Buoyant flows in street canyons: Comparison of RANS and LES at reduced and full scales
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preprint - corrected and finalized.pdf
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1.24 MB
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26c6c8d6ca646c01f30c3f0460b2ebaf
Author(s)
Chew, Lup Wai
Glicksman, Leon R
Norford, Leslie Keith
Date Issued
December 2018
Journal
Building and Environment
Publisher
Elsevier BV
Citation
Chew, Lup Wai et al. "Buoyant flows in street canyons: Comparison of RANS and LES at reduced and full scales." Building and Environment 146 (December 2018): 77-87
Version
Author's final manuscript
Abstract
Reduced-scale experiments and full-scale field measurements show contradictory buoyancy effects from heated windward walls. Reduced-scale experiments exhibit significant thermal effects, but full-scale field measurements show a negligible thermal effect on the overall flow fields. This paper investigates this discrepancy by using at both scales Computational Fluid Dynamics simulations with Reynolds-Averaged Navier-Stokes (RANS) and Large Eddy Simulation (LES). Compared to experimental and field measurements, RANS models perform well at reduced scale but over-predict the thermal effects of heated windward walls at full scale. On the other hand, LES results agree well with measurements at both scales. Therefore, LES should be used for full-scale simulations of street canyon flows with heated windward walls. To date, there has been no explanation for the discrepancy of opposing thermal effects between reduced-scale experiments and full-scale field measurements although Richardson number similarity is satisfied. We provide an explanation by showing that in reduced-scale experiments with heated windward walls, the assumption of Reynolds number independence is invalid. In canyon flows with thermally induced buoyancy, unless the flow is proven independent of both Reynolds number and Grashof number, we should not generalize results from reduced-scale experiments to full-scale street canyons. Keywords: Urban street canyon; Large eddy simulation; Reynolds number independence; Dimensionless group similarity; Full-scale simulation; Buoyant flow
MIT Department
Massachusetts Institute of Technology. Department of Mechanical Engineering
Massachusetts Institute of Technology. Department of Architecture
Terms of Use
Creative Commons Attribution-NonCommercial-NoDerivs License
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1016/j.buildenv.2018.09.026
