Atmosphere (대기)

Korean Meteorological Society (한국기상학회)
권호 표지
DOI QR코드

DOI QR Code

Effects of Trees on Flow and Scalar Dispersion in an Urban Street Canyon

도시 협곡에서 수목이 흐름과 스칼라 물질 확산에 미치는 영향

  • Kang, Geon (Department of Environmental Atmospheric Sciences, Pukyong National University) ;
  • Kim, Jae-Jin (Department of Environmental Atmospheric Sciences, Pukyong National University)
  • 강건 (부경대학교 환경대기과학과) ;
  • 김재진 (부경대학교 환경대기과학과)
  • Received : 2015.09.03
  • Accepted : 2015.12.03
  • Published : 2015.12.31
Download PDF
⟨ Previous Next ⟩

Abstract

In this study, the effects of trees on flow and scalar dispersion in an urban street canyon were investigated using a computational fluid dynamics (CFD) model. For this, we implemented the drag terms of trees to the CFD model, and compared the CFD-simulated results to the wind-tunnel results. For comparison, we considered the same building configuration as the wind-tunnel experiment. The trees were located at the center of street canyon with the aspect ratio (defined as the ratio of the street width to the building height) of 1. First, the flow characteristics were analyzed in the tree-free and high-density tree cases and the results showed that the CFD model reproduced well the flow pattern of the wind-tunnel experiment and reflected the drag effect of trees in the street canyon. Then, the dispersion characteristics of scalar pollutants were investigated for the tree-free, low-density tree and medium-density tree cases. In the tree-free case, the nondimensionalized concentration distribution simulated by the CFD model was quite similar to that in the wind-tunnel experiment in magnitude and pattern. The correlation coefficients between the measured and simulated concentrations are more than 0.9 in all the cases. As the tree density increased, nondimensionalized concentration increased (decreased) near the wall of the upwind (downwind) building, which resulted from the decrease in wind speed case by the drag effect of trees. However, the CFD model underestimated (overestimated) the concentration near the wall of upwind (downwind) building.

Keywords

References

  1. Baik, J.-J., and J.-J. Kim, 1999: A numerical study of flow and pollutant dispersion characteristics in urban street canyons. J. Appl. Meteorol., 38, 1576-1589. https://doi.org/10.1175/1520-0450(1999)038<1576:ANSOFA>2.0.CO;2
  2. Balczo, M., C. Gromke, and B. Ruck, 2009: Numerical modeling of flow and pollutant dispersion in street canyons with tree planting. Meteorol. Z., 18, 197-206. https://doi.org/10.1127/0941-2948/2009/0361
  3. Chang, J. C., and S. R. Hanna, 2004: Air quality model performance evaluation. Meteorol. Atmos. Phys., 87, 167-196.
  4. Gromke, C., R. Buccolieri, S. Di Sabatino, and B. Ruck, 2008: Dispersion study in a street canyon with tree planting by means of wind tunnel and numerical investigations-evaluation of CFD data with experimental data. Atmos. Environ., 42, 8640-8650. https://doi.org/10.1016/j.atmosenv.2008.08.019
  5. Gromke, C., B. Blocken, W. Janssen, B. Merema, T. van Hooff, and H. Timmermans, 2015: CFD analysis of transpirational cooling by vegetation: Case study for specific meteorological conditions during a heat wave in Arnhem, Netherlands. Build. Environ., 83, 11-26. https://doi.org/10.1016/j.buildenv.2014.04.022
  6. Gross, G., 1987: A numerical study of the air flow within and around a single tree. Bound-lay. Meteorol., 40, 311-327. https://doi.org/10.1007/BF00116099
  7. Gross, G., 1993: Numerical simulation of canopy flow. Springer, 167 pp.
  8. Hosker, R. P., 1984: Flow and diffusion near obstacles. Atmos. Sci. Power. Prod., 3, 241-326.
  9. Jo, H.-K., Y.-H. Yun, and K.-E. Lee, 1995: Atmospheric $CO_2$ Sequestration by Urban Greenspace-In the Case of Chuncheon. J. Korean. Inst. Tradit. Landsc. Archit., 23, 80-93.
  10. Joo, O.-J., and Y.-K. Park, 2004: A Study on the Environment-friendly Evaluating Strategies of Green Space in a Housing Complex-Focused on the Amount of $O_2$Production and Atmospheric Purification of the trees. J. Archit. Inst. Korea, 20, 67-74.
  11. Kim, S.-B., and H.-D. Kim, 2002: Influences of urban tree on the control of the temperature. J. Korean Inst. Tradit. Landsc. Archit., 30, 25-34.
  12. Kim, J.-J., and J.-J. Baik, 2004: A numerical study of the effects of ambient wind direction on flow and dispersion in urban street canyons using the RNG k-${\varepsilon}$ turbulence model. Atmos. Environ., 38, 3039-3048. https://doi.org/10.1016/j.atmosenv.2004.02.047
  13. Kim, J.-J., and J.-J. Baik, 2010: Effects of street-bottom and building-roof heating on flow in three-dimensional street canyons. Adv. Atmos. Sci., 27, 513-527. https://doi.org/10.1007/s00376-009-9095-2
  14. Liu, C. H., and M. C. Barth, 2002: Large-eddy simulation of flow and scalar transport in a modeled street canyon. J. Appl. Meteorol., 41, 660-673. https://doi.org/10.1175/1520-0450(2002)041<0660:LESOFA>2.0.CO;2
  15. Nowak, D. J., and D. E. Crane, 2002: Carbon storage and sequestration by urban trees in the USA. Environ. Pollut., 116, 381-389. https://doi.org/10.1016/S0269-7491(01)00214-7
  16. Ries, K., and J. Eichhorn, 2001: Simulation of effects of vegetation on the dispersion of pollutants in street canyons. Meteorol. Z., 10, 229-233. https://doi.org/10.1127/0941-2948/2001/0010-0229
  17. Ruck, B., and F. Schmitt, 1986: Das stromungsfeld der einzelbaumumstromung. Forstwissenschaftliches Centralblatt, 105, 178-196. https://doi.org/10.1007/BF02741710
  18. Sabatino, S. D., R. Buccolieri, H. R. Olesen, M. Ketzel, R. Berkowicz, J. Franke, and A. Starchenko, 2011: COST 732 in practice: the MUST model evaluation exercise. Int. J. Environ. Pollut., 44, 403-418. https://doi.org/10.1504/IJEP.2011.038442
  19. Versteeg, H. K., and W. Malalasekera, 1995: An Introduction to Computational Fluid Dynamics: The Finite Volume Method. Longman, 257 pp.
  20. Yakhot, V., S. A. Orszag, S. Thangam, T. B. Gatski, and C. G. Speziale, 1992: Development of turbulence models for shear flow by a double expansion technique. Phys. Fluids, A4, 1510-1520.