in this region.

Characteristics of Zonda wind in South American Andes

Acir M. Loredo-Souza,Adrian R. Wittwer,Hugo G. Castro,Matthew B.Vallis 한국풍공학회 2017 Wind and Structures, An International Journal (WAS Vol.24 No.6

This paper discusses some features and conditions that characterize the Zonda wind, focusing particularly on the implications for wind engineering applications. This kind of wind, typical of mountainous regions, is far from being adequately characterized for computational simulations and proper modeling in experimental facilities such as boundary layer wind tunnels. The objective of this article is to report the research works that are being developed on this kind of wind, describing the main obtained results, and also to establish some general guidelines for the proper analysis of the Zonda in the wind engineering context. A classification for the Zonda wind is indicated and different cases of structural and environmental effects are described. Available meteorological data is analyzed from the wind engineering point of view to obtain the Zonda wind gust factors, as well as basic wind speeds relevant for structural design. Some considerations and possible directions for the Zonda wind-tunnel and computational modeling are provided. Gust factor values larger than those used for open terrain were obtained, nevertheless, the basic wind speed values obtained are similar to values presented by the Argentinian Wind Code for three-second gust, principally at Mendoza airport.