Influence of thermal stability on the ventilation of a 3-D building array

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journal

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Original languageEnglish
Article number106969
Journal / PublicationBuilding and Environment
Online published14 Jun 2020
Publication statusOnline published - 14 Jun 2020


The influence of thermal stability on the ventilation of a cubic building array is examined via large-eddy simulation. For unstable stratification (with bulk Richardson numbers in the range −0.5≲Rb < 0), ventilation timescales decrease as the ground-level heating increases; in particular, the mean tracer age and pollutant retention timescale scale linearly with the mean circulation timescale. For stable stratification (0 < Rb≲0.3), however, the ventilation timescales increase with stronger ground-level cooling even though the mean streamwise wind speed and turbulence kinetic energy remain approximately constant. The ventilation pathway changes for stable stratification because pollutants preferentially escape through the lateral openings rather than the roof level. It is argued that conventional time-averaged turbulence statistics (e.g. Reynolds stresses) provide an incomplete picture of the ventilation mechanism under stable stratification.

Research Area(s)

  • Flow regime, Pollutant dispersion, Stable stratification, Tracer age, Urban boundary layer