Relation of puff and continuous dispersion within urban canopy

0437112 - ÚT 2015 BG eng C - Conference Paper (international conference)
Chaloupecká, Hana - Jurčáková, Klára - Jaňour, Zbyněk
Relation of puff and continuous dispersion within urban canopy.
16th International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes. Varna: National Institute if Meteorology and Hydrology, 2014, s. 694-698.
[International Conference on Harmonisation within Atmospheric Dispersion Modelling for Regulatory Purposes /16./. Varna (BG), 08.09.2014-11.09.2014]
R&D Projects: GA MŠMT LD12007
Institutional support: RVO:61388998
Keywords : atmospheric boundary layer * pollution dispersion * instantaneous release * wind tunnel
Subject RIV: DG - Athmosphere Sciences, Meteorology
http://www.harmo.org/conferences/Proceedings/_Varna/publishedSections/H16-144-Chaloupecka-EA.pdf

Protection of inhabitants of densely populated urban areas is a very important topic. Residents can be threatened by accidental releases of toxic gases. These releases can occur e.g. from a factory working with chemicals, a vessel transporting chemicals, or by an intentional attack. Most of such releases have duration of few minutes to one hour. This leads to dispersion pattern called puff. Due to stochastic nature of turbulence of the atmospheric flow the prediction of puff dispersion is possible only in statistical sense. The presented paper will introduce dispersion experiments of both puff and continuous releases within an urban canopy. The experiments were conducted at the environmental wind tunnel of the Institute of Themomechanics. The model of an idealised urban canopy representing typical European architecture consisting of rectangular blocks of buildings with pitched roofs and inner courtyards was manufactured in the scale 1:400. A point source of tracer gas was mounted at the ground level. Flow and dispersion was measured by time resolving instruments (Laser Doppler Anemometry and Flame Ionisation Detector, respectively). At each point concentration time series from continuous and puff (i.e. ensembles of puff realisations) releases were recorded. Characteristics of the puff case as well as the continuous case were calculated. Linear relationship between mean concentrations in the continuous case and mean 99%, as well as mean 95% quantile of concentrations in the puff case within separate traverse streets in view of flow is perceptible from the results. Assessment of puff ensemble characteristics by continuous dispersion characteristics is highly valuable, since many numerical models calculate only with Reynolds averaged equations and they are able to predict only statistics of continuous dispersion.
Permanent Link: http://hdl.handle.net/11104/0242795