Flow and dispersion over a cluster of ‘real-world’ tall buildings

Wang, C., Mishra, A., Clements, D., Bi, D., Placidi, M., Lasagna, D., Coceal, O. ORCID: https://orcid.org/0000-0003-0705-6755, Barlow, J. ORCID: https://orcid.org/0000-0002-9022-6833, Carpentieri, M., Grimmond, S. ORCID: https://orcid.org/0000-0002-3166-9415, Robins, A. and Xie, Z.-T. (2026) Flow and dispersion over a cluster of ‘real-world’ tall buildings. Urban Climate, 67. 102916. ISSN ISSN 2212-0955 doi: 10.1016/j.uclim.2026.102916

Abstract/Summary

We focus on a cluster of tall buildings in the City of London, situated within a compact area approximately 700 m in diameter. We uniquely bring together three methodologies to address the impact of densely packed tall buildings on flow and dispersion. We use real-world wind sonic anemometer observations (191 m above ground level) to identify a day with nearly neutral, stationary urban boundary layer flow and determine the integral time and length scales. We use these conditions to inform wind tunnel experiments (1:500 scale) and full-scale high-fidelity large-eddy simulations (LES) with the corresponding integral time and length scales approximated and synthetic inflow turbulence generation applied in the LES. We examine the impact on the building cluster wake region and dispersion of a ground-level release by considering multiple wind directions, and use the wind tunnel-scale observations to evaluate the LES. There is good agreement, with Reynolds number independence of the flow characteristics confirmed under the investigated conditions. The 17 tall buildings exhibit a cluster effect (i.e. acting with unitary effect) on the flow and a ground-level tracer release plume as they pass through the buildings. Despite the cluster porosity having large variations with wind direction, the cluster-area-averaged turbulent stresses are much less sensitive to wind direction than the dispersive stresses. For the least porous direction (SW), the Strouhal number based on the identified primary vortex shedding frequency, freestream velocity and effective cluster width corrected for porosity, is found to be close to that of an isolated tall building. In the far wake, the wake width increases following an approximate power-law trend with an exponent of 0.5, while the peak velocity deficit decreases according to a power-law with an exponent of about . The peak velocity deficit remains above 10% of the freestream velocity even at approximately 3 km downstream of the building cluster. The tracer plume width increases more rapidly than a linear trend in both horizontal and vertical directions just upwind of the cluster, but downstream its growth follows a power-law trend with an exponent of approximately 0.5. This novel combination of methodologies in the challenging environment of tall buildings offers important insights for a wide range of applications across multiple scales. These findings are becoming increasingly important as urban populations grow and densification trends drive cities to expand vertically.

Item Type	Article
URI	https://centaur.reading.ac.uk/id/eprint/129760
Identification Number/DOI	10.1016/j.uclim.2026.102916
Refereed	Yes
Divisions	Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
Publisher	Elsevier
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