• Title, Summary, Keyword: wind flow

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Experimental investigation of wind flow characteristics over hills and escarpments - A review

  • Wani, Abdul Haseeb;Varma, Rajendra K.;Ahuja, Ashok K.
    • Wind and Structures
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    • v.32 no.4
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    • pp.393-403
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    • 2021
  • A comprehensive knowledge of the wind flow in hilly terrains is of great interest in many engineering applications, be it wind energy distribution for suitable site selection for wind farms, pollution dispersion, forest fire propagation or agrometerological studies. Several researchers have shown that wind flow over a hilly terrain may be significantly different when compared with the wind flow over a flat terrain. Complex hilly terrains may alter the wind speed to a great extent. Therefore, this effect of terrain must be properly assessed by designers and planners to arrive at a proper wind flow distribution. This paper reviews the work done in this area over the past three decades. Wind flow over two-dimensional hills and two-dimensional escarpments investigated in wind tunnels by various researchers is presented in this paper.

Wind flow modification by a jet roof for mitigation of snow cornice formation

  • Kumar, Ganesh;Gairola, Ajay;Vaid, Aditya
    • Wind and Structures
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    • v.32 no.2
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    • pp.115-126
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    • 2021
  • The snow cornice mass on the formation zone had triggered avalanches which led to the loss of human life and property. Snow cornice is formed due to flow separation on the leeward side. Effect of lee slope is more prominent in the formation of snow cornices as compared to the windward slope. The analysis of wind flow pattern has been carried out to evaluate the performance of a jet roof. Computational Fluid Dynamics (CFD) analysis of wind flow over a 2D hill model was carried out using RNG based k-∈ turbulence models available in ANSYS Fluent. Effect of varying leeward hill slope (1:2 to 1:6) on flow separation for the given windward slope was observed and a critical slope of 1:4 was found at which the separation zone ceased to exist. The modification of wind flow over a hill due to the installation of jet roof was simulated. It was observed that jet roof had significantly modified the wind flow pattern around hill ridgeline and ultimately snow cornice formation had mitigated. The results of the wind flow pattern were validated with the wind data collected at the experimental site, Banihal Top (Jammu and Kashmir, India). The wind flow simulation over the hill and mitigation of cornice formation by the jet roof has been explained in the present paper.

Wind tunnel tests on flow fields of full-scale railway wind barriers

  • Su, Yang;Xiang, Huoyue;Fang, Chen;Wang, Lei;Li, Yongle
    • Wind and Structures
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    • v.24 no.2
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    • pp.171-184
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    • 2017
  • The present study provides a deeper understanding of the flow fields of a full-scale railway wind barriers by means of a wind tunnel test. First, the drag forces of the three wind barriers were measured using a force sensor, and the drag force coefficients were compared with a similar scale model. On this basis, the mean wind velocity and turbulence upwind and downwind of the wind barriers were measured. The effects of pore size and opening forms of the wind barrier were discussed. The results show that the test of the scaled wind barrier model may be unsafe, and it is suitable to adopt the full-scale wind barrier model. The pore size and the opening forms of wind barriers have a slight influence on the flow fields upwind of the wind barrier but have some influences on the flow fields and power spectra downwind of the wind barrier. The smaller pore size generates a lower turbulence density and value of the power spectrum near the wind barrier, and the porous wind barriers clearly provide better shelter than the bar-type wind barriers.

A numerical simulation of flow field in a wind farm on complex terrain

  • Lee, Myungsung;Lee, Seung Ho;Hur, Nahmkeon;Choi, Chang-Koon
    • Wind and Structures
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    • v.13 no.4
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    • pp.375-383
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    • 2010
  • A three-dimensional flow simulation was performed to investigate the wind flow around wind-power generation facilities on mountainous area of complex terrain. A digital map of eastern mountainous area of Korea including a wind farm was used to model actual complex terrain. Rotating wind turbines in the wind farm were also modeled in the computational domain with detailed geometry of blade by using the frozen rotor method. Wind direction and speed to be used as a boundary condition were taken from local meteorological reports. The numerical results showed not only details of flow distribution in the wind farm but also the variation in the performance of the wind turbines due to the installed location of the turbines on complex terrain. The wake effect of the upstream turbine on the performance of the downstream one was also examined. The methodology presented in this study may be used in selecting future wind farm site and wind turbine locations in the selected site for possible maximum power generation.

Wind Effects on Tidal Currents in Gamak Bay

  • Lee, Moon-Ock;Kim, Byeong-Kuk
    • Journal of Ocean Engineering and Technology
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    • v.23 no.2
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    • pp.18-27
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    • 2009
  • This study was conducted to examine the effect of wind on the circulation of seawater in Gamak Bay, which contains numerous farms for fish and shellfish but suffers a significant loss by fisheries nearly annually from harmful algal blooms. In numerical experiments with a simplified bathymetry for Gamak Bay, the wind in summer appeared to more strongly influence the east-westward flow than the south-northward flow. In winter, this trend was nearly similar to the summer but seemed to have a greater effect on the flow at the north-west of the bay than the flow at the south mouth of the bay. On the other hand, in numerical experiments with a realistic bathymetry for Gamak Bay, the wind in summer appeared to more strongly influence the east-westward flow than the south-northward flow. Furthermore, the effect of the wind was stronger at the south mouth of the bay than at the north-west of the bay. In contrast, the wind in winter affected the east-westward flow more strongly and its effect appeared stronger at the north-west of the bay than at the south mouth of the bay. In addition, the effect of the wind tended to increase with distance from the east to the west. Therefore, the tidal currents in Gamak Bay proved to be strongly influenced by the wind, in particular east-westward. However, some measures are urgently required to improve the water quality of the bay, since the south-northward flow turned out to be obstructed by an east-westward shoal located in the middle of the bay.

Numerical Analysis on the Flow Noise Characteristics of Savonius Wind Turbines (사보니우스 풍력발전기의 유동소음특성에 관한 수치적 연구)

  • Kim, Sanghyeon;Cheong, Cheolung
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.23 no.6
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    • pp.502-511
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    • 2013
  • Noise performance of small wind turbines is critical since these are generally installed near the community. In this study, flow noise characteristics of Savonius wind turbines are numerically investigated. Flow field around the turbine are computed by solving unsteady RANS equation using CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow data. Parametric study is then carried out to investigate the effects of operating conditions and geometric design factors of the Savonius wind turbine. Tonal noise components with higher harmonic frequency than the BPF are identified in the predicted noise spectra from a Savonius wind turbine. The end-plates and helical blades are shown to reduce overall noise levels. These results can be used to design low-noise Savonius wind turbines.

Evaluation and CFD Modelling of Flow behind Livestock Ventilation Fan for Small-Scale Wind Power Generation (축사 환기팬 후류의 풍에너지 평가 및 기류 형상의 전산유체역학 모델링)

  • Hong, Se-Woon;Lee, In-Bok;Seo, Il-Hwan;Kwon, Kyeong-Seok;Ha, Tae-Hwan;Hwang, Hyun-Seob
    • Journal of The Korean Society of Agricultural Engineers
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    • v.54 no.5
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    • pp.79-89
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    • 2012
  • The objectives of this paper were to evaluate the wind flow behind the livestock ventilation fan for small-scale wind power generation and to make flow profiles of imaginary ventilation fan for future simulation works. The field experiments using typical 50-inch fan indicated that the wind flow behind the ventilation fan had a good possibility of power generation with its high and steady wind speeds up to a distance of 2 m. The expected electricity yield was almost 101~369 W with a small (0.8 m radius) wind turbine. The decline of ventilation fan performance caused by the obstacle was also not significant with about 4 % from a distance of 2 m. The flow profiles for the computational fluid dynamics (CFD) simulation was created by combining the direction vectors analyzed from tuft visualization test and the flow predicted by the rotating fan modeling. The flow profiles are expected to provide an efficient saving of computational time and cost to design a better wind turbine system in future works.

A Numerical Study on the Wintertime Upwind flow of the Yellow Sen in an Idealized Basin

  • Kyung, Tae-Jung;Park, Chang-Wook;Oh, Im-Sang;Lee, Ho-Jin;Kang, Hyoun-Woo
    • Journal of the korean society of oceanography
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    • v.37 no.3
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    • pp.91-107
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    • 2002
  • The wintertime upwind flow in the Yellow Sea has been investigated through a series of two-dimensional numerical experiments in an idealized basin. A total of 10 experiments have been carried out to examine the effects of wind forcing, bottom friction and the presence of oceanic currents sweeping the shelf of the East China Sea. A spatially uniform steady and periodic wind stresses are considered along with comparison of linear and quadratic formulations. The wind-driven flow in the absence of oceanic current has been computed using Proudman open boundary condition (POBC), while the wind-driven current in the presence of oceanic current has been computed using Flather’s radiation condition (FOBC). The oceanic currents to be prescribed at the open boundary have been simulated by specifying uniform sea level gradients across the Taiwan Strait and the eastern ECS shelf, Calculations show that, as seen in Lee et al. (2000), oceanic flow little penetrates into the Yellow Sea in the absence of wind forcing unless a unrealistically low rate of bottom frictional dissipation is assumed. Both steady and time-periodic wind stresses invoke the upwind flow along the central trough of the Yellow Sea, independently of the presence of the oceanic current. The presence of oceanic currents very marginally alters the north-south gradient of the sea surface elevation in the Yellow Sea. Changes in the intensity and direction of the wind-induced mean upwind flow are hardly noticeable in the Yellow Sea but are found to be significant near Cheju Island where the gradient is reduced and therewith contribution of Ekman transport increases. In case of steady wind forcing circulation patterns such as two gyres on the slope sides, a cyclonic gyre on the western slope and an anticyclonic gyre on the eastern slope persist and the upwind flow composes part of the cyclonic gyre in the Yellow Sea. While in case of the time-periodic wind stress the appearance and disappearance of the patterns are repeated according to the time variation of the wind stress and the upwind flow accordingly varies with phase delay, mostly intensifying near the time when the wind forcing is approximately near the middle of the decaying stage.

Comparative Analysis of Wind Flows in Wind Corridor Based on Spatial and Geomorphological Characteristics to Improve Urban Thermal Environments (도시 열환경개선을 위한 공간지형적 특성에 따른 바람길 유동 비교 분석)

  • SEO, Bo-Yong;JUNG, Eung-Ho
    • Journal of the Korean Association of Geographic Information Studies
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    • v.20 no.2
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    • pp.75-88
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    • 2017
  • This study analyzed wind flows based on spatial and geomorphological characteristics of Daegu Metropolitan City. A three-stage analysis was performed, starting with a comparison of meteorological relationships between local wind direction (synoptic wind) and local wind flow. In the second stage the study area was subdivided into districts and suburban districts to analyze the relative change of local wind flow. In stage three, the formation of wind corridor for local wind flow, wind flow for the entire urban space, and spatial relationships between flows were verified comparatively using KLAM_21. Three results are notable, the first of which is a low correlation between synoptic wind of a region, and local wind, flow in terms of meteorology. Secondly, observations of local wind flow at five downtown districts and two suburban districts showed that there were diverse wind directions at each measurement point. This indicates that the spatial and geomorphological characteristics of areas neighboring the measurement points could affect the local wind flow. Thirdly, verifying the results analyzed using KLAM_21, compared to Atomatic Weather System(AWS) measurement data, confirmed the reliability of the numerical modelling analysis. It was determined that local wind flow in a city performs a spatial function and role in ameliorating the urban heat island phenomena. This indicates that, when an urban planning project is designed, the urban heat island phenomena could be ameliorated effectively and sustainably if local wind flow caused by immediate spatial and geomorphological characteristics is confirmed systematically and techniques are intentionally applied to connect the flows spatially within areas where urban heat islands occur.

A Study on a Novel Flow Control Valve for Wind Power Heat Generation Hydraulic Systems (풍력 열발생 유압 시스템을 위한 새로운 유량제어밸브에 관한 연구)

  • Choi, Sae Ryung;Lee, Ill Yeong;Han, Bong Jun
    • Journal of Drive and Control
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    • v.14 no.1
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    • pp.23-28
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    • 2017
  • A wind power heat generation system that converts wind power directly to heat instead of electric power is considered in this study. The system consists of a wind turbine part and a heat generation part. The heat generation part is materialized by a hydraulic system including a hydraulic pump, a flow control valve, a hydraulic oil tank, etc. The flow control valve primarily converts hydraulic energy generated in the pump to heat energy. It should have a function of overspeed protection under excessive wind speeds. In this study, a novel flow control valve design is proposed for excellent flow control characteristics under excessive pump driving torque (excessive wind speed). The performance of the suggested valve is analyzed using numerical simulation.