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	Quadrant analysis of turbulent pollution flux above the modelled street intersection Kukačka, Libor ; Nosek, Štěpán ; Kellnerová, Radka ; Jurčáková, Klára ; Jaňour, Zbyněk The objective of this experimental study is to determine processes of a vertical turbulent pollution transport above the X-shaped street intersection in an idealised symmetric urban area for several approach flow directions. An experimental set-up for simultaneous measurement of the flow velocity and the tracer gas con-centration in a high temporal resolution is assembled. Vertical turbulent scalar fluxes are computed from the measured data in a horizontal plane above the street intersection. The quadrant analysis was applied to the vertical turbulent pollution fluxes data. Events with dominant contribution to vertical turbulent pollution flux were detected. The mean duration, repetition frequency and the duration percentage were computed for these events. A strong influence of the approach flow direction on the type of dominant events and their characteristics was resolved. Detailed record
	Wind tunnel measurement of turbulent and advective scalar fluxes, case study on an intersection ventilation Kukačka, Libor ; Nosek, Štěpán ; Kellnerová, Radka ; Jurčáková, Klára ; Jaňour, Zbyněk The objective of this study is to determine processes of vertical ventilation above the X-shaped intersection in an idealised symmetric urban area in several approach flow directions. An experimental set-up for simultaneous measurement of the flow velocity and the tracer gas concentration was assembled. Vertical advective and turbulent fluxes of passive contaminant were computed from synchronised measured velocity and concentration signals in a regular grid placed at the roof top level above the studied intersection. Spatial distribution and contributions of the turbulent transport to ventilation of the area were determined. Detailed record
	Fyzikální modelování změn difúze znečišťujících látek v oblasti křižovatky v závislosti na směru nabíhajícího proudění Kukačka, Libor ; Jurčáková, Klára ; Kellnerová, Radka ; Jaňour, Zbyněk The objective of this study is physical modelling of emissions from vehicle exhausts in street canyons within an urban area and the influence of the approach flow direction on contaminant spreading. The requirements of the similarity of the atmospheric boundary layer and a boundary layer in the wind tunnel are satisfied. For several flow directions mean velocity and concentration fields are measured within street canyon intersection inside symmetrical urban built-up area. Scalar fluxes are computed from measured data to quantify pollutant spreading. Results of the experiment show a significant sensitivity of the mean velocity field on the approach flow direction. The approach flow extensively influence contaminant spreading within the built-up area and therefore intensity of street canyons ventilation vary with the approach flow direction. The approximate flow direction with the most favourable dispersion conditions in the studied area is found out. Detailed record

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