• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.440-448
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• 2003

In the present paper, numerical simulations of buoyant plume dispersion in a neutral and stable atmospheric boundary layer have been carride out. A Lagrangian Stochastic Model (LSM) with a Non-Linear Eddy Viscosity Model (NLEVM) for turbulence is used to generate a Reynolds stress field as an input condition of dispersion simulation. A modified plume-rise equation is included in dispersion simulation in order to consider momentum effect in an initial stage of plume rise resulting in an improved prediction by comparing with the experimental data. The LSM is validated by comparing with the prediction of an Eulerian Dispersion Model (EDM) and by the measured results of vertical profiles of mean concentration in the downstream of an elevated source in an atmospheric boundary layer. The LSM predicts accurate results especially in the vicinity of the source where the EDM underestimates the peak concentration by 40% due to inherent limitations of gradient diffusion theory. As a verification study, the LSM simulation of buoyant plume dispersions under a neutral and stable atmospheric condition is compared with a wind-tunnel experiment, which shows good qualitative agreements.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.507-514
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• 2012

In the present research, NASA LRB plume radiation models are reconstructed with Thermal Desktop software, where the radiation to vehicle base environment can be calculated. The calculation shows the similar radiation heat compared to NASA prediction. Based on LRB plume radiation model, a KSLV-II thermal radiation model is proposed.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.358-361
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• 2008

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

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.118-128
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• 2004

Exhaust plume effects on longitudinal aerodynamics of missile were investigated by wind tunnel tests using a solid plume simulator and CFD analyses with both the solid plume and air jet plumes. Approximate plume boundary prediction technique was used to produce the outer shape of the solid plumer and chamber conditions and nozzle shapes of the air jet plumes were determined through plume modeling technique to compensate the difference in thermodynamic properties between air and real plume. From comparisons among turbulence models in case of external flow interaction with the air jet plume, Spalart-Allmaras model turned out to give accurate result and to be less grid-dependent. Effects induced by the plume were evaluated through the computations with Spalart-Allmaras turbulence model and the air jet plume to account for various ratios of chamber and ambient pressure and Reynolds number under the flight test condition.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.440-443
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• 2008

Plume radiation has been measured during ground tests of KSLV-I kick motor in order to predict the thermal load on the equipment around the kick motor at flight. The measuring positions are the kick motor base, and the measured heats were about 2${\sim}$5 w/cm$^2$. The measured heat showed a lot of shot fluctuation in their values, and the radiative heats at the latter half of time are higher than those of the first half. A plausible explanation for these phenomena was given as the variation of alumina particles with time. The radiative heats along the plume axis were also measured recently at 8 positions with 1.5m radius from plume axis, but only the initial parts of the results could be acceptable because the sensor were damaged by the accumulated heat. The strongest heat occurred at the middle of the plume, which can be explained with different view factors. Despite of the plausible explanation, it seems to need more analysis because the plume structure such as temperature, alumina particle, after burning has not been revealed until yet. The measure heat flux has been reflected in the prediction of the plume radiation at high altitude where the kick motor operates.

• Journal of computational fluids engineering
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• v.9 no.3
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• pp.18-25
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• 2004

Multi plume effects on the base heating have been Investigated with a CFD program. As the flight altitude increases, the plume expansion angle increases regardless of the single or clustered engine. The plume interaction of the clustered engine makes a high temperature thermal shear in the center of four plumes. At low altitude, the high temperature shear flow stays in the center of plumes, but it increases up to engine base with the increasing altitude. At high altitude, the flow from plume to base and the flow from base into outer free stream are supersonic, which transfers the high heat in the center of plumes to the base region. The radiative heat of the clustered engine varies from 220 kW/m² to 469 kW/m² with increasing altitude while those of the single engine are 10 kW/m² and 43.7 kW/m². And the base temperature of the clustered engine varies from 985K to 1223K, and those of the single engine are 483K and 726K. This big radiative heat of clustered engine can be explained by the active high temperature base flow and strong plume interactions.

• Journal of Korean Society for Atmospheric Environment
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• v.14 no.2
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• pp.81-94
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• 1998

Six complex terrain dispersion models recommended by the U. S. Environmental Protection Agency were investigated using a hypothetical case in which a plume approaches complex terrain. The six models considered were Valley, CTSCREEN, COMPLEX 1, SHORTZ, RTDM, and CTDMPLUS, the latter four being closely studied. Highest concentrations were predicted for 48 receptors and plume behaviors were compared for stable and unstable meteorological conditions. Under stable conditions, ground-level concentrations were determined by the height of the plume centerline above the terrain. The concentrations estimated by SHORTZ and COMPLEX I were higher than those estimated by CTSCREEN, with CTDMPLUS predicting the lowest concentrations. In particular, the height of the lift midpoint, as well as the co.nterline of the plume, are important in the model calculation of CTDMPLUS. Under unstable conditions, the vertical dispersion plays a key role in determining ground -level concentrations. For this case, concentrations predicted by CTDMPLUS were the 'highest, whereas those predicted by SHORTZ were the lowest. Concentration distributions predicted by CTDMPLUS are quite similar to typical Gaussian distributions even on complex terrain, except for a slight shift of the plume centerline due to the of(tract of the geostrophic wind. In addition,24-hour average concentrations were estimated for comparison with results from the Valley model. Among the four models studied closely, CTDMPLUS predicted the lowest 24-hour average concentrations, but the concentrations estimated by Valley were lower than those estimated by CTDMPLUS.

• Journal of the Korea Institute of Military Science and Technology
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• v.16 no.4
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• pp.545-552
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• 2013

This paper is a part of developing a computer code that can be used to generate IR images of a naval ship by considering the emitted and reflected infrared signals. The spectral radiance received by an IR sensor is consisted of the self-emitted component from the ship surface, the reflected component of the solar/sky irradiance at the ship surface, the emitted radiance from the ship surface and the exhaust plume gas, and the scattered radiance by the atmosphere. The plume gas radiance occupies a large part of the emitted radiance from a naval ship in operation. Therefore plume gas radiance must be taken into account when calculating the radiance from a naval ship for reliable IR images. In this paper, IR images of a naval ship with the exhaust gas effect in various environmental conditions are generated by using an exhaust gas prediction model called the JPL model. The contrast radiance (CR) values of the IR images are calculated to analyze the effect of the exhaust gas radiance quantitatively. The results obtained by quantitative analysis show that the IR signatures with the exhaust plume gas are 2.26 times larger than those neglecting the plume gas effect. The effect of the exhaust plume gas is shown to be more eminent in winter than in summer in the daytime.

• Aerospace Engineering and Technology
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• v.8 no.1
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• pp.17-25
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• 2009

The precise calculation of gas absorption coefficient in the radiative transfer equation is very important to the prediction of radiative heat transfer induced from liquid engine plume in view of base insulation design. For this purpose, the WNB model for gas absorption coefficient is described with the selection of important parameters and then the calculated results are compared with those of SNB model for validation. Total emissivity, narrow band averaged intensity and total intensity are calculated and compared to the results of SNB model. As results, the total emissivity and the total intensity are well matched within 3.1% and roughly 5 % error, respectively. Moreover, the gas modeling database is constructed with estimation of the combustion gas composition of $CO_2$ and $H_2O$ for liquid engine plume.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.368-376
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• 2004

The estimation of the diffusion coefficients of the Gaussian plume model and the release rate by assimilation of tracer-gas measurements on Younggwang site was tested. Diffusion coefficients were modified by linear programming of both the measurements and the simulated using the Gaussian plume model. The application of the modified diffusion coefficients improved the prediction ability of the Gaussian plume model on both 3 km and 8 km arc lines. And, the release rate of tracer gas was estimated using least squares method. The optimal source rate was estimated by minimizing the errors between the measured concentrations and the computed ones by the Gaussian plume model. The obtained release rate showed a good agreement with the real release rate of the Younggwang experiment in 24%.