Pollutant Dispersion in Boundary Layers Exposed to Rural-to-Urban Transitions: Varying the Spanwise Length Scale of the Roughness

27Citations
Citations of this article
56Readers
Mendeley users who have this article in their library.

Abstract

Both large-eddy simulations (LES) and water-tunnel experiments, using simultaneous stereoscopic particle image velocimetry and laser-induced fluorescence, have been used to investigate pollutant dispersion mechanisms in regions where the surface changes from rural to urban roughness. The urban roughness was characterized by an array of rectangular obstacles in an in-line arrangement. The streamwise length scale of the roughness was kept constant, while the spanwise length scale was varied by varying the obstacle aspect ratio l / h between 1 and 8, where l is the spanwise dimension of the obstacles and h is the height of the obstacles. Additionally, the case of two-dimensional roughness (riblets) was considered in LES. A smooth-wall turbulent boundary layer of depth 10h was used as the approaching flow, and a line source of passive tracer was placed 2h upstream of the urban canopy. The experimental and numerical results show good agreement, while minor discrepancies are readily explained. It is found that for l/ h= 2 the drag induced by the urban canopy is largest of all considered cases, and is caused by a large-scale secondary flow. In addition, due to the roughness transition the vertical advective pollutant flux is the main ventilation mechanism in the first three streets. Furthermore, by means of linear stochastic estimation the mean flow structure is identified that is responsible for street-canyon ventilation for the sixth street and onwards. Moreover, it is shown that the vertical length scale of this structure increases with increasing aspect ratio of the obstacles in the canopy, while the streamwise length scale does not show a similar trend.

References Powered by Scopus

Street design and urban canopy layer climate

1429Citations
N/AReaders
Get full text

Generation of Turbulent Inflow Data for Spatially-Developing Boundary Layer Simulations

1399Citations
N/AReaders
Get full text

An eddy-viscosity subgrid-scale model for turbulent shear flow: Algebraic theory and applications

1142Citations
N/AReaders
Get full text

Cited by Powered by Scopus

Urban morphology as a passive strategy in promoting outdoor air quality

57Citations
N/AReaders
Get full text

Pollutant fluxes in two-dimensional street canyons

53Citations
N/AReaders
Get full text

Pollutant dispersion by tall buildings: laboratory experiments and Large-Eddy Simulation

30Citations
N/AReaders
Get full text

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Cite

CITATION STYLE

APA

Tomas, J. M., Eisma, H. E., Pourquie, M. J. B. M., Elsinga, G. E., Jonker, H. J. J., & Westerweel, J. (2017). Pollutant Dispersion in Boundary Layers Exposed to Rural-to-Urban Transitions: Varying the Spanwise Length Scale of the Roughness. Boundary-Layer Meteorology, 163(2), 225–251. https://doi.org/10.1007/s10546-016-0226-x

Readers' Seniority

Tooltip

PhD / Post grad / Masters / Doc 20

53%

Professor / Associate Prof. 7

18%

Lecturer / Post doc 6

16%

Researcher 5

13%

Readers' Discipline

Tooltip

Engineering 25

74%

Environmental Science 4

12%

Earth and Planetary Sciences 3

9%

Physics and Astronomy 2

6%

Save time finding and organizing research with Mendeley

Sign up for free