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.

Field measurement and CFD simulation of wind pressures on rectangular attic

Yongbo Peng,Weijie Zhao,Xiaoqiu Ai 한국풍공학회 2019 Wind and Structures, An International Journal (WAS Vol.29 No.6

Wind pressure is a critical argument for the wind-resistant design of structures. The attempt, however, to explore the wind pressure field on buildings still encounters challenges though a large body of researches utilizing wind tunnel tests and wind field simulations were carried out, due to the difficulty in logical treatments on the scale effect and the modeling error. The full-scale measurement has not yet received sufficient attention. By performing a field measurement, the present paper systematically addresses wind pressures on the rectangular attic of a double-tower building. The spatial and temporal correlations among wind speed and wind pressures at measured points are discussed. In order to better understand the wind pressure distribution on the attic facades and its relationship against the approaching flow, a full-scale CFD simulation on the similar rectangular attic is conducted as well. Comparative studies between wind pressure coefficients and those provided in wind-load codes are carried out. It is revealed that in the case of wind attack angle being zero, the wind pressure coefficient of the cross-wind facades exposes remarkable variations along both horizontal and vertical directions; while the wind pressure coefficient of the windward facade remains stable along horizontal direction but exposes remarkable variations along vertical direction. The pattern of wind pressure coefficients, however, is not properly described in the existing wind-load codes.

남해안 어민들의 바람에 대한 인지 양상 연구-전남 해남, 경남 욕지도, 경남 가덕도의 바람을 중심으로-

홍기옥 비교민속학회 2020 비교민속학 Vol.- No.71

The purpose of this study was to summarize the 'cognitive classification system for fishermen's winds' through surveys of wind-related expressions used by fishermen in areas of Haenam-gun, Jeollanam-do, Yokji Island Gyeongsangnam-do, and Gadeok Island, Busan. Since 2011, 19 reporters surveyed the expressions related to wind used by fishermen to summarize their perception of wind. The fishermen's perception of wind was classified according to defense, evaluation, season, weather and harvest. The name of the wind according to the defense was used in combination with the ‘bird, honey, horse’ and ‘wind’, which are the native words. The name of the wind reflects local people's perception of wind, such as [direction], [speed], [intensity], [concentration], [influence], [high and low], [region], [evaluation], based on the naming base appear. In addition, fishermen assessed the winds based on their experience with fishing activities. The winds used for fishing activities were classified as good winds, but otherwise, bad winds. Folk knowledge of climate change caused by wind is based on tradition and experience. The wind blowing varies from season to season and its characteristics are different. Depending on the season, some of the winds are useful for fishing, but some are unfavorable. In addition, the distinction related to weather and harvest due to wind has been solidified with an idiomatic expression in fishing villages, and has been transmitted and learned. 본 연구는 남해안 어촌지역인 전라남도 해남군 송지면(중리/ 어란리), 경상남도 통영시 욕지도 동항리, 부산시 가덕도 대항동에서 어민들이 사용하는 바람에 대한 어휘 조사를 통해 ‘어민들의 바람에 대한 인지 양상’을 정리하고자 하였다. 2011년부터 19명의 제보자를 대상으로 개방형 면담 조사를 통해 어민들은 바람에 대해 방위(정방, 간방), 평가, 계절, 날씨․수확에 따라 구분하여 인지함을 확인하였다. 방위에 따른 바람 이름은 고유어인 ‘새, 하늬, 마, 노(높-)’ 어형을 핵어인 ‘바람’과 결합하여 사용하고 있었다. 바람 이름에 바람의 [방향], [속도], [세기], [농도], [영향], [고저], [지역], [평가] 등 지역민의 바람에 대한 인지 양상이 명명 기반으로 반영되어 나타났다. 또한 어민들은 어업 활동과 연관하여 전승된 경험을 바탕으로 바람을 평가하였다. 어업 활동에 도움이 되는 바람은 좋은 바람이지만 그렇지 않은 경우는 나쁜 바람이라 구분하였다. 바람으로 인한 기후 변화에 대한 민속지식은 전승과 경험을 바탕으로 하고 있다. 계절에 따라 부는 바람이 다르고 그 특성도 다르다. 계절에 따라 부는 바람 중 어떤 바람은 어로 활동에 도움이 되지만 어떤 바람은 불리하다. 또한 바람으로 인한 날씨․수확에 관련된 구분은 어촌지역에서는 관용 표현으로 굳어져 전승, 학습되고 있다.

Influence of a community of buildings on tornadic wind fields

Zhi Li,Ryan Honerkamp,Gui-rong Yan,Ruoqiang Feng 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.2

To determine tornadic wind loads, the wind pressure, forces and moments induced by tornadoes on civil structures have been studied. However, in most previous studies, only the individual building of interest was included in the wind field, which may be suitable to simulate the case where a tornado strikes rural areas. The statistical data has indicated that tornadoes induce more significant fatalities and property loss when they attack densely populated areas. To simulate this case, all buildings in the community of interest should be included in the wind field. However, this has been rarely studied. To bridge this research gap, this study will systematically investigate the influence of a community of buildings on tornadic wind fields by modeling all buildings in the community into the wind field (designated as “the Community case under tornadic winds”). For comparison, the case in which only a single building is included in the tornadic wind field (designated as “the Single-building case under tornadic winds”) and the case where a community of buildings are included in the equivalent straight-line wind field (designated as “the Community case under straight-line winds”) are also simulated. The results demonstrate that the presence of a number of buildings completely destroys the pattern of regular circular strips in the distribution of tangential velocity and pressure on horizontal planes. Above the roof height, the maximum tangential velocity is lower in the Community case under tornadic winds than that in the Single-building case under tornadic winds because of the higher surface friction in the Community case; below the roof height, greater tangential velocity and pressure are observed in the Community case under tornadic wind fields, and more unfavorable conditions are observed in the Community case under tornadic winds than under the equivalent straight-line winds.

Operation Scheme for a Wind Farm to Mitigate Output Power Variation

Lee, Sung-Eun,Won, Dong-Jun,Chung, Il-Yop The Korean Institute of Electrical Engineers 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.

A remote long-term and high-frequency wind measurement system: design, comparison and field testing

Ning Zhao,Guoqing Huang,Ruili Liu,Liuliu Peng 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.1

The wind field measurement of severe winds such as hurricanes (or typhoons), thunderstorm downbursts and other gales is important issue in wind engineering community, both for the construction and health monitoring of the wind-sensitive structures. Although several wireless data transmission systems have been available for the wind field measurement, most of them are not specially designed for the wind data measurement in structural wind engineering. Therefore, the field collection is still dominant in the field of structural wind engineering at present, especially for the measurement of the long-term and high-frequency wind speed data. In this study, for remote wind field measurement, a novel wireless long-term and high-frequency wind data acquisition system with the functions such as remote control and data compression is developed. The system structure and the collector are firstly presented. Subsequently, main functions of the collector are introduced. Also novel functions of the system and the comparison with existing systems are presented. Furthermore, the performance of this system is evaluated. In addition to as the wireless transmission for wind data and hardware integration for the collector, the developed system possesses a few novel features, such as the modification of wind data collection parameters by the remote control, the remarkable data compression before the data wireless transmission and monitoring the data collection by the cell phone application. It can be expected that this system would have wide applications in wind, meteorological and other communities.

기상뜰개로 관측된 동해에서의 취송류

이동규 한국해양과학기술원 2014 Ocean and Polar Research Vol.36 No.2

A wind-driven current in the East Sea from Lagrangian measurements of wind and current at 15 m using MiniMet drifters was analyzed. Spectral analysis of the current from 217 pieces of a 10 daylong time series shows the dominant energy at the inertial frequency for the current at 15 m. Wind has energy peaks at a 0.2-0.5 cycles per day (cpd) frequency band. The power spectrum of the clockwise rotating component is predominant for the current and was 1.5-2 times larger than the anticlockwise rotating component for wind. Co-spectra between the wind and current show two peak frequency bands at subinertial frequency and 0.5-0.3 cpd. Coherences between the wind and current at those peak frequencies are significant with 95% confidence and phase differences were 90-100o. From the phase differences, the efolding depth is estimated as 17 m and this e-folding depth is smaller than the estimation by Chereskin’s (1999) 25 m using a moored Acoustic Doppler Current Profiler and an anemometer installed at the surface buoy. The angle between the wind-driven current (or ageostrophic current) and wind from this study was also much larger than the global estimate by Rio and Hernandez (2003) using reanalysis wind and drifters. The possible explanation for the discrepancy comes from the fact that the current is driven by a wind of smaller length scale than 250 km but the satellite or the reanalysis products do not resolve winds of length scale smaller than 250 km. Large rms differences between Mini-Met and QuickSCAT wind on spatial lags smaller than 175 km substantiate this explanation.

Wind-induced responses and equivalent static wind loads of tower-blade coupled large wind turbine system

S.T. Ke,T.G. Wang,Y.J. Ge,Y. Tamura 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.3

This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.

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.

Design criteria of wind barriers for traffic. Part 1: wind barrier performance

권순덕,김동현,이승호,송호성 한국풍공학회 2011 Wind and Structures, An International Journal (WAS Vol.14 No.1

This study investigates the design criteria required for wind barriers to protect vehicles running on an expressway under a high side wind. At the first stage of this study, the lateral deviations of vehicles in crosswinds were computed from the commercial software, CarSim and TruckSim, and the critical wind speeds for a car accident were then evaluated from a predefined car accident index. The critical wind speeds for driving stability were found to be 35 m/s for a small passenger car, yet 30 m/s for a truck and a bus. From the wind tunnel tests, the minimum height of a wind barrier required to reduce the wind speed by 50% was found to be 12.5% of the road width. In the case of parallel bridges, the placement of two edge wind barriers plus one wind barrier at center was recommended for a separation distance larger than 20 m (four lanes) and 10 m (six lanes) respectively, otherwise two wind barriers were recommended.