Laboratory of Environmental Aerodynamics
Department: Department D 1 - Fluid Dynamics
Head: Ing. Štěpán Nosek, Ph.D.
The flow in the atmospheric surface layer is very turbulent and difficult to predict due to the nature of the earth's surface. Therefore, the prediction of pollutant transport, for example in cities, is challenging and varies from case to case. One of the main goals of the laboratory is to understand better the effect of turbulent flow on the pollutant transport in such complex situations and to find general rules that would help to make better predictions. An integral part of the laboratory is also applied studies, in which the knowledge from basic research is used to solve specific practical cases. For these purposes, the laboratory uses methods of physical modelling in a wind tunnel. The technique makes it possible to study the processes in detail, under controllable conditions and at lower costs than in real situations.
Head of laboratory
Dr. Štěpán Nosek
Prof. Zbyněk Jaňour
Dr. Klára Jurčáková
Dr. Radka Kellnerová
Dr. Hanka Chaloupecká
Technical and support staff
The impact of turbulence on scalar transfer
Although turbulent flow at first glance represents a chaotic and disordered motion of fluid (air) molecules, it has recently been shown to exhibit some features of the order. In the field of turbulent research, these features are called coherent structures and might be represented by various vortex structures, which can help to transfer the passive substance (pollutant) or heat (scalar in general) more efficiently. However, coherent structures may or may not be eye-observable, and so current research in this area is developing various experimental and mathematical tools to find them. One of the main research intentions of the laboratory is to understand the role of these structures on the passive pollutant transport in turbulent flow and to find general validity for its prediction. As an illustrative example, we present the results of the project (LTC18070) in which the laboratory dealt with the flow and dispersion of pollutants in naturally ventilated agricultural buildings (such as a cow barn).
Vid. 1. Capture the development of a turbulent flow field within the barn model time-resolved particle image velocimetry (TR-PIV) within 1 s. The camera acquisition frequency corresponds to 200 Hz. Coloured contours indicate the flow velocity in m/s.
Vid. 2. Decomposition of the same flow inside the barn using Oscillating Pattern Decomposition (OPD) method. The video shows the coherent structures shed by the Kelvin-Helmholtz instability into the flow. Coloured contours indicate the vorticity of structures in 1/s.
Relevant grants: GA18-09539S, GA15-18964S, GAP101 / 12/1554, LTC18070
Short-term leakage of pollutant into the atmosphere
Another issue that the laboratory deals with is the so-called short-term leaks (puffs) of toxic gaseous substances, which can be encountered, for example, in chemical accidents or terrorist attacks. Due to the moment of a gas leak into turbulent flow, an accurate prediction of the spread of a hazardous substance in a complicated environment (such as cities) is impossible, and it is necessary to rely on various statistical characteristics. As part of this issue, the laboratory developed a new rapid emergency model in the solution of the TJ01000383 project, predicting the situation arising after a short-term gas leak. The model is based on the relationships between short-term and long-term gas leaks (see Fig. 1) and was designed for the needs of the Ministry of the Interior of the Czech Republic for the daily use of emergency services - Emergency Call Center 112.
Fig. 1. Time series of concentrations measured at the same point for the five different realizations under the same time-average experimental conditions.
Relevant grants: TJ04000365, TJ01000383, LD12007
The laboratory applies the knowledge gained from basic research to specific practical cases. Since 2001, studies have been carried out on air pollution from factories located near cities (Jablonné nad Orlicí, Příbram) or from car traffic (studies of street canyon pollution situated in the centre of Hannnover, see Fig. 2). Furthermore, emergency cases of chlorine leakage from the chemical plant of Synthesia and a railway tank at Pardubice Railway Station (Fig. 3), or a leak of dangerous gas on Old Town Square in Prague has been addressed by the laboratory. The use of physical modelling of atmospheric flow over complicated terrain has also solved the spread of dust from the Libouš coal mine, located near the town Chomutov (Fig. 4).
Fig. 2. Model of a street canyon of the city of Hannover located in a wind tunnel (left) and measured concentrations of passive pollutant (coloured contours in the picture on the right) in the same model 3 m above the ground for the investigated wind direction (black arrow).
Fig. 3. Model of the Pardubice railway station (left) and the concentrations of passive pollutant measured on it at the height of the terrain (middle) and 10 m above the ground (right) for the investigated wind direction (blue arrow).
Fig. 4. Measured advective flux (red contours) of passive pollutant escaping from a point source (red arrow) above the Libouš coal mine model from 2014 (left) and during the planned coal extraction (right). Both cases were simulated for the westerly wind direction.
A wind tunnel (cross dimensions of 1.5 m × 1.5 m and length of 30 m)
Planar and point laser anemometry (Stereo TR-PIV a 2D LDA system, Dantec Dynamics A/S)
Fast flame ionisation detector (FFID, Cambustion Ltd.)
Fig. 1. PIV measurement in the wind tunnel.
Fig. 2. LDA measurement above a model of urban array in the wind tunnel
The topics of doctoral studies primarily focus on the study of processes in the atmospheric boundary layer, which are related to the transfer of air pollutant by the flow and diffusion. Both general laws and their applications are solved during these studies. For instance, the ventilation of urban area, livestock buildings or surface quarries, or the transport of accidentally or deliberately release of hazardous gases in complex terrain. The method of physical modelling in a unique wind tunnel is mainly applied, which, unlike nature, provides precisely defined experimental conditions. The measurements in the wind tunnel are performed using sophisticated methods (e.g., a laser Doppler anemometry, a fast ionization detector) and allow doctoral students to gain skills in experimental fluid mechanics. The students also get insight into the validation of numerical models which are developed in cooperation with specialists. The topics are mostly solved within the EU COST projects, grants from GAČR and TAČR, and in collaboration with foreign universities.
Overview of the completed studies (supervised by prof. Zbyněk Jaňour):
- RNDr. Klára Jurčáková, Ph.D. (2007) – Physical Modelling of Flow and Diffusion in Urban Canopy
- Mgr. Radka Kellnerová, Ph.D. (2014) – Wind-tunnel Modelling of Turbulent Flow Inside the Street Canyon
- RNDr. Ing. Libor Kukačka, Ph.D. (2018) – Urban Ventilation Dependence on Geometric Configuration
- Mgr. Hana Chaloupecká, Ph.D. (2018) – Sudden release of toxic gas in built-up environment
Overview of the runnig studies (supervised by prof. Zbyněk Jaňour):
- Mgr. Zuzana Kluková (2016 –) – The influence of the roughness elements three-dimensionality on transfer of momentum and passive scalar in the surface layer of the atmosphere.
For new applicants of doctoral studies, topics will be selected according to the currently running projects or grants. Therefore, the topics should be within the scope of the laboratory as the flow and diffusion in an urban canopy of various configurations, transport and diffusion of accidentally or deliberately release of hazardous gases or the study of turbulent coherent structures. Trainers or the consultants will be younger employees of the laboratory, mostly the investigators of the corresponding grants.
List of relevant publications
- Yi, Q., Janke, D., Thormann, L., Zhang, G., Amon, B., Hempel, S., Nosek, Š., Hartung, E., Amon, T. Airflow Characteristics Downwind a Naturally Ventilated Pig Building with a Roofed Outdoor Exercise Yard and Implications on Pollutant Distribution. Applied Sciences-Basel. 2020, 10(14). ISSN 2076-3417. doi: 10.3390/app10144931
- Nosek, Š., Kluková, Z., Jakubcová, M., Qianying, Y., Janke, D., Demeyer, P., Jaňour, Z. The impact of atmospheric boundary layer, opening configuration and presence of animals on the ventilation of a cattle barn. Journal of Wind Engineering and Industrial Aerodynamics. 2020, 201, 104185. ISSN 0167-6105. doi: 10.1016/j.jweia.2020.104185
- Jaňour, Z. Modelování mezní vrstvy atmosféry. Praha: ACADEMIA, 2019. GERSTNER, 12. ISBN 978-80-200-2854-9.
- Chaloupecká, H., Jakubcová, M., Jaňour, Z., Jurčáková, K., Kellnerová, R. Equations of a new puff model for idealized urban canopy. Process Safety and Environmental Protection. 2019, 126(June), 382-392. ISSN 0957-5820.
- doi: 10.1016/j.jlp.2018.09.007
- Chaloupecká, H., Jaňour, Z., Jurčáková, K., Kellnerová, R. Sensitivity of puff characteristics to maximum-concentration-based definition of departure time. Journal of Loss Prevention in the Process Industries. 2018, 56(November), 242-253. ISSN 0950-4230. doi: 10.1016/j.jlp.2018.09.007
- Nosek, Š., Fuka, V., Kukačka, L., Kluková, Z., Jaňour, Z. Street-canyon pollution with respect to urban-array complexity: The role of lateral and mean pollution fluxes. Building and Environment. 2018, 138(June), 221-234. ISSN 0360-1323. doi: 10.1016/j.buildenv.2018.04.036
- Kellnerová, R., Fuka, V., Uruba, V., Jurčáková, K., Nosek, Š., Chaloupecká, H., Jaňour, Z. On Street-Canyon Flow Dynamics: Advanced Validation of LES by Time-Resolved PIV. Atmosphere. 2018, 9(5), 161. ISSN 2073-4433. doi: 10.3390/atmos9050161
- Chaloupecká, H., Jaňour, Z., Mikšovský, J., Jurčáková, K., Kellnerová, R. Evaluation of a new method for puff arrival time as assessed through wind tunnel modelling. Process Safety and Environmental Protection. 2017, 111(October), 194-210. ISSN 0957-5820. doi: 10.1016/j.psep.2017.07.006
- Nosek, Š., Kukačka, L., Jurčáková, K., Kellnerová, R., Jaňour, Z. Impact of roof height non-uniformity on pollutant transport between a street canyon and intersections. Environmental Pollution. 2017, 227(August), 125-138. ISSN 0269-7491. doi: 10.1016/j.envpol.2017.03.073
- Nosek, Š., Kukačka, L., Kellnerová, R., Jurčáková, K., Jaňour, Z. Ventilation Processes in a Three-Dimensional Street Canyon. Boundary Layer Meteorology. 2016, 159(2), 259-284. ISSN 0006-8314. doi: 10.1007/s10546-016-0132-2
- Kukačka, L., Nosek, Š., Kellnerová, R., Jurčáková, K., Jaňour, Z. Wind Tunnel Measurement of Turbulent and Advective Scalar Fluxes: A Case Study on Intersection Ventilation. Scientific World Journal. 2012, 2012(381357), 1-13. ISSN 1537-744X. doi: 10.1100/2012/381357
- Kellnerová, R., Kukačka, L., Jurčáková, K., Uruba, V., Jaňour, Z. PIV measurement of turbulent flow within a street canyon: Detection of coherent motion. Journal of Wind Engineering and Industrial Aerodynamics. 2012, 104(SI), 302-313. ISSN 0167-6105. doi: 10.1016/j.jweia.2012.02.017
- Kellnerová, R., Jaňour, Z. Flow instabilities within an urban intersection. International Journal of Environment and Pollution. 2011, 47(1-4), 268-277. ISSN 0957-4352
- Yassin, M.F., Kellnerová, R., Jaňour, Z. Experimental simulation on vehicle emission dispersion in urban street intersections. Kuwait Journal of Science & Engineering. 2009, 36(2B), 13-31. ISSN 1024-8684
- Matějíček, L., Engst, P., Jaňour, Z. A GIS-based approach to spatio-temporal analysis of environmental pollution in urban areas: A case study of Prague's environment extended by LIDAR data. Ecological Modelling. 2006, 199(3), 261-277. ISSN 0304-3800doi: 10.1016/j.ecolmodel.2006.05.018
- Jaňour, Z., Jurčáková, K., Brych, K., Dittrt, F., Dittrich, F. Potential risks at an industrial site: A wind tunnel study. Process Safety and Environmental Protection. 2010, 88(3), 185-190. ISSN 0957-5820. doi: 10.1016/j.psep.2010.01.003
- Yassin, M. F., Kellnerová, R., Jaňour, Z. Numerical simulation on pollutant dispersion from vehicle exhaust in street configurations. Environmental Monitoring and Assessment. 2009, 156(1-4), 257-273. ISSN 0167-6369. doi: 10.1007/s10661-008-0482-4
- Zelinger, Z., Střižík, M., Kubát, P., Civiš, S., Grigorová, E., Janečková, R., Zavila, O., Nevrlý, V., Herecová, L., Bailleux, S., Horká-Zelenková, V., Ferus, M., Skříňský, J., Kozubková, M., Drábková, S., Jaňour, Z. Dispersion of Light and Heavy Pollutants in Urban Scale Models: CO2 Laser Photoacoustic Studies. Applied Spectroscopy. 2009, 63(4), 430-436. ISSN 0003-7028.
- Yassin, M.F., Kellnerová, R., Jaňour, Z. Impact of street intersections on air quality in an urban environment. Atmospheric Environment. 2008, 42(20), 4948-4963. ISSN 1352-2310. doi: 10.1016/j.atmosenv.2008.02.019
- Matějíček, L., Jaňour, Z., Beneš, L., Bodnár, T., Gulíková, E. Spatio-temporal modelling of dust transport over surface mining areas and neighbouring residential zones. Sensors. 2008, 8(6), 3830-3847. ISSN 1424-8220. doi: 10.3390/s8063830
- Bezpalcová, K., Jaňour, Z., Prior, V., Soriano, C., Strizik, M. On the wind velocity profiles over urban area. International Journal of Environment and Pollution. 2003, 20(1), 196-206. ISSN 0957-4352
- Civiš, S., Střižík, M., Jaňour, Z., Holpuch, J., Zelinger, Z. Wind Tunnel Simulation of Air Pollution Dispersion in a Street Canyon. Journal of Aoac International. 2002, 85(1), 243-248. ISSN 1060-3271
- Zelinger, Z., Civiš, S., Jaňour, Z. Laser Photoacoustic Spectrometry and its Application for Simulation of Air Pollution in a Wind Tunnel. Analyst. 1999, 124(8), 1205-1208. ISSN 0003-2654
- Zelinger, Z., Střižík, M., Kubát, P., Jaňour, Z., Berger, P., Černý, A., Engst, P. Laser Remote Sensing and Photoacoustic Spectrometry Applied in Air Pollution Investigation. Optics and Lasers in Engineering. 2004, 42(-), 403-412. ISSN 0143-8166
- Zelinger, Z., Střižík, M., Kubát, P., Lang, K., Bezpalcová, K., Jaňour, Z. Model and real pollutant dispersion: concentration studies by conventional analytics and by laser spectrometry. International Journal of Environmental Analytical Chemistry. 2006, 86(12), 889-903. ISSN 0306-7319