• 한국환경과학회지
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• 제16권9호
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• pp.1063-1069
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• 2007

The present study investigated the causes and intensity of the urban heat island phenomenon by the seasons according to the pattern of land use in Chungju City. Highest temperature and lowest moisture areas of the urban were very similar to the distribution of commercial districts, on the other hand, lowest temperature and highest moisture areas were distributed in manufacturing districts, green zones and the Hoam Lake. If appear at intensity of the distance from the outer circumference of commercial districts, wind direction and the rise of temperature, we could observe the remarkable expansion of high temperature from commercial districts toward residential districts around of downwind in all seasons. In case the effect of the wind was not significant as well, high temperature in commercial districts appeared tendency that a little spread to 1, 2 residential districts around. But checked up the intimate relations between the amount of moving heat and wind, when out of consideration that size of area was not much compared than residential areas of downwind affected by the wind. These phenomenon was relatively obvious in summer, the other side, in spring and autumn appeared a similar tendency.

• Wind and Structures
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• 제13권6호
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• pp.557-580
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• 2010

A new inflow turbulence generation method and a combined dynamic SGS model recently developed by the authors were applied to evaluate the wind effects on 508 m high Taipei 101 Tower. Unlike the majority of the past studies on large eddy simulation (LES) of wind effects on tall buildings, the present numerical simulations were conducted for the full-scale tall building with Reynolds number greater than $10^8$. The inflow turbulent flow field was generated based on the new method called discretizing and synthesizing of random flow generation technique (DSRFG) with a prominent feature that the generated wind velocity fluctuations satisfy any target spectrum and target profiles of turbulence intensity and turbulence integral length scale. The new dynamic SGS model takes both advantages of one-equation SGS model and a dynamic production term without test-filtering operation, which is particular suitable to relative coarse grid situations and high Reynolds number flows. The results of comparative investigations with and without generation of inflow turbulence show that: (1) proper simulation of an inflow turbulent field is essential in accurate evaluation of dynamic wind loads on a tall building and the prescribed inflow turbulence characteristics can be adequately imposed on the inflow boundary by the DSRFG method; (2) the DSRFG can generate a large number of random vortex-like patterns in oncoming flow, leading to good agreements of both mean and dynamic forces with wind tunnel test results; (3) The dynamic mechanism of the adopted SGS model behaves adequately in the present LES and its integration with the DSRFG technique can provide satisfactory predictions of the wind effects on the super-tall building.

• Wind and Structures
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• 제18권5호
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• pp.473-495
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• 2014

Localized wind events, in the form of tornadoes and downbursts, are the main cause of the large number of failure incidents of electrical transmission line structures worldwide. In this study, a numerical model has been developed to study the behaviour of self-supported transmission lines under various tornado events. The tornado wind fields used were based on a full three-dimensional computational fluid dynamics analysis that was developed in an earlier study. A three-dimensional finite element model of an existing self-supported transmission line was developed. The tornado velocity wind fields were then used to predict the forces applied to the modelled transmission line system. A comprehensive parametric study was performed in order to assess the effects of the location of the tornado relative to the transmission line under F2 and F4 tornado wind fields. The study was used to identify critical tornado configurations which can be used when designing transmission line systems. The results were used to assess the sensitivity of the members' axial forces to changes in the location of the tornado relative to the transmission line. The results were then used to explain the behaviour of the transmission line when subjected to the identified critical tornado configurations.

• 한국환경과학회지
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• 제21권2호
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• pp.145-152
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• 2012

The mean wind speed and turbulence intensity profiles in the atmospheric boundary layer were extracted from a LIDAR remote sensing campaign in order to apply for CFD validation. After considering the semi-steady state field data requirements to be used for CFD validation, a neutral atmosphere campaign period, in which the main wind direction and the power-law exponent of the wind profile were constantly maintained, was chosen. The campaign site at the Pohang Accelerator Laboratory, surrounded by 40~50m high hills, with an apartment district spread beyond the hills, is to be classified as a semi-complex terrain. Nevertheless, wind speed profiles measured up to 100m above the ground fitted well into a theoretical-experimental logarithmic-law equation. The LIDAR remote-sensing data of the sub-layer of the atmospheric boundary layer has been proven to be superior to the data obtained by conventional extrapolation of the wind profile with 2 or 3 anemometer measurements.

• Journal of Astronomy and Space Sciences
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• 제21권2호
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• pp.93-100
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• 2004

We have investigated characteristic solar wind dynamics associated with relativistic electron events at geosynchronous orbit. Most of the events for April, 1999 through December, 2002 are found to be accompanied by a prolonged solar quiet period which is characterized as low solar wind density, weak interplanetary magnetic field (IMF), and fast alfvenic fluctuations in IMF $B_z$. In a typical relativistic event, electron fluxes begin to increase by orders of magnitude when solar wind parameters drop to low values (e.g., $n_{sw}∼5 cm^{-3}$ and ｜$B_{IMF}$∼5 nT) after sharp peaks. Then the elevated electron fluxes stay at the high level during the solar quiet period. This observation may suggest the following scenario for the occurrence of a geosynchronous relativistic event: (ⅰ) Quiet solar winds can yield a stable and more dipole-like magnetospheric configurations in which the geosynchronous orbit locates well inside the trapping boundary of the energetic electrons. (ⅱ) If a large population of MeV electrons are generated (by whatever acceleration process(es)) in the inner magnetosphere, they can be trapped and effectively accumulated to a high intensity. (ⅲ) The high electron flux can persist for a number of days in the geosynchronous region as long as the solar wind dynamics stays quiet. Therefore the scenario indicates that the occurrence of a relativistic event would be a result of a delicate balance between the effects of electron acceleration and loss. In addition, the sensitive dependence of a relativistic event on the solar wind conditions makes the prediction of solar wind variability as important as understanding of electron acceleration processes in the forecast of a relativistic event.

• Wind and Structures
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• 제27권1호
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• pp.11-27
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• 2018

The straight-cone steel cooling tower is a novel type of structure, which has a distinct aerodynamic distribution on the internal surface of the tower cylinder compared with conventional hyperbolic concrete cooling towers. Especially in the extreme weather conditions of strong wind and heavy rain, heavy rain also has a direct impact on aerodynamic force on the internal surface and changes the turbulence effect of pulsating wind, but existing studies mainly focus on the impact effect brought by wind-driven rain to structure surface. In addition, for the indirect air cooled cooling tower, different additional ventilation rate of shutters produces a considerable interference to air movement inside the tower and also to the action mechanism of loads. To solve the problem, a straight-cone steel cooling towerstanding 189 m high and currently being constructed is taken as the research object in this study. The algorithm for two-way coupling between wind and rain is adopted. Simulation of wind field and raindrops is performed with continuous phase and discrete phase models, respectively, under the general principles of computational fluid dynamics (CFD). Firstly, the rule of influence of 9 combinations of wind sped and rainfall intensity on flow field mechanism, the volume of wind-driven rain, additional action force of raindrops and equivalent internal pressure coefficient of the tower cylinder is analyzed. On this basis, the internal pressures of the cooling tower under the most unfavorable working condition are compared between four ventilation rates of shutters (0%, 15%, 30% and 100%). The results show that the 3D effect of equivalent internal pressure coefficient is the most significant when considering two-way coupling between wind and rain. Additional load imposed by raindrops on the internal surface of the tower accounts for an extremely small proportion of total wind load, the maximum being only 0.245%. This occurs under the combination of 20 m/s wind velocity and 200 mm/h rainfall intensity. Ventilation rate of shutters not only changes the air movement inside the tower, but also affects the accumulated amount and distribution of raindrops on the internal surface.

• Wind and Structures
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• 제19권4호
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• pp.421-441
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• 2014

With the assistance of typhoon field data at aerial elevation level observed by meteorological satellites and wind velocity and direction records nearby the ground gathered in Guangzhou Weather Station between 1985 and 2001, some key wind field parameters under typhoon climate in Guangzhou region were calibrated based on Monte-Carlo stochastic algorithm and Meng's typhoon numerical model. By using Peak Over Threshold method (POT) and Generalized Pareto Distribution (GPD), Wind field characteristics during typhoons for various return periods in several typical engineering fields were predicted, showing that some distribution rules in relation to gradient height of atmosphere boundary layer, power-law component of wind profile, gust factor and extreme wind velocity at 1-3s time interval are obviously different from corresponding items in Chinese wind load Codes. In order to evaluate the influence of typhoon field parameters on long-span flexible bridges, 1:100 reduced-scale wind field of type B terrain was reillustrated under typhoon and normal conditions utilizing passive turbulence generators in TJ-3 wind tunnel, and wind-induced performance tests of aero-elastic model of long-span Guangzhou Xinguang arch bridge were carried out as well. Furthermore, aerodynamic admittance function about lattice cross section in mid-span arch lib under the condition of higher turbulence intensity of typhoon field was identified via using high-frequency force-measured balance. Based on identified aerodynamic admittance expressions, Wind-induced stochastic vibration of Xinguang arch bridge under typhoon and normal climates was calculated and compared, considering structural geometrical non-linearity, stochastic wind attack angle effects, etc. Thus, the aerodynamic response characteristics under typhoon and normal conditions can be illustrated and checked, which are of satisfactory response results for different oncoming wind velocities with resemblance to those wind tunnel testing data under the two types of climate modes.

• 한국지구과학회지
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• 제32권5호
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• pp.453-460
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• 2011

By performing a statistical change-point analysis of activities of the tropical cyclones (TCs) that have affected Korea (K-TCs), it was found that there was a significant change between 1983 and 1984. During the period of 1984-2004 (P2), more TCs migrated toward the west, recurved in the southwest, and affected Korea, compared to the period of 1965-1983 (P1). These changes for P2 were related to the southwestward expansion of the subtropical western North Pacific high (SWNPH) and simultaneously elongation of its elliptical shape toward Korea. Because of these changes, the central pressure and lifetime of K-TC during P2 were deeper and longer, respectively, than figures for P1. This stronger K-TC intensity for P2 was related to the more southwestward genesis due to the southwestward expansion of the SWNPH. The weaker vertical wind shear environment during P2 was more favorable for K-TC to maintain a strong intensity in the mid-latitudes of East Asia.

• 환경영향평가
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• 제19권6호
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• pp.583-590
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• 2010

To determine nocturnal inversion characteristics at the leeward side of high-rise building, air temperature data were observed at 10 minute interval from February 22, 2010 to April 15, 2010. The observed data were compared, analyzed and examined to illustrate air temperature differences between the roof (XAR) and surface (XAG) of X apartment. The wind speed, wind direction and precipitation data were also observed at XAR and YJL (Yangjae Stream) sites at the same time. After the analysis, the maximum nocturnal inversion was observed by $4.0^{\circ}C$ at 3:40, 3:50, 4:10 on February 24th 2010, at that time the weather condition was clear and weak wind. Air temperature inversions at the leeward side of high-rise building were observed on whole day in wintertime and air temperature inversion intensity was also higher than other nearby area (SMG).

• 한국태양에너지학회 논문집
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• 제32권3호
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• pp.33-41
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• 2012

As the wind farms in large scale demand enormous amount of construction cost, minimizing the economic burden is essential and also it is very important to measure the wind resources and forecast annual energy production correctly to judge the economic feasibility of the proposed site by way of installing a Met mast at or nearby the site. Wind resources were measured by installing a 80[m] high Met mast at WangdeungYeo Island to conduct the research incorporated in this paper and offshore wind farm was designed using WindPRO. Wind farm of 100[MW] was designed making use of 3 and 4.5[MW] wind generator at the place selected to compare their annual energy production and capacity factor applying the loss factor of 10[%] and 20[%] respectively to each farm. As a result, 336,599[MWh] was generated by applying 3[MW] wind generator while 358,565 [MWh] was produced by 4.5[MW] wind generator. Difference in the energy production by 3[MW] generator was 33,660 [MWh] according to the loss factor with the difference in its capacity factor by 3.8[%]. On the other hand, 23 units of 4.5 [MW] wind generators showed the difference of annual energy production by 35,857 [MWh] with 4.0[%] capacity factor difference.