Side ratio effects on flow and pollutant dispersion around an isolated high-rise building in a turbulent boundary layer

Jiang, Guoyi; Yoshie, Ryuichiro

doi:10.1016/j.buildenv.2020.107078

Cited by 23 publications

(17 citation statements)

References 37 publications

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“…In addition, the recirculation areas caused by the two buildings overlap to form a complete curve b. Therefore, the overall streamline distribution is similar to that of the isolated building terrain [28]. The comparison of the results in Figure 5a,b shows that the differences are concentrated in the interior and both ends of the street canyons.…”

Section: Effects Of Street Canyon Aspect Ratio On Pollutant Dispersionmentioning

confidence: 71%

Study of Heavy Gas Pollutants’ Dispersion in Street Canyon Terrain

et al. 2021

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This study focused on heavy gas dispersion under the terrain conditions of street canyons. The effects of street aspect ratio and height ratio were investigated, and the influence of environmental wind speed in the typical ideal street canyon terrain was explored. The results indicated that the surrounding flow field distributions in street terrains were dominated by higher buildings. In addition, when the building height was held constant, the flow field was affected by the joint influence of the two isolated buildings. The interception effect of the street canyon on upstream pollutants declined with the decrease in the street canyon’s aspect ratio. In addition, when the height ratios were different, a large quantity of upstream pollutants accumulated on the windward side of higher buildings. The relative concentration per unit area inside the canyon was affected by the air circulation inside and outside the canyon and the size of the dispersion space. The increase in the environmental wind speed promotes the entry of pollutants into the street while aggravating the overall dispersion of the pollutants. Therefore, the emergence of the most unsafe wind speeds caused most of the pollutants to gather in the street canyons.

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Section: Effects Of Street Canyon Aspect Ratio On Pollutant Dispersionmentioning

confidence: 71%

Study of Heavy Gas Pollutants’ Dispersion in Street Canyon Terrain

et al. 2021

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“…Studies investigating such effects are either based on experimental observations, physical models, numerical simulations, or combined approaches of varying complexity. To mention a few examples, studies have been carried out for isolated buildings (Higson et al, 1996;Foroutan et al, 2018;Jiang and Yoshie, 2020), arrays of mounted obstacles (Coceal et al, 2014;Fuka et al, 2018;Goulart et al, 2019), and urban canopies close to reality (Auguste et al, 2020;Hertwig et al, 2021). While for single buildings, the number of variables reduces to the shape and orientation of the obstacle relative to the approaching flow, the relative position of obstacles to each other (aligned vs. staggered) is at least as important for building arrays.…”

Section: Introductionmentioning

confidence: 99%

On the application and grid-size sensitivity of the urban dispersion model CAIRDIO v2.0 under real city weather conditions

et al. 2022

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Abstract. There is a gap between the need for city-wide air-quality simulations considering the intra-urban variability and mircoscale dispersion features and the computational capacities that conventional urban microscale models require. This gap can be bridged by targeting model applications on the gray zone situated between the mesoscale and large-eddy scale. The urban dispersion model CAIRDIO is a new contribution to the class of computational-fluid dynamics models operating in this scale range. It uses a diffuse-obstacle boundary method to represent buildings as physical obstacles at gray-zone resolutions in the order of tens of meters. The main objective of this approach is to find an acceptable compromise between computationally inexpensive grid sizes for spatially comprehensive applications and the required accuracy in the description of building and boundary-layer effects. In this paper, CAIRDIO is applied on the simulation of black carbon and particulate matter dispersion for an entire mid-size city using a uniform horizontal grid spacing of 40 m. For model evaluation, measurements from five operational air monitoring stations representative for the urban background and high-traffic roads are used. The comparison also includes the mesoscale host simulation, which provides the boundary conditions. The measurements show a dominant influence of the mixing layer evolution at background sites, and therefore both the mesoscale and large-eddy simulation (LES) results are in good agreement with the observed air pollution levels. In contrast, at the high-traffic sites the proximity to emissions and the interactions with the building environment lead to a significantly amplified diurnal variability in pollutant concentrations. These urban road conditions can only be reasonably well represented by CAIRDIO while the meosocale simulation indiscriminately reproduces a typical urban-background profile, resulting in a large positive model bias. Remaining model discrepancies are further addressed by a grid-spacing sensitivity study using offline-nested refined domains. The results show that modeled peak concentrations within street canyons can be further improved by decreasing the horizontal grid spacing down to 10 m, but not beyond. Obviously, the default grid spacing of 40 m is too coarse to represent the specific environment within narrow street canyons. The accuracy gains from the grid refinements are still only modest compared to the remaining model error, which to a large extent can be attributed to uncertainties in the emissions. Finally, the study shows that the proposed gray-scale modeling is a promising downscaling approach for urban air-quality applications. The results, however, also show that aspects other than the actual resolution of flow patterns and numerical effects can determine the simulations at the urban microscale.

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“…Attempts have been made in recent years to perfect the numerical modeling of atmospheric dispersion flows in simplified geometries (e.g., isolated buildings, the street canyon between two buildings, flat terrain, etc.) [20][21][22][23][24]. However, many studies have pointed out the unique and considerable impacts of the neighboring buildings and urban morphologies on the wind and dispersion fields and emphasized the importance of these types of investigations [18,25,26].…”

Section: Introductionmentioning

confidence: 99%

Performance Evaluation of the RANS Models in Predicting the Pollutant Concentration Field within a Compact Urban Setting: Effects of the Source Location and Turbulent Schmidt Number

2022

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Computational Fluid Dynamics (CFD) is used to accurately model and predict the dispersion of a passive scalar in the atmospheric wind flow field within an urban setting. The Mock Urban Setting Tests (MUST) experiment was recreated in this work to test and evaluate various modeling settings and to form a framework for reliable representation of dispersion flow in compact urban geometries. Four case studies with distinct source locations and configurations are modeled using Reynolds-Averaged Navier–Stokes (RANS) equations with ANSYS CFX. The performance of three widely suggested closure models of standard k−ε, RNG k−ε, and SST k−ω is assessed by calculating and interpreting the statistical performance metrics with a specific emphasis on the effects of the source locations. This work demonstrates that the overprediction of the turbulent kinetic energy by the standard k−ε counteracts the general underpredictions by RANS in geometries with building complexes. As a result, the superiority of the standard k−ε in predicting the scalar concentration field over the two other closures in all four cases is observed, with SST k−ω showing the most discrepancies with the field measurements. Additionally, a sensitivity study is also conducted to find the optimum turbulent Schmidt number (Sct) using two approaches of the constant and locally variable values.

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Side ratio effects on flow and pollutant dispersion around an isolated high-rise building in a turbulent boundary layer

Cited by 23 publications

References 37 publications

Study of Heavy Gas Pollutants’ Dispersion in Street Canyon Terrain

Study of Heavy Gas Pollutants’ Dispersion in Street Canyon Terrain

On the application and grid-size sensitivity of the urban dispersion model CAIRDIO v2.0 under real city weather conditions

Performance Evaluation of the RANS Models in Predicting the Pollutant Concentration Field within a Compact Urban Setting: Effects of the Source Location and Turbulent Schmidt Number

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