Multi-scale analysis of flow over heterogeneous urban environments
File(s)
Published version
Author(s)
van Reeuwijk, Maarten
Huang, Jingzi
Type
Journal Article
Abstract
A computationally efficient multi-scale planar-averaging framework for urban areas is developed, which enables efficient computation of coarse-grained velocity and scalar fields. We apply the multi-scale framework to a large-eddy simulation of an idealised heterogeneous urban environment of 512 buildings based on a typical London height distribution. We observe that for this geometry, the characteristic urban lengthscale ℓ ≈ 50 m, which is the averaging lengthscale L at which as much variance in the mean flow is resolved as is unresolved. For L > 400 m, the statistics become approximately homogeneous, suggesting that non-building-resolving numerical weather prediction (NWP) models can be applied without modification at resolutions of 400 m and above for the case under consideration. We derive the multi-scale planar- and Reynolds-averaged momentum equation and show that for neutral cases, NWP models require parameterisation of the distributed drag and the unresolved turbulence and dispersive stress. An a priori analysis reveals that the drag parameterisation from Sützl et al. (Bound-Layer Meteorol 178:225–248, 2020) holds reasonably well for resolutions L above 200 m. Below this value, the problem becomes inhomogeneous and the parameterisation works less well. The unresolved stresses are well represented by a k− ω closure with a value of ω = 0.4s−¹. However, an even more accurate closure can be derived from the Sützl drag parameterisation that does not require further turbulence information.
Date Issued
2025-10-10
Date Acceptance
2025-09-16
Citation
Boundary-Layer Meteorology, 2025, 191 (11)
ISSN
0006-8314
Publisher
Springer
Journal / Book Title
Boundary-Layer Meteorology
Volume
191
Issue
11
Copyright Statement
© The Author(s) 2025 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
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Subjects
CLIMATE ZONES
Drag parameterisation
Heterogeneity
Large-eddy simulation
LARGE-EDDY SIMULATION
MEAN FLOW
Meteorology & Atmospheric Sciences
MODEL
Multi-scale analysis
Physical Sciences
ROUGHNESS SUBLAYER
Science & Technology
STATISTICS
TRANSPORT
TURBULENCE
Urban canopy
Publication Status
Published
Article Number
47
Date Publish Online
2025-10-10