Large-Eddy Simulation of plume dispersion within various actual urban areas

Nakayama, Hiromasa; Jurčáková, Klára; Nagai, Hiroki

doi:10.5194/asr-10-33-2013

Cited by 13 publications

(4 citation statements)

References 19 publications

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“…Many investigations have been devoted to better understanding of flow and pollutant dispersion in urban areas (e.g. Britter and Hanna, 2003;Rotach et al, 2004;Edussuriya et al, 2011;Nakayama et al, 2013;Panagiotou et al, 2013). One of the crucial factors that affect flow and pollutant dispersion in urban areas is buildings.…”

Section: Introductionmentioning

confidence: 99%

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Han

Park

Baik

et al. 2017

Quart J Royal Meteoro Soc

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Understanding turbulent flow and pollutant dispersion in urban areas is one of the important problems in urban meteorology and environmental fluid mechanics. In this study, we examine turbulent flow and pollutant dispersion in a densely built‐up area in Seoul, South Korea, using the parallelized large‐eddy simulation model (PALM). In particular, we focus on vortex streets and associated pollutant dispersion behind high‐rise buildings. The turbulence recycling method is used to produce inflow profiles. Vortices are generated near the high‐rise buildings and propagate downstream forming vortex streets behind the high‐rise buildings. To investigate characteristics of the vortex streets, spectral and correlation analyses are performed. The spectral analysis reveals that vortices have a non‐dimensional vortex shedding frequency of 0.1–0.2, and this periodicity is weakened due to the influence of other buildings. The correlation analysis shows that vortices appear frequently in regions of negative pressure perturbation. The vertical turbulent momentum fluxes induced by ejections and sweeps largely contribute to the total vertical turbulent momentum flux downstream of the high‐rise buildings. Especially, ejections in the wake region are stronger compared to other regions because ejections are induced by vortices near the top of the high‐rise buildings. It is found that pollutant dispersion is interrupted by both low‐rise and high‐rise buildings. Strong updraughts behind the high‐rise buildings transport pollutant upward and increase the mean pollutant concentration at upper levels. Vortices forming the vortex streets play a role in pollutant mixing in such a way that the vortices eject air of high pollutant concentration from the wake region behind the high‐rise buildings and entrain air of low pollutant concentration into the wake region. The mixing by vortices is verified by the correlation between vorticity and pollutant concentration.

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Section: Introductionmentioning

confidence: 99%

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Han

Park

Baik

et al. 2017

Quart J Royal Meteoro Soc

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“…The release location and measuring points are shown in Figure 3. In our previous study, it was shown that the spatial extent of concentration distribution patterns significantly influenced by urban surface geometries is a few hundred meters from a point source (Nakayama et al [27]). By comparing with the experimental data of the high-frequency concentration fluctuations measured in the very short range, we estimate prediction accuracy for the area where individual urban buildings largely influence the formation of plume concentration distributions.…”

Section: Dataset Of the Field Experiments For Estimating Prediction Amentioning

confidence: 99%

Development ofLOcal-scaleHigh-resolution atmosphericDIspersionModel usingLarge-EddySimulation. Part 5: detailed simulation of turbulent flows and plume dispersion in an actual urban area under real meteorological conditions

Nakayama

Takemi

Nagai

2015

Journal of Nuclear Science and Technology

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We have developed a LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation (LOHDIM-LES) to assess the safety at nuclear facilities and to respond to emergency situations resulting from accidental or deliberate releases of radioactive materials (e.g., a terrorist attack in an urban area). In parts 1-4, LESs of turbulent flows and plume dispersion over a flat terrain, around an isolated building, within building arrays with different obstacle densities, and within an actual urban area were performed, which showed the basic performance comparable to wind tunnel experimental technique. In this study, we extend the LOHDIM-LES to turbulent flows and plume dispersion in an actual urban area under real meteorological conditions by coupling with a meso-scale meteorological simulation model. The LES results of wind speed, wind direction, and concentration values are generally reproduced well. It is concluded that our coupling approach between LES and meso-scale meteorological models is effective in detailed simulations of turbulent flows and plume dispersion in urban areas under real meteorological conditions.

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“…According to the building morphological analysis by Kanda et al [13], the horizontal average scale of urban buildings ranges from 14.5 to 19.5 m. In this case, the horizontal grid spacing less than about 1.0 m is required for accurate results. In addition, we have investigated a necessary computational domain size to capture the spatial extent of distribution patterns of plume concentrations influenced by urban surface geometries by LES comparative analysis [14]. It was shown that centerline mean concentration distributions for various urban areas are converging for downwind distances from the point source greater than 1.0 km and concluded that a necessary horizontal domain size of a computational model is at least 1.0 km.…”

Section: Computational Settingsmentioning

confidence: 99%

Development of local-scale high-resolution atmospheric dispersion model using large-eddy simulation. Part 4: turbulent flows and plume dispersion in an actual urban area

Nakayama

Leitl

Harms

et al. 2014

Journal of Nuclear Science and Technology

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We have developed a local-scale high-resolution atmospheric dispersion model using large-eddy simulation (LOHDIM-LES) to assess the safety at nuclear facilities and to respond to emergency situations resulting from accidental or deliberate releases of radioactive materials (e.g., a terrorist attack in an urban area). In Part 1, the unsteady behavior of a plume dispersing over a flat terrain was successfully simulated. In Parts 2 and 3, LESs of turbulent flows and plume dispersion around an isolated building and in building arrays with different obstacle densities were performed, which showed the basic performance comparable to wind tunnel experimental technique. In this study, we apply the LES model to turbulent flows and plume dispersion in an actual urban area. Although some of the turbulence and dispersion characteristics are quantitatively different from the wind tunnel experimental data, the distribution patterns are generally similar to those of the experiments. It is concluded that our LES model simulates reasonably the unsteady behavior of turbulent flows and plume dispersion even for complex heterogeneous urban areas.

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Large-Eddy Simulation of plume dispersion within various actual urban areas

Cited by 13 publications

References 19 publications

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Large‐eddy simulation of vortex streets and pollutant dispersion behind high‐rise buildings

Development ofLOcal-scaleHigh-resolution atmosphericDIspersionModel usingLarge-EddySimulation. Part 5: detailed simulation of turbulent flows and plume dispersion in an actual urban area under real meteorological conditions

Development of local-scale high-resolution atmospheric dispersion model using large-eddy simulation. Part 4: turbulent flows and plume dispersion in an actual urban area

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