This work deals with study of swirling flows where the spiral vortical structure appears. The main relation is to flow seen in the draft tube cone of hydraulic turbines operated out of the design point (i.e. best efficiency point). In this cases large coherent vortex structure (vortex rope) appears and consequently high pressure pulsations are propagated to the whole machine system leading to possible restriction of turbine operation. This flow features are consequence of flow instability called vortex breakdown in case of Francis turbine operated at part load (flow rate lower than optimal one). The present study is carried out using simplified device of swirl generator in order to access similar flow conditions as can be found in real hydraulic turbines. Both the dynamic and dissipation effect of spiral vortex breakdown are investigated. The first part of thesis deals with spiral form of vortex breakdown. The experimentally measured velocity profiles (LDA) and wall static pressures are correlated with numerical simulations carried out using open-source CFD package OpenFOAM 2.2.2. The high speed camera recording of cavitating vortex core is used to obtain image ensemble for further post-processing. The dissipation effect of spiral vortex structure is in detail discussed based on computed flow fields. The second part of thesis is dedicated to the application of POD decomposition to the study of spatio-temporal features of spiral vortex dynamics. Firstly the POD is applied to the both the experimentally obtained image ensemble of cavitating vortex and numerically computed static pressure fields. Secondly the comprehensive analysis of spiral vortex mitigation effect by the axial water jet is analyzed. The collaborative study employing the swirl generator apparatus designed by the researchers from Politehnica University of Timisoara in Romania is performed and changes in spatio-temporal vortex dynamic are studied. In this study the numerical data (in a form of three-dimensional pressure and velocity fields) are obtained using commercial CFD software ANSYS Fluent R14.

The subject of this final thesis was to elaborate variant proposal and to assess supporting steel structure roof bus station in the shape of a hyperbolic paraboloid. 2 variants were proposed, one of which was chosen as a more appropriate and this was processed details and drawings. Both variants are used as cover glass panels. Structures are made of steel with 235J0.

The aim of the diploma thesis "The use of alternative fuels in heating buildings " is the application of the heat sources using alternative fuels for heating of the production hall. The source of heat is a gas boiler, wood chips and dark gas infrared heaters. Appliances are then convection heaters, tubular registers and hot-air units.

Orientador: Celso Eduardo Tuna / Resumo: A agroindústria nacional brasileira dispõe de uma grande variedade de unidades agrícolas que geram elevada quantidade de resíduos como o bagaço de cana-de-açúcar. Mesmo diante da crescente utilização desse material, o excedente ainda é da ordem de milhões de toneladas, causando problemas de estocagem e poluição ambiental. Devido a sua estrutura complexa e sua recalcitrância, a etapa de pré-tratamento representa o desafio mais crítico para a viabilização da utilização do bagaço de cana-de-açúcar dentro do contexto de uma biorrefinaria. O pré-tratamento busca facilitar o acesso aos componentes estruturais da biomassa, permitindo sua utilização na cadeia produtiva. Existem diferentes métodos de pré-tratamento como os físicos, químicos e biológicos ou uma combinação de todos esses, de modo que a geração de resíduos ambientalmente perigosos e/ou altos insumos energéticos é o gargalo. Neste sentido, rotas tecnológicas alternativas vem sendo estudadas e a cavitação hidrodinâmica desponta-se como uma promissora rota para o pré-tratamento de biomassa liberando grandes magnitudes de energia e induzindo a transformações físicas e químicas, favorecendo o rompimento da matriz carboidrato-lignina. Neste contexto, este trabalho empregou a cavitação hidrodinâmica para potencializar o pré-tratamento alcalino do bagaço de cana-de-açúcar. Para isto, projetou-se um reator de cavitação hidrodinâmica com tubo de Venturi utilizando como base uma abordagem computacional para a dinâmica dos fluidos. ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The Brazilian national agroindustry has a large variety of agricultural units that generate high amounts of waste such as sugarcane bagasse. Even with the increasing use of this material, the surplus is still in the order of millions of tons, causing problems of stocking and environmental pollution. Due to its complex structure and recalcitrance, the pretreatment stage represents the most critical challenge for the feasibility of using sugarcane bagasse within the context of biorefinery. Pretreatment seeks to facilitate access to the structural components of biomass, allowing its use in the production chain. There are different pretreatment methods such as physical, chemical, physicochemical and biological or a combination of all of these, so that the generation of environmentally hazardous waste and / or high energy inputs is the bottleneck. In this sense, alternative technological routes have been studied and hydrodynamic cavitation emerges as a promising route for biomass pretreatment releasing large energy magnitudes and inducing physical and chemical transformations, favoring the rupture of the carbohydrate-lignin matrix. In this context, this thesis employed hydrodynamic cavitation as a physical means to improve the alkaline pre-treatment of sugarcane bagasse. The hydrodynamic cavitation reactor with Venturi tube was modeled by a computational approach to fluid dynamics, in order to evaluate the influence of the pressure ratio, the length and diameter of the throat and ... (Complete abstract click electronic access below) / Doutor

This study focused on a numerical second law analysis and optimisation of a receiver tube op- erating in a parabolic trough solar collector for small-scale application. The receiver functioned in a Rankine cycle. The focus was on entropy generation minimisation in the receiver due to the high quality exergy losses in this component. Water functioned as the working uid and was heated from ambient conditions (liquid) to a superheated state (vapour), consequently, the receiver tube was subject to both single phase as well as two-phase ow. Entropy generation in the receiver tube was mainly due to nite temperature di erences as well as uid friction. The contribution of each of these components was investigated. Geometrical as well as operating conditions were investigated to obtain good guidelines for receiver tube and plant design. An operating pressure in the range of 1 MPa (Tsat = 180 C) to 10 MPa (Tsat = 311 C) was considered. Furthermore a mass ow range of 0:15 kg=s to 0:4 kg=s was investigated. Results showed that beyond a diameter of 20 mm, the main contributor to the entropy generation was the nite temperature di erences for most conditions. Generally, operating pressures below 3 MPa showed bad performance since the uid friction component was too large for small operating pressures. This phenomenon was due to long two-phase lengths and high pressure drops in this region. The nite temperature di erence component increased linearly when the tube diameter was increased (due to the increase in exposed area) if the focused heat ux was kept constant. However, the uid friction component increased quadratically when the diameter was reduced. In general when the concentration ratio was increased, the entropy generation was decreased. This was due to more focused heat on each section of the receiver pipe and, in general, resulted in shorter receiver lengths. Unfortunately, there is a limit to the highest concentration ratio that can be achieved and in this study, it was assumed to be 45 for two-dimensional trough technology. A Simulated Annealing (SA) optimisation algorithm was implemented to obtain certain optimum parameters. The optimisation showed that increasing the diameter could result in a decrease in entropy generation, provided that the concentration ratio is kept constant. However, beyond a certain point gains in minimising the entropy generation became negligible. Optimal operating pressure would generally increase if the mass ow rate was increased. Finally, it was seen that the highest operating pressure under consideration (10 MPa) showed the best performance when considering the minimisation of entropy in conjunction with the maximisation of the thermodynamic work output. / Dissertation (MEng)--University of Pretoria, 2014. / tm2015 / Mechanical and Aeronautical Engineering / MEng / Unrestricted

Bakgrunden till examensarbetet var att vårdpersonal ska arbeta för att främja amning och för detta arbete behövs tydliga riktlinjer. Syftet med examensarbetet var att beskriva och jämföra omvårdnad och amningsutfall hos ammande barn som inte gick upp i vikt under sina första levnadsveckor. Metoden för arbetet var en retrospektiv journalgranskningsstudie där ett extraktionsprotokoll användes för att komma fram till resultatet. I studien inkluderades totalt 144 barn som vårdats inneliggande på barn- eller neonatalavdelning under perioden juli 2016 till juli 2019. Resultatet från studien visade att de flesta barn tillmatades med bröstmjölk och modersmjölksersättning via antingen bröst eller ventrikelsond samt att andelen barn som helammade var låg. Vidare visade studien att faktorer som minskade oddsen för helamning i samband med utskrivning var tillmatning med nappflaska, användande av modersmjölksersättning eller om barnen om barnets kön var en pojke. Slutsatsen var att barnen i första hand bör tillmatas via ventrikelsond då behov av tillägg utöver amning finns och att bröstmjölk bör vara förstahandsval vid tillmatning eftersom det främjar den fortsatta amningen. Barnsjuksköterskans roll för att främja amningen är att ge en god omvårdnad av barnet och fngera som ett stöd för mamman.

This thesis presents the results of a research program examining the effects of macro-synthetic fibers on the shear and flexural behaviour of high-strength concrete (HSC) beams subjected to static and blast loads. As part of the study, a series of seventeen fiber-reinforced HSC beams are built and tested under either quasi-static four-point bending or simulated blast loads using a shock-tube. The investigated test parameters include the effects of: macro-synthetic fibers, fiber hybridization, combined use of fibers and stirrups and longitudinal steel ratio and type. The results show that under slowly applied loads, the provision of synthetic fibers improves the shear capacity of the beams by allowing for the development of yield stresses in the longitudinal reinforcement, while the combined use of synthetic fibers and stirrups is found to improve flexural ductility and cracking behaviour. The results also show that the provision of synthetic fibers delays shear failure in beams tested under blast pressures, with improved control of blast-induced displacements and increased damage tolerance in beams designed with combined fibers and stirrups. The study also shows that the use of hybrid fibers was capable of effectively replacing transverse reinforcement under both loading types, allowing for ductile flexural failure. Moreover, the use of synthetic fibers was effective in better controlling crushing and spalling in beams designed with Grade 690 MPa high-strength reinforcement. Furthermore, the results demonstrate that synthetic fibers can possibly be used to relax the stringent detailing required by modern blast codes by increasing the transverse reinforcement hoop spacing without compromising performance. As part of the analytical study, the load-deflection responses (resistance functions) of the beams are predicted using sectional (moment-curvature) analysis, as well as more advanced 2D finite element modelling. Dynamic resistance functions developed using both approaches, and incorporating material strain-rate effects, are then used to conduct non-linear single-degree-of-freedom (SDOF) analyses of the blast-tested beams. In general, the results show that both methods resulted in reasonably accurate predictions of the static and dynamic experimental results.

The aim of the diploma thesis was an improvement of the efficiency of electrochemical generation of volatile form of cadmium used in atomic spectrometric methods. The increase of the efficiency of electrochemical generation of volatile form results in overall improvement of the sensitivity of measurement and therefore, it is possible to achieve lower values of detection limits and limits of determination. One of all the possibilities for improving of overall efficiency is a minimization of loss of volatile form of Cd during transport. Another essential possibility is coupling of the technique of electrochemical generation of volatile form of Cd with in-situ collection (and atomization) in graphite furnace of atomic absorption spectrometer. Keywords: Atomic absorption spectrometry, electrochemical generation of volatile compounds, generation efficiency, electrolytic flow-through generation cell, quartz-tube atomizer, graphite furnace, in-situ trapping, cadmium

The first part of the thesis focuses on developing a numerical methodology to simulate the acoustic properties of a hybrid liner consisting of a perforated plate, a porous layer and a Helmholtz cavity. Liners are always a standard way to reduce noise in today’s aeroengines, e.g. the fan noise can be reduced effectively through the installation of acoustic liners as wall treatments in the ducts. In order to optimize a liner in the design phase, an accurate and efficient prediction tool is of interests. Hence, a unified Linearized Navier-Stokes equations(LNSE) approach has been implemented in the thesis, combining the LNSE in frequency domain with the fluid equivalent model. The LNSE is applied in the vicinity of the perforated plate to simulate sound propagation including viscous damping effect, and the fluid equivalent model is used to model the sound propagation in the porous material including absorption. The second part of the thesis focuses on the prediction of thermoacoustic instabilities. Thermoacoustic instabilities arise when positive coupling occurs between the flame and the acoustics in the feedback loop, i.e. the flame acts as an amplifier of the disturbances (acoustic or fluid) at a natural frequency of the combustion system. Once the thermoacoustic instabilities occur, it will lead to extremely high noise levels within a relatively narrow frequency range, resulting in a huge damage to the structure of the combustors. Hence, a solution must be found, which breaks the link between the combustion process and the structural acoustics. The numerical prediction of thermoacoustic instabilities in the thesis is performed by two different numerical methodologies. One solves the Helmholtz equation in combination of the flame n − tau model with the low Mach number assumptions, and the other solves the Linearized Navier-Stokes equations in frequency domain with mean flow. The result show that the mean flow has a significant effect on the thermoacoustic instabilities, which is non-negligible when the Mach number reaches to 0.15. / <p>QC 20151221</p> / TANGO

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / This article proposes an algorithm oriented to the detection of the level of blood filling in patients, with detection capacity in millimeters. The objective of the software is to detect the amount of blood stored into the venipuncture tube and avoid coagulation problems due to excess fluid. It also aims to avoid blood levels below that required, depending on the type of analysis to be performed. The algorithm acquires images from a camera positioned in a rectangular structure located within an enclosure, which has its own internal lighting to ensure adequate segmentation of the pixels of the region of interest. The algorithm consists of an image improvement stage based on gamma correction, followed by a segmentation stage of the area of ​​pixels of interest, which is based on thresholding by HSI model, in addition to filtering to accentuate the contrast between the level of filling and staining, and as a penultimate stage, the location of the filling level due to changes in the vertical tonality of the image. Finally, the level of blood contained in the tube is obtained from the detection of the number of pixels that make up the vertical dimension of the tube filling. This number of pixels is then converted to physical dimensions expressed in millimeters. The validation results show an average percentage error of 0.96% by the proposed algorithm. / Revisión por pares