• Journal of Korean Society for Atmospheric Environment
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• v.20 no.1
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• pp.47-58
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• 2004

The $textsc{k}$-$\varepsilon$ algebraic stress model (KEASM) was applied to atmospheric dispersion simulation using the Lagrangian particle dispersion model and was compared with the most popular turbulence closure model in the field of atmospheric simulation, the Mellor-Yamada (MY) model. KEASM has been rarely applied to atmospheric simulation, but it includes the pressure redistribution effect of buoyancy due to heat and momentum fluxes. On the other hand, such effect is excluded from MY model. In the simulation study, the difference in the two turbulence models was reflected to both the turbulent velocity and the Lagrangian time scale. There was little difference in the vertical diffusion coefficient $\sigma$$_{z}$. However, the horizontal diffusion coefficient or calculated by KEASM was larger than that by MY model, coincided with the Pasquill-Gifford (PG) chart. The applicability of KEASM to atmospheric simulations was demonstrated by the simulations.s.

• 한국태양에너지학회:학술대회논문집
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• 2009.11a
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• pp.342-349
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• 2009

The purpose of this study is to estimate efficiently an odor dispersion from waste treatment facility for a crematory and a neighborhood facility, then propose planning, a location of an opening or the arrangement of the trees. Hence, offer a comfortable environment for a resident. For this, first the research data about estimating odor dispersion from waste treatment facility and odor are analyzed, then research an ingredient, characteristic, a direct effect for human and a method of measurement. Second, with on-site survey, check odorimetry and the source of odor dispersion, then apply this to the boundary condition of CFD simulation. Third, analyse by the hour for the 2008 standard weather data of Cheon-an, then apply summer data that odor dispersion is active, winter data relatively slow and an annual mean velocity and wind to the simulation. Even if a crematory and neighborhood facility located on south and north from waste treatment facility are at the low rate, the south and north wind will be applied to the simulation. Fourth, with CFD simulation result, predict an odor dispersion, then propose a solution which is considered an odor dispersion, a location of an opening and the arrangement of the trees. Consequently, this study will have an effect on an environment of a resident.

• Proceedings of the KSME Conference
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• 2001.06e
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• pp.94-99
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• 2001

The numerical simulation of the particle dispersion in the vortical flows provides insight into the mechanism of particle-fluid interaction. The simulation results show that the mixing layers are characterized by the large-scale vortical structures undergoing pairing process. The particle dispersion is strongly influenced by the large-scale structures and the particle sizes. The analysis shows that the mixing layers grows like a step-function.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.39-44
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• 2008

Stress wave propagation plays an important role in many engineering problems for reducing industrial noise and vibrations. In this paper, the dispersion-corrected finite element model is proposed for reducing the dispersion error in simulation of stress wave propagation. At eliminating the numerical dispersion error arising from the numerical simulation of stress wave propagation, numerical dispersion characteristics of the wave equation based finite element model are analyzed and some dispersion control scheme are proposed. The validity of the dispersion correction techniques is demonstrated by comparing the numerical solutions obtained using the present techniques.

• 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.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.125-135
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• 2004

This paper describes the calculation technique for guided wave propagation with a semi-analytical finite element method (SAFEM) and shows some results of numerical calculation and guided wave simulation for plates, pipes and railway rails. The SAFEM calculation gives dispersion curves and wave structures for bar-like structures. Dispersion curve software for a pipe is introduced, and also dispersion corves for a rail are given and experimentally verified. The mode conversions in a plate with a defect and in a pipe with an elbow or a defect are shown as examples of our guided wave simulations.

• Journal of Advanced Navigation Technology
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• v.17 no.2
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• pp.208-217
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• 2013

The optimal residual dispersion per span (RDPS) slope is induced through the analyses of the compensation characteristics of the wavelength division multiplexed (WDM) channels depending on RDPS slope in the optical links with a dispersion management (DM) and an optical phase conjugation. The simulation results show that the effective launch power of WDM is more increased and the performance difference between the channels is more decreased as RDPS slope is more increased. The simulation results also show that the effective net residual dispersion (NRD) range is more increased as RDPS slope is more increased, and consequently, it is more advantageous to use the large RDPS slope for implementing the flexible optical links.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.6
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• pp.767-777
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• 1999

In the coastal region air flow changes due to the abrupt change of surface temperature between land and sea. So a numerical simulation for atmospheric flow fields must be considered the correct fields of sea surface temperature(SST). In this study, we used variables such as latent heat flux, sensible heat flux, short and long wave radiation of ocean and atmosphere which exchanged across the sea surface between atmosphere and ocean model. We found that this consideration simulated the more precise SST fields by comparing with those of the observated results. Simulated horizontal SST differences in season were 2.5~4$^{\circ}C$. Therefore we simulated the more precise atmospheric flow fields and the movement and dispersion of the pollutants with the Lagrangian particle dispersion model. In the daytime dispersion pattern of the pollutants emitted from ship sources moved toward inland, in the night time moved toward sea by land/sea breeze criculation. But air pollutants dispersion can be affected by inland topography, especially Yangsan and coastal area because of nocturnal wind speed decrease.

• Current Optics and Photonics
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• v.7 no.4
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• pp.443-448
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• 2023

The ±1-order Kelly sidebands with dispersion-dependent spacing of mode-locking fiber lasers are investigated for frequency-tunable terahertz signal generation. The principle of dispersion dependence of Kelly sidebands is analyzed. A new method, which is a dispersion-management mechanism introduced into the fiber-laser cavity, is proposed to generate Kelly sidebands with widely tunable wavelength spacing. A spacing tuning range of up to 28.46 nm of the ±1-order Kelly sidebands is obtained in simulation. Using the data of the optical spectrum with dispersion-dependent Kelly sidebands, the frequency spectrum of generated terahertz signals is calculated. Consequently, the signal frequency can be changed from 0.09 to 2.27 THz.

• Journal of information and communication convergence engineering
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• v.20 no.4
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• pp.235-241
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• 2022

A dispersion map was proposed to improve the compensation effect of a distorted WDM (wavelength division multiplexed) channel in a dispersion-managed link coupled with optical phase conjugation. The dispersion map is an origin-symmetric structure around the optical phase conjugator in the middle of the transmission path. In addition, the dispersion map has a form in which a constant dispersion accumulation pattern is repeated regularly. Through simulation, we confirmed that the application of the origin-symmetric dispersion map with a repetitively shaped configuration was more effective in compensating for the distorted WDM channel than in the dispersion-managed link with a conventional dispersion map. In addition, we confirmed that the compensation effect could be increased when the cumulative dispersion distribution of the origin-symmetric distribution map had a positive value in the first half section and a negative value in the second half section. Further, we observed that as the number of repeated dispersion accumulation patterns increased, the residual dispersion per span should also be increased.