Development of Local-Scale High-Resolution Atmospheric Dispersion Model Using Large-Eddy Simulation Part 1: Turbulent Flow and Plume Dispersion over a Flat Terrain

We have developed a local-scale atmospheric dispersion model using large-eddy simulation (LES) to accurately predict the dispersion behavior of radioactive materials for the safety assessment of nuclear facilities and emergency responses against accidental release from nuclear facilities and intentional release by terrorist attack within a populated urban area. In this study, we validate LES basic performance on plume dispersion over a flat terrain within the atmospheric turbulent boundary layer, as a first step. When compared to previous experimental data, we have found that the LES model has successfully generated a spatially-developing turbulent boundary layer flow that has characteristics corresponding to those of atmospheric wind. Furthermore, the dispersion characteristics obtained by LES, such as mean concentrations, variances of concentration fluctuation, peak concentrations, and concentration fluxes, are similar to previous experimental results. Although the current numerical simulation model requires considerable CPU time statistics of concentrations, the LES model can be used as an effective tool for accurately assessing the spatial extent of contaminated areas in detail. We anticipate reducing the computational burden by using an advanced computational method, and, as a practical matter, using the LES model for emergency responses.