• Wind and Structures
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• 제10권2호
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• pp.99-119
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• 2007

Estimations of wind flow over terrain are often needed for applications such as pollutant dispersion, transport safety or wind farm location. Whilst field studies offer very detailed information regarding the wind potential over a small region, the cost of instrumenting a natural fetch alone is prohibitive. Wind tunnels offer one alternative although wind tunnel simulations can suffer from scale effects and high costs as well. Computational Fluid Dynamics (CFD) offers a second alternative which is increasingly seen as a viable one by wind engineers. There are two issues associated with CFD however, that of accuracy of the predictions and set-up and simulation times. This paper aims to address the two issues by demonstrating, by way of an investigation of wind potential for the Askervein Hill, that a good level of accuracy can be obtained with CFD (10% for the speed up ratio) and that it is possible to automate the simulations in order to compute a full wind rose efficiently. The paper shows how a combination of script and session files can be written to drive and automate CFD simulations based on commercial software. It proposes a general methodology for the automation of CFD applied to the computation of wind flow over a region of interest.

• 한국태양에너지학회 논문집
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• 제25권1호
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• pp.79-86
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• 2005

The external conditions for estimating dynamic wind loads of wind turbines, such as the turbulence, the extreme wind, the mean velocity gradients and the flow angles, are simulated over GangWon Wind Energy Test Field placed in one of the most complex terrain in Korea. Reference meteorological data has been gathered at a height of 30m from 2003 to 2004 with a ultrasonic anemometer. The absolute value of the spectral energy are simulated and the verification of this prediction has been carried out with comparing to the experimental data. The most desirable place for constructing new wind turbine are resulted as Point 2 and Point 3 due to the lower value of Turbulence Intensity and the higher value of wind resource relatively.

• 한국대기환경학회지
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• 제21권2호
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• pp.179-189
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• 2005

Recently air quality modeling studies for industrial complex and large cities located in the coastal regions have been carried out. Especially, the representation of atmospheric flow fields within a model domain is very important, because an adequate air quality simulation requires an accurate portrayal of the realistic three -dimensional wind fields. Therefore this study investigated effect of using high resolution terrain height data in numerical simulation. So the experiments were designed according to the detail terrain height with 3second resolution or not. Case 30s was the experiment using the terrain height data of USGS and Case 3s was the other using the detail terrain height data of Ministry of Environment. The results of experimental were more remarkable. In Case 3s, temperature indicated similar tendency comparing to observational data predicting maximum temperature during the daytime and wind speed made weakly for difference of terrain height.

• 한국대기환경학회지
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• 제12권4호
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• pp.459-472
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• 1996

An experimental investigation on the wind flow over smooth bell-shaped two-dimensional hills with hill slopes (the ratio of height to half width) of 0.3 and 0.5 is performed in an atmospheric boundary-layer wind tunnel. Two categories of the models are used in the present investigation; six two-dimensional single-hills, and four continuous double-hills. The measurements of the flow field and surface static-pressure distribution are carried out over the Reynolds number (based on the hill height) of 1.9 $\times 10^4, 3.3 \times 10^4, and 5.6 \times 10^4$. The velocity profiles and turbulence characteristics are measured by the pitot-tube and X-type hot-wire anemometer, respectively. The undisturbed boundary-layer profile on the bottom surface of the wind tunnel is reasonably consistent with the power-law profile with $\alpha = 7.0 (1/\alpha$ is the power-law exponent) and shows good spanwise uniformities. The profiles of turbulent intensity are found to be consistent along the centerline of the wind tunnel. The measured non-dimensional speed-up profiles at the hill crest show good agreements with the predictions of Jackson and Hunt's linear theory. The flow separation occurs in the hill slope of 0.5, and the oil-ink dot method is used to find the reattachment points in the leeside of the hill. The measured reattachment points are compared with the numerical predictions. Comparisons of the mean velocity profiles and surface pressure distributions between the numerical predictions and the experimental results show good agreements.

• 한국대기환경학회지
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• 제14권3호
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• pp.219-228
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• 1998

In the present investigation, a numerical model developed for the prediction of the wind flow over complex terrain is validated by comparing with the field experiments. For the solution of the Reynolds - Averaged Clavier- stokes equations which are the governing equations of the microscale atmospheric flow, the model is constructed based on the finite-volume formulation and the SIMPLEC pressure-correction algorithm for the hydrodynamic computation. The boundary- fitted coordinate system is employed for the detailed depiction of topography. The boundary conditions and the modified turbulence constants suitable for an atmospheric boundary- layer are applied together with the k- s turbulence model. The full- scale experiments of Cooper's Ridge, Kettles Hill and Askervein Hill are chosen as the validation cases . Comparisons of the mean flow field between the field measurements and the predicted results show good agreement. In the simulation of the wind flow over Askervein Hill , the numerical model predicts the three dimensional flow separation in the downslope of the hill including the blockage effect due to neighboring hills . Such a flow behavior has not been simulated by the theoretical predictions. Therefore, the present model may offer the most accurate prediction of flow behavior in the leeside of the hill among the existing theoretical and numerical predictions.

• 설비공학논문집
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• 제17권11호
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• pp.1050-1059
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• 2005

Heat and $SF_6$ gas dispersions over a complex terrain were investigated using wind tunnel. The wind speed, temperature and concentration profiles were measured for the 1/1000 scale complicated terrain model in an Eiffel type boundary layer wind tunnel with test section of 2.5m in height and 4.5m in width. The scale model was mounted on the top of a plate which can rotate with respect to the approaching wind. Dispersion processes from a continuous emission source driven by various wind direction were investigated, including plume climbing over the steep up-slope of the mountain and down-spreading toward the lower level of the valley. Extensive dispersion experiment data (wind speeds and concentration profiles) were provided for verification and validation of dispersion models. Under the identical flow and emission conditions, the independently measured profiles of the temperature and $SF_6$ concentration showed an excellent agreement which ensured the credibility of the results.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.222-227
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• 2008

Complex terrain like hill, mountain, and escarpment etc. makes complex air flow. This topographic condition will affect not only speed but also turbulence of wind over the complex terrain. In this paper, turbulence intensities are considered to investigate characteristics of wind over cone-type hills. There are five simple hill models with different slope 0.1${\sim}$0.5(tan${\theta}$) for wind tunnel test. It was observed through wind tunnel tests that turbulence intensities of down-slope wind at the end of the 3-Dimensional hills remarkably increased but ones of windward slope wind at the front side of the hills slightly increased. Also, turbulence intensities proportionally increased with slope of the cone-type hills.

• 산업기술연구
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• 제25권B호
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• pp.157-164
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• 2005

Two methods, the bin averaging method and least square method, are often used in calibrating wind turbine test sites. The objective of this work was to determine a better method to predict the wind speed at wind turbine installing point. The calibration was done at the test site on a complex terrain located in Daegwallyeong, Korea. It was performed for two different cases based on the IEC 61400-12 power performance measurement standard. The wind speeds averaged for 10 minutes ranged between 4 m/s and 16 m/s. The wind-direction bins of each meteorological mast were 10 degrees apart, and only the bins having data measured for more than 24 hours were employed for the test site calibration. For both cases, the two methods were found to yield almost same results which estimated real wind speed very closely.

• 한국대기환경학회지
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• 제8권3호
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• pp.169-178
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• 1992

Dispersion of pollutant in a mountainous area is simulated in a wind tunnel. In the northwest side of the terrain model, the sea level is assumed. Wind from the sea initially confronts hills along the shoreline, a line of large buildings next, and finally a valley between high mountains in the south and in the east. In the northwest wind conditions, severe flow separation occurs in the lee side of hills, even beyond the building area. Pollutant from the buildings is trapped in this region and its concentration is the highest. In the west wind conditions, pollutant from the buildings flows along the hills aslant the main wind direction in this case. Since large valley is located in the downstream, pollutant tends to disperse along the valley.

• 환경영향평가
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• 제20권4호
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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.