• Title/Summary/Keyword: Three-Dimensional wind speed

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Analysis on the Train-wind Pressure applied to Screen Door in Island-type Platform of Subway (지하철의 섬식 정거장에 설치된 스크린도어에 가해지는 열차풍압 해석)

  • Kim, Jung-Yup
    • 한국전산유체공학회:학술대회논문집
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    • 2008.03b
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    • pp.138-141
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    • 2008
  • The screen doors installed in the station of subway are subject to the train-wind pressure caused by the operation of trains. The train-wind pressure has to be correctly estimated for the design of safe structure of screen doors. As three-dimensional numerical flow analysis technology has been significantly developed, the analysis on the train-wind pressure with diverse variables such as train specifications, train speed, tunnel and station configurations, and blockage ratio can be effectively carried out with three-dimensional numerical method. In this study, computational analysis of train-induced wind in a subway tunnel employing the screen doors are carried out by using the three-dimensional numerical method with the model of the moving boundary for the run of trains. While the numerical analysis of train-wind pressure was applied on the one island-type station in the Seoul Subway Line 2, maximum pressure of 494 Pa was estimated on the screen door when two trains pass each other at the speed of 80km/h in the platform.

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PERFORMANCE ANALYSIS OF NREL PHASE VI WIND TURBINES UNDER VARIOUS SCALE CONDITIONS (스케일 변화에 따른 NREL PHASE VI 풍력터빈의 성능해석)

  • Park, Y.M.;Chang, B.H.
    • 한국전산유체공학회:학술대회논문집
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    • 2006.10a
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    • pp.155-158
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    • 2006
  • In the present paper, the scale effects of two-dimensional airfoil and three-dimensional wind turbine were investigated by using FLUENT software. For two dimensional analysis, flow around S809 airfoil with various Reynolds No. and Mach No. conditions were simulated. For three dimensional analysis, scaled NREL Phase VI wind turbine models from 6% to 1,600% were simulated under the same tip speed ratio condition. Finally, aerodynamic comparisons between two-dimensional flow and three dimensional wind turbine flow are made for the feasibility study of scale effect corrections. Currently, KARI(Korea Aerospace Research Institute) is preparing for the wind tunnel test of 12% NREL Phase VI wind turbine and the performance analysis of the scaled NREL wind turbine model will be validated by the wind tunnel test.

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Development of 3 - Dimensional Ultrasonic Wind Direction Anemometer Measurement Technique Using Time Division Method (시분할 방식을 이용한 3차원 초음파 풍향풍속계 측정기술 개발)

  • Lee, Woo-Jin;Choi, Jae-Young;Kim, Kyung-Won;Yim, Jae-Hong
    • Journal of Sensor Science and Technology
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    • v.26 no.1
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    • pp.66-72
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    • 2017
  • The three dimensional ultrasonic anemometer was constructed to reduce the disadvantages of the two-dimensional anemometer and to be free from the use environment. Three pairs of transmitting and receiving ultrasonic sensors were designed to face each other at an angle of $45^{\circ}$ to the upper and lower surfaces at intervals of $120^{\circ}$. 200 kHz ultrasonic sensor Oscillation, transmission and reception, level detection, power supply circuit were designed and U, V, W wind speed vector components were obtained by measuring the time of first received ultrasonic pulse by transmitting pulse ultrasound. It is implemented as firmware in ARM Coretex-M3 processor so that horizontal and vertical wind direction and wind speed can be converted into digital signal by vector calculation. In this study, The three-dimensional ultrasonic anemometer can complement the disadvantages of the two-dimensional anemometer (mechanical and ultrasonic), and it is expected to gradually replace the two-dimensional anemometer due to its high utilization rate by collecting additional information such as vertical wind.

Verification of Speed-up Mechanism of Pedestrian-level Winds Around Square Buildings by CFD

  • Hideyuki Tanaka;Qiang Lin;Yasuhiko Azegami;Yukio Tamura
    • International Journal of High-Rise Buildings
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    • v.11 no.4
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    • pp.301-314
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    • 2022
  • Various studies have been conducted on pedestrian-level wind environments around buildings. With regard to the speed-up mechanism of pedestrian-level winds, there are references to downwash effect due to the vertical pressure gradient of boundary layer flow and venturi effect due to flow blocking by the building. Two factors contribute to increase or decrease of downwash effect: change in twodimensional / three-dimensional air flow pattern (Type 1) and change in downwash wind speed due to building size that does not accompany change in airflow pattern (Type 2). Previous studies have shown that downwash effect has a greater influence in increasing or decreasing the area of strong wind than venturi effect. However, these considerations are derived from the horizontal mean wind speed distribution at pedestrian level and are not the result of three-dimensional flow field around the building. Therefore, in this study, Computational Fluid Dynamics using Large Eddy Simulation were performed to verify the downwash phenomena that contributes to increase in wind speed at pedestrian level.

Numerical Assessment of Wake Effect by Prevailing Wind Around Wido Island (주풍향에 의한 위도(蝟島) 근방의 후류 영향 평가)

  • Ryu, Ki-Wahn;Jang, Jea-Kyung
    • Journal of Wind Energy
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    • v.9 no.4
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    • pp.40-46
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    • 2018
  • In this study, a three-dimensional Navier-Stokes simulation around Wido Island was performed to analyze the wake effect behind an island. A 10 m/s wind speed and pressure boundary conditions were assigned for the inflow and outflow boundary conditions, respectively. Wido Island was modeled using GIS data. A prevailing wind from the north-northwest direction was determined based on QuikSCAT satellite data. A computational domain of $40km{\times}20km{\times}5km$ covering Wido Island was applied for numerical analysis. Sixty points were specified to extract the wind speed data. A wind speed profile inside the atmospheric boundary layer was compared with a wind profile using a simple power law. It turns out that the wake effect decreases the mean wind speed by 5% more or less, which corresponds to a 14% decrease in wind energy. Thus, the installation of a meteorological mast or development of a wind farm behind Wido Island is not highly recommended.

Investigation on wind stability of three-tower cable-stayed-suspension hybrid bridges under skew wind

  • Xin-Jun Zhang;Li Bowen;Nan Zhou
    • Wind and Structures
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    • v.38 no.6
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    • pp.427-443
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    • 2024
  • By using a computational program of three-dimensional aerostatic and aerodynamic stability analysis of long-span bridges under skew wind, the dynamic characteristics and structural stability(including the aerostatic and aerodynamic stability) of a three-tower cable-stayed-suspension hybrid bridge with main span of 1 400 meters are investigated numerically under skew wind, and the skew wind and aerostatic effects on the aerostatic and aerodynamic stability of three-tower cable-stayedsuspension hybrid bridge are ascertained. The results show that the three-tower cable-stayed-suspension hybrid bridge is a longspan structure with greater flexibility, and it is more susceptible to the wind action. The aerostatic instability of three-tower cable-stayed-suspension hybrid bridges is characterized by the coupling of vertical bending and torsion of the girder, and the skew wind does not affect the aerostatic instability mode. The skew wind has positive or negative effects on the aerostatic stability of the bridge, the influence is between -5.38% and 4.64%, and in most cases, it reduces the aerostatic stability of the bridge. With the increase of wind yaw angle, the critical wind speed of aerostatic instability does not vary as the cosine rule as proposed by the skew wind decomposition method, the skew wind decomposition method may overestimate the aerostatic stability, and the maximum overestimation is 16.7%. The flutter critical wind speed fluctuates with the increase of wind yaw angle, and it may reach to the minimum value under the skew wind. The skew wind has limited effect on the aerodynamic stability of three-tower cable-stayed-suspension hybrid bridge, however the aerostatic effect significantly reduces the aerodynamic stability of the bridge under skew wind, the reduction is between 3.66% and 21.86%, with an overall average drop of 11.59%. The combined effect of skew and static winds further reduces the critical flutter wind speed, the decrease is between 7.91% and 19.37%, with an overall average decrease of 11.85%. Therefore, the effects of skew and static winds must be comprehensively considered in the aerostatic and aerodynamic stability analysis of three-tower cable-stayed-suspension hybrid bridges.

Resonance Characteristics for 3-Dimensional Circular Wind Tunnel (3차원 원형 풍동의 공진 특성)

  • Baik, Ki-Young;Lee, In;Shin, Hyun-Dong
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1096-1103
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    • 1990
  • A finite element method is used for analyzing the resonant characteristics of three- dimensional wind tunnel with circular cross section. The resonant frequencies of wind tunnel is nearly constant in Mach number range of 0.0-0.2. The resonant frequencies and modes of three-dimensional low speed wind tunnel have been calculated. The 20-node isoparametric element gives accurate results compared with the experimental results.

Severe Downslope Windstorms of Gangneung in the Springtime (봄철 강릉지역에서 발생하는 강풍에 대한 연구)

  • Jang, Wook;Chun, Hye-Yeong
    • Atmosphere
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    • v.18 no.3
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    • pp.207-224
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    • 2008
  • Severe downslope windstorms observed at Gangneung, Korea in the springtime during the last 30 years are studied to understand their generation mechanisms. 92 severe wind cases are selected for which the maximum instantaneous wind speeds exceed two standard deviation of total mean plus ($18.7ms^{-1}$). They are categorized into the three mechanisms (hydraulic jump, partial reflection, and critical-level reflection) proposed in previous studies based on the flow condition, which is calculated using the wind and temperature profile observed at one upstream rawinsonde station, Osan. Among the three, partial reflection is found to be the most frequent mechanism for the last 30 years (1976 - 2005). To understand the role of inversion in generating severe downslope windstorms, horizontal velocity perturbation was calculated analytically for the atmosphere with an inversion layer. It turned out that the intensity of downslope wind was increased by inversion layer of specific heights, which are well matched with the observations. For better understanding the generation mechanisms, two-dimensional numerical simulations are conducted for the 92 severe wind cases using the ARPS model. In most simulations, surface wind speed exceeds the value of the severe-wind criterion, and each simulated case can be explained by its own generation mechanism. However, in most simulations, the simulated surface wind speed is larger than the observed, due to ignoring the flow-splitting effect in the two-dimensional framework.

Feedforward Pitch Control Using Wind Speed Estimation

  • Nam, Yoon-Su;Kim, Jeong-Gi;Paek, In-Su;Moon, Young-Hwan;Kim, Seog-Joo;Kim, Dong-Joon
    • Journal of Power Electronics
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    • v.11 no.2
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    • pp.211-217
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    • 2011
  • The dynamic response of a multi-MW wind turbine to a sudden change in wind speed is usually slow, because of the slow pitch control system. This could cause a large excursion of the rotor speed and an output power over the rated. A feedforward pitch control can be applied to minimize the fluctuations of these parameters. This paper introduces the complete design steps for a feedforward pitch controller, which consist of three stages, i.e. the aerodynamic torque estimation, the 3-dimensional lookup table for the wind seed estimation, and the calculation of the feedforward pitch amount. The effectiveness of the feedforward control is verified through numerical simulations of a multi-MW wind turbine.

Analysis of the Effect of Met Tower Shadow using Computational Fluid Dynamics (전산유체역학을 이용한 풍황탑 차폐효과 해석)

  • Kim, Taesung;Rhee, Huinam;Kim, Hyun-Goo
    • 한국신재생에너지학회:학술대회논문집
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    • 2011.11a
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    • pp.35.1-35.1
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    • 2011
  • When the wind speed is measured by the met-mast sensor it is distorted due to the shadow effect of tower. In this paper the tower shadow effect is analyzed by a computational fluid dynamics code. First three dimensional modeling and flow analysis of the met-mast system were performed. The results were compared with the available experimental wind-tunnel test data to confirm the validity of the meshes and turbulence model. Two-dimensional model was then developed based on the three-dimensional works and experimental data. 2D analysis for various Reynolds numbers and turbulence strengths were then performed to establish the tower shadow effect database, which can be utilized as correction factors for the measured wind energy.

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