Effects of a fence on pollutant dispersion in a boundary layer exposed to a rural-to-urban transition

Journal article (2018)

Authors

H.E. Eisma Fluid Mechanics - Mechanical, Maritime and Materials Engineering
J.M. Tomas Fluid Mechanics - Mechanical, Maritime and Materials Engineering
M.J.B.M. Pourquie Fluid Mechanics - Mechanical, Maritime and Materials Engineering
G.E. Elsinga Fluid Mechanics - Mechanical, Maritime and Materials Engineering
H.J.J. Jonker Atmospheric Physics
J. Westerweel Fluid Mechanics - Mechanical, Maritime and Materials Engineering
Research Group
Fluid Mechanics (Mechanical, Maritime and Materials Engineering) (TU Delft)
Copyright: © 2018 H.E. Eisma, J.M. Tomas, M.J.B.M. Pourquie, G.E. Elsinga, H.J.J. Jonker, J. Westerweel
DOI
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https://doi.org/10.1007/s10546-018-0367-1
Laser-induced fluorescence Large-eddy simulation Pollutant dispersion Mixing-length model Stereoscopic particle-image velocimetry
More Info
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Published Date

2018

Language

English

Faculty

Mechanical, Maritime and Materials Engineering

Department

Process and Energy

Research Group

Fluid Mechanics

Abstract

Simultaneous particle-image velocimetry and laser-induced fluorescence combined with large-eddy simulations are used to investigate the flow and pollutant dispersion behaviour in a rural-to-urban roughness transition. The urban roughness is characterized by an array of cubical obstacles in an aligned arrangement. A plane fence is added one obstacle height h upstream of the urban roughness elements, with three different fence heights considered. A smooth-wall turbulent boundary layer with a depth of 10h is used as the approaching flow, and a passive tracer is released from a uniform line source 1h upstream of the fence. A shear layer is formed at the top of the fence, which increases in strength for the higher fence cases, resulting in a deeper internal boundary layer (IBL). It is found that the mean flow for the rural-to-urban transition can be described by means of a mixing-length model provided that the transitional effects are accounted for. The mixing-length formulation for sparse urban canopies, as found in the literature, is extended to take into account the blockage effect in dense canopies. Additionally, the average mean concentration field is found to scale with the IBL depth and the bulk velocity in the IBL.