A simple network approach to modelling dispersion among large groups of obstacles

Hamlyn, D. W.; Hilderman, Trevor; Britter, Rex

doi:10.1016/j.atmosenv.2007.03.047

Cited by 34 publications

(28 citation statements)

References 10 publications

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“…It can be observed that u E is within the range 2.0 to 2.5% of u 3H . Such a result is in good agreement with other CFD-based studies, where u E was estimated from the transfer of scalar tracers, such as heat (Solazzo and Britter 2007), and mass release (Hamlyn et al 2007).…”

Section: Urban Heat Island Effectsupporting

confidence: 83%

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Coupling Mesoscale Modelling with a Simple Urban Model: The Lisbon Case Study

Solazzo

Sabatino

Aquilina

et al. 2010

Boundary-Layer Meteorol

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The ongoing trend of urbanisation worldwide is leading to a growing requirement for detailed flow and transport parameterisations to be included within numerical weather prediction (NWP) models. Such models often employ a simple roughness parameterisation for urban areas, which is not particularly accurate in predicting or assessing the flow and dispersion at street scale. Moreover, this kind of parameterisation offers too poor a representation of the mechanical and thermal forcing exerted by urban areas on the larger scale flow. At present, high computational costs and long simulation running times are among the constraints for the implementation of more detailed urban sub-models within NWP models. To overcome such limitations, a downscaling procedure from the atmospheric flow at the synoptic scale to the neighbourhood scale and below, is presented in this study. This is achieved by means of a simple urban model based on a parameterised formulation of the drag exerted by the building on the airflow. Application of the urban model for estimating spatially-averaged mean wind speed and the urban heat island over a selected neighbourhood area in Lisbon, Portugal, is presented. The results show the capability of the urban model to provide more accurate mean wind and temperature profiles. Moreover, the urban model has the advantage of being cost effective, as it requires small computational resources, and thus 123 442 E. Solazzo et al. is suitable to be adopted in an operational context. The model is simple enough to be also used to assess how the resolving of urban surface processes may affect those at the larger scales.

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Section: Urban Heat Island Effectsupporting

confidence: 83%

“…It is important to notice that d and z 0 have meaning only if Eq. 1 is applied over a statistically homogeneous fetch (Hamlyn et al 2007). For application over urban areas, d and z 0 need to be defined based on the characteristics of the underlying roughness (Kastner-Klein and Rotach 2004).…”

Section: Horizontal and Vertical Scalesmentioning

confidence: 99%

Coupling Mesoscale Modelling with a Simple Urban Model: The Lisbon Case Study

Solazzo

Sabatino

Aquilina

et al. 2010

Boundary-Layer Meteorol

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“…Recently, research has been undertaken to study dispersion and ventilation in actual or generic building block arrays with tree-free streets (e.g. Boppana et al, 2010;Borrego et al, 2006Borrego et al, , 2003Buccolieri et al, 2010;Carpentieri et al, 2012;Di Sabatino et al, 2007;Garbero et al, 2010;Hamlyn et al, 2007;Hang et al, 2011;Panagiotou et al, 2013;Pascheke et al, 2008;Princevac et al, 2010;Ramponi et al, 2014;Soulhac et al, 2012Soulhac et al, , 2011Soulhac et al, , 2003Xie and Castro, 2009). It is evident that such study areas provide a more relevant description of the effects of trees on flow and pollutant dispersion than those with isolated street canyons or intersections.…”

Section: Introductionmentioning

confidence: 99%

Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level

Gromke

Blocken

2015

Environmental Pollution

139

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a b s t r a c tFlow and dispersion of traffic-emitted pollutants were studied in a generic urban neighborhood for various avenue-tree layouts by employing 3D steady RANS simulations with the realizable k-ε turbulence model. In comparison to the tree-free situation quantitative and qualitative changes with flow reversal in the wind field were observed. Low to moderate increases (<13.2%) in the neighborhood-averaged pollutant concentration were found at pedestrian level. An approximately 1% increase in the neighborhood-averaged concentration was obtained with each percent of the street canyon volumes being occupied by vegetation for occupation fractions between 4 and 14%. The overall pattern of concentration changes relative to the tree-free situation was similar for all avenue-tree layouts. However, pronounced locally restricted decreases or increases in concentration (À87 to þ1378%) occurred. The results indicate the necessity to account for existing or planned avenue-trees in neighborhood scale dispersion studies. Their consideration is prerequisite for reliable urban air quality assessment.

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“…With the development of computer hardware and algorithms, the computational fluid dynamics (CFD) technique has become a popular and powerful tool in urban street-canyon research due to its efficiency and relatively low cost (Li et al 2006). Of the many CFD models, Reynolds-averaged Navier-Stokes equations (RANS) models have provided many insights into the characteristics of the airflow and dispersion in urban street canyons (Cheng et al 2007;Coceal et al 2007;Hamlyn et al 2007;Blocken et al 2008;Reynolds and Castro 2008;Buccolieri et al 2010). Recently, large-eddy simulation (LES) has become popular in street-canyon studies, mainly owing to its power of handling transient and unsteady turbulent processes (e.g., Liu and Barth 2002;Cui et al 2004;Liu et al 2004Liu et al , 2005Cai et al 2008;Letzel et al 2008;Li et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Flow and Pollutant Transport in Urban Street Canyons of Different Aspect Ratios with Ground Heating: Large-Eddy Simulation

Britter

Norford

et al. 2011

Boundary-Layer Meteorol

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A validated large-eddy simulation model was employed to study the effect of the aspect ratio and ground heating on the flow and pollutant dispersion in urban street canyons. Three ground-heating intensities (neutral, weak and strong) were imposed in street canyons of aspect ratio 1, 2, and 0.5. The detailed patterns of flow, turbulence, temperature and pollutant transport were analyzed and compared. Significant changes of flow and scalar patterns were caused by ground heating in the street canyon of aspect ratio 2 and 0.5, while only the street canyon of aspect ratio 0.5 showed a change in flow regime (from wake interference flow to skimming flow). The street canyon of aspect ratio 1 does not show any significant change in the flow field. Ground heating generated strong mixing of heat and pollutant; the normalized temperature inside street canyons was approximately spatially uniform and somewhat insensitive to the aspect ratio and heating intensity. This study helps elucidate the combined effects of urban geometry and thermal stratification on the urban canyon flow and pollutant dispersion.

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A simple network approach to modelling dispersion among large groups of obstacles

Cited by 34 publications

References 10 publications

Coupling Mesoscale Modelling with a Simple Urban Model: The Lisbon Case Study

Coupling Mesoscale Modelling with a Simple Urban Model: The Lisbon Case Study

Influence of avenue-trees on air quality at the urban neighborhood scale. Part II: Traffic pollutant concentrations at pedestrian level

Flow and Pollutant Transport in Urban Street Canyons of Different Aspect Ratios with Ground Heating: Large-Eddy Simulation

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