• Journal of Korean Association for Spatial Structures
• /
• v.13 no.1
• /
• pp.97-104
• /
• 2013

Recent tall buildings tend to have unconventional shapes as a prevailing, which is effective for suppressing across-wind responses. Suppression of across-wind responses is a major factor in tall building projects, and the so called aerodynamic modification method is comprehensively used. The purpose of the present study is to investigate the pressure fluctuations on tapered and setback tall buildings, including peak pressures, power spectra and coherences through the synchronous multi-pressure sensing system techniques. And flow measurements around the models were conducted to investigate the condition of vortex shedding. The results show that by tapering and setback, different distributions of mean pressure coefficients at leeward surface were found, which is caused by the geometric characteristics of the models. And the power spectra of wind pressures at sideward surface become wideband and the peak frequencies are different depending on heights, which makes the correlation near the Strouhal component low or even negative. The differences in shedding frequencies were also confirmed by the flow fields around the models.

• Journal of Environmental Science International
• /
• v.3 no.1
• /
• pp.39-47
• /
• 1994

Dispersion characteristics of air pollutants in the mountainous coastal area are investigated in considering with the mesoscale local circulations using a two dimensional numerical model with two kinds of topograpy of 500m and 300m. In the model, land-sea breezes and mountain-valley wind are mainly considered under the condition of the absence of large scale prevailing flow in the circulation analysis, and the pollutants dispersion is traced by the Lagrangian methods. According to the results, the wind velocity is affected by topography and is stronger in the case of 500m height mountain than that of 300m, the Pollutants that source is near the coast transported over the mountain and dispersed to behind inland area. It is classified that the topography change control affects the wind velocity and the circulations. The pollutants that source is different transported and concentrated to behind inland and/or diffused to the sea area by the combination of the wind system with topographic changes. The results can be applied to the air pollution control with the arrangement design of industrial area and the planning of coastal developments.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.18 no.11
• /
• pp.923-932
• /
• 2006

In this paper, reentering ratio and cooling capacity of individual cooling towers arrayed on a building roof were studied by a numerical method. The number of 16 cooling towers were divided into 4 banks. It was considered the summer prevailing wind characteristics as west wind and south wind of 5 m/s. It was also considered the roofwall types as the curtainwall and the louverwall that had the outdoor air intake louver in the curtainwall. In this case, the louver was suggested as the solution that could prevent reentering phenomenon due to recirculation and interference of the discharge air. In the case of the curtainwall, the averaged reentering ratio are predicted 13.3% and 24.4% for the west and south wind of 5 m/s, respectively. In the case of the louverwall, the averaged reentering ratio are predicted 2.5% and 9.7% for the west and south wind of 5 m/s, respectively. Therefore, the louverwall is a appropriate solution for reducing the reentering phenomenon.

• Wind and Structures
• /
• v.33 no.6
• /
• pp.471-480
• /
• 2021

This present paper leads to investigation of blade-fluid interactions of cambered blade H-Darrieus rotor having EN0005 airfoil blades using comprehensive Computational Fluid Dynamics (CFD) analysis to understand its performance in low wind streams. For several blade azimuthal angle positions, the effects of three different low wind speeds are studied regarding their influence on the blade-fluid interactions of the EN0005 blade rotor. In the prevailing studies by various researchers, such CFD analysis of H-Darrieus rotors are very less, hence it is needed to improve their steady-state performance in low wind velocities. Such a study is also important to obtain important performance insights of such thin cambered blade rotor in its complete rotational cycle. It has been seen that the vortex generated at the suction side of the EN0005 blade rolls back to its leading edge due to the camber of the blade and thus a peak velocity occurs near to the nose position of this blade at its leading edge, which leads to peak performance of this rotor. Again, in the returning phase of the blade, a secondary recirculating vortex is generated that acts on the pressure side of EN0005 blade rotor that increases the performance of this cambered EN0005 blade rotor in its downstream position as well. Here, the aerodynamic performances have been compared considering Standard k-ε and SST k-ω models to check the better suited turbulence model for the cambered EN0005 blade H-Darrieus rotor in low tip speed ratios.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.2
• /
• pp.496-503
• /
• 2015

In order to let a wind generator (WG) support the frequency control of a power system, a conventional inertial control algorithm using the rate of change of frequency (ROCOF) and frequency deviation loops was suggested. The ROCOF loop is prevailing at the initial stage of the disturbance, but the contribution becomes smaller as time goes on. Moreover, its contribution becomes negative after the frequency rebound. This paper proposes an inertial control algorithm of a wind power plant (WPP) using the maximum ROCOF and frequency deviation loops. The proposed algorithm replaces the ROCOF loop in the conventional inertial control algorithm with the maximum ROCOF loop to retain the maximum value of the ROCOF and eliminate the negative effect after the frequency rebound. The algorithm releases more kinetic energy both before and after the frequency rebound and increases the frequency nadir more than the conventional ROCOF and frequency loops. The performance of the algorithm was investigated under various wind conditions in a model system, which includes a doubly-fed induction generator-based WPP using an EMTP-RV simulator. The results indicate that the algorithm can improve the frequency drop for a disturbance by releasing more kinetic energy.

• Journal of the Korean earth science society
• /
• v.24 no.5
• /
• pp.449-455
• /
• 2003

Climatic elements were investigated in order to understand the atmospheric environment around the Pohang area and for use as basic information in prediction. In this analysis, we could find that the annual mean temperature, relative humidity, and precipitation are 14.39$^{\circ}C$, 63.3%, and 1.178mm, respectively. The prevailing wind direction was southwestern, and the mean wind speed is 2.7m/s. The amount of cloud was abundant during the summer because of the Jang-ma phenomenon and convective clouds induced by terrain effect. The annual mean duration of sunshine represented about 2,221 hours.

• Bulletin of the Korean Space Science Society
• /
• 2009.10a
• /
• pp.36.3-37
• /
• 2009

This is an attempt to improve a formula to predict variations of geomagnetic storm indices (Dst) from solar wind parameters. A formula which is most widely accepted was given by Burton et al. (1975) over 30 years ago. Their formula is: dDst*/dt = Q(t) - Dst*(t)/$\tau$, where Q(t) is the Dst injection rate given by the convolution of dawn-to-dusk electric field generated by southward solar wind magnetic field and some response function. However, they did not clearly specify the response function. As a result, misunderstanding seems to be prevailing that the injection rate is proportional to the dawn-to-dusk electric field. In this study we tried to determine the response function by examining 12 intense geomagnetic storms with minimum Dst < -200 nT for which solar wind data are available. The method is as follows. First we assume the form of response function that is specified by several time constants, so that we can calculate the injection rate Q1(t) from the solar wind data. On the other hand, Burton et al. expression provide the observed injection rate Q2(t) = dDst*/dt + Dst*(t)/$\tau$. Thus, it is possible to determine the time constants of response function by a least-squares method to minimize the difference between Q1(t) and Q2(t). We have found this simple method successful enough to reproduce the observed Dst variations from the corresponding solar wind data. The present result provides a scheme to predict the development of Dst 30 minutes to 1 hour in advance by using the real time solar wind data from the ACE spacecraft.

• Journal of the Korean Geographical Society
• /
• v.38 no.2
• /
• pp.145-155
• /
• 2003

In this research, the primary factors affected to the formation of lake current of surface layer and thermal stratification of temperate lake have been analyzed, the daily change of water temperature, relationship with lake current and the research about the elements of meteorological phenomenon have been implemented. As a result, the lake current of surface layer occurring while the period of thermal stratification is showing the proportional difference of water temperature, thermal exchange caused by this has been known as the main energy source, and this is, secondly, considering as the interaction of the wind driven current by the prevailing wind. On the other hand, during the night time when the water surface is cooled, and it is considering as the vertical convection is occurring than horizontal circumfluence. Also, there exists the water mass, which is circumfluent counterclockwise and clockwise direction separately. The prevailing md is rather affected to the moving direction and moving speed of water mass, but it doesn't affect to the whole flowing direction.

• Journal of Environmental Science International
• /
• v.9 no.5
• /
• pp.385-388
• /
• 2000

Visibility reduction is a barometer of air pollution which people can notice easily. First of all we need to measure quantified visibility continuously in order to examine visibility reduction. Prevailing visibility is not practical to measure visibility depending on observer's expertness. Scattering visibility using Forward Scattering Meter(Belfort Visibility Sensor 6230) has been measured at Kwangan-Dong in Pusan and analysed since July 1998. According to the analysis the correlation coefficient(R) between prevailing visibility and scattering visibility was 0.7235. The visibility appeared that each frequency of poor visibility(under 6km) and good visibility(over 25km) was 10.6%, 9.7% on summertime in Pusan and the visibility range from 10km to 20km ranked high frequency as a half of whole ranges. The order of correlation coefficients between visibility an air pollutants are ranking CO. PM10 and NO2 that values are 0.5878, 0.5369,l 0.5284 respectively. In meteorolgical factor the case of poor visibility presented more weakly wind speed and higher relative humidity than the case of good visibility. The correlation coefficient between calculated visibility of multiple linear regression model and observed visibility was 0.7215. But the trend of calculated and observed visibility variation was similar with the exception of several good visibility cases.

• Journal of Korean Society for Atmospheric Environment
• /
• v.21 no.E3
• /
• pp.107-113
• /
• 2005

Using a sampling device of our own making, airborne pollen has been monitored in Kyoto, Japan from the middle of February to the end of May 2004. From the morphological analysis of pollen grains by Scanning Electron Microscope (SEM), it was possible to identify some pollen types like Cryptomeria, Pine, Alder, Cyclobalanopsis, Chamaecyparis, and Equisetum. Daily average airborne pollen counts show strong variations from the day to day which makes the appropriate daily forecasts that could be of practical use for patients difficult. Diurnal variation of airborne pollen grains at our local sampling site is very irregular and shows no similarity between pollen types. The highest concentrations of Cryptomeria and Alder pollens in the south -west wind directions might be attributed to the airborne pollen transport, while the increase in Pine pollen grain in the southern wind direction was probably due to the local spread. Prevailing wind direction (SW) during the pollinating periods of Cryptomeria and Alder pollens could suggest a long-distance transport from a distant mountain.