• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.11-22
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• 1992

It this study, the aerodynamic responses of circular cylinder behind a pair of circular cylinders arranged side by side in a uniform flow were investigated. We confirmed that four types of oscillation are occured on downstream cylinder in such an arrangement. Influenced by upstream cylinders, the amplitude of vortex induced oscillation is increased and wake buffeting occured when S/D(S: distance between the centers of upstream cylinders, D: diameter of cylinder) is smaller than 1.2. When S/D is larger than 1.2, gap flow introduces to oscillation which maintains a uniform amplitude in spite of increasing wind speed. This oscillation is reduced to "wake galloping" if its amplitude exceeds the limit point.

• Journal of Environmental Impact Assessment
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• v.22 no.1
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• pp.79-87
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• 2013

The purpose of this study is to establish PM-10 management manual for developing large scale sites by assessing the status of PM-10 reduction at ongoing large scale development sites. After analyzing the meteorological conditions and air quality characteristics of Sihwa MTV development site, ISCST3 (Industrial Source Complex Short Term Model 3) was implemented to predict PM-10 generation. The outcomes of ISCST3 modelling were utilized for verification of site survey data. As a result of applying air pollution modeling, the diffusion rate of PM-10 decreases according as the wind speed decreases. And the emission rate of PM-10 increase is linear to the concentration of PM-10. The reduction target of PM-10 can be derived quantitatively from the difference between the forecasted emission rate and the permissible emission limit of PM-10. The assessment of PM-10 characteristics which is deduced from ISCST3 and site survey can be practically applied to accomplish environmentally acceptable air quality manual for large scale development sites.

• Korean Journal of Remote Sensing
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• v.28 no.5
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• pp.477-487
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• 2012

Sea surface winds in the sea off the east coast of Korea were derived from L-band ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band Synthetic Aperture Radar) data and their characteristics of errors were analyzed. We could retrieve high-resolution wind vectors off the east coast of Korea including the coastal region, which has been substantially unavailable from satellite scatterometers. Retrieved SAR-wind speeds showed a good agreement with in-situ buoy measurement by showing relatively small an root-mean-square (RMS) error of 0.67 m/s. Comparisons of the wind vectors from SAR and scatterometer presented RMS errors of 2.16 m/s and $19.24^{\circ}$, 3.62 m/s and $28.02^{\circ}$ for L-band GMF (Geophysical Model Function) algorithm 2009 and 2007, respectively, which tended to be somewhat higher than the expected limit of satellite scatterometer winds errors. L-band SAR-derived wind field exhibited the characteristic dependence on wind direction and incidence angle. The previous version (L-band GMF 2007) revealed large errors at small incidence angles of less than $21^{\circ}$. By contrast, the L-band GMF 2009, which improved the effect of incidence angle on the model function by considering a quadratic function instead of a linear relationship, greatly enhanced the quality of wind speed from 6.80 m/s to 1.14 m/s at small incident angles. This study addressed that the causes of wind retrieval errors should be intensively studied for diverse applications of L-band SAR-derived winds, especially in terms of the effects of wind direction and incidence angle, and other potential error sources.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.1
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• pp.29-39
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• 2017

In this research, thermal design data such as heat transfer coefficient on the wall surface required for ventilation system design which is to prevent the temperature rise in the underground utility tunnel that three sides are adjoined with the ground was investigated in numerical analalysis. The numerical model has been devised including the tunnel lining of the underground utility tunnel in order to take account for the heat transfer in the tunnel walls. The air temperature in the tunnel, wall temperature, and the heating value through the wall based on heating value(117~468 kW/km) of the power cable installed in the tunnel and the wind speed in the tunnel(0.5~4.0 m/s) were calculated by CFD simulation. In addition, the wall heat transfer coefficient was computed from the results analysis, and the limit distance used to keep the air temperature in the tunnel stable was examined through the research. The convective heat transfer coefficient at the wall surface shows unstable pattern at the inlet area. However, it converges to a constant value beyond approximately 100 meter. The tunnel wall heat transfer coefficient is $3.1{\sim}9.16W/m^2^{\circ}C$ depending on the wind speed, and following is the dimensionless number:$Nu=1.081Re^{0.4927}({\mu}/{\mu}_w)^{0.14}$. This study has suggested the prediction model of temperature in the tunnel based on the thermal resistance analysis technique, and it is appraised that deviation can be used in the range of 3% estimation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.157-162
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• 2018

The increase of risk in port due to the increase in ship size and sea level rises, the standard crown height will increase. In this study, cruise and container ships will need to raise their crown height due to the projected wind pressure areas becoming larger due to the ships' size increase. The mooring assessment was evaluated with the rise of the crown height. The cruise ship of GT 100,000 tons exceeded the permissible breaking force of the mooring line under the crown height conditions of wind speed of 30 kts when the wind direction was $45^{\circ}$ to the direction of the bow. Also, the elevation angle of the pier and mooring line was analyzed and exceeded the crown height, and it was determined that it is necessary to adjust the crown height. Container ships of DWT 100,000 tons were analyzed to exceed the limit of sway motion at the crown height and it was determined that they need to be adjusted to the minimum crown height standard.

• Fire Science and Engineering
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• v.31 no.3
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• pp.1-10
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• 2017

This study examined the risk of accidents when handling hazardous materials in hazardous materials storage facilities without safety facilities. In the case of illegal dangerous cargo containers, the burning rate is very fast in the case of fire, which leads to explosions, that are damaging and difficult to control. In addition, accidents that occur in flammable liquid hazardous materials are caused mostly by accidents that occur in the space due to leakage. Therefore, the variables that affect these accidents were derived and the influence of these variables was investigated. Numerical and computational fluid dynamics programs were used to obtain the following final results. First, when a flammable liquid leaks into a specific space, it is influenced by temperature and relative humidity until a certain concentration (lower limit of combustion) is reached. In the case of temperature, it was found that the reaching time was shorter than the flash point In addition, the effect of variables on pool fire accidents of leakage tanks is somewhat different, but the variables that have the largest influence are the wind speed. Therefore, it is expected that the results of this study will be used as basic data for similar numerical analysis and it will provide useful numerical information about the accidental leakage of hazardous materials under various research conditions.

• Journal of the Korean Institute of Landscape Architecture
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• v.41 no.6
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• pp.52-61
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• 2013

This study was conducted to investigate the effects of pergola's shading on the thermal comfort index in the summer. The 3 type of pergolas($4m{\times}4m{\times}h2.7m$) which were screened overhead(I)/overhead west(II)/overhead west north(III) plane with reed blind for summer shading and winter wind break, were constructed on the 4th floor rooftop. Thereafter the meteorological variables(air temperature, humidity, radiation, and wind speed) of pergola I, III and rooftop were measured from 14 to 16 August 2013(1st experiment), those of pergola I, II and rooftop were measured from 26 to 28 August 2013(2nd experiment). The effects of pergola's shading on the radiation environment and mean radiant temperature($T_{mrt}$), standard effective temperature($SET^*$) were as follows. The maximum 1 h mean values of differences ${\Delta}$ of the sums of shortwave radiant flux densities absorbed by the human body (${\Delta}K_{abs,max}$) between pergola I, III and nearby sunny rooftop were $-119W/m^2$, $-158W/m^2$, those between pergola I, II and rooftop were $-145W/m^2$, $-159W/m^2$. The maximum 1 h mean values of differences ${\Delta}$ of the sums of long wave radiant flux densities absorbed by the human body (${\Delta}L_{abs,max}$) between pergola I, III and nearby sunny rooftop, were $-15W/m^2$, $-17W/m^2$, those between pergola I, II and nearby rooftop, were $-8W/m^2$, $-7W/m^2$. The response of the direction dependent long wave radiant flux densities $L_1$ on the pergola's shading turned out to be distinctly weaker as compared to shortwave radiant flux densities $K_1$. The pergola's shading leads to a lowering of $T_{mrt}$ and $SET^*$. The peak values of $T_{mrt}$ absorbed by the human body were decreased $16^{\circ}C$ and $21.4^{\circ}C$ under pergola I and III as compared to that of nearby rooftop in the 1st experiment. Those were decreased $18.8^{\circ}C$ and $20.8^{\circ}C$ under pergola I and II as compared to that of nearby rooftop in the 2nd experiment. The peak values of $SET^*$ absorbed by the human body were decreased $2.9^{\circ}C$ and $2.6^{\circ}C$ under pergola I and III as compared to that of nearby rooftop in the 1st experiment. Those were decreased $3.5^{\circ}C$ and $2.6^{\circ}C$ under pergola I and II as compared to that of nearby rooftop in the 2nd experiment. The relative $SET^*$ decrease in pergola II, III compared to nearby sunny rooftop $SET^*$ were lower than that in pergola I, revealing the influence of the wind speed. Therefore it is essential to design pergola to maximize wind speed and minimize solar radiation to achieve comfort in the hot summer. The $SET^*$ under pergola I, III were exceeded $28.7^{\circ}C$ and $30.4^{\circ}C$ which were the upper limit of thermal comfort and tolerable zone during all most daytimes in the 1st experiment(maximum air temperature $37.5^{\circ}C$). The $SET^*$ under pergola I was exceeded $28.7^{\circ}C$ which was the upper limit of thermal comfort zone at 13h, that under pergola II was exceeded $28.7^{\circ}C$ from 8h to 14h, meanwhile the $SET^*$ under pergola I, II were within thermal tolerable zone during most daytimes in the 2nd experiment(maximum air temperature $34.4^{\circ}C$). Therefore to ensure the thermal comfort of pergola for summer hottest days, pergola should be shaded with not only reed blind but also climbing and shade plants. $T_{mrt}$ and $SET^*$ were suitable index for the evaluation of pergola's shading effects and outdoors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.445-449
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• 2017

Most studies using drone is confined utilization on the ground and regulation. The drone in the water is rarely used in hydrographic surveying because of the limit of flight time and image matching. This paper is the basic research for drone hydrographic photogrammetry. The accuracy of hydrographic photogrammetry, using buoys for water reference point, was evaluated. The accuracy is influenced by the accuracy of the water reference points like the photogrammetry. The position of water reference points set up on water, keep on changing due to various environmental factors such as wind speed and water velocity. The position continuously changed of the water reference points were measured 3 times using Total Station and VRS. Experiments were conducted at two reservoirs in Gimhae City, and the accuracy of the manual image matching using the water reference points is 40 cm and 80 cm. Allowable accuracy of the ocean boundary survey is ${\pm}2m$, the results of this study are fully available. The maximum position error of the water reference point for ensuring accuracy within ${\pm}2m$ is 1.8 m.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.4
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• pp.305-316
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• 2022

Hydrogen energy is emerging as an alternative to the depletion of fossil fuels and environmental problems, and the use of hydrogen vehicles is increasing in the automobile industry as well. However, since hydrogen has a wide flammability limit of 4 to 75%, there is a high concern about safety in case of a hydrogen car accident. In particular, in semi-enclosed spaces such as tunnels and underground parking lots, a fire or explosion accompanied by hydrogen leakage is highly likely to cause a major accident. Therefore, it is necessary to review hydrogen safety through analysis of flammability areas caused by hydrogen leakage. Therefore, in this study, the effect of the air velocity in the tunnel on the flammability area was investigated by analyzing the hydrogen concentration according to the hydrogen leakage conditions of hydrogen vehicles and the air velocity in the tunnel in a road tunnel with standard section. Hydrogen leakage conditions were set as one tank leaking and three tanks leaking through the TPRD at the same time and a condition in which a large crack occurred and leaked. And the air velocity in the tunnel were considered 0, 1, 2.5, and 4.0 m/s. As a result of the analysis of the flammability area, it is shown that when the air velocity of 1 m/s or more exists, it is reduced by up to 25% compared to the case of air velocity of 0 m/s. But there is little effect of reducing the flammability area according to the increase of the wind speed. In particular, when a large crack occurs and completely leaks in about 2.5 seconds, the flammability area slightly increases as the air velocity increases. It was found that in the case of downward ejection, hydrogen gas remains under the vehicle for a considerably long time.

• Korean Journal of Agricultural and Forest Meteorology
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• v.24 no.4
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• pp.346-352
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• 2022

Mountain meteorology in South Korea that is covered mountains with complex terrain is important for understanding and managing the forest disaster and forest ecosystems. In particular, recent changes in dryness and/or rainfall intensity due to climate change may cause an increase in the possibility of forest disasters. Therefore, accurate monitoring of mountain meteorology is needed for efficient forest management. Korea Forest Service (KFS) is establishing the Automatic Mountain Meteorology Observation Stations (AMOS) in the mountain regions since 2012. 464 AMOSs are observing various meteorological variables such as air temperature, relative humidity, wind speed and direction, precipitation, soil temperature, and air pressure for every minute, which is conducted the quality control (QC) to retain data reliability. QC process includes the physical limit test, step test, internal consistency test, persistence test, climate range test, and median filter test. All of AMOS observations are open to use, which can be found from the Korean Mountain Meteorology Information System (KoMIS, http://mtweather.nifos.go.kr/) of the National Institute of Forest Science and the Public Data Portal (https://public.go.kr/). AMOS observations with guaranteed quality can be used in various forest fields including the public safety, forest recreation, forest leisure activities, etc., and can contribute to the advancement of forest science and technology. In this paper, a series of processes are introduced to collect and use the AMOS dataset in the mountain region in South Korea.