Numerical Simulation of Wind Flow Structures and Pollutant Dispersion within Street Canyon under Thermally Unstable Atmospheric Conditions

Abstract:

Numerical studies were conducted to envisage the wind flow structures in street canyon for differential heated wall and Richardson numbers. Two-equation turbulence models, namely the Standard k-ε, Renormalization Group (RNG) k-ε and Realizable k-ε were applied to investigate the effect of flow structure on pollutant dispersion in a square street canyon. The obtained results demonstrate that the differentially heated wall/floor gives significant effects on the wind flow field compared with those under isothermal conditions. At low Richardson number, vortex intensification was observed for the case of ground or leeward heated wall. Meanwhile, for the case of windward heated wall, the ventilation was much reduced due to the buoyancy force that produces upward motion near the wall to form the secondary vortex. At higher Froude number (convective flows) case, the buoyancy flow has no discernible effects on the flow structures. Keywords— Street canyon; thermal flow; wind flow structures; pollutant dispersion; turbulence models

• Periodical: Applied Mechanics and Materials (Volume 554)
• Pages: 655-659
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.554.655
• Online since: June 2014
• Authors: Afiq Muhammad Yazid Witri, Nor Azwadi Che Sidik*, Salim Mohamed Salim
• Keywords: Pollutant Dispersion, Street Canyon, Thermal Flow, Turbulence Model, Wind Flow Structures

References

[1] M. Cretu, V. Teleaba, S. Ionescu, A. Ionescu. Pollution scenarios through atmospheric dispersion modelling based on real measurements - impact on human health Acoustics and Air Quality Laboratory. WSEAS Trans. Environ Develop 6 (2010) 604–613.

[2] A.W.M. Yazid, N.A.C. Sidik K.M. Saqr. Effects of building aspect ratio, wind speed and wind direction on flow structure and pollutant dispersion in symmetric street canyons: a review. Int. J. of Mech Mat Eng 7 (2012) 158-165.

[3] K. Uehara, S. Murakami, S. Oikawa, S. Wakamatsu. Wind tunnel experiments on how thermal stratification affects flow in and above urban street canyons. Atmos Environ 34 (2000) 1553-1562.

DOI: 10.1016/s1352-2310(99)00410-0

[4] S. Vardoulakis, R. Dimitrova, K. Richards et al. Numerical model inter-comparison for wind flow and turbulence around single-block buildings. Environ Monit Assess 16 (2010) 169–181.

DOI: 10.1007/s10666-010-9236-0

[5] X. Xie, Z. Huang, J. Wang, Z. Xie. The impact of solar radiation and street layout on pollutant dispersion in street canyon. Build Environ 40 (2005) 201–212.

DOI: 10.1016/j.buildenv.2004.07.013

[6] J. Franke, A. Hellsten, H. Schlünzen, B. Carissimo. Best practice guideline for the cfd simulation of flows in the urban environment. (2007).

[7] R.N. Meroney, B.M. Leitl, S. Rafailidis, M. Schatzmann. Wind-tunnel and numerical modeling of flow and dispersion about several building shapes. J Wind Eng Ind Aerod 81 (1999) 333–345.

DOI: 10.1016/s0167-6105(99)00028-8

[8] T.L. Chan, G. Dong, C.W. Leung, C.S. Cheung, W.T. Hung. Validation of a two-dimensional pollutant dispersion model in an isolated street canyon. Atmos Environ 36 (2002) 861–872.

DOI: 10.1016/s1352-2310(01)00490-3

[9] A. Tablada, S. Roels. Numerical study on the influence of wind and thermal stack on street canyon airflow pattern. in The 7th International Conference on Urban Climate (2009).

[10] R.A. Memon, D.Y.C. Leung, C.H. Liu. Effects of building aspect ratio and wind speed on air temperatures in urban-like street canyons. Build Environ 45 (2010) 176–188.

DOI: 10.1016/j.buildenv.2009.05.015

[11] Inc., A. FLUENT Documentation: User guide. (2005).

[12] J. Allegrini, V. Dorer, J. Carmeliet. Wind tunnel measurements of buoyant flows in street canyons. Build Environ 59 (2013) 315–326.

DOI: 10.1016/j.buildenv.2012.08.029

[13] Informationon http: /www. ifh. uni-karlsruhe. de/science/aerodyn/CODASC. htm.

[14] R.N. Meroney, M. Pavageau, S. Rafailidis S et al. Study of line source characteristics for 2-D physical modelling of pollutant dispersion in street canyons. J Wind Eng Ind Aerod 62 (1996) 37-56.

DOI: 10.1016/s0167-6105(96)00057-8