Effect of stack height and exhaust velocity on pollutant dispersion in the wake of a building

The dispersion of pollutants exhausted from a building roof stack located in the wake of a tower is investigated by means of the realizable k–ɛ turbulence model. Variations in stack height and pollutant exhaust velocity are considered to assess their influence on the distribution of pollutant concentrations in the neighbourhood of the emitting building. In order to determine optimum locations for fresh-air intakes, the worst case is considered, namely when the wind originates directly upstream of the tower and places the emitting building in its wake. Special attention is given to the evolution of the plume and distribution of pollutant concentrations on the roof and windward wall of the emitting building, as well as on the leeward wall of the upwind tower. Simulation results are compared to wind tunnel experiments conducted in a boundary layer wind tunnel. For this particular configuration, the paper shows that increasing the stack height has an effect similar to that obtained by increasing the momentum ratio, but with some differences, depending upon which wall of the two buildings is considered. On the emitting building, the leeward wall has the lowest concentration values for all stack heights and momentum ratios considered; thus this is the best location for fresh-air intakes. However, for the tower, fresh-air intakes should not be located on the leeward wall due to high pollutant concentrations. The results show completely different pollutant dispersion patterns from those for an isolated building. This highlights the importance of accounting for structures that lie in close proximity to the emitting building.

[1]  Bert Blocken,et al.  CFD simulation of near-field pollutant dispersion on a high-resolution grid : a case study by LES and RANS for a building group in downtown Montreal , 2011 .

[2]  Xiaoguang Wang.  Numerical simulation of wind-induced dispersion of emissions from rooftop stacks , 2006 .

[3]  T. Stathopoulos,et al.  CFD simulation of the atmospheric boundary layer: wall function problems , 2007 .

[4]  Ilias Mavroidis,et al.  Numerical simulation of flow and dispersion around an isolated cubical building: The effect of the atmospheric stratification , 2009 .

[5]  D. Grawe,et al.  BEST PRACTICE GUIDELINE FOR THE CFD SIMULATION OF FLOWS IN THE URBAN ENVIRONMENT , 2007 .

[6]  Theodore Stathopoulos,et al.  Numerical evaluation of pollutant dispersion in the built environment: comparisons between models and experiments , 2008 .

[7]  Theodore Stathopoulos,et al.  Near-field pollutant dispersion in the built environment by CFD and wind tunnel simulations , 2011 .

[8]  Alan Robins,et al.  Effects of Reynolds number on stack plume trajectories simulated with small scale models in a wind tunnel , 2009 .

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

[10]  T. Stathopoulos,et al.  On the use of CFD for modelling air pollutant dispersion around buildings , 2008 .

[11]  Yoshihiko Hayashi,et al.  Numerical simulation of velocity field and diffusion field in an urban area , 1990 .

[12]  Jörg Franke,et al.  The COST 732 Best Practice Guideline for CFD simulation of flows in the urban environment: a summary , 2011 .

[13]  Theodore Stathopoulos,et al.  Pedestrian Level Winds and Outdoor Human Comfort , 2006 .

[14]  Bruce R. White,et al.  Wind-Tunnel studies of variable stack heights for a low-profile building , 1990 .

[15]  Yoshihide Tominaga,et al.  Numerical simulation of dispersion around an isolated cubic building: Comparison of various types of k–ɛ models , 2009 .

[16]  Refrigerating.  ASHRAE handbook. Heating, ventilating, and air-conditioning applications , 1991 .

[17]  Theodore Stathopoulos,et al.  Application of computational fluid dynamics in building performance simulation for the outdoor environment: an overview , 2011 .

[18]  S. Onbaşıoǧlu,et al.  On the simulation of the plume from stacks of buildings , 2001 .

[19]  Kemal Hanjalic,et al.  Vortex structure and heat transfer in turbulent flow over a wall-mounted matrix of cubes , 1999 .

[20]  Theodore Stathopoulos,et al.  Influence of turbulence models on pollutant dispersion studies around a building complex , 2010 .

[21]  U. Ghia,et al.  Procedure for Estimation and Reporting of Uncertainty Due to Discretization in CFD Applications , 2007 .

[22]  Theodore Stathopoulos,et al.  Numerical simulation of pollutant dispersion around a building complex , 2010 .

[23]  Refrigerating.  ASHRAE handbook of fundamentals , 1967 .

[24]  Michael Schatzmann,et al.  Wind-tunnel and numerical modeling of flow and dispersion about several building shapes , 1999 .

[25]  Ryozo Ooka,et al.  Field and wind-tunnel study of pollutant dispersion in a built-up area under various meteorological conditions , 2005 .

[26]  Catherine Gorle,et al.  Stack gas dispersion measurements with large-scale PIV, aspiration probes and light scattering techniques and comparison with CFD , 2009 .

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