• Title/Summary/Keyword: Wind direction and velocity

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Dynamic analysis of wind turbine wake (풍력 발전 터빈 후류의 동적 분석)

  • Um, Young Han;Kim, Yun Gu;Park, Sung Goon
    • Journal of the Korean Society of Visualization
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    • v.18 no.2
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    • pp.59-65
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    • 2020
  • Vertical axis wind energy systems including 3 and 4 blades are numerically investigated in a two-dimensional (2D) computational domain. The power coefficient (Cp) is adopted to measure the efficiency of the system and the effect of the rotating velocity on the power coefficient is analyzed for the two different systems. The rotating velocity varies from 30 rad/s to 90 rad/s, which corresponds to the tip speed ratio (T.S.R) of 0.5 to 1.5. The torque exerted on the blades is mainly determined by the aerodynamic force in the x-direction and maximized when the blade is positioned at around θ = 186°. The efficiency of the 4-blade system is higher than that of the 3-blade system within the tip speed ratio range between 0.5 and 0.67, besides where the 3-blade system shows a better performance. For the 3-blade system, the maximum efficiency is reached to 0.082 at the tip speed ratio of 1.083. The maximum efficiency of the 4-blade system is 0.071 at T.S.R. = 0.92. The velocity fields in the x-direction, pressure fields, and the vorticity magnitude are analyzed in detail for the optimal cases of the 3- and 4-blades systems, respectively.

An Analysis of Wind Force Coefficient Distributions for Optimum Design of Single-Span Arched Greenhouse (아치형 단동온실의 최적설계를 위한 풍력계수분포도의 분석)

  • 이석건;이현우;권무남
    • Journal of Bio-Environment Control
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    • v.4 no.1
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    • pp.1-8
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    • 1995
  • One of the most destructive forces around greenhouses is wind. Wind loads can be obtained by multiplying velocity pressure by dimensionless wind force coefficient. Generally, wind force coefficients can be determined by wind tunnel experiments. The wind force coefficient distribution on a single - span arched greenhouse was estimated using experimental data and compared with reported values from various countries. The results obtained are as follows : 1. The coefficients obtained from this study agree with the values proposed by G. L. Nelson except about 0.5 of difference in the middle region of roof section. This discrepancy is mainly attributed to the dissimilarity of experimental conditions (or wind tunnel test such as Reynolds number, type of terrain, surface roughness of model, location of the lapping and measuring methods. 2. Considering that the wind force coefficients are varied along the height of a wall at wind direction perpendicular to wall, structural analysis using subdivided wind force coefficient distribution is more resonable for wall. 3. It is recommendable that wind force coefficient distribution on a roof should take more subdivision than the existing four equal divisions for more accurate structural design. 4. Structural design using wind forces close to real values is more advantageous in safety and expense.

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Wind Field Change Simulation before and after the Regional Development of the Eunpyeong Area at Seoul Using a CFD_NIMR_SNU Model (CFD_NIMR_SNU 모형을 활용한 은평구 건설 전후의 바람환경 변화 모사 연구)

  • Cho, Kyoungmi;Koo, Hae-Jung;Kim, Kyu Rang;Choi, Young-Jean
    • Journal of Environmental Impact Assessment
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    • v.20 no.4
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    • pp.539-555
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    • 2011
  • Newly constructed, high-rise dense building areas by urban development can cause changes in local wind fields. Wind fields were analyzed to assess the impact on the local meteorology due to the land use changes during the urban redevelopment called "Eunpyeong new town" in north-western Seoul using CFD_NIMR_SNU (Computational Fluid Dynamics, National Institute of Meteorological Research, Seoul National University) model. Initial value of wind speed and direction use analysis value of AWS (Automatic Weather Station) data during 5 years. In the case of the pre-construction with low rise built-up area, it was simulated that the spatial distribution of horizontal wind fields depends on the topography and wind direction of initial inflow. But, in the case of the post-construction with high rise built-up area, it was analyzed that the wind field was affected by high rise buildings as well as terrain. High-rise buildings can generate new circulations among buildings. In addition, small size vortexes were newly generated by terrain and high rise buildings after the construction. As high-rise buildings act as a barrier, we found that the horizontal wind flow was separated and wind speed was reduced behind the buildings. CFD_NIMR_SNU was able to analyze the impact of high-rise buildings during the urban development. With the support of high power computing, it will be more common to utilize sophisticated numerical analysis models such as CFD_NIMR_SNU in evaluating the impact of urban development on wind flow or channel.

Wind Load Analysis of 61ton-class Container Crane using the Computation Fluid Dynamics (61ton 컨테이너 크레인의 전산유동해석을 통한 풍하중 분석)

  • Lee, Su-Hong;Lee, Seong-Wook;Han, Dong-Seop;Kim, Tae-Hyung;Han, Geun-Jo
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 2007.12a
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    • pp.228-229
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    • 2007
  • Container cranes are vulnerable structure to difficult weather conditions because there is no shielding facility to protect them from high wind This study carried out to analyze the wind load have an effect on container crane according to a wind direction variation The container crane for this research is a model of a 61-ton class tint used broadly in the current ports. The dimension of an external fluid field set up 500m ${\times}$ 200m. In this study, Mean wind load conformed to the 'Design Criteria of Wind Load' in 'Load Criteria of Building Structures' and an external fluid field divided in interval of 10 degrees to analyze effect according to a wind direction From there, we carried out to the computation fluid dynamic analysis using a CFX-10 Therefore as consequence of computation fluid dynamic analysis and wind velocity experiment make a comparative study, we analyzed a wind load for construction design if container crane.

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Experimental study of the loads induced by a large-scale tornado simulation on a HAWT model

  • Lopez, Juan P.;Hangan, Horia;El Damatty, Ashraf
    • Wind and Structures
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    • v.33 no.6
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    • pp.437-446
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    • 2021
  • As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

Experimental study of the loads induced by a large-scale tornado simulation on a HAWT model

  • Lopez, Juan P.;Hangan, Horia;El Damatty, Ashraf
    • Wind and Structures
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    • v.34 no.3
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    • pp.303-312
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    • 2022
  • As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

A NUMERICAL STUDY ON THE WIND EFFECTS OF MOUNTAINOUS TERRAIN FOR THE SKI RESORT (스키장의 풍환경 개선을 위한 수치해석 연구)

  • Jung, Jae-Hyuk;Hur, Nahm-Keon
    • 한국전산유체공학회:학술대회논문집
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    • 2010.05a
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    • pp.493-495
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    • 2010
  • A three-dimensional flow simulation is performed to investigate the flow field in the ski resort on complex terrain. The present paper aims to study the wind effects of mountainous terrain on the gondola safety. Strong wind happens in the ski resort on the mountain by complex terrain and it causes the dangerous accident of gondola. A digital map around the ski resort area is used to model the actual complex terrain for a 3-D analysis domain. Wind direction and speed to be used as a boundary condition are taken from local meteorological reports. The numerical results show details of the velocity distribution around a ski resort. From the results, we can suggest the modification of the installation of gondola for the safety due to strong wind.

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A Study on the Evaporation and Distribution Velocity a Volatile Mixtures (가연성 혼합액체의 증발 및 분포 속도에 관한 연구)

  • An, Hyung-Whan
    • Journal of the Korean Institute of Gas
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    • v.18 no.6
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    • pp.1-6
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    • 2014
  • This study is based on a investigation regarding the evaporation rate of a volatile liquid(methanol, tetrahydrofuran, xylene) according to changes of the temperature and wind. The weight of a volatile liquid was standardized to 24 g and the mixture was formed with the same weight ratio. In order to discover about the effect of the wind velocity, small fan was installed at 10 cm above the entrance and 30 cm away in the direction of the cylinder. The effect of the wind velocity was tested at 0 m/s, 1.63 m/s, 2.03 m/s respectively and the effect of the temperature on the volatile liquid was experimented at the temperature of $21^{\circ}C$, $32^{\circ}C$, $52^{\circ}C$ in the constant temperature water base. As a result, in case of Xylene, the evaporation rate of the tetrahydrofuran and methanol showed 1.4 mg/min, 19.8 mg/min and 10.2 mg/min respectively. Also, the effect of the evaporation rate on the temperature of the volatile liquid and on the velocity of wind was shown to be very sensitive. At the same time, the evaporation rate of the mixture showed large difference compared to that of the single volatile liquid.

An Analysis of Wind Field around the Air Quality Monitoring Station in the Urban Area by Using the Envi-met Model (Envi-met 모델을 이용한 도심지역 대기오염측정망 주변의 바람장 분석)

  • Kim, Min-Kyoung;Lee, Hwa Woon;Dou, Woo-Gon;Jung, Woo-Sik
    • Journal of Environmental Science International
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    • v.18 no.9
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    • pp.941-952
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    • 2009
  • The urban microscale wind field around the air quality monitoring station was investigated in order to check how a building complex influences it. For this study as the high density areas Jwa-dong and Yeonsan-dong monitoring sites in Busan were chosen. As the direction of inflow which is perpendicular to the building of the monitoring station was expected to cause the considerable variation of the wind field, that direction was selected. The model Envi-met was used as the diagnostic numerical model for this study. It is suitable for this investigation because Envi-met has the microscale resolution. After simulating it, on the leeward side around a building complex the decrease of flow velocity and some of vortexes or circulation area were discovered. In addition, on the edge of the top at the building and at the back of the building the upward flow was developed. If the sampling hole of monitoring site were located in this upward flow, it would be under the influence of upward flow from the near street.

Martian Bow Shock and Magnetic Pile-Up Barrier Formation Due to the Exosphere Ion Mass-Loading

  • Kim, Eo-Jin;Sohn, Jong-Dae;Yi, Yu;Ogino, Tatsuki;Lee, Joo-Hee;Park, Jae-Woo;Song, Young-Joo
    • Journal of Astronomy and Space Sciences
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    • v.28 no.1
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    • pp.17-26
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    • 2011
  • Bow shock, formed by the interaction between the solar wind and a planet, is generated in different patterns depending on the conditions of the planet. In the case of the earth, its own strong magnetic field plays a critical role in determining the position of the bow shock. However, in the case of Mars of which has very a small intrinsic magnetic field, the bow shock is formed by the direct interaction between the solar wind and the Martian ionosphere. It is known that the position of the Martian bow shock is affected by the mass loading-effect by which the supersonic solar wind velocity becomes subsonic as the heavy ions originating from the planet are loaded on the solar wind. We simulated the Martian magnetosphere depending on the changes of the density and velocity of the solar wind by using the three-dimensional magnetohydrodynamic model built by modifying the comet code that includes the mass loading effect. The Martian exosphere model of was employed as the Martian atmosphere model, and only the photoionization by the solar radiation was considered in the ionization process of the neutral atmosphere. In the simulation result under the normal solar wind conditions, the Martian bow shock position in the subsolar point direction was consistent with the result of the previous studies. The three-dimensional simulation results produced by varying the solar wind density and velocity were all included in the range of the Martian bow shock position observed by Mariner 4, Mars 2, 3, 5, and Phobos 2. Additionally, the simulation result also showed that the change of the solar wind density had a greater effect on the Martian bow shock position than the change of the solar wind velocity. Our result may be useful in analyzing the future observation data by Martian probes.