I present in this thesis a fluid flow and heat transfer model for porous media using the lattice Boltzmann method (LBM). A computer simulation of this process has been developed and it is written using MATLAB software. The simulation code is based on a two dimensional model, D2Q9. Three physical experiments were designed to prove the simulation model through comparision with numerical results. In the experiments, physical properties of the air flow and the porous media were used as input for the computer model. The study results are not conclusive but show that the LBM model may become a reliable tool for the simulation of natural convection heat transfer in porous media. Simulations leading to improved understanding of the processes of air flow and heat transfer in porous media may be important into improving the efficiency of methods of air heating or cooling by passing air through fragmented rock.

The study focuses on an alluvial plain situated within a large meander of the Logan River at Josephville near Beaudesert which supports a factory that processes gelatine. The plant draws water from on site bores, as well as the Logan River, for its production processes and produces approximately 1.5 ML per day (Douglas Partners, 2004) of waste water containing high levels of dissolved ions. At present a series of treatment ponds are used to aerate the waste water reducing the level of organic matter; the water is then used to irrigate grazing land around the site. Within the study the hydrogeology is investigated, a conceptual groundwater model is produced and a numerical groundwater flow model is developed from this. On the site are several bores that access groundwater, plus a network of monitoring bores. Assessment of drilling logs shows the area is formed from a mixture of poorly sorted Quaternary alluvial sediments with a laterally continuous aquifer comprised of coarse sands and fine gravels that is in contact with the river. This aquifer occurs at a depth of between 11 and 15 metres and is overlain by a heterogeneous mixture of silts, sands and clays. The study investigates the degree of interaction between the river and the groundwater within the fluvially derived sediments for reasons of both environmental monitoring and sustainability of the potential local groundwater resource. A conceptual hydrogeological model of the site proposes two hydrostratigraphic units, a basal aquifer of coarse-grained materials overlain by a thick semi-confining unit of finer materials. From this, a two-layer groundwater flow model and hydraulic conductivity distribution was developed based on bore monitoring and rainfall data using MODFLOW (McDonald and Harbaugh, 1988) and PEST (Doherty, 2004) based on GMS 6.5 software (EMSI, 2008). A second model was also considered with the alluvium represented as a single hydrogeological unit. Both models were calibrated to steady state conditions and sensitivity analyses of the parameters has demonstrated that both models are very stable for changes in the range of ± 10% for all parameters and still reasonably stable for changes up to ± 20% with RMS errors in the model always less that 10%. The preferred two-layer model was found to give the more realistic representation of the site, where water level variations and the numerical modeling showed that the basal layer of coarse sands and fine gravels is hydraulically connected to the river and the upper layer comprising a poorly sorted mixture of silt-rich clays and sands of very low permeability limits infiltration from the surface to the lower layer. The paucity of historical data has limited the numerical modelling to a steady state one based on groundwater levels during a drought period and forecasts for varying hydrological conditions (e.g. short term as well as prolonged dry and wet conditions) cannot reasonably be made from such a model. If future modelling is to be undertaken it is necessary to establish a regular program of groundwater monitoring and maintain a long term database of water levels to enable a transient model to be developed at a later stage. This will require a valid monitoring network to be designed with additional bores required for adequate coverage of the hydrogeological conditions at the Josephville site. Further investigations would also be enhanced by undertaking pump testing to investigate hydrogeological properties in the aquifer.

Title: Solution of inverse problem for a flow around an airfoil Author: Mgr. Jan Šimák Department: Department of Numerical Mathematics Supervisor: prof. RNDr. Miloslav Feistauer, DrSc., dr. h. c., Department of Numerical Mathematics Abstract: The method described in this thesis deals with a solution of an inverse problem for a flow around an airfoil. It can be used to design an airfoil shape according to a specified velocity or pressure distribution along the chord line. The method is based on searching for a fixed point of an operator, which combines an approximate inverse and direct operator. The approximate inverse operator, derived on the basis of the thin airfoil theory, assigns a corresponding shape to the specified distribution. The resulting shape is then constructed using the mean camber line and thickness function. The direct operator determines the pressure or velocity distribution on the airfoil surface. We can apply a fast, simplified model of potential flow solved using the Fredholm integral equation, or a slower but more accurate model of RANS equations with a k-omega turbulence model. The method is intended for a subsonic flow.

abstract: Due to great challenges from aggressive environmental regulations, increased demand due to new technologies and the integration of renewable energy sources, the energy industry may radically change the way the power system is operated and designed. With the motivation of studying and planning the future power system under these new challenges, the development of the new tools is required. A network equivalent that can be used in such planning tools needs to be generated based on an accurate power flow model and an equivalencing procedure that preserves the key characteristics of the original system. Considering the pervasive use of the dc power flow models, their accuracy is of great concern. The industry seems to be sanguine about the performance of dc power flow models, but recent research has shown that the performance of different formulations is highly variable. In this thesis, several dc power-flow models are analyzed theoretically and evaluated numerically in IEEE 118-bus system and Eastern Interconnection 62,000-bus system. As shown in the numerical example, the alpha-matching dc power flow model performs best in matching the original ac power flow solution. Also, the possibility of applying these dc models in the various applications has been explored and demonstrated. Furthermore, a novel hot-start optimal dc power-flow model based on ac power transfer distribution factors (PTDFs) is proposed, implemented and tested. This optimal-reactance-only dc model not only matches the original ac PF solution well, but also preserves the congestion pattern obtain from the OPF results of the original ac model. Three improved strategies were proposed for applying the bus-aggregation technique to the large-scale systems, like EI and ERCOT, to improve the execution time, and memory requirements when building a reduced equivalent model. Speed improvements of up to a factor of 200 were observed. / Dissertation/Thesis / M.S. Engineering 2013

Motivado pela ocorrência de instabilidade do motor do veículo de Fórmula SAE da equipe Poli Racing da Escola Politécnica da Universidade de São Paulo quando operando em altas rotações, o escoamento no conduto de admissão, mais especificamente no último conduto antes do flange do motor, conhecido como runner, foi então analisado. A suspeita de que o descolamento do escoamento da parede na região interna da curvatura fosse a causa da instabilidade do motor foi então estudada de duas maneiras: um estudo numérico e outro experimental. O estudo numérico se inicia pela caracterização do escoamento real e desenvolvimento de hipóteses simplificadores e considerações sobre os pontos mais relevantes do escoamento. Em seguida, uma malha de elementos é construída no computador com auxílio de um programa de CFD. Ressalta-se que sua geometria reproduz a geometria interna do duto de interesse (runner). Posteriormente, a mesma é simulada utilizando um modelo de duas equações (SST k-w), obtendo-se assim o perfil de pressão ao longo da região interna e externa da parede do runner.O estudo experimental se inicia pela construção do runner em prototipagem rápida, mantendo sua geometria fiel à geometria do runner utilizado no veículo de referência, adaptando a esse, tomadas de pressão ao longo da sua seção meridional. Ele é então montado em laboratório e as pressões nas diversas tomadas de pressão são então medidas para diferentes valores de vazão.Os resultados acima obtidos são então comparados com as referências bibliográficas relevantes.De maneira geral, tanto os resultados numéricos como os resultados experimentais estão de acordo com as referências bibliográficas, indicando que até valores do número de Reynolds iguais a aproximadamente 210000 (o que corresponde para as condições de temperatura e pressão do ar de admissão durante a operação do motor, a uma velocidade média no runner de cerca de 80 m/s) não ocorre descolamento na região interna da curvatura do runner. / Motivated by the occurrence of instability of the engine of the Formula SAE vehicle of the Poli Racing team from the Polytechnic School of University of São Paulo when operating at high engine speeds, the flow in the intake manifold, more specifically in the last duct before the engine flange, known as runner, became focus of deeper analysis. The suspicion that the detachment of the flow from the wall in the inner region of curvature was the cause of engine instability was studied in two approaches: a numerical study and an experimental study. The numerical study begins by characterizing the real flow and development of simplifying assumptions and considerations on the most relevant points of the flow. Then, a mesh is built into the computer with the aid of a CFD program. Its geometry is equal to the internal geometry of the studied duct (runner). Subsequently, the mesh is simulated using a two equations model (SST k-w) and a pressure profile in the inner and outer wall is calculated. The experimental study begins with the construction of the runner using rapid prototyping, keeping its geometry equal to the geometry of the runner used in the reference vehicle, but adapting to this, pressure taps along the inner and outer wall of the curvature. It is then assembled in the laboratory and the pressure in different pressure taps are measured for different flow rates.The above results are then compared with the relevant bibliographic references.In general, both the numerical results and the experimental results are in agreement with the references indicating that up to Reynolds numbers values equal to approximately 210 000 (which considering the air temperature and pressure while engine is operating, corresponds to an average speed in the runner around 80 m/s) does not occur any detachment in the inner region of curvature of the runner.

The acquisition of representative subsea fluid sampling from offshore field development asset is crucial for the correct evaluation of oil reserves and for the design of subsea production facilities. Due to rising operational expenditures, operators and manufacturers have been working hard to provide systems to enable cost effective subsea fluid sampling solutions. To achieve this, any system has to collect sufficient sample volumes to ensure statistically valid characterisation of the sampled fluids. In executing the research project, various subsea sampling methods used in the offshore industry were examined and ranked using multi criteria decision making; a solution using a remote operated vehicle was selected as the preferred method, to compliment the subsea multiphase flowmeter capability, used to provide well diagnostics to measure individual phases – oil, gas, and water. A mechanistic (compositional fluid tracking) model is employed, using the fluid properties that are equivalent to the production flow stream being measured, to predict reliable reservoir fluid characteristics on the subsea production system. This is applicable even under conditions where significant variations in the reservoir fluid composition occur in transient production operations. The model also adds value in the decision to employ subsea processing in managing water breakthrough as the field matures. This can be achieved through efficient processing of the fluid with separation and boosting delivered to the topside facilities or for water re-injection to the reservoir. The combination of multiphase flowmeter, remote operated vehicle deployed fluid sampling and the mechanistic model provides a balanced approach to reservoir performance monitoring. Therefore, regular and systematic field tailored application of subsea fluid sampling should provide detailed understanding on formation fluid, a basis for accurate prediction of reservoir fluid characteristic, to maximize well production in offshore field development.

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The aim of this diploma thesis is to determine the market value of the company Svijany, a.s. as of 31. 12. 2014 using the discounted cash flow methods FCFF and FCFE. The purpose of valuation is for company owners. The thesis is divided into two main chapters. A theoretical chapter defines the concepts, reasons for valuation and the main processes and principles of valuation. A practical chapter applies the methods specified in theoretical part. The practical part contains strategic and financial analysis necessary to determine the future value of the company. As a next, the results of previous analyses are applied to identify value drivers and create financial plan. Finally, based on previous calculations it is possible to focus on valuation of the company using the discounted cash flow methods. In the end the individual methods of valuation are compared.

This work deals with system dynamics. Its main task is to create and description of the add-in to Excel that allows users to model the stock and flow model directly in Excel. Furthermore, there is discussed about the general theory of system dynamics, systems and models. There is also described the history of programming languages and their development to C #, in which the supplement was created. The thesis also presents competition created add-in.

This diploma thesis focuses on the phenomena of multiphase flow in a steam generator as a one of probable causes of tubes and tubesheet weld cracking. In the first part of the work, a research was carried out focusing on the boiling and the phenomenon of two-phase flow in technical applications, its characteristics and properties. The thesis continuous with an overview of available numerical multiphase models in the ANSYS Fluent 2021 R1 and a research of previously published works focused on two-phase flow with the presence of boiling. The research is followed by a description of the particular boiler, which is part of the nitric acid production plant in the chemical company DUSLO, a.s., its operating conditions and a more detailed description of the issue that is being addressed in this thesis. The second part of the work continuous with a description of the computational model, including a description of the geometry of the model and used simplifications, the computational mesh and the description of boundary conditions. Important part is the description of calculation setting of steady-state and transient CFD simulations in ANSYS Fluent. Finally, the results of the two-phase flow calculation are presented and then discussed in the conclusions.