• Journal of Advanced Marine Engineering and Technology
• /
• v.30 no.1
• /
• pp.116-124
• /
• 2006

A model test was carried out, in order to verify the hydrodynamic performances of public 30 feet class sailing yacht. In the initial design stage, the performances and the running attitude of sail yacht including the hull form and sail plan, appendages were estimated by VPP, from which made the representative test conditions. A new experiment system such as captive model device was composed because the running attitude could be changed by wind conditions. The test results show that the minimum resistance is generated in the heeling 20 degree. which was expected in the initial design stage. It is thought to be the useful informations that the keel has an effects on hydrodynamic forces and resistance differences between the upwind and the downwind condition. Also this paper is associated with the state-of-the-art of calculating sailing yacht performance as this is performed in velocity Prediction program (VPP) The VPP results shows a typical shape of a sailing yacht and the designed yacht has the best performance at 120 degree angle of true wind with 20 knots.

• Journal of Environmental Impact Assessment
• /
• v.15 no.3
• /
• pp.193-206
• /
• 2006

Recently, high ozone episode occurred frequently in Korea. Moreover ozone episode occurred not only in the city but also in background area where local anthropogenic sources are not important. It analyzed frequency exceeding 100ppb ozone at air quality monitoring stations in Seoul and rural area during 1995-2004. This paper reports on the use of the Community Multiscale Air Quality (CMAQ) modelling system to predict hourly ozone levels. Domain resolutions of 30km, 10km, 3.333km (innermost) have been employed for this study. Summer periods in June 2004 have been simulated and the predicted results have been compared to data for metropolitan and rural air quality monitoring stations. The model performance has been evaluated with measured data through a range of statistical measures. Although, the CMAQ model reproduces the ozone temporal spatial trends it was not able to simulate the peak magnitudes consistently.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.7 no.2
• /
• pp.13-22
• /
• 2001

We studied the characteristics of marine casualties within the area under control of Korea National Maritime Police and leeway of drifting vessel. According to 5 years＇(1995~1999) data of casualties, it was found that the occurrence of casualties by fishing boats ranked the highest and a considerable numbers of casualties took place more than 20 miles off the shore. From a result of field experiment of G/T 50 tons vessel off Busan harbor on Apr. 26~28, 2000, we computed that the linear equation of leeway speed(cm/s) was 1.01$\times$U(U : wind speed in m/s)+11.36 with correlation coefficient between wind speed and leeway speed being 0.252 and we found leeway angle range from $+87^{\circ}$(right) to $-78^{\circ}$(left ) of the downwind direction.

• Journal of Korean Society for Atmospheric Environment
• /
• v.2 no.1
• /
• pp.23-31
• /
• 1986

Meteorological Measurement was performed for evaluation of the horizontal vertical standard deviation $(\sigma_y, \sigma_z)$, surface roughness length and stmospheric stability during the period of March to October 1985 The major results are as follows; 1) The average value of surface roughness length was 144cm at NEPI. 2) In frequency distribution of atmospheric stability, neutral state (D class) was dominent in Seoul (29%) and Pusan (30%). Unstable states (A. B. C. class) were 26% in Seoul and 24% in Pusan. Also, stable states (D. E. F class) were 74% in Seoul and 76% in Pusan. 3) Standard deviations of horizontal ad vertical direction were evaluated as a function of downwind distance and atmospheric stability at NEPI, Jamsil and Pujeondong (Pusan). Standard deviation of horizontal direction was largest at NEPI among 3 areas because of mechanical turbulence resulting from difference of surface roughness length.

• Journal of Korean Society for Atmospheric Environment
• /
• v.10 no.3
• /
• pp.197-202
• /
• 1994

The research described in this paper is conducted to estimate the short-term concentrations of nonreactive pollutants such as CO and TSP from vehicle emissions near Kyungbu Highway. An emphasis is placed on the development of a model for a hourly traffic volume for each vehicle type, which is based on real traffic data. By using the model and the calculated emission factor due to vehicle speed for each vehicle type, the emission rate of CO and TSP for each traffic line is computed. The hourly emission rate and meteorological data are used to simulate by HIWAY-2 for the distance of 5m and 10m from the downwind edge of Kyungbu Highway located in relatively uncomplicated terrain.

• Wind and Structures
• /
• v.17 no.2
• /
• pp.135-162
• /
• 2013

The majority of experiments to characterize the turbulence in the surface layer have been performed in flat, open expanses. In order to characterize the turbulence in built-up terrain, two mobile towers were deployed during Hurricane Ike (2008) in close proximity, but downwind of different terrain conditions: suburban and open. Due to the significant non-stationarity of the data primarily caused by changes in wind direction, empirical mode decomposition was employed to de-trend the signal. Analysis of the data showed that the along-wind mean turbulence intensity of the suburban terrain was 37% higher than that of the open terrain. For the mean vertical turbulence intensity, the increase for the suburban terrain was as high as 74%, which may have important implications in structural engineering. The gust factor of the suburban terrain was also 16% higher than that of the open terrain. Compared to non-hurricane spectral models, the obtained spectra showed significantly higher energy in low frequencies especially for the open terrain.

• Journal of Korean Society for Atmospheric Environment
• /
• v.15 no.5
• /
• pp.639-647
• /
• 1999

Experimental methods of plume dispersion in convective boundary layer using a composite turbulence water tank have been established through (ⅰ) manufacturing of water tank system, (ⅱ) providing of tracer whose volatility is relatively low, (ⅲ) development of software for image processing of dispersed particles in fluid, and (ⅳ) application of appropriate similarity law. Using these methods, the vertical dispersion coefficient $$\sigma$_2$ at long distances on mesoscale and the centerline height $Z_c$ of plumes have been measured. Measurement of $$\sigma$_2$ have been validated through comparison with CONDORS field experiments, and analysed with respect to the intensity of heat flux and mechanical turbulence as well as plume release height. Downwind distance where plume center height approaches to final level has also been analysed in respect of these three parameters.

• Journal of Korean Society for Atmospheric Environment
• /
• v.27 no.1
• /
• pp.87-96
• /
• 2011

In this study, the AERMOD dispersion model was used for predicting odor concentrations and back-calculating industrial area source odor emission rate. The studied area was Sihwa industrial complex in Korea. Odor samples were collected during two days over a year period in 2009. The comparison between the predicted and observed concentrations indicates that the AERMOD model could fairly well predict average downwind odor concentrations. The results show odor emission rates of Sihwa industrial complex area source were ranged from 0.204 to 2.320 $OUms^{-1}$ (average 0.476 $OUms^{-1}$). The results also show wind speed and direction are important parameters to the odor dispersion.

• Journal of Environmental Science International
• /
• v.9 no.1
• /
• pp.57-64
• /
• 2000

The sensitivity analysis of two short-term models (ISCST3, INPUFF2.5) is performed to improve the model accuracy. It appears that the sensitivities on the changes of wind speed, stack height and stack inner diameter in the near distance from source, stability and mixing height in the remote distance form source, are significant. Also the gas exit velocity, stack inner diameter, gas temperature and air temperature which affect the plume rise have some effects on the concentration values of each model within the downwind distance where final plume rise is determined. And in modeling for the atmospheric dispersion of point pollutant source INPUFF2.5 can calculate amount, trajectory of puff and concentration versus time at each receptors. So, it is compatible to analyze distribution of point pollutants concentration at modeling area.

• Proceedings of the Korean Society of Marine Engineers Conference
• /
• 2005.06a
• /
• pp.824-831
• /
• 2005

A model test was carried out, in order to verify the hydrodynamic performances of public 30 feet class sailing yacht. In the initial design stage, the performances and the running attitude of sail yacht including the hull form and sail plan, appendages were estimated by VPP, from which made the representative test conditions. A new experiment system such as captive model device was composed because the running attitude could be changed by wind conditions. The test results show that the minimum resistance is generated in the heeling 20 degree, which was expected in the initial design stage. It is thought to be the useful informations that the keel has an effects on hydrodynamic forces and resistance differences between the upwind and the downwind condition. Also this paper is associated with the state-of-the-art of calculating sailing yacht performance as this is performed in velocity prediction program (VPP). The VPP results shows a typical shape of a sailing yacht and the designed yacht has the best performance at 120 degree angle of true wind with 20 knots.