• Journal of Korean Society for Atmospheric Environment
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• v.23 no.4
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• pp.449-456
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• 2007

Dispersion coefficient preprocessing schemes have been examined to improve plume dispersion model performance in complex coastal areas. The performances of various schemes for constructing the sigma correction order were evaluated through estimations of statistical measures, such as bias, gross error, R, FB, NMSE, within FAC2, MG, VG, IOA, UAPC and MRE. This was undertaken for the results of dispersion modeling, which applied each scheme. Environmental factors such as sampling time, surface roughness, plume rising, plume height and terrain rolling were considered in this study. Gaussian plume dispersion model was used to calculate 1 hr $SO_2$ concentration 4 km downwind from a power plant in Boryeung coastal area. Here, measured data for January to December of 2002 were obtained so that modelling results could be compared. To compare the performances between various schemes, integrated scores of statistical measures were obtained by giving weights for each measure and then summing each score. This was done because each statistical measure has its own function and criteria; as a result, no measure can be taken as a sole index indicative of the performance level for each modeling scheme. The best preprocessing scheme was discerned using the step-wise method. The most significant factor influencing the magnitude of real dispersion coefficients appeared to be sampling time. A second significant factor appeared to be surface roughness, with the rolling terrain being the least significant for elevated sources in a gently rolling terrain. The best sequence of correcting the sigma from P-G scheme was found to be the combination of (1) sampling time, (2) surface roughness, (3) plume rising, (4) plume height, and (5) terrain rolling.

• The KSFM Journal of Fluid Machinery
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• v.12 no.1
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• pp.7-15
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• 2009

A study is made of thermal plume flow model for the development of helicopter simulator over the forest fire. For the numerical analysis, a line fire model with Boussinesq fluid approximation, which is idealized by the spreading shape of forest fire on the ground, is adopted. Comparing full 2-D and 3-D numerical solutions with 2-D similarity solution, it has been built a new model that is useful for temperature prediction along the symmetric vertical axis of fire model for both cases of laminar and turbulent flow.

• Journal of computational fluids engineering
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• v.4 no.3
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• pp.12-20
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• 1999

The computations of the flowfield and pollutant dispersion over a flat plate and the Russian hills of various slopes are described. The Gaussian plume and the puff model have been used to calculate concentration of pollutant. The Reynolds-averaged unsteady incompressible Navier-Stokes equation with low Reynolds κ-ε model has been used to calculate the flowfield. The flow data of a flat plate and the Russian hills from Navier-Stokes equation solutions has been used as the input data for the puff model. The computational results of flowfield agree well with experimental results of both a flat plate and Russian hills. The concentration prediction by the Gaussian plume model and the Gaussian puff model also agrees flirty well with experiments.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.6
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• pp.643-650
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• 1998

Many atmospheric dispersion models have been based on the Gaussian distribution concept of plume spread. In application of Gaussian plume dispersion models, vertical dispersion coefficient 3 has been known as a sensitive variable. Vertical diffusivity K2 (=Oz2/2t) tends to increase with surface roughness, and the value of K3 in urban area is larger than that in rural area due to heat emission as well as increased roughness. Though Pasquill proposed a modification scheme for qz vs x system of Pasquill-Gifford under consideration of roughness effect in 1976, there appears not to be realistic reexamination on the modification scheme. In this study literature review on the effect of terrain or roughness on venical plume dispersion has been carried out in order to improve the prediction results of atmospheric pollution concentration. Again a few research objectives on vertical atmospheric dispersion in complex terrain were Proposed.

• Environmental Engineering Research
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• v.22 no.2
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• pp.216-223
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• 2017

For the prediction of the ventilation rate for removing the non-isothermal concentrated fume from the semi-enclosed space, the computational fluid dynamics (CFD) analysis was done. Securing the proper ventilation conditions in emergency state such as in fire is crucial factor for the protection of the resident in the space. In the analysis for the determining the proper ventilation rate, the experimental study had the limitation for simulating the versatile conditions of fume development. The theoretical and computational method had been chosen as the alternate tool for the experimental analysis. In this study, the CFD analysis was done on the defined model which already had been done the experimental analysis by the previous workers. By comparing the prediction on the plume heights and the ventilation rates by the CFD analysis at, and in the parametric model of $1m^3$ with those of the previous experimental works, the feasibility of the computational analysis was evaluated. For the required ventilation rate analyzed by the CFD analysis was over predicted in 7.1% difference with that of the experimental results depending on the different plume height. With the comparison with the analytical Zukoski model at, the CFD analysis on the ventilation was under predicted in 8.3%. By the verification of the feasibility of the CFD analysis, the extended analysis was done for getting the extra information such as the water vapor distribution and $CO^2$ distribution in the semi-enclosed spaces.

• Journal of Korean Society for Atmospheric Environment
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• v.13 no.6
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• pp.427-437
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• 1997

Complex terrain which is rather typical topographic character in Korea would greatly influence the dispersion of air pollutant. In this study, we investigated how the complex terrain in the vicinity of the coal-fired plant affects the air dispersion modeling results by using several US EPA models: SCREEN, CTSCREEN, ISCLT3, ISCST3, and RTDM. Screening analysis was followed by long-term analysis, and the plume movement over the terrain was precisely tracked for selected cases. Screening analysis revealed that the highest concentration of sulfur dioxide occurs at the downwind distance of 1.3 km under the unstable conditions with weak winds. However, this highest level of $SO_2$ could be raised by 4 times even in the presence of a hill of 170 m at a distance of 2 to 3 km. Seasonal and annual average concentrations predicted with the ISCLT3, ISCST3, and RTDM models showed a rapid incrase of $SO_2$ levels in front of the high mountains which are located more than 15 km away fromt the source. The highest concentrations predicted with ISCST3 were significantly higher than those with ISCLT3 and RTDM mainly because ISCST3 chooses simple-terrain model calculations for receptors between stack height and plume height. Although the highest levels under the stable conditions were usually found in the areas beyond 15 km or more, their absolute values were not so high due to enough dispersion effects between the source and the receptors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.725-730
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• 2020

This study was conducted to reduce the computation time required for the computational acoustic analysis of the supersonic rocket jet plume. In order to reduce the computation time, computational acoustic analysis was performed assuming that the supersonic jet plume is a two-dimensional axis-symmetric problem. The results of computational acoustic analysis showed similar results to the acoustic load measurement results. Through this study, it was confirmed that the acoustic load prediction of the supersonic rocket jet plume can be predicted using a two-dimensional axis-symmetric computational analysis.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.4
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• pp.22-29
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• 1997

This paper presents results on dynamic analysis of the missile initial motion arising from the missile detent force. Using ADAMS (Automatic Dynamic Analysis of Mechanical Syatem) software, a non- linear46-DOF (Degree of Freedom) model is developed for the launcher system including missile and lunch tube contact problem. From the dynamic analysis, it is found that initial angular velocity of the missile incre- ases when the missile detent force increases and also when rocket exhaust plume is taken into account. To achieve the missile launching stability, it needs to reduce the missile initial detent force and exhaust plume area of the lancher. Results of the dynamic analysis on the system natural frequency agree well with those obtained from experimental modal tests. The overall results suggest that the proposed method is a useful tool for prediction of initial missile stability as well as design of the missile launcher system.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.1017-1022
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• 1996

This paper presents results of dynamic analysis of the missile initial motion arising from the missile detent force. Using ADAMS (Automatic Dynamic Analysis of Mechanical System) software, a non-linear 46-DOF (Degree of Freedom) model is developed for the launcher system including missile and launch tube contact problem. From the dynamic analysis, it is found that initial angular velocity of the missile increases when the missile detent force increases (more than 18 g) and also rocket exhaust plume is taken into account. To achieve the missile launching s ability, it needs to reduce the missile initial detent force and exhaust plume area of the launcher. Results of the dynamic analysis on the system natural frequency agree well with those obtained from experimental modal tests. The overall results suggest that the proposed method is a useful tool for prediction of initial missile stability as well as d :sign of the missile launcher system.

• Journal of the Korean Society of Propulsion Engineers
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• v.19 no.4
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• pp.24-36
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• 2015

In the present study, numerical predictions of infrared spectrum of rocket plume with considering effect of particles based on approximation theories were performed by using a line-by-line radiation model with radiation databases. The high-resolution radiation databases were used to predict thermal emission spectra of gas molecules within the rocket plume regime. The particles were modeled as soot particles by using 1st term approximation of Mie theory and Rayleigh approximation. The reliability of modeled effect of soot particles using the two approximation theories was verified, and the spectral radiance of rocket plume was predicted based on the verification. The results were improved in the short wavelength range by considering the effect of soot particles.