Numerical simulation of pollutant dispersion in street canyons: Geometric and thermal effects

Abstract Numerical investigations on pollutant dispersion in street canyons with emission sources located near the ground level are performed in the present work. Pollutant dispersion problems in urban areas are usually studied considering the street canyon model, which consists of long streets laterally confined by buildings. Significant changes can be observed in wind flow patterns and pollutant concentration fields when thermal and geometric effects are considered. Thus, the objective of this study is to investigate numerically the wind flow and pollutant dispersion for the following cases: (a) a two-dimensional street canyon model considering three different aspect ratios and four different wall heating configurations; (b) a flow domain with two immersed buildings arranged in two distinct configurations; (c) a three-dimensional urban area model composed of a building set and street intersections. Expected flow structures were obtained inside the canyon when different aspect ratios and wall heating configurations were considered. Flow phenomena such as separation/reattachment were observed when two-buildings models were analyzed. Finally, three-dimensional flow structures, with some characteristic that are not observed in two-dimensional models, affecting the pollutant removal, were simulated in the last case, highlighting the relevance of model dimensionality. The wind flow and pollutant dispersion are investigated using a numerical model based on the finite element formulation utilized by some of the authors of this work, which is extended here to deal with problems of heat and mass transport in the urban micro-scale. Turbulence is reproduced using Large Eddy Simulation (LES) and thermal effects on the momentum equations are considered as a buoyancy force, according to Boussinesq approximation.

[1]  Jong-Jin Baik.  Flow and Dispersion in Street Canyons , 2012 .

[2]  Zhen Huang,et al.  The impact of solar radiation and street layout on pollutant dispersion in street canyon , 2005 .

[3]  Yoshihide Tominaga,et al.  CFD modeling of pollution dispersion in a street canyon: Comparison between LES and RANS , 2011 .

[4]  Mohamed F. Yassin,et al.  Impact of street intersections on air quality in an urban environment , 2008 .

[5]  Sang Jin Jeong,et al.  Application of the k–ε turbulence model to the high Reynolds number skimming flow field of an urban street canyon , 2002 .

[6]  Louis Lazure,et al.  Contamination of Fresh Air Intakes Due to Downwash from a Rooftop Structure , 2009, Journal of the Air & Waste Management Association.

[7]  Bodhisatta Hajra.  RETRACTED ARTICLE: Recent studies in CFD modelling of pollutant dispersion in street canyons , 2015 .

[8]  Y. Tominaga,et al.  Numerical simulation of dispersion around an isolated cubic building: Model evaluation of RANS and LES , 2010 .

[9]  Pietro Salizzoni,et al.  Flow and dispersion in street intersections , 2009 .

[10]  A. Chan,et al.  Strategic guidelines for street canyon geometry to achieve sustainable street air quality—part II: multiple canopies and canyons , 2003 .

[11]  Armando Miguel Awruch,et al.  Aerodynamic and aeroelastic analyses on the CAARC standard tall building model using numerical simulation , 2009 .

[12]  P. Moin,et al.  A dynamic subgrid‐scale eddy viscosity model , 1990 .

[13]  Riccardo Buccolieri,et al.  Dispersion study in a street canyon with tree planting by means of wind tunnel and numerical investigations – Evaluation of CFD data with experimental data , 2008 .

[14]  Theodore Stathopoulos,et al.  The effect of upstream buildings on near-field pollutant dispersion in the built environment , 2011 .

[15]  Dennis Y.C. Leung,et al.  Characteristics of air exchange in a street canyon with ground heating , 2006 .

[16]  Chun-Ho Liu,et al.  Large-eddy simulation of turbulent transport in urban street canyons in different thermal stabilities , 2010 .

[17]  Jong-Jin Baik,et al.  A Numerical Study of Flow and Pollutant Dispersion Characteristics in Urban Street Canyons , 1999 .

[18]  J. Smagorinsky,et al.  GENERAL CIRCULATION EXPERIMENTS WITH THE PRIMITIVE EQUATIONS , 1963 .

[19]  Bodo Ruck,et al.  Pollutant Concentrations in Street Canyons of Different Aspect Ratio with Avenues of Trees for Various Wind Directions , 2012, Boundary-Layer Meteorology.

[20]  Helen ApSimon,et al.  A numerical study of atmospheric pollutant dispersion in different two-dimensional street canyon configurations , 2003 .

[21]  Sandrine Anquetin,et al.  Pollutant dispersion and thermal effects in urban street canyons , 1996 .

[22]  Shaodong Xie,et al.  Spatial distribution of traffic-related pollutant concentrations in street canyons , 2003 .

[23]  Dennis Y.C. Leung,et al.  Large-Eddy Simulation of Flow and Pollutant Transport in Street Canyons of Different Building-Height-to-Street-Width Ratios , 2004 .

[24]  Andy Chan,et al.  Numerical simulation of dispersion in urban street canyons with avenue-like tree plantings: Comparis , 2011 .

[25]  Mukesh Khare,et al.  Wind tunnel simulation studies on dispersion at urban street canyons and intersections—a review , 2005 .

[26]  Kit Ming Lam,et al.  Recent progress in CFD modelling of wind field and pollutant transport in street canyons , 2006 .

[27]  A. Y. Cheng,et al.  Large-eddy simulation of pollution dispersion in an urban street canyon—Part I: comparison with field data , 2002 .

[28]  K. Pericleous,et al.  Modelling air quality in street canyons : a review , 2003 .

[29]  H. Park,et al.  PARAMETERIZATION OF THE POLLUTANT TRANSPORT AND DISPERSION IN URBAN STREET CANYONS , 1994 .

[30]  T. Stathopoulos,et al.  Computer simulation of wind environmental conditions around buildings , 1996 .

[31]  Michael Schatzmann,et al.  Wind tunnel measurements of concentration fluctuations in an urban street canyon , 1999 .

[32]  Bodo Ruck,et al.  Influence of trees on the dispersion of pollutants in an urban street canyon - experimental investigation of the flow and concentration field , 2007 .

[33]  Jong-Jin Baik,et al.  A Numerical Study of Thermal Effects on Flow and Pollutant Dispersion in Urban Street Canyons , 1999 .

[34]  A. G. Marathe,et al.  Computations of laminar and turbulent mixed convection in a driven cavity using pseudo-compressibility approach , 2001 .

[35]  Michael Schatzmann,et al.  Study of line source characteristics for 2-D physical modelling of pollutant dispersion in street canyons , 1996 .

[36]  Bodo Ruck,et al.  On the Impact of Trees on Dispersion Processes of Traffic Emissions in Street Canyons , 2009 .

[37]  W. Hung,et al.  Validation of a two-dimensional pollutant dispersion model in an isolated street canyon , 2002 .

[38]  Dennis Y.C. Leung,et al.  On the prediction of air and pollutant exchange rates in street canyons of different aspect ratios using large-eddy simulation , 2005 .

[39]  D. Lilly,et al.  A proposed modification of the Germano subgrid‐scale closure method , 1992 .

[40]  T. Oke.  Street design and urban canopy layer climate , 1988 .

[41]  U. Ghia,et al.  High-Re solutions for incompressible flow using the Navier-Stokes equations and a multigrid method , 1982 .

[42]  Jong-Jin Baik,et al.  A CFD Model for Simulating Urban Flow and Dispersion , 2003 .