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2 results on '"Wind tunnel and CFD"'

1. Aerodynamic effects of trees on pollutant concentration in street canyons

Author

Buccolieri, Riccardo, Gromke, Christof, Di Sabatino, Silvana, and Ruck, Bodo

Subjects
*PLANTS & the environment, *AERODYNAMICS, *TREE planting, *URBAN pollution, *CANYONS, *PLANT morphology, *COMPUTATIONAL fluid dynamics, *POROSITY, *CROWNS (Botany), *SCIENTIFIC experimentation
Abstract

Abstract: This paper deals with aerodynamic effects of avenue-like tree planting on flow and traffic-originated pollutant dispersion in urban street canyons by means of wind tunnel experiments and numerical simulations. Several parameters affecting pedestrian level concentration are investigated, namely plant morphology, positioning and arrangement. We extend our previous work in this novel aspect of research to new configurations which comprise tree planting of different crown porosity and stand density, planted in two rows within a canyon of street width to building height ratio W/H =2 with perpendicular approaching wind. Sulfur hexafluoride was used as tracer gas to model the traffic emissions. Complementary to wind tunnel experiments, 3D numerical simulations were performed with the Computational Fluid Dynamics (CFD) code FLUENT™ using a Reynolds Stress turbulence closure for flow and the advection–diffusion method for concentration calculations. In the presence of trees, both measurements and simulations showed considerable larger pollutant concentrations near the leeward wall and slightly lower concentrations near the windward wall in comparison with the tree-less case. Tree stand density and crown porosity were found to be of minor importance in affecting pollutant concentration. On the other hand, the analysis indicated that W/H is a more crucial parameter. The larger the value of W/H the smaller is the effect of trees on pedestrian level concentration regardless of tree morphology and arrangement. A preliminary analysis of approaching flow velocities showed that at low wind speed the effect of trees on concentrations is worst than at higher speed. The investigations carried out in this work allowed us to set up an appropriate CFD modelling methodology for the study of the aerodynamic effects of tree planting in street canyons. The results obtained can be used by city planners for the design of tree planting in the urban environment with regard to air quality issues. [Copyright &y& Elsevier]

Published
2009
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2. Aerodynamic effects of trees on pollutant concentration in street canyons

Author

Silvana Di Sabatino, CB Christof Gromke, Riccardo Buccolieri, Bodo Ruck, Buccolieri, Riccardo, Gromke, C., Di Sabatino, S., Ruck, B., Buccolieri, R., DI SABATINO, Silvana, Buccolieri R., Gromke C., Di Sabatino S., Ruck B., and Building Physics

Subjects
Environmental Engineering, Wind, Reynolds stress, Computational fluid dynamics, Atmospheric sciences, Wind speed, Trees, Crown porosity, Air Pollution, Environmental Chemistry, Tree planting, City Planning, Waste Management and Disposal, Vehicle Emissions, Wind tunnel, Hydrology, Air Pollutants, Geography, Turbulence, business.industry, Traffic pollutant concentration, Aerodynamics, Atmospheric dispersion modeling, Pollution, SDG 11 – Duurzame steden en gemeenschappen, SDG 11 - Sustainable Cities and Communities, Crown porosity, Street canyon, Traffic pollutant concentration, Tree planting, Wind tunnel and CFD, Street canyon, Kinetics, Wind tunnel and CFD, Tree stand, Models, Chemical, business
Abstract

This paper deals with aerodynamic effects of avenue-like tree planting on flow and traffic-originated pollutant dispersion in urban street canyons by means of wind tunnel experiments and numerical simulations. Several parameters affecting pedestrian level concentration are investigated, namely plant morphology, positioning and arrangement. We extend our previous work in this novel aspect of research to new configurations which comprise tree planting of different crown porosity and stand density, planted in two rows within a canyon of street width to building height ratio W/H = 2 with perpendicular approaching wind. Sulfur hexafluoride was used as tracer gas to model the traffic emissions. Complementary to wind tunnel experiments, 3D numerical simulations were performed with the Computational Fluid Dynamics (CFD) code FLUENT (TM) using a Reynolds Stress turbulence closure for flow and the advection-diffusion method for concentration calculations. In the presence of trees, both measurements and simulations showed considerable larger pollutant concentrations near the leeward wall and slightly lower concentrations near the windward wall in comparison with the tree-less case. Tree stand density and crown porosity were found to be of minor importance in affecting pollutant concentration. On the other hand, the analysis indicated that W/H is a more crucial parameter. The larger the value of W/H the smaller is the effect of trees on pedestrian level concentration regardless of tree morphology and arrangement. A preliminary analysis of approaching flow velocities showed that at low wind speed the effect of trees on concentrations is worst than at higher speed. The investigations carried out in this work allowed us to set up an appropriate CFD modelling methodology for the study of the aerodynamic effects of tree planting in street canyons. The results obtained can be used by city planners for the design of tree planting in the urban environment with regard to air quality issues.

Published
2009

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