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DES modelling of the turbulent flow
Benešová, Stanislava ; Brechler, Josef (advisor) ; Dolejší, Vít (referee)
This thesis deals with the study of hybrid RANS/LES methods for modeling of turbulent flow with a focus on the DES method and its modifications. The theoretical part focuses on the description of turbulent flow and classical methods for its modeling. The following describes the hybrid RANS/LES methods, their principles and categories. Finally, the DES method is described in detail together with its improvement in form of DDES and IDDES methods. The practical part is devoted to the testing of DES and DDES on benchmark problems. We describe here used software OpenFOAM and numerical methods used to discretize the equations. One part is devoted to grid generation. The DES and the DDES methods are tested on two benchmarks: flat plate with zero pressure gradient and backward facing step. The simulaton results are compared with experimental data, with a focus on good modeling of the velocity profile near wall, turbulent viscosity and skin friction coefficient. Powered by TCPDF (www.tcpdf.org)
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Microscale flow and diffusion characteristics inside the urban area
Kukačka, Libor ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee)
Dispersion of pollutants in the atmosphere of urban areas is the important task in environmental sciences. The main goal was the quantitative studying of a flow in a symmetrical urban built-up area depending on a running on flow direction. There was given a theoretical base of the physical modeling of the atmospheric boundary layer in this work. The measurement was done with a model of the urban build-up area at a scale of 1:200 in the aerodynamic wind tunnel of the IT AS CR, v.v.i. in Nový Knín. The requirements to the similarity to a real atmospheric boundary layer and a model boundary layer in the wind tunnel were accomplished. Velocity fields, concentration fields and fields of scalar uxes were measured in the area of a rectangular intersection. Results of the experiment showed significant sensitivity of the velocity field about the running on flow direction that extensively inuenced ventilation of street canyons.
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Zlepšení metod předpovědi termické konvekce pro účely letecké meteorologie
Dvořák, Petr ; Řezáčová, Daniela (advisor) ; Brechler, Josef (referee)
This rigorous thesis is engaging by some processes in boundary layer of the atmosphere, namely rise and running of thermals, focused on vertical motion and speeds of thermals, and on methods of their measurement and forecasting. It exploits data, measured by the GPS receivers and loggers aboard of gliders and paragliders during flying over Czech Republic, and data from aerological soundings, provided by Praha-Libus observatory. Measurement was in progress in so called cross-country flight season 2007 and 2008. The solution of this research is improvement of forecasting of vertical velocity of thermals and can be used in specialised forecasts for private and recreative flying and in forecasts of thermal turbulence.
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Flow and diffusion characteristics inside the urban area
Chaloupecká, Hana ; Jaňour, Zbyněk (advisor) ; Brechler, Josef (referee)
Title: Flow and diffusion characteristics inside the urban area Author: Hana Chaloupecká Department: Department of meteorology and enviroment protection Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., IT AS CR, v. v. i. Supervisor's e - mail: janour@it.cas.cz Abstract: Uniqueness of different towns, consists of various shapes of buildings. The main topic of this work is to compare concentration diffusion within groups of buildings of various types. We pursued houses made of single blocks of two different lengths - they were placed parallel or in courtyards. For research of pollution diffusion within the housing estates a method of physical modelling has been used. For this purpose we summarized a theory of atmospheric boundary layer and physical modelling at first. Then we pursued experiments. Measuring took place in a model in scale 1 : 300 inside an aerodynamic wind tunnel of the Institute of Thermomechanics AS in Nový Knín. We checked out the requirements placed on similarity of the real boundary layer and boundary layer modelled in the tunnel. By the measuring of concentration in urban areas we weren't watching a plume from the pollution source but we were studying an inversion task. We measured concentrations in two fixed points from different point sources inside the defined areas. A sensitivity of...
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The Impact of the Macroeconomic Environment on Insurance Companies
Čepeláková, Lenka ; Jakubík, Petr (advisor) ; Brechler, Josef (referee)
i Abstract: This thesis assesses the impact of economic, institutional and demographic factors on the life and non-life gross written premiums of insurance companies. A dynamic panel data regression using the system generalized method of mo- ments is applied on data of 29 European countries collected by EIOPA covering the period from 2005 to 2013. The results reveal that economic and institutio- nal factors drive both life and non-life insurance industry. On the other hand, we cannot confirm that demographic factors are significant determinants of the growth in GWPs. Subsequently, the hypothesis that there are substantial cross-countries differences among the importance of different macroeconomic determinants on the insurance sector development is explored and confirmed. This work shines new light on the development of the quantitative macro- prudential framework used to determine different economic scenarios affecting insurance companies' balance sheets. Moreover, a broader set of panel data and more variables explaining the growth in insurance sector bring new contributi- ons to the current discussion in academic literature.
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