TY - JOUR
T1 - Effects of a fence on pollutant dispersion in a boundary layer exposed to a rural-to-urban transition
AU - Eisma, H. E.
AU - Tomas, J. M.
AU - Pourquie, M. J.B.M.
AU - Elsinga, G. E.
AU - Jonker, H. J.J.
AU - Westerweel, J.
PY - 2018
Y1 - 2018
N2 - 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.
AB - 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.
KW - Large-eddy simulation
KW - Laser-induced fluorescence
KW - Mixing-length model
KW - Pollutant dispersion
KW - Stereoscopic particle-image velocimetry
UR - http://resolver.tudelft.nl/uuid:c5ee953e-21c0-4dbd-b3d2-e51fd782e708
UR - http://www.scopus.com/inward/record.url?scp=85049585817&partnerID=8YFLogxK
U2 - 10.1007/s10546-018-0367-1
DO - 10.1007/s10546-018-0367-1
M3 - Article
AN - SCOPUS:85049585817
SN - 0006-8314
VL - 169
SP - 185
EP - 208
JO - Boundary-Layer Meteorology
JF - Boundary-Layer Meteorology
IS - 2
ER -