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Nakayama, Hiromasa; Takemi, Tetsuya*; Nagai, Haruyasu
Advances in Science & Research (Internet), 12(1), p.127 - 133, 2015/00
Times Cited Count：8 Percentile：92.53(Multidisciplinary Sciences)One of the important issues to be solved to couple LES and MM models is to impose time-dependent turbulent inflow data for LESs from the MM model outputs, because the MM models are not able to reproduce high-frequency turbulent fluctuations appropriate to drive LES models. In this study, we apply the recycling technique to couple the CFD and MM models. We conduct an LES of turbulent winds during the Fukushima Daiichi Nuclear Power Plant accident and report the usefulness of our approach by comparing the simulated results with the observations.
Nakayama, Hiromasa; Takemi, Tetsuya*; Nagai, Haruyasu
Advances in Science & Research (Internet), 11, p.75 - 81, 2014/07
Times Cited Count：9 Percentile：97.6(Multidisciplinary Sciences)We have developed a local-scale high-resolution atmospheric dispersion model using Large-Eddy Simulation and tried to introduce it into SPEEDI-MP. In this study, our objectives are to first create a numerical model for LES on atmospheric dispersion in spatially-developing stable and unstable boundary layer flows which and compare to the existing wind tunnel experimental data. Based on the comparison, we discuss the basic performance of the LES model.
Nakayama, Hiromasa; Jurcakova, K.*; Nagai, Haruyasu
Advances in Science & Research (Internet), 10, p.33 - 41, 2013/02
Times Cited Count：11 Percentile：98.37(Multidisciplinary Sciences)There is a potential problem that hazardous and flammable materials are accidentally or intentionally released within urban areas. Our objective is to compare our LES results for distribution patterns of mean and fluctuating concentrations in various actual urban areas with the existing LES and experimental results for those in regularly arrayed obstacles, and investigate the influence of actual urban surface geometries on the characteristics of mean and fluctuating concentrations.
Nakayama, Hiromasa; Jurcakova, K.*; Nagai, Haruyasu
Advances in Science & Research (Internet), 6, p.79 - 86, 2011/04
Times Cited Count：0 Percentile：1.11(Multidisciplinary Sciences)In this study, the cubic building arrays with roughness density of 0.16, 0.25 and 0.33 are set up. These surface geometries consist of 20
6, 257 and 289 arrays in streamwise and spanwise directions, respectively. Three cases of plume source located at the ground surface behind the building in the 6th, 7th and 8th row of the building array are tested. As a result, we can capture the dispersion process of a plume and the spatial distribution of mean and fluctuating concentrations depending on roughness density.
Nakayama, Hiromasa; Nagai, Haruyasu
Advances in Science & Research (Internet), 4, p.71 - 76, 2010/05
The dispersion analysis of airborne contaminant including radioactive substances from industrial or nuclear facilities is the important issue for maintenance of air quality or safety assessment. Many studies on the plume dispersion behavior in the simulated atmospheric boundary layer flow over flat plain have been conducted mainly by wind tunnel experiments. However, many nuclear power plants are located at complex coastal terrains in Japan. In this case, topographical effects on the turbulent flow and plume dispersion should be investigated. Therefore, we perform Large-Eddy Simulations (LES) on turbulent flows and plume dispersions. As the first step of this study, we try it for a 2-dimensional hill flow and investigate the characteristics of mean and fluctuation concentrations.
