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Syfte: Syftet med denna uppsats är att undersöka finansiella institutioners syn på hävstångsinstrument och utifrån detta utreda om instrumenten är ett bra investeringsalternativ för småsparare. Metod: Uppsatsen har en kvalitativ inriktning då tre intervjuer har genomförts för att besvara syftet. De finansiella institutionerna som intervjuades är Handelsbanken, CMC Markets och SIP Nordic fondkommission. Vidare har studien en deduktiv infallsvinkel där teorier används som grund för det empiriska materialet. Utifrån intervjuer och tidigare studier har en slutsats sedan utformats för att besvara syftet. Resultat & Slutsats: Uppsatsens resultat talar för att hävstångsinstrumenten är ett bra alternativ för småsparare som är intresserade, risktoleranta och aktivt söker kunskap. Småspa­rare som har dessa egenskaper och dessutom har ett bra kompletterande sparande kan därför med fördel investera i dessa instrument. För småsparare som inte har den risktolerans och kunskap som krävs för ett lyckat resultat, kan dock andra sparalternativ vara ett bättre val. Förslag till fortsatt forskning: Då resultatet av denna uppsats är baserat på finansiella institutioners syn på hävstångsinstrument, vore det intressant att utreda samma sak men att då basera det empiriska materialet på intervjuer eller enkäter med småsparare som använder instrumenten. Detta skulle i sådana fall ge forskaren svar på hur instrumenten uppfattas av småspararna själva. Uppsatsens bidrag: Tidigare forskning inom detta område finns enbart i liten utsträckning. Därmed bidrar vår studie med att öka kunskapen om hävstångsinstrument. Uppsatsen ger en bred bild av hävstångsinstrument som sparalternativ och bidrar med att ge en förståelse för vilka hävstångsinstrumenten passar till.

The average and fluctuating components in a model ring-type gas turbine combustor are characterized using a Large Eddy Simulation at a Reynolds number of 11,000, based on the bulk velocity and the mean channel height. A spatial filter is applied to the incompressible Navier-Stokes equations, and a high pass filtered Smagorinsky model is used to model the sub-grid scales. Two cases are studied: one with only the swirler inlet active, and one with a single row of dilution jets activated, operating at a momentum flux ratio J of 100. The goal of both of these studies is to validate the capabilities of the solver NEK5000 to resolve important flow features inherent to gas turbine combustors by comparing qualitatively to the work of Jakirlic. Both cases show strong evidence of the Precessing Vortex Core, an essential flow feature in gas turbine combustors. Each case captures other important flow characteristics, such as corner eddies, and in general predicts bulk flow movements well. However, the simulations performed quite poorly in terms of predicting turbulence shear stress quantities. Difficulties in properly emulating the turbulent velocity entering the combustor for the swirl, as well as mesh quality concerns, may have skewed the results. Overall, though small length scale quantities were not accurately captured, the large scale quantities were, and this stress test on the HPF LES model will be built upon in future work that looks at more complex combustors.

This thesis deals with the problems of scaling aerodynamic data from wind tunnel to free flight  conditions. The main challenges when this scaling should be performed is how the model support, wall interference and the potentially lower Reynolds number in the windtunnel should be corrected. Computational Fluid Dynamics (CFD) simulations have been performed on a modern transonic transport aircraft in order to reveal Reynolds number effects and how these should be scaled accurately. A methodology for scaling drag and identifying scaling effects in general is presented.  This investigation also examines how the European Transonic Wind tunnel twin sting model support influences the flow over the aircraft. When the Reynolds number is differing between the wind tunnel and free flight conditions, a change in boundary layer transition position can occur. In order to estimate first order boundary layer transition effects a correlation based transition prediction method, previously presented by Menter and Langtry, is implemented in the CFD solver Edge. The transition model is further developed and a novel set of equations for the production terms is found through a CFD/optimizer coupling. The transition data, used to calibrate the CFD transition model,  have been extracted from a low Mach number wind tunnel campaign. At these low Mach numbers many compressible CFD solvers suffer of poor convergence rates and a deficiency in robustness and accuracy might appear. The low Mach number effects are investigated, and an effort to prevent these is done by implementing different preconditioning techniques in the compressible CFD solver Edge. The preconditioners are mainly based on the general Turkel preconditioner, but a novel formulation is also presented in order to make the numerical technique less problem dependent. / QC 20100903

Ventilation systems are closely connected to indoor environment. In industrial spaces it has a major impact due to air quality and thermal comfort requirements, which leads into health and economy improvements. Confluent jets ventilation system has been assess in Söderhamn Eriksson, a machinery company located in Mariannelund, Sweden, since it has been proved as the best ventilation performance. Moreover this system is worthy for both heating and cooling purposes, although just heating case will be developed in this thesis. By means of modelling software such as Gambit and Airpak, the company’s case could have been analyzed via Computational Fluid Dynamics (CFD) software, i.e. Fluent. The analyzed models were accepted after a thorough study of meshing parameters, bearing in mind computational limitations. Every temperature data gathered from simulation results has been verified with infrared camera figures taken at the company, thus contributing to reach reliable conclusions. As it is inferred from previous papers and empiric theory, the flow field observed is also justified. Then, thermal comfort and air quality analysis relies on consistent facts. It has been found that current ventilation at the company is slightly misadjusted, since supplied air’s temperature and velocity are slightly off point. Therefore, it is recommended to reduce these values to reach better working environment.

Phenols are priority pollutants that are commonly found in a large number of industrial wastewaters. Different processes are currently available for the elimination of phenol from wastewater but present some disadvantages like low efficiency, high energy-consumption, the necessity of acclimatisation of the sludges or the limitation of the treatment capacity. The need to find alternatives has made the enzymatic processes a good option. In the last two decades, several processes were implemented with different enzymes from plants and microorganisms, including peroxidases from several sources, as the horseradish peroxidase.Also, different enzyme configurations, free or immobilised enzyme and different supports for immobilisation have been studied. Substantial attention has been devoted to the covalent immobilisation of enzymes on porous insoluble supports such as glass, alumina, silica, and chitosan.The main novelty of this work is the utilisation of a torus reactor for the removal of organic contaminants from wastewaters. This reactor, which can be considered as a loop reactor, presents some advantages over other stirred tank reactors.The goal of this work is the study of the hydrodynamics of a torus reactor for its further application in the enzymatic elimination of phenol and the coupling of the kinetics and the modelisation.In a first step, the enzymatic elimination of phenol was experimentally studied in the torus reactor. In order to compare the performances, several assays were also carried out with a stirred reactor. A high degree of conversion was obtained for the enzymatic elimination of phenol in both reactors with the tested quantities of phenol. It was concluded that, keeping a ratio of 1:1 between the phenol and the H2O2 initial molar quantities, the highest final reaction conversion was obtained. Using the torus reactor was obtained 97% of phenol conversion when the optimal concentrations of substrates were usedIn order to improve economically the process, the enzyme should be used in a continuous regime over a long time period to exploit it completely. For this reason it was necessary to immobilise the enzyme. This work presents a new configuration that has never been tested: the horseradish peroxidase supported on Eupergit.In a second step, the characterisation using the CFD of the flow-field in a torus reactor of 100 ml, similar to the experimental reactor, was carried out for two different configurations, batch and continuous operating modes. Moreover, the scale-up of the volume of the torus reactor was carried out using CFD for a 300 ml reactor.Finally, the enzymatic reaction of phenol with the HRP was modelled using the CFD coupled to the kinetic model of the enzymatic reaction to the flow simulation. These results allowed the possibility of optimising and scaling-up the process using the CFD modelisation. / Los compuestos fenólicos son contaminantes prioritarios que se encuentran comúnmente en una gran cantidad de efluentes industriales. Diferentes procesos están disponibles actualmente para la eliminación de fenol desde dicho efluentes pero los mismos presentan algunas desventajas como pueden ser una baja eficiencia, un mayor consumo de energía, la producción de lodos conteniendo hierro o limitaciones en la capacidad de tratamiento. La necesidad de encontrar alternativas a estos problemas ha hecho del proceso enzimático una buena opción. En las últimas dos décadas, varios procesos han sido implementados utilizando diferentes enzimas extraídas de plantas y microorganismos como pueden ser las peroxidasas de diversas fuentes, incluyendo la horseradish peroxidasa.Diferentes configuraciones de enzimas, libre e inmovilizada y diferentes soportes para la inmovilización han sido también estudiados. Sustancial atención ha sido dedicada a la inmovilización de enzimas por enlace covalente sobre soportes porosos insolubles tales como vidrio, aluminio, sílice y chitosan. El objetivo de este trabajo es el estudio de la hidrodinámica dentro de un reactor tórico para su posterior aplicación en la eliminación enzimática de fenol y el acople entre las cinéticas y la modelización.En una primera etapa, la eliminación enzimática de fenol es estudiada experimentalmente en el reactor tórico. Con el objetivo de comparar el rendimiento de dicho reactor, varios ensayos se realizaron en un reactor agitado tradicional. Un alto grado de conversión de fenol ha sido obtenido para la eliminación enzimática de fenol en ambos reactores para las cantidades estudiadas de fenol. Ha sido observado que es necesario mantener una relación de 1:1 entre la concentración inicial de fenol y la de peróxido de hidrógeno para lograr la mayor conversión de fenol. Usando el reactor tórico ha sido obtenido un 97% de conversión de fenol cuando las concentraciones óptimas de substratos y enzimas fueron utilizados. Con el objetivo de mejorar económicamente el proceso y hacerlo factible para su uso a escala industrial, la enzima debería ser utilizada en un proceso en continuo sobre un largo período de tiempo para explotarla completamente. Por esta razón, ha sido necesario inmovilizar la enzima. Este trabajo muestra una nueva configuración que no ha sido aún probada: la horseradish peroxidase soportada en Eupergit. Asimismo, la caracterización usando CFD del campo de flujo de un reactor tórico similar al experimental de 100 ml ha sido realizada para un reactor trabajando de forma batch y continua. Un escalado en el volumen del reactor tórico ha sido realizado utilizando CFD para un reactor de 300 ml. Finalmente, la reacción enzimática de fenol con HRP has sido modelada acoplando el modelo cinético obtenido experimentalmente con las simulaciones del campo de flujo dentro del reactor. Estos resultados permitirán la optimización y el escalado del proceso usando CFD.

The main purpose of the dissertation is to contribute to the development of numerical techniques for computational heat transfer and fluid flow, suitable for low cost (loosely coupled) parallel computers. It is focused on implicit integration schemes, using finite control volumes with multigrid (MG) algorithms.Natural convection in closed cavities is used as a problem model to introduce different aspects related with the integration of the incompressible Navier-Stokes equations, such as the solution of the pressure correction (or similar) equations that is the bottleneck of the algorithms for parallel computers. The main goal of the dissertation has been to develop new algorithms to advance in the solution of this problem rather than to implement a complete parallel CFD code. An overview of different sequential multigrid algorithms is presented, pointing out the difference between geometric and algebraic multigrid. A detailed description of segregated ACM is given. The direct simulation of a turbulent natural convection flow is presented as an application example. A short description of the coupled ACM variant is given.Background information of parallel computing technology is provided and the the key aspects for its efficient use in CFD are discussed. The limitations of low cost, loosely coupled cost parallel computers (high latency and low bandwidth) are introduced. An overview of different control-volume based PCFD and linear equation solvers is done. As an example, a code to solve reactive flows using Schwartz Alternating Method that runs particularly well on Beowulf clusters is given.Different alternatives for latency-tolerant parallel multigrid are examined, mainly the DDV cycle proposed by Brandt and Diskin in a theoretical paper. One of its main features is that, supressing pre-smoothing, it allows to reduce the each-to-neighbours communications to one per MG iteration. In the dissertation, the cycle is extended to two-dimensional domain decompositions. The effect of each of its features is separately analyzed, concluding that the use of a direct solver for the coarsest level and the overlapping areas are important aspects. The conclusion is not so clear respect to the suppression of the pre-smoothing iterations.A very efficient direct method to solve the coarser MG level is needed for efficient parallel MG. In this work, variant of the Schur complement algorithm, specific for relatively small, constant matrices has been developed. It is based on the implicit solution of the interfaces of the processors subdomains. In the implementation proposed in this work, a parallel evaluation and storage of the inverse of the interface matrix is used. The inner nodes of each domain are also solved with a direct algorithm. The resulting algorithm, after a pre-processing stage, allows a very efficient solution of pressure correction equations of incompressible flows in loosely coupled parallel computers.Finally, all the elements presented in the work are combined in the DDACM algorithm, an algebraic MG equivalent to the DDV cycle, that is as a combination of a parallel ACM algorithm with BILU smoothing and a specific version of the Schur complement direct solver. It can be treated as a black-box linear solver and tailored to different parallel architectures.The parallel algorithms analysed (different variants of V cycle and DDV) and developed in the work (a specific version of the Schur complement algorithm and the DDACM multigrid algorithm) are benchmarked using a cluster of 16 PCs with a switched 100 Mbits/s network.The general conclusion is that the algorithms developed are suitable options to solve the pressure correction equation, that is the main bottleneck for the solution of implicit flows on loosely coupled parallel computers.

La Tesi en qüestió presenta una metodologia per a l'estudi de les Vàlvules Limitadores de Pressió i concretament en les que presenten un tamany reduït, taps de 10 [mm] i amb seccions de pas de fins a 2 [mm], amb prestacions definides per a Q<5 [l/min] i P<150 [bar]. L'estudi es presenta en base a aprofundir en el coneixement dels fenòmens estàtics, dinàmics i fluidodinàmics que es produeixen durant el funcionament de la mini VLP i la variació d'aquest comportament en funció de variables pròpies de disseny. Aquest estudi s'enfoca en dos vessants diferenciades però complementàries.Es pretén deduir criteris de disseny en base a- Comportament dinàmic. Estudi de l'equació del moviment de l'obturador en funció dels paràmetres globals de disseny com, rigidesa de la molla, diàmetre d'entrada, massa del tap de la mini VLP. - La fluidodinàmica interna. Estudi de la fluidodinàmica interna de la mini VLP en funció dels paràmetres de disseny específics del tap o obturador de la mateixa. per tal de realitzar aquesta tasca s'utilitza el programa de simulació numèrica Fluent.La Tesi s'estructura en base a aquests dos estudis i presenta les següents etapes.- Anàlisis crític de l'estat de l'art.- Desenvolupament d'un model teòric de funcionament en règim permanent i transitori d'una mini VLP. Aquesta modelització es realitza per mitjà de la linealització de les equacions governants del procés i la posterior implementació en un programa de simulació, Matlab-Simulink, per a la obtenció de les corbes de funcionament i les zones d'estabilitat de la mini VLP.- Anàlisis, mitjançant simulació numèrica, de la fluidodinàmica interna de la mini VLP en funció d'una geometria definida.- Anàlisis experimental. Es dissenya i construeix un banc experimental d'assaig per a contrastar i validar experimentalment els models proposats de la mini VLP.L'objectiu de la Tesi es desenvolupar una nova metodologia que combini les eines de simulació amb equacions governants amb mètodes computacionals avançats i test de laboratori profund per tal de comprendre el comportament de nous components oleohidràulics de tamany reduït, aprofundint en aquells criteris de disseny que són més sensibles a la miniaturització. S'ha aplicat aquesta metodologia en diferents tipologies geomètriques de tap. S'han simulat i assajat geometries còniques guiades i no guiades, geometries amb valona (xamfrà) sense guiar i geometries planes amb disseny singular guiades i sense guiar.Es presenta a continuació un recull dels aspectes més importants del desenvolupament de la Tesi.Els resultats de la simulació fluidodinàmica posa d'evidència la importància de la simetria del fluxe i el guiat de l'obturador amb l'objecte d'evitar inestabilitats no desitjables. El guiat del tap és clau per a l'obtenció d'un nivell de funcionament òptim. Sobret tot en el cas del nivell sonor.Les inestabilitats i sorolls generats com a conseqüència de l'aparició de cavitació són inevitables. En general es manifesten en una gamma de freqüències superiors als 3000 [Hz]. La seva incidència en el comportament global de la mini VLP es pot considerar moderat i acceptable.Les inestabilitats els efectes de les quals són més severes són conseqüència dels graus de llibertat que posseeix l'obturador. La autoexcitació en aquests casos pot arribar a efectes sonors molt apreciables i molestos. S'ha de facilitar per tots els mitjans el guiat de l'obturador. Ha quedat demostrat la idoneïtat de la metodologia de pre disseny de la mini VLP basada en l'aplicació dels principis bàsics de conservació de la massa, quantitat de moviment i energia en forma de balanços integrals. Per estudiar el comportament dinàmic i predir la influència de paràmetres bàsics tals com massa de l'obturador, constant elàstica de la molla, etc, és suficient deduir el criteri d'estabilitat a partir de la linealització de les equacions anteriors. De tots els resultats es destaquen les idees següents.Utilització de carcassa de metacrilat en la realització de les proves experimentals que ha permès entendre la fenomologia fluidodinàmica existent i relacionar-la amb els valors de les variables de funcionament, poden establir zones diferents de funcionament.La utilització de les eines de simulació, concretament el mòdul de malla dinàmica del programa de volums finits Fluent, ha permès obtenir resultats fins ara no presentats. Considerant-ne un avanç important, la introducció d'aquest tipus de simulacions en el sector oleohidràulic.Els fenòmens de vibració en valors de freqüència pròpia es destaquen com els més perjudicials en el funcionament de la mini VLP. Es demostra que la geometria no juga cap paper esmorteïdor d'aquest fenomen. / This Thesis presents a methodology for the study of mini relief valve of small size, plugs of 10 [mm] and flow paths of about 2 [mm]. The main characteristics of this component are Q<5 [l/min] i P<150 [bar]. This work is focused in a better understanding of the static, dynamic and fluid dynamic behaviour and how this is afected by the cariation of own design variables. This study has two main areas, - Dynamic behaviour. Study of the movement equation of the plug as a function of the global design parameters like for example spring stiffness, inlet diameter or plug mass.- Internal fluid dynamic. Study of the internal fluid dynamic behaviour of the mini relief valve as a function of the specific design characteristics of the plug. This work is made by the use of numerical simulations.The Thesis is structured as follow,- State of the art. Critical analysis.- Development of a theoric model in steady and transient state. This modelization is done with Matlab-Simulink and the stability zones are obtained.- Analysis using numerical simulations of the internal flow as function of a defined geometry.- Experimental test. A test bench has been designed and constructed to obtain the real behavior of the mini relief valve and to be compared with theoric models.The aim of this Thesis is to develop a new methodology that assembly the theoretical models, the numerical simulation tools and experimental tests, to understand the behavior of mini hydraulic components and the design variables that are more affected by the miniaturization.This methodology has been applied to different plug geometries. Conical or non conical plugs, guided or non guided plugs have been simulated and tested. Is shown briefly the most important results of this work.The numerical simulation results show how important is the flow symmetry and the plug guidance in order to eliminate non desired instabilities. This is a key point in the attenuation of the sound level. The instabilities and noise generated as a consequence of cavitation are non avoidable. They appear at 3000 [Hz] or higher. The affectation degree in the mini relief valve global behavior is acceptable.Depending on the freedom degrees of the plug, the instabilities increase and the global behavior can be really affected. Guidance is strongly recommended. The application of the main equations as a predesign methodology has allowed the obtaining of the stability criterion related to the mini relief valve basic parameters.The use of a methacrilate body in the test has made possible the understanding of the internal fluid dynamic and the relation with the global working parameters. The results obtained with the dynamic mesh used in the numerical simulations open a new and interesting research field in hydraulic components. The most detrimental behavior is related with the mini relief valve resonance frequency. The geometry does not attenuate this vibration behavior.

Multi-scale modeling of chemical vapor deposition (CVD) is a very broad topic because a large number of physical processes affect the quality and speed of film deposition. These processes have different length scales associated with them creating the need for a multi-scale model. The three main scales of importance to the modeling of CVD are the reactor scale, the feature scale, and the atomic scale. The reactor scale ranges from meters to millimeters and is called the reactor scale because it corresponds with the scale of the reactor geometry. The micrometer scale is labeled as the feature scale in this study because this is the scale related to the feature geometries. However, this is also the scale at which grain boundaries and surface quality can be discussed. The final scale of importance to the CVD process is the atomic scale. The focus of this study is on the reactor and feature scales with special focus on the coupling between these two scales. Currently there are two main methods of coupling between the reactor and feature scales. The first method is mainly applied when a modified line of sight feature scale model is used, with coupling occurring through a mass balance performed at the wafer surface. The second method is only applicable to Monte Carlo based feature scale models. Coupling in this second method is accomplished through a mass balance performed at a plane offset from the surface. During this study a means of using an offset plane to couple a continuum based reactor/meso scale model to a modified line of sight feature scale model was developed. This new model is then applied to several test cases and compared with the surface coupling method. In order to facilitate coupling at an offset plane a new feature scale model called the Ballistic Transport with Local Sticking Factors (BTLSF) was developed. The BTLSF model uses a source plane instead of a hemispherical source to calculate the initial deposition flux arriving from the source volume. The advantage of using a source plane is that it can be made to be the same plane as the coupling plane. The presence of only one interface between the feature and reactor/meso scales simplifies coupling. Modifications were also made to the surface coupling method to allow it to model non-uniform patterned features. Comparison of the two coupling methods showed that they produced similar results with a maximum of 4.6% percent difference in their effective growth rate maps. However, the shapes of individual effective reactivity functions produced by the offset coupling method are more realistic, without the step functions present in the effective reactivity functions of the surface coupling method. Also the cell size of the continuum based component of the multi-scale model was shown to be limited when the surface coupling method was used. Thanks to the work done in this study researchers using a modified line of sight feature scale model now have a choice of using either a surface or an offset coupling method to link their reactor/meso and feature scales. Furthermore, the comparative study of these two methods in this thesis highlights the differences between the two methods allowing their selection to be an informed decision.