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Atmospheric aerosol vertical distribution in boudary layer
Dočekalová, Veronika ; Hovorka, Jan (advisor) ; Jančík, Petr (referee)
Particulate matter (PM) air pollution is one of the most important topics in the field of environmental protection, and coal strip mining is a significant source of coarse atmospheric aerosol. In order to implement appropriate regulations to improve air quality, we need to identify the major sources of pollution. PM is usually measured in a ground-based manner and its dispersion is only modelled. Therefore, the objective of this study was to measure concentrations of coarse aerosol in the atmospheric boundary layer above the area of the coal strip mine through experimental airborne measurements and to estimate pollution contribution of mining to the surroundings. Measurements were carried out from November 11 to November 26, 2012, at Vršany coal mine, Czech Republic. An electrically powered airship was used with a specially designed gondola carrying aerosol monitors DustTrak DRX and P-Trak. Temperature and relative humidity data were also recorded. Repeated flights were performed at several heights above mine edge level. PM1-10 and GPS data were recorded every second. Average airship velocity ranged from 6 to 7 ms-1 . Flight measurements were also compared to ground-based measurements of PM10 and meteorological data. Weather during our measurements was characterised by low temperatures, high relative...
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Choice of the SUPG parameter for higher order finite elements
Kohutka, Jiří ; Knobloch, Petr (advisor) ; Dolejší, Vít (referee)
In this work, we deal with the finite element method Streamline Upwind/Petrov-Galerkin (SUPG) and use it to solve boundary value problem for the stationary convection-diffusion equation with dominant convection with Dirichlet boundary condition on the whole boundary of bounded polyhedral computational domain of dimension 1 and 2, respectively. We consider a quadratic Lagrangian finite elements on the line segments and triangles, respectively. The core of the work is a proposition of choice of stabilizing parameter of SUPG method as an elementwise affine function in outflow boundary layer and as an elementwise constant function in the rest of the computational domain. We show that this choice gives a more accurate solution than the choice of the stabilization parameter as a constant in each element. 1
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Temperature inversions in the boundary layer over Prague
Stryhal, Jan ; Sládek, Ivan (advisor) ; Huth, Radan (referee)
Temperature inversions in the boundary layer over Prague Abstract The main objective of this study is to analyze temperature inversions in the atmospheric boundary layer (ABL) over Prague. In the first part, the concept of the ABL is defined and main theoretical aspects of air stratification are explored. The main part of the background research summarizes current knowledge of temperature inversions, especially how the landscape pattern influences their development and parameters under different synoptic situations, and methods used for their detection, measurement and evaluation. Considering the theme of the thesis, main geographic factors influencing temperature inversions in the area of Prague are also defined. The focus of actions is placed on inversions analysis based upon time series of Praha-Libuš rawinsonde station. Homogeneity of used data is tested and all inversions within the 2000- meters-thick-layer close to the ground are derived. Diurnal, annual and interannual frequency variations are described. Significance of long-term trends is tested and trends are compared to data from Prostějov and Kümmersbruck stations. Keywords: temperature inversions, boundary layer, climate, Prague
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Wind shear as a dangerous fenomenon in aviation
Novozámský, Adam ; Jebáček, Ivo (referee) ; Krška, Karel (advisor)
This thesis is about wind shear and its influence on aviation. There is wide theoretical description of wind shear and it’s implemented into aviation practice. There are also methods of observation, forecasting and reporting, for both pilots and meteorologist described. In this thesis, pilots can find useful recommendations for dealing with wind shear during the flight. Every reader can also read about famous aviation accidents and look at models of weather that caused those accidents. At the end of thesis there are analyses of a rawiosonde measurements related to wind shear reports. This whole thesis is focused on increasing awareness of wind shear in aviation from angle of view of both pilots and aviation meteorologist.
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Aerodynamics of axial wind turbines
Just, Jan ; Pospíšil, Jiří (referee) ; Škorpík, Jiří (advisor)
This master thesis concerns about problematics of wind turbines. The document summarizes basic theory based on the law of momentum conservation which is essential tool for the design and calculation of wind turbines. The theory is complemented by number of correction factors and then used in the design of wind turbine for specific parameters. The calculation is performed iteratively using Matlab software and the actual code is given in appendix. Graphs summarizing the progress of various units along the blades are presented in the document. The final section briefly describes advanced topics of aerodynamics concerning other important factors that the field of wind energy deal with in recent time.
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Air flow load on a roof structure induced by a helicopter during erection works
Fidler, Tomáš ; Križan, Jiří (referee) ; Nevařil, Aleš (advisor)
Diploma thesis is focused on modeling rotor downwash generated by the main rotor of helicopter and analyzing its effects on the roof structure. Theoretical definition of rotor downwash flow is described in the first part of the text. Governing equations of computational fluid dynamics are briefly explained as well as boundary layer and finite volume method. Next part inquires into numerical simulation of rotor downwash based on height of rotor above the roof, shape of roof plane and climatic conditions. Results are compared with climatic load values provided by actual Czech construction standard in the end of the text.
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Wind loads of building structures
Štěrba, Martin ; Kala, Jiří (referee) ; Hradil, Petr (advisor)
The bachelor thesis deals with the analysis of the effects of wind load on building structures. In the context of the work is solved the numerical modeling of flow around the solid cylindrical bodies at high Reynolds numbers. To the simulations has been used computational software ANSYS CFX. The outputs of the work are the values of Strouhal numbers and the values of drag and lift coefficient depending on the Reynolds number.
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High-Frequency, Small-Scale Fluidic Oscillators for Boundary Layer Control
Tesař, Václav
No-moving-part fluidic oscillators are promising candidates for use in jet-type actuators for suppressing the separation in adverse pressure gradient flows and for elmination of the effect of hairpin vortices that absorb the turbulent fluid flow energy. The requests for very high oscillation frequency has led to several new ideas applied to the oscillator configurations.
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