• Wind and Structures
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• 제19권5호
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• pp.505-522
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• 2014

While effects of the atmospheric boundary layer flow on engineering infrastructure are more or less known, some local transient winds create difficulties for structures, traffic and human activities. Hence, further research is required to fully elucidate flow characteristics of some of those very unique local winds. In this study, important characteristics of observed vertical velocity profiles along the main wind direction for the gusty Bora wind blowing along the eastern Adriatic coast are presented. Commonly used empirical power-law and the logarithmic-law profiles are compared against unique 3-level high-frequency Bora measurements. The experimental data agree well with the power-law and logarithmic-law approximations. An interesting feature observed is a decrease in the power-law exponent and aerodynamic surface roughness length, and an increase in friction velocity with increasing Bora wind velocity. This indicates an urban-like velocity profile for smaller wind velocities and rural-like velocity profile for larger wind velocities, which is due to a stronger increase in absolute velocity at each of the heights observed as compared to the respective velocity gradient (difference in average velocity among two different heights). The trends observed are similar during both the day and night. The thermal stratification is near neutral due to a strong mechanical mixing. The differences in aerodynamic surface roughness length are negligible for different time averaging periods when using the median. For the friction velocity, the arithmetic mean proved to be independent of the time record length, while for the power-law exponent both the arithmetic mean and the median are not influenced by the time averaging period. Another issue is a large difference in aerodynamic surface roughness length when calculating using the arithmetic mean and the median. This indicates that the more robust median is a more suitable parameter to determine the aerodynamic surface roughness length than the arithmetic mean value. Variations in velocity profiles at the same site during different wind periods are interesting because, in the engineering community, it has been commonly accepted that the aerodynamic characteristics at a particular site remain the same during various wind regimes.

• Journal of Preventive Medicine and Public Health
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• 제16권1호
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• pp.67-77
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• 1983

To investigate the an air pollution by particulate matter and its dispersion, a cement plant produceing portland cement 600,000 ton/year and its vicinity were surveyed from Obtober, 1980 to April, 1983. The survey was mainly focused on main stack emmission rate of the cement plant and particle size distribution in the dust, dustfall and total suspended particulate concentration in the area by month and distance from the stack. The results of the study were as follows; 1. The main stack emission rate was surveyed before and after the spray tower was additionally installed to the original E.P bag filter. Before the spray tower installed, the main stack emission rate was higher ($0.64g/Nm^3$) than the emission standard of Korean Environmental Preservation Law's ($0.59g/Nm^3$, amended to $0.4g/Nm^3$ on April 1983), but after the spray tower was installed, its main stack emission rate was markedly decreased to the standard ($0.43g/Nm^3$). 2. $2{\sim}3{\mu}m$ of the particle size was the largest portion (20.8%) of the dust particulate from the main stack and 50% of the frequency distribution was $1.5{\mu}m$ of the size. Most particle size was below $10{\mu}m$. 3. The spray tower reduced the dustfall to $37.81{\sim}9.76\;ton/km^2/month$ while dustfall appeared at $45.29-15.45ton/km^2/month$, in the vicinity of plant before spray tower installed 4. Mean concentrations of total suspended particulate for 24 hours of the various stations were determined in $20.6-200.0{\mu}g/m^3$, 3 stations of tham were higher than the value of Harry and William's arthmetic average standard $130{\mu}g/m^3$. 5. Linear regression between dustfall [X] and total suspended particulate[Y] concentration was an equation, Y=4.024X+11.479.[r=0.91] 6. During the whole seasons in the opposite area 100m apart from the omission source the prevailing wind direction was with estimated more than $30ton/km^2/month$, and the concentration of total suspended particulate for 24 hours averaging time was more than $140{\mu}g/m^3$ in the same area and direction. 7. Assuming the wind direction were constant through the day dustfalls for a day were estimated at $13.40ton/km^2/day,\;10.79ton/km^2/day$ and $4.55ton/km^2/day$ at various distances of 100m, 500m and 1,500m from the emission source respectively. 8. In the simutalion of dustfall and suspended dust by area, Gaussian dispersion model modified by size distribution of particulate matter was not applicated since the emission of dust were from multi sources other them stack. From the above results, it could be applied that the dispersion of dust from the cement plant is estimated and regulated for the purpose of environmental protection.

• 전기의세계
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• 제17권3호
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• pp.43-56
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• 1968

The design of this antenna tower on the publication had been prepared by writer in order to compare with that of towers for power transmission line or to show the differences on designs existing on their design standards. The design of this antenna tower is also featuring on the following points; (1) the height of tower is 150meters high, (2) combined steel angles are adopted besides angles, (3) the direction of 45degree wind is taken account into design, (4) the additional stresses of horizontal members located in the bending points of main posts are contemplated though these additional stressess are not shown on stress diagram.

• 한국태양에너지학회 논문집
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• 제32권6호
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• pp.76-84
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• 2012

This study conducted experiments to measure air currents in an experimental building according to external conditions, types of induction ducts, and types of internal sockets by applying an external induction duct comprised of inducing openings and lines and induction units to the kitchen and bathroom vents at the rooftop of a super high-rise apartment building in order to help to improve the venting performance. The study also proposed the optimization of the external induction-style kitchen and bathroom vents capable of wind power generation. (1) As for air current distribution according to vent velocity changes, it increased the venting performance of the kitchen and bathroom by 1.0m/s at vent velocity of 2.0m/s or higher and allowed for wind power generation. (2)As for air current distribution according to external velocity changes, it increased the venting performance of the kitchen and bathroom by 1.2m/s at external velocity of 2.0m/s or higher and allowed for wind power generation. (3)As for air current distribution according to wind direction changes($0{\sim}180^{\circ}$), it was favorable for higher vent velocity when the angle between the external induction duct direction and prevailing wind direction was within ${\pm}30^{\circ}$. (4)As for air current distribution according to induction duct type, the[M1] type combining the inducing openings and lines with the induction units recorded the highest improvement effects in the kitchen and bathroom venting performance by increasing vent velocity by 46%. (5)As for air current distribution according to the changing types of internal sockets where the main ducts of the kitchen and bathroom are connected to the external induction ducts, the venturi tube type[Sv] increased vent velocity by 66% based on the smoothest external inflow.

• 한국구조물진단유지관리공학회 논문집
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• 제17권3호
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• pp.56-64
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• 2013

200m 이하의 아치 교량에서 동적 내풍 안정성은 일반적으로 일본의 Wind Resistant Design Manual for Highway Bridges에 따라 검토된다. 또한 내풍 안정성 검토는 모드 형상에 관계없이 1차 연직 진동수를 적용한다. 일본의 매뉴얼에 따라 설계된 경간장 183m의 닐슨 아치 교량에서 예상치 못한 와류 진동이 발생하였으며 이는 태풍시 교량의 모니터링 시스템에 의해 계측되었다. 본 논문에서는 태풍 발생시에 계측된 풍속, 풍향, 진동 변위와 가속도를 기반으로 닐슨 아치교량의 와류진동 특성을 분석하였다. 분석 결과 1차 연직 진동 모드가 역대칭 형상이고 2차 연직 진동 모드가 대칭 형상인 닐슨 아치교의 경우 와류 진동이 2차 연직 모드에서 지배적이다. 따라서 본 논문에서는 2차 연직 진동 모드가 대칭 형상인 닐슨 아치교의 내풍 안정성 평가시에는 1차 보다 2차 연직 진동 모드가 중요한 설계 요소임을 제시하였다.

• 한국산림과학회지
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• 제77권2호
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• pp.178-185
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• 1988

해수욕장(海水浴場) 녹지대(綠地帶)는 휴식시설기능(休息施設機能)과 방재기능(防災機能)을 만족(滿足)할 수 있도록 조성(造成)하여야 되므로 통리해수욕장(桶里海水浴場)에 녹지대(綠地帶)를 조성(造成)하기 위(爲)하여 방재기능측면(防災機能側面)에서 각종재해요인(各種災害要因)을 분석(分析)한 바 다음과 같다. (1) 하계(夏季)의 주풍방향(主風方向)은 SE방위(方位)이다. (2) 하계(夏季)의 1시간평균풍속(時間平均風速)은 2.1~3.0m/sec가, 순간풍속(瞬間風速)은 1.1~2.0m/sec가 발생빈도(發生頻度)가 제일 높다. (3) 구사(丘砂)의 입경(粒徑)은 세립(細粒)이며 광물조성(鑛物組成)은 양적(量的)으로 Quartz, Calcite, Feldspars, Sericite 순(順)이다. (4) 구사(丘砂)의 사별입경급(篩別粒徑級)이 작을수록 Quartz의 수량(數量)은 대단(大端)히 많아지고 Calcite와 Feldspars의 양(量)은 감소(減少)되며 Sericite의 양(量)은 증가(增加)한다. (5) 구사(丘砂)의 직경급(直徑級)에 따른 한계마찰풍속식(限界摩擦風速式) $y=4.191x^{0.221}$이다. (6) 비래염분량(飛來鹽分量)은 정선(汀線)가까이에서 제일 많고 내지(內地)로 향(向)하면서 급격(急激)히 감소(減少)한다. 포착염분량(捕捉鹽分量)의 회귀식(回歸式)은 $y=28.181{\times}(-0.369^x)$이다. (7) 해수함염량(海水含鹽量)은 33‰이다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.605-614
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• 2010

In this paper, the initial behavior of transmission tower was analyzed. This tower was firstly constructed by rock anchor foundation in domestic 154 kV transmission line and wireless real-time monitoring system was installed to obtain the measured data for analysis of the structure behavior. For this purpose, 16 strain gauges was installed in anchors of foundation and strain gauges, clinometers, anemoscope and settlement sensors was installed at superstructure. As the results, the main factor which influence the behavior of superstructure is wind velocity, wind direction, rainfall and temperature change. Especially, the uplift load at stub of transmission structure revealed about 35.4 percentages of design load. Hereafter the long term stability will be analyzed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.202-206
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• 1994

Mathematical model of the pollution rate of substation insulators is constructed, taking the model parameters as wind speed, wind direction, typhoon conditions and rainfall in an hourly basis. The main feature of model construction is to distinguish the effect of each parameter by separately analyzing the positive and negative pollution causing factors. Model parameters for the insulators of Karatsu substation, Saga, Japan were estimated and model validation was done using the actual data, in which the pollution deposits on the insulators were measured using pilot insulator and 'salt meter'. The proposed model of the pollution rate [mg/cm$^{2}$/hr] enables the identification of the effective parameters and prediction of the pollution rate so that it helps for the automatic decision making for insulator cleaning or the model can be used as a tool for the substation engineers to make precautionary measures.

• 한국전산유체공학회지
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• 제14권3호
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• pp.9-15
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• 2009

Numerical investigation has been carried out for laminar flow past an inclined square cylinder in cross freestream. In particular, inclination of a square cylinder with respect to the main flow direction can cause sudden shift of the separation points to other edges, resulting in drastic change of flow-induced forces on the cylinder such as Strouhal number (St) of vortex shedding, drag and lift forces on the cylinder, depending upon the inclination angle. Collecting all the numerical results obtained, we propose contour diagrams of drag/lift coefficients and Strouhal number on an Re-Angle plane. This study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind from the viewpoint of wind hazards.

• Journal of Mechanical Science and Technology
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• 제18권10호
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• pp.1819-1828
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• 2004

The purpose of this paper is to investigate the effects of slits and swirl vanes on the turbulence augmentation in the flow fields of a gun-type gas burner using an X-type hot-wire probe. The gun-type gas burner adopted in this study is composed of eight slits and swirl vanes located on the surface of an inclined baffle plate. Experiment was carried out at a flow rate of 450 ι/min in burner model installed in the test section of subsonic wind tunnel. Swirl vanes playa role diffusing main flow more remarkably toward the radial direction than axial one, but slits show a reverse feature. Consequently, both slits and swirl vanes remarkably increase turbulence intensity in the whole range of a gun-type gas burner with a cone-type baffle plate.