89 research outputs found
Large-Eddy Simulation of plume dispersion within various actual urban areas
Plume dispersion of hazardous materials within urban area resulting from
accidental or intentional releases is of great concern to public health.
Many researchers have developed local-scale atmospheric dispersion models
using building-resolving computational fluid dynamics. However, an important
issue is encountered when determining a reasonable domain size of the
computational model in order to capture concentration distribution patterns
influenced by urban surface geometries. In this study, we carried out
Large-Eddy Simulations (LES) of plume dispersion within various urban areas
with a wide range of obstacle density and building height variability. The
difference of centerline mean and r.m.s. concentration distributions among
various complex urban surface geometries becomes small for downwind
distances from the point source greater than 1.0 km. From these results, it
can be concluded that a length of a computational model should be at least
1.0 km from a point source
Large-eddy simulation of plume dispersion within regular arrays of cubic buildings
There is a potential problem that hazardous and flammable materials are
accidentally or intentionally released within populated urban areas. For the
assessment of human health hazard from toxic substances, the existence of
high concentration peaks in a plume should be considered. For the safety
analysis of flammable gas, certain critical threshold levels should be
evaluated. Therefore, in such a situation, not only average levels but also
instantaneous magnitudes of concentration should be accurately predicted. In
this study, we perform Large-Eddy Simulation (LES) of plume dispersion
within regular arrays of cubic buildings with large obstacle densities and
investigate the influence of the building arrangement on the characteristics
of mean and fluctuating concentrations
Neutrally stratified flow modelling over complex terrain at meso-scale: open-cut coal mine study
The objective of this case study was to determine the influence of the coal mine cavity and its vicinity on the main flow field with respect to prevailing wind direction. In order to model the neutrally stratified flow over extremely huge open-cut coal mine Libouš situated at north-west of Czech Republic the laminar flow analogy was applied. The model was scaled down to 1:9000 according to dimensions of wind-tunnel and selected coal mine surroundings. The measurements of longitudinal and lateral velocity components in selected vertical, resp. horizontal planes were performed by LDA. The measured data will be used for validation of CFD simulation and for selections of area of interest at bigger scales where turbulent flow modelling will be performed. The results revealed that not only of cavity shape and deepness but also the surroundings orography has influence on flow pattern, hence on ventilation, within the area of interest
Atmospheric dispersion modelling over complex terrain at small scale
Previous study concerned of qualitative modelling neutrally stratified flow over open-cut coal mine and important surrounding topography at meso-scale (1:9000) revealed an important area for quantitative modelling of atmospheric dispersion at small-scale (1:3300). The selected area includes a necessary part of the coal mine topography with respect to its future expansion and surrounding populated areas. At this small-scale simultaneous measurement of velocity components and concentrations in specified points of vertical and horizontal planes were performed by two-dimensional Laser Doppler Anemometry (LDA) and Fast-Response Flame Ionization Detector (FFID), respectively. The impact of the complex terrain on passive pollutant dispersion with respect to the prevailing wind direction was observed and the prediction of the air quality at populated areas is discussed. The measured data will be used for comparison with another model taking into account the future coal mine transformation. Thus, the impact of coal mine transformation on pollutant dispersion can be observed
Ni-induced stepwise capacity increase in Ni-poor Li-rich cathode materials for high performance lithium ion batteries
Li-rich cathode materials have been considered as promising candidates for high-energy lithium ion batteries (LIBs). In this study, we report a new series of Li-rich materials (Li[Li(1/3-2x/3)Mn(2/3-x/3)N(i)x]O-2 (0.0
Neutrally stratified flow modelling over complex terrain at meso-scale: open-cut coal mine study
Development of local-scale high-resolution atmospheric dispersion model using large-eddy simulation. Part 3: turbulent flow and plume dispersion in building arrays
Nitrogen-Enriched Nanocarbons with a 3-D Continuous Mesopore Structure from Polyacrylonitrile for Supercapacitor Application
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