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Measurement of the photocatalytic efficiency of FN NANO®2 coating on an idealized urban model
Nosek, Štěpán
An experiment was conducted to test the effectiveness of the FN NANO®2 coating in removing a harmful pollutant (NOX) by photocatalysis on a surface in a model of an urban street canyon. The experiment was conducted in a wind tunnel under controlled conditions, simulating two cases of street canyon pollution: from a line source within the canyon and a polluted incoming boundary layer. The results showed that the coating has an average efficiency of 15% when removed from NOX, with the efficiency decreasing with height within the street canyon. The removal efficiency depends on the type of pollution. In the case of the polluted incoming boundary layer, the coating showed very high efficiency in removing NO (average efficiency of 19%) and NO2 (average efficiency of 7%). These results show that both methods can be used to analyse the removal of NOX concentrations by the FN NANO®2 coating in a street canyon.
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Measurement of photocatalytic efficiency of FN NANO®2 coating on Legerova street model
Nosek, Štěpán
An experiment was conducted to test the effectiveness of the FN NANO®2 coating in removing a pollutant (NOX) by photocatalysis on a surface in a model of a real urban street canyon. The experiment was conducted in a wind tunnel under controlled conditions and simulated the case of pollution of a Legerova street model by an upwind boundary layer polluted by NOX concentrations from a car. The results showed that the coating has a higher degradation efficiency for NO (up to 15%) than for NOX (max. 12%), with the efficiency depending on the investigated position. The lowest efficiency was achieved in streets aligned parallel to the upwind boundary layer, which are naturally better ventilated.
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Urban Ventilation Dependence on Geometric Configuration
Kukačka, Libor ; Jaňour, Zbyněk (advisor) ; Carpentieri, Matteo (referee) ; Uruba, Václav (referee)
Title: Urban Ventilation Dependence on Geometric Configuration Author: RNDr. Ing. Libor Kukačka Department: Department of Atmospheric Physics Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., Academy of Sciences of the Czech Republic, Institute of Thermomechanics, v. v. i. Abstract: The main goal of the thesis is to investigate the impact of urban geometry on the urban ventilation using wind-tunnel modelling. To measure the pollutant transport, both advective and turbulent, within complex urban geometries with a high temporal resolution a special measurement method was developed. At first, the pollution of a simplified urban area was simulated by a ground-level point source and the ventilation of the intersection with respect to four wind directions was studied. Later, the pollution of other simplified and complex urban areas was simulated by a ground-level line source and the ventilation of three different street canyons with respect to wind direction perpendicular and oblique to their along-canyon axis was investigated. The clear impact of urban complexity and wind direction on street canyon ventilation is demonstrated at lateral and top openings of all investigated canyons and the intersection. Whilst the dominance of the pollutant advection is demonstrated at the eaves of pitched roofs, at the roof ridges...
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Wind-tunnel Modelling of Turbulent Flow Inside the Street Canyon
Kellnerová, Radka ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee) ; Jonáš, Pavel (referee)
Turbulent flow inside a street canyon was investigated in an open circuit wind tunnel and in a blow-down wind channel. Two geometries were used for comparison purposes: buildings with pitched roofs and with flat roofs. Both generate the flow of a different category, so the induced ventilation regimes are fundamentally different. Quadrant, Fourier and Wavelet analysis, Proper Orthogonal Decomposition (POD) and vortex detection methods are used to identify coherent structures in the flow and establish their impact on the ventilation of pollution. Two types of the organised motions are detected: the compact areas of sweep and ejection with the scale comparable to the size of building and the small vortices generated in the shear layer behind the building roof. POD identifies the most dominant modes with high coherency in the flow and evaluates the relative contributions of each mode to the overall kinetic energy of turbulence. Rigorous analysis of the correctness of the physical interpretation for such a decomposition is carried out. Wavelet analysis is applied to the time-series of the POD expansion coefficients in order to reveal control mechanism of the dynamics of the modes. Vorticity, calculated from the original velocity data, is decomposed by POD as well. Finally, the correlation between the vorticity...
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Urban Ventilation Dependence on Geometric Configuration
Kukačka, Libor ; Jaňour, Zbyněk (advisor) ; Carpentieri, Matteo (referee) ; Uruba, Václav (referee)
Title: Urban Ventilation Dependence on Geometric Configuration Author: RNDr. Ing. Libor Kukačka Department: Department of Atmospheric Physics Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., Academy of Sciences of the Czech Republic, Institute of Thermomechanics, v. v. i. Abstract: The main goal of the thesis is to investigate the impact of urban geometry on the urban ventilation using wind-tunnel modelling. To measure the pollutant transport, both advective and turbulent, within complex urban geometries with a high temporal resolution a special measurement method was developed. At first, the pollution of a simplified urban area was simulated by a ground-level point source and the ventilation of the intersection with respect to four wind directions was studied. Later, the pollution of other simplified and complex urban areas was simulated by a ground-level line source and the ventilation of three different street canyons with respect to wind direction perpendicular and oblique to their along-canyon axis was investigated. The clear impact of urban complexity and wind direction on street canyon ventilation is demonstrated at lateral and top openings of all investigated canyons and the intersection. Whilst the dominance of the pollutant advection is demonstrated at the eaves of pitched roofs, at the roof ridges...
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Wind-tunnel Modelling of Turbulent Flow Inside the Street Canyon
Kellnerová, Radka ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee) ; Jonáš, Pavel (referee)
Turbulent flow inside a street canyon was investigated in an open circuit wind tunnel and in a blow-down wind channel. Two geometries were used for comparison purposes: buildings with pitched roofs and with flat roofs. Both generate the flow of a different category, so the induced ventilation regimes are fundamentally different. Quadrant, Fourier and Wavelet analysis, Proper Orthogonal Decomposition (POD) and vortex detection methods are used to identify coherent structures in the flow and establish their impact on the ventilation of pollution. Two types of the organised motions are detected: the compact areas of sweep and ejection with the scale comparable to the size of building and the small vortices generated in the shear layer behind the building roof. POD identifies the most dominant modes with high coherency in the flow and evaluates the relative contributions of each mode to the overall kinetic energy of turbulence. Rigorous analysis of the correctness of the physical interpretation for such a decomposition is carried out. Wavelet analysis is applied to the time-series of the POD expansion coefficients in order to reveal control mechanism of the dynamics of the modes. Vorticity, calculated from the original velocity data, is decomposed by POD as well. Finally, the correlation between the vorticity...
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Analýza nestacionárního proudění uvnitř ulice a dvoru
Kellnerová, Radka ; Jaňour, Zbyněk
Spatial distribution of momentum flux and moments of third order of velocity components obtained from one-point measurement are investigated. The area of interest covers an inner part of street canyon and adjacent intersection. Time-averaged momentum flux were divided into particular quadrants using Quadrant analysis method. Comparison between flux events and skewness provides some insight into the spatial distribution of strong intermittent tendency and explain better the spatially local dominance of sweep and ejection.
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Turbulent Boundary Layer generated Over Two Urban Roughnesses
Kellnerová, Radka ; Jaňour, Zbyněk
As a basis for PIV measurement, turbulent characteristics of a flow were investigated by LDA over two different types of urban roughness in wind-tunnel. The roughness consists from long series of street canyons with unit aspect ratio. Different shapes of roof - flat and pitched - provide a different internal boundary layer above canyons. The latter one, generated by pitched roofs, is significantly more turbulent and thus slower then above flat roofs. Momentum flux and corresponding transport exhibits the largest deviation specially at the roof level. Ventilation in the streets is therefore distinct from each other. Quadrant analysis was applied for vertical profiles and cross-sectional areas in canyons in order to detect a domination of sweep or ejection events and to find a linkage to the third moment of velocity for both cases. The overall goal of the project is to find any of coherent structure produced by the roof edge as a low momentum region or an ejection formed by hairpin.
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Dynamika proudění uvnitř městské křižovatky: charakteristiky šikmosti a špičatosti
Kellnerová, Radka ; Jaňour, Zbyněk
The experiment uses wind-tunnel modeling method to investigate an intermittent ventilation of pollutants within an urban intersection and adjacent canyon. The skewness and kurtosis of velocity components were obtained in order to identify an area with strong intermittent tendency. Pollutants have released from line source and mean concentration was obtained using slow flame ionization detector. Vertical vortices as well as corner vortices are responsible for accumulation of emissions emitted by vehicle traffic. However, flow instabilities corresponding to enhancement of skewness can reduce or enhance the instantaneous level of exhalations. Vertical and horizontal momentum flux was analyzed by quadrant analysis. The method has detected the localities with highest momentum transfer from free stream down to the canyon. The connection between sweep and skewness in this area was found.
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Wind tunnel concentration field study in a urban area
Jaňour, Zbyněk ; Kellnerová, Radka ; Bezpalcová, Klára
The aim of the project was to study the influence of boundary conditions on contaminant spreading in a urban area model. The experiment was conducted a low-speed open-circuit tunnel. The urban area model was scaled down to 1:200. The model aimed to simulate a typical street with intense traffic, in our case specifically the Podbielski Strasse in Hannover (Germany). The downstreet flow was at an aproximate angle of 45 degrees to the street axis. Traffic was simulated by a double-line source. In the course of the experiment we have replaced a convoluted model of a park in the upstream area with simpler elements of varying size and density. We then compared the concentration field of the new arrangement with the original concentration field. All configurations led to a decrease of concentration . In ares where the original concentration had reached the highest values, the most significant decrease was obtained.
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