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1
Björk, Johan. "Compressor CFD simulation method development : A CFD study". Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-69880.
Testo completoAbstract (sommario):
This master thesis project consisted of three parts that all were performed through CFD simulations with the purpose to develop Scania's methods in the subject of CFD. All parts included simulations on Scania's SC92T70 centrifugal compressor. Part one consisted of performing a mesh study for the purpose of reliability, to investigate the convergence of different parameters by refining the boundary layer. The method used is an inflation option called First layer thickness. Five different meshes were generated where the Richardson extrapolation method was used to examine the parameters between the mesh renements. From the result from the examined parameters, an approximate relative error could be calculated to be less than 0.52 %, and a numerical uncertainty of less than 0.35 %, between Mesh3 and Mesh4. In addition to that, Mesh3 had a simulation time of one hour less than for Mesh4. These results motivated the use of mesh3 to be refined enough for further work in this thesis project. This mesh ended at 37, 915, 257 number of elements. The second part consisted of performing steady state CFD simulations, to examine different parameters in order to find indications of the phenomena surge. Here, experimental data was used as reliance to perform CFD simulations on the compressor. Design points from experimental data was used, that ranged from low mass flow rates where surge arises, to high mass flow rates where another phenomena called choke occur. Except for the design points taken from experimental data, a few extra design points where included at low mass flow rates (in the region of surge). The goal was that the analysis of the different parameters would generate fluctuations on the result for the design points in surge region. Four different rotational speeds on the compressor were examined, 56k, 69k, 87k and 110k revolutions per minute. A total of 140 different parameters were examined, where 10 of these indicated on surge. All of these parameters that indicated on surge where found in regions of vicinity to the compressor wheel, which are the regions subjected to the phenomena.The parameters indicating on surge where mass flow, pressure coefficient, static pressure and temperature. Indications where found at the wheel inlet, ported shroud, and wheel outlet interfaces. The indications were only found for the two lower rotational speeds of the compressor wheel. To capture the behaviour on higher rotational speeds, more design points in the region of surge are needed, or transient simulations. Part three of the thesis project consisted of investigating the methodology of performing a Conjugate Heat Transfer model (CHT) with the CFD code CFX. This part has not been performed by Scania before, so a big part of the problem was to investigate if it actually was achievable. The goal was to use this model to calculate the heat transfer between fluid and solid parts, as well as between the solid parts and the ambient. One question Scania wanted to answer was if the CHT model could generate aerodynamic performance that corresponds to Scania's traditional adiabatic model, as well as to experimental data of the compressor. In this part, both solid and fluid domains were included in the geometryto calculate heat transport, in contrast to the traditional adiabatic model that only uses the fluid domains. Because of that, a big part of the work consisted of defining all interfaces connecting together surfaces between all domains. This is needed to model heat transport between the domains. In the set up part in CFX, the CHT model differed a lot from the traditional adiabatic model in that way that the outer walls was not set up as adiabatic anymore. In the CHT model, instead heat transfer is allowed between the outer walls of the fluids and the solids. From the result simulations, one could see that the CHT model was able to compute the heat transfer between fluids and solids. It also managed to export thermal data such as heat flux and wall heat transfer coefficient to be used for mechanical analysis, which is an important part in Scania's work. From the analysis of aerodynamic performance, a conclusion was drawn that the CHT model was able to compute efficiency and pressure ratio that followed the behaviour ofthe traditional adiabatic model as well as experimental data. However, for lowermass flows, the CHT model started to underpredict which could be explained by the geometrical differences between the CHT and adiabatic model. By analysis of temperature, one could see quantitative differences compared to the traditional adiabatic model. For other parameters (static and total pressure), there were no experimental data to be used for comparison. Because of that, an important part in future work of this CHT method development is to perform more experimental test for CFD data to be compared against. Another important part to compare the models is to have an identical geometry. Without an identical geometry, deviations in result will occur that depends on geometry.
2
King, Matthew Lee. "A CAD-centric Approach to CFD Analysis With Discrete Features". Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd570.pdf.
Testo completo
3
Du, Jianyi. "Combustion CFD simulation". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/NQ56437.pdf.
Testo completo
4
Gilani, Mohammad Nejad Hamzeei. "CFD of droplet entrainment". Thesis, Imperial College London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542939.
Testo completo
5
Heinz, Matthias. "CFD- Berechnung von Axialkolbenpumpen". Technische Universität Chemnitz, 2019. https://monarch.qucosa.de/id/qucosa%3A34344.
Testo completoAbstract (sommario):
Axialkolbenpumpen bieten eine hohe Leistungsdichten und einfache Regelbarkeit.
Allerdings neigen sie zu Kavitation, mit der Gefahr der Beschädigung und erhöhter Geräuschbildung durch Druckpulsationen. Die numerische Strömungssimulation bietet die Möglichkeit, die transienten Prozesse innerhalb dieser Pumpen zu verstehen und Optimierungsmöglichkeiten aufzuzeigen.
Die komplexe Bewegung der Kolben erfordert bewegte Gitter, die translatorische und rotatorische Bewegungen sehr genau abbilden müssen. Die zu fördernde Hydraulikflüssigkeit muss als kompressibles Medium behandelt werden, insbesondere da sie zu bestimmten Zeiten (Kompressions- und Dekompressionsphase) in geschlossen Kammern einer Volumenänderung unterworfen ist, die eine Dichte- und Druckänderung mit sich bringt. Im Falle des Auftretens von Kavitation ist eine Modellierung der gasförmigen und flüssigen Phase notwendig.
Der Vortrag zeigt auf, wie das vollständige transiente Verhalten von Axialkolbenpumpen simuliert werden kann. Dadurch ist es möglich, Steuerzeitenoptimierungen durchzuführen, die zu geringerer Kavitationsneigung und reduzierten Druckpulsationen führen.
6
Svedjeland, Magnus. "CFD-simulering av luft- och temperaturflöde i ett apparatskåp". Thesis, University West, Department of Technology, Mathematics and Computer Science, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-756.
Testo completo
7
Zaffagnini, Alberto. "Modellazione CFD di manufatti idraulici". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016.
Cerca il testo completoAbstract (sommario):
Nel presente lavoro di tesi vengono studiati, per mezzo di simulazioni numeriche di fluidodinamica computazionale, diversi manufatti idraulici, partendo da casi più semplici la cui trattazione teorica e sperimentale è ampiamente conosciuta, come flusso attraverso una soglia e moto uniforme in canale rettangolare, fino a casi complessi di cui non esistono formulazioni teoriche ma solo sperimentali come pozzetti di salto cilindrici. In particolare, come caso conclusivo, si studia il comportamento di un manufatto ripartitore realmente esistente in un impianto di trattamento delle acque reflue.
8
Nøttveit, Erlend. "Numerisk analyse (CFD) av stempelpumpe". Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10575.
Testo completoAbstract (sommario):
I denne oppgåva er det sett nærare på lekkasjar i stempelpumper. I starten presenterast den nødvendige teorien for CFD, pumper og spalter. Ein definerer deformasjons-lekkasje/trykk-lekkasje som eit forhold. Berekningar blir gjort på bakgrunn av teorien slik at ein konkret kan talfesta dette forholdet. Etter dette blir simuleringane som er utført presangtert og diskutert. Den første simuleringa er for ein enkel sylinder utan veggar. Det er med andre ord berre veskevolumet som er med. Denne modellen er brukt til å lære teknikken for deforming mesh. Dette er ein teknikk som er nødvendig for å kunne ha forandring av veskevolumet sin geometri i løpet av simuleringa. Den neste simuleringa er eigentlig ein vidareføring av den første. Hovudskilnaden er at her er det tatt med ein vegg som representerer spalta mellom stempelet og sylinderveggen. Spalta i modellen er mykje større ein kva den er i røynda. I modellen ser den meir ut som ein sylinder enn ei spalte. Innerveggen av spalta er ein open vegg frå sylinderen sitt veskevolum og inn i spalta, medan ytterveggen er ein tett vegg. Dette gjer at veska har høve til å lekke gjennom spalta og ut på endane. Det er lagt inn porøsitet i spalta som skapar strøymingsmotstand som om det var ei lita spalte. Denne modellen blei kjørt fleire gongar for å få den rette verdien på strøymingsmotstanden. Då verdien for porøsitet var på plass, blei det laga ein modell med sju sylindrar. Toppen av sylindrane ligg inn mot ei spalte. Denne spalta er mellom sylinderblokka og ventilplata. Sidan det er sju stempel i denne modellen og ikkje eit som i dei føregåande, er det brukt UDFer (User-Defined Function) for å styre stempela sin aksialrørsle som er faseforskyvd i forhold til kvarandre. Også denne modellen blir kjørt fleire gongar og det blir utvikla spissar på avslutningane av opningane i ventilplata. Resultata for kjøringar med og utan spiss blir samanlikna og diskutert. I denne modellen er det ikkje med noko inn- og utløpsprofil, så endå ein modell er utvikla der det er med ein geometri også for inn- og utløp. Denne modellen får dermed ein 3d form på avslutninga av opningane i ventilplata. I tillegg er den modellen forsøkt gjort meir korrekt i overgang mellom sylindrane og ventilplate. Sjølv i desse enkle modellane med forenkla spalter finn ein at celletalet i spaltene utgjer ein signifikant del av cellene i modellen.
9
Vangbo, Petter Olav. "CFD in conceptual ship design". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-15480.
Testo completoAbstract (sommario):
Computational Fluid Dynamics (CFD) has been around for many years. It is a computer tool that can be used to find the hydrodynamic fluid performances. In ship design it is used in a wide area from smoke propagation to resistance estimations. It is however in resistance estimations that CFD have had most focus and research. There are many tools a designer can make use of nowadays. Most of the tools are computer based. This is optimization algorithms, computer aided design (CAD) and computational fluid dynamics (CFD). Using the tools should shorten the time of ship design and make better solutions. I have used a computer tool that mixes optimization with model variation (CAD) and verification (CFD). My conclusion is that it is a powerful tool to use, but should be handled with care. Few variables in the optimization process are important. Conceptual design methodology could be broken down to two outer ranges; point based design and set based design. The methods are quite different when approaching a complex design problem. There seems to be some favor in set based design when coming to a global ‘optimized’ solution to the design problem. More knowledge is gathered in set based design before deciding the final requirements and parameters. This is especially in new developing design where little knowledge is produced in the past. CFD is a broad term. There is many different methods and area of use. In this thesis I will break it down to two terms; potential codes and RANSE codes. Potential codes are easy, robust and well developed. RANSE codes are difficult, takes a lot of time and not so well developed. Potential codes are used in areas where turbulent flows are not present, while RANSE codes are used when it is present and important to the result. If designing new innovative hulls CFD should be used earlier in the design process and with a simulation driven design approach. Simulation driven design could be used with potential codes or RANSE codes. To have a high value rate of the modeling potential codes should be used when many sets of variation I needed and turbulence is not important to the answers. RANSE code should be used when turbulent flow is important to the answer, but must be done with few sets of variations because of high computational effort. If designing a more standard ship, CFD should be used in a modeling design approach to verify the performance estimations that have been done earlier in the process.
10
Erlandsson, Johan, e Patrik Berg. "Analys av turbulensmodeller för CFD". Thesis, Uppsala universitet, Kärnfysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-161110.
Testo completoAbstract (sommario):
This thesis has been a part of Forsmarks Kraftgrupp AB's evaluation of a turbulence model used in simulation of turbulent flow called PRNS (Partially Resolved Numerical Simulation). This model has promising properties and may be of use in saving computational resources. The purpose of this thesis was to analyze this model and compare it with industrially applied models such as k-omega SST and LES (Large Eddy Simulations). PRNS works as a hybrid of the k-omega SST and DNS (Direct Numerical Simulation) where a constant, RCP (Resolution Control Parameter) with a value between 0 and 1 are selected. This constant is then used in the calculations and determines the behavior of the simulation. When RCP is set to zero the equation are the same as for a DNS simulation and when RCP is set to one the equations for k-omega SST is solved. In this report four different PRNS models have been used, three where RCP was given a constant value (0.1, 0.4 and 0.6). In the fourth model RCP is calculated from the flow field variables The models have been compared to an experiment from 2008 and simulations have been made to resemble the experiment. In the experiment a Particle Image Velocimeter (PIV) was used as method of measurement. From the experimental report data such as velocity (U), turbulent kinetic energy (k) and standard deviation (URMS) have been obtained and have formed the basis for comparison. The models have been simulated in two different software programs: OpenFOAM and Fluent. The data have thereafter been post processed in the software programs MatLab and ParaView, to be compared with experimental data. The results of the simulations have shown that PRNS models generally show a good accordance with experimental data. In particular, PRNS models with constant RCP have shown good results, however, there are some discrepancies. The PRNS model with varying RCP has in most cases showed the largest deviation from experimental data but also a deviation from the other models, including the reference models. Due to the design of the mesh (coarse) further evaluation of the PRNS models will be needed. First, simulate with a finer mesh, but also more complex geometries should be simulated in order to sort out PRNS strengths and weaknesses and thus determine if the model can be used in the daily work at Forsmarks Kraftgrupp AB.
11
Vusirikala, Shanti. "CFD simulation of contact planarization". Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Vusirikala_09007dcc80446043.pdf.
Testo completoAbstract (sommario):
Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 25, 2008) Includes bibliographical references (p. 77-79).
12
Jain, Arnav. "CFD beräkning på en jetmotorinstallation". Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-21746.
Testo completoAbstract (sommario):
Hawk Turbine AB tillverkar mindre jetmotorer som ofta används i små obemannade och radiostyrda flygplan. I flygplansmodellen Lockheed T-33 Shooting Star är motorn monterad inuti planet varför luften måste ledas ut till atmosfären. För bästa möjliga prestanda måste ejektorn och utblåsröret som leder luften dimensioneras efter motor och flyghastighet. En 3-dimensionell CAD modell av flygplanets installation skapades och därefter simulerats i en virtuell vindtunnel med hjälp av datorprogrammet SolidWorks Flow Simulation. Flera olika utblåsrör i varierande storlekar samt olika former har testats för att avgöra om ändringar kan förbättra prestandan ytterligare. Simulationsresultat visar att det går att förbättra nuvarande konfiguration med 5,99 % om diametern på utblåsröret minskas från 75 mm till 70 mm med en bibehållen form på utblåsröret.Hawk Turbine AB is a company that manufactures small jet engines which are often used in smaller unmanned and radio-controlled aircrafts. In the Lockheed T-33 Shooting Star aircraft the engine is mounted in the center of the aircraft and therefore requires ducts to be used for directing the exhaust to the atmosphere. For optimum performance the ejector and the exhaust manifold must be designed for the engine and the flight velocity. A 3-dimentional CAD model of the aircrafts ducts was created. The model was then used in virtual wind tunnel testing using the software SolidWorks Flow Simulation. Different shapes and sizes of the manifolds were tested in the simulations to determine if modifications can further improve the performance. The simulations show that the performance of the current manifold can be improved by 5,99 % if the diameter of the manifold is reduced from 75 mm to 70 mm while keeping the shape of the manifold unaltered.
13
Hartinger, Markus. "CFD modelling of elastohydrodynamic lubrication". Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444143.
Testo completoAbstract (sommario):
Usually elastohydrodynamic lubrication (EHL) is modelled using the Reynolds equation for the fluid flow and the elastic deformation is calculated following the Hertzian contact theory. In this thesis a CFD approach for modelling EHL is established. The full Navier-Stokes equations are used which enables the entire flow domain to be modelled and which can resolve all gradients inside the contact. Liquid properties are introduced where the viscosity is piezo-viscous, shear-thinning and temperature dependent and where the density is a function of pressure. The phenomenon of cavitation is taken into account by two homogeneous equilibrium cavitation models which are compared with each other. For one cavitation model an energy equation is developed which considers the effects of heat conduction and convection, viscous heating and the heat of evaporation. The Hertzian contact theory is implemented and parallelised within the CFD method and validated against analytical solutions. Then, the cavitation models and the Hertzian contact theory are occupied together in a forward iterative manner. The developed method is applied to glass-on-steel and metal-on-metal line contacts and isothermal results are compared to the Reynolds theory. Very good agreement was found with the Reynolds theory in most cases. For high viscosity, high velocity and rolling conditions small differences to the Reynolds theory were found. The influence of temperature is studied for a series of test cases and the results are compared to their isothermal counterparts. All thermal calculations under sliding conditions developed a temperature-induced shear-band which is closer towards the slower, thus hotter, surface. The thermal, high viscosity calculations under sliding conditions showed significant pressure variation across the film thickness due to very large viscosity gradients. The impact of temperature on the friction force is very significant. Results of a three-dimensional, isothermal point contact are shown to demonstrate the feasibility of such calculations. The developed method is capable of giving new insights into the physics of elastohydrodynamic lubrication, especially in cases where the usual assumptions of the Reynolds theory break down.
14
Forster, Robin Norman George. "CFD modelling of vortex combustors". Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/770204/.
Testo completoAbstract (sommario):
This dissertation examines the suitability of Computational Fluid Dynamics (CFD) modelling for the production of realistic flowfields and temperature fields within a series of vortex combustion chambers of differing geometries and operating under various conditions. Initial validation of the CFD predictions was obtained through modelling of a series of isothermal vortex chambers for which a comprehensive set of experimental data was available. It was observed that CFD did indeed produce representative flowfield predictions for chambers of various geometries and operating conditions. A vortex unit used for the incineration of sewage sludge (US Navy Waste Incinerator) was subsequently investigated, and it was shown that due to the high moisture content of the waste material used, temperature profiles obtained with a modified coal combustion model were similar to those obtained with a more straightforward and computationally less expensive spray drier model. Results from both models were similar to experimentally observed conditions. However, comprehensive validation was not possible. In order that full validation could be provided for a CFD model of a vortex combustion unit, a model was developed of a commercial thermal oxidiser used for the incineration of liquid and gaseous wastes. CFD temperature predictions for the BASF Thermal Oxidiser were validated by a series of experimental measurements obtained from the operating unit. In general, it was found that the Reynolds Stress Model for turbulence produced the most representative velocity flowfields, with the less computationally demanding k-e model being applicable only under certain limited circumstances. Furthermore, insufficient grid refinement resulted in significantly distorted velocity profiles.
15
Graysmith, J. L. "Using CFD in engine design". Thesis, University of Warwick, 1995. http://wrap.warwick.ac.uk/4252/.
Testo completoAbstract (sommario):
In this thesis the author presents two areas of work; exploring the integration of Computational Fluid Dynamics (CFD) into engine design for Jaguar Cars Ltd and developing a novel 'mesh construction' method for making mesh generation both easy and fast. It is concluded that Jaguar can use CFD in the evaluation stage of the engine design process, although not in the concept stage of design. The CFD predictions are shown to be useful for detecting flow related faults and determining the general flow trends, but they should not be used as an absolute measure of the flow variables. The author has determined an efficient method for obtaining good quality meshes using commercial modelling and mesh generation software which requires a skilled CFD analyst. Steady flow analysis of an engine port and cylinder design could currently be completed in about six weeks using a high-powered workstation. The author recommends dedicated workstations for CFD analysis and training Jaguar's draughtsmen to create CAD models with computer analysis requirements in mind. The author's mesh construction program automatically joins two overlapping meshes or cuts one mesh from another. Whilst the program works well on the test cases considered, it is not at a stage for commercial exploitation. Further development is therefore recommended.
16
Somarathne, Shini. "Dynamic thermal modelling using CFD". Thesis, Brunel University, 2003. http://bura.brunel.ac.uk/handle/2438/5523.
Testo completoAbstract (sommario):
Buildings expend vast quantities of energy, which has a detrimental impact on the environment. Buildings systems are often oversized to cope with possible extreme environmental conditions. Building simulation provides an opportunity to improve building thermal design, but the available tools are typically used in combination in order to overcome their individual deficiencies. Two such tools, often used in tandem are computational fluid dynamics (CFD) and dynamic thermal modelling (DTM). DTM provides a coarse analysis, by considering external and internal thermal conditions over a building (including its fabric) over time. CFD is usually used to provide steady state analysis. Boundary conditions typically in the form of surface temperatures are manually input from DTM into CFD. CFD can model buildings dynamically, but is not commonly used, since solving for hugely different time constants of solid and air pose significant limitations, due to data generated and time consumed. A technique is developed in this study to tackle these limitations. There are two main strands to the research. DTM techniques had to be incorporated into CFD, starting from first principles of modelling heat transfer through solid materials. These were developed into employing the use of functions such as the 'freeze flow' function (FEF) and the 'boundary freeze' function (BFF) in combination with a time-varying grid schedule to model solids and air simultaneously. The FFF pauses the solution of all governing equations of fluid flow, except temperature. The BFF can be applied to solid boundaries to lock their temperatures whilst all other equations are solved. After extensive research the established DTM-CFD Procedure eventually used the FEF and BFF with transient periods and steady state updates, respectively. The second strand of research involved the application of the DTM-CFD Procedure to a typical office space over a period of 24-hours. Through inter-model comparisons with a fully transient simulation, the DTM-CFD Procedure proved to be capable of providing dynamic thermal simulations 16.4% more efficiently than a typical CFD code and more accurately than a typical DTM code. Additional research is recommended for the further improvement of the DTM-CFD Procedure.
17
Vince, Tomáš. "CFD analýza tepelného zatížení trubkovnice". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443458.
Testo completoAbstract (sommario):
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.
18
Kubíček, Radek. "CFD simulace vibrací vyvolaných prouděním". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-403865.
Testo completoAbstract (sommario):
The presented diploma thesis focuses on flow-induced vibrations of a tube. The main aim and benefit is the analysis of tube stiffness in contact with the other one and the following use of obtained values and characteristics in CFD simulations. The work can be divided into three parts. The first part is about the current state of knowledge of flow-induced vibrations. It introduces the basic mechanisms of vibration and methods for their suppression. The second part deals with the determination of stiffness of defined geometry tube including the collision with the other tube. The final part demonstrates and evaluates the application of obtained characteristics in CFD simulations.
19
Zach, Jiří. "Obchodování s akciovými CFD kontrakty". Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2014. http://www.nusl.cz/ntk/nusl-224713.
Testo completoAbstract (sommario):
The aim of this thesis is to design an investment strategy focused on tool called CFD. The first theoretical part contains basic information about financial derivates and explains basic principles of trading on stock market with contracts for difference. Chapter of the investment analysis explains the methods and rules used in trading. The practical part presents the results of my trading CFDs and evaluated my proposed strategy along with the benefits of work.
20
Stromský, Ondřej. "Optimalizace geometrie výměníku pomocí CFD". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2008. http://www.nusl.cz/ntk/nusl-228337.
Testo completoAbstract (sommario):
The main task of thesis is to find optimum geometry of the heat exchanger. The biggest emphases is placed to finding the most optimum of streaming liquid in the heat exchanger and to minimisation pressure losses. There is a effort to regulate the streaming liquids in heat exchangers so that in multitube and on the shell side don´t create dead areas, it means to avoid sedimentation of particle in these places. Dead areas cause rising resistance against heat transfer and necessity of frequently cleaning the heat exchanger. For these reasons is necessary to do analyse of flowing and to looking for the optimal geometry of the heat exchanger.
21
Kroupa, Michal. "CFD simulace poryvu bočního větru". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318722.
Testo completoAbstract (sommario):
This thesis deals with the investigation of unsteady effects on vehicle that has been exposed to a crosswind gust. First crosswind velocity function was created, which is a function of both time and space. A comparison of continual and trapeze gust model was carried out. Next step was to compare unsteady and quasi-steady evolution of the aerodynamic loads using accumulated forces, surface pressures and flow field around the car. The penultimate part deals with investigation of unsteady behaviour of drag and in the last part the influence of rear geometry of the car on unsteady phenomena was investigated.
22
Garcia, Barceló Roger. "Mesh sensitivity analysis on wind farms using CFD wind flow models and CFD wake models". Mémoire, École de technologie supérieure, 2012. http://espace.etsmtl.ca/1087/1/GARCIA_BARCELO_Roger.pdf.
Testo completoAbstract (sommario):
Actuellement, les énergies renouvelables semblent prendre au jour le jour plus de poids dans les politiques énergétiques actuelles. Entre les multiples formes, l’énergie éolienne, ayant une grande présence de nos jours, est celle qui présente des prévisions de majeure croissance lors des prochaines décennies.
Un outil très efficace pour la prédiction de la ressource éolienne sont les simulations CFD. Cette technique permet de résoudre les équations qui gouvernent le mouvement d’écoulement en tenant compte des effets de recirculation et de séparation. Evidemment, les résultats d’une simulation CFD pour la prédiction de la ressource éolienne dépendent de la modélisation que l’on effectue mais aussi du maillage.
Le maillage du domaine d’étude doit être le résultat d’une fonction optimisée tenant en compte deux paramètres: la qualité des résultats et les coûts de simulation. Visant cette fonction, deux analyses de sensibilité de maillage à travers une batterie de cas. Les paramètres géométriques visé sont la résolution des différentes zones d’études, l’extension des zones, hauteur du domaine, etc.
L’objectif principal est de recommander un guide de paramètres de maillage aux usagers de CFDWind1.0 lors de l’étude de l’écoulement du vent en CFD sur terrain complexe puis offshore, tout en ayant atteint la convergence de maillage. Les résultats obtenus lors du maillage en terrain complexe sont très satisfaisant alors que lors de l’étude de l’écoulement en sillage, la modélisation doit être améliorée. Plusieurs voies d’amélioration sont proposées en visant des futures études.
23
Thompson, Peter Mark. "Computation of CAD-based design velocities for aerodynamic design optimisation with adjoint CFD data". Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675476.
Testo completoAbstract (sommario):
This thesis describes the investigation and development of a novel CAD-based aerodynamic optimisation system, with the aim of allowing gradient-based optimisation of feature-based, parametric models within commercial CAD packages in timescales acceptable for industrial design processes. The process developed is based on linking parametric design velocities (geometric sensitivities computed from the CAD model representing the displacement of a point on the model boundary due to a perturbation of a CAD model parameter) with adjoint surface mesh sensitivities (which represent the derivative of a goal function with respect to surface mesh node position). A CAD-based design velocity computation method has been developed based on projection between discrete representations of perturbed geometries which can be linked to virtually any existing commercial CAD system. A key characteristic of the approach is that it can cope with the discontinuous changes in CAD model topology and face labelling that can occur under even small changes in CAD parameters. Use of the above approach allows computation of parametric sensitivities with respect to aerodynamic coefficients for native CAD parameters within feature-based commercial CAD modelling systems using adjoint data at a computational cost of just one adjoint analysis per objective function and one design velocity field evaluation per parameter. Gradient computation is demonstrated on test cases for an aerofoil model, a turbine blade model and a 3D wing model. Using these computed sensitivities enables the creation of a truly CAD-based aerodynamic optimisation system incorporating adjoint CFD data and using design velocities for computing geometric sensitivities and as input to a mesh deformation step. A prototype implementation of this system is presented and used to optimise a parametric CAD-based aerofoil model. In order to develop the approach further, future work should focus on resolving issues encountered when using design velocities for mesh deformation, extending the approach to more complex test cases, and potentially incorporating parametric effectiveness as a measure of the suitability of a given CAD parameterisation for optimisation purposes.
24
Poutiainen, Aaron. "Undertray Design and Development Procedure with CFD : An Optimization Study of Different UndertrayDesigns with CFD Computations". Thesis, KTH, Strömningsmekanik och Teknisk Akustik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-301732.
Testo completoAbstract (sommario):
Race car aerodynamics has played a vital part to improve lap times over the years of motor racing. Having good road adhesion with slick tires and aerodynamic downforce will increase the vehicles maximum lateral force and thus higher cornering speeds can be achieved. The undertray and diffuser is the most efficient aerodynamic component on most racing vehicles and is capable of producing six times more downforce than its contribution to drag plus, if optimized correctly, able to significantly reduce the vehicle's drag coefficient. The intent of this project is to optimize a completely unique undertray design for the KTH Formula Student teams racing vehicle DeV17. The undertray is inspired by the Aston Martin Valkyrie venturi tunnel design and is optimized by iterative change in CAD design parameters for three different chassis designs. The results are obtained with CFD RANS simulations using the k-ω (SST) turbulence model with the Siemens Star-CCM+software. The optimum design gave 530 N and 90 N of downforce and drag respectively at a velocity of 80km/h. The venturi tunnel design is proven to give a 29% downforce improvement over a conventional flat plate design with stronger longitudainal vortices and lower, more widespread, minimum pressure distribution. The most important aspects that affect downforce in undertray design is concluded to be a diffuser outlet height, upsweep and vehicle ground clearance. No specific aerodynamic advantages in having a convergent tapering of the tunnel cross-section is observed, meaning the undertray can be represented as only consisting of an expanding diffuser. The tunnel design is considered to give promising track testing results and be a spark for further innovative ideas with aerodynamic design for both the automotive and racing industry.Tävlingsbilars aerodynamik has spelat en viktig roll för att förbättra varvtiderna under åren inom motorsport. Att ha god väghäftning med 'slicks' däck och aerodynamisk nedåtkraft kommer att öka fordonets maximala sidokraft förmåga och därmed kan högre hastigheter i kurvor uppnås. Underredet och diffusern är den mest effektiva aerodynamiska komponenten på de flesta racerfordon och kan producera sex gånger mer nedåtkraft än dess bidrag till luftmotståndet och, om den optimeras korrekt, kan den avsevärt minska fordonets luftmotståndskoefficient. Syftet med detta projekt är att optimera en helt unik underredes design för KTH Formula Student lagets racingfordon DeV17. Underredet är inspirerat av Aston MArtin Valkyrie venturitunnel design och optimeras av iterativ förändring av CAD designparametrar för tre olika chassidesigner. Resultaten erhålls med CFD RANS-simuleringar med turbulensmodellen k-ω (SST) och programvaran Siemens Star-CCM+. Den optimala designen gav 530 N och 90 N nedåtkraft respektive luftmotstånd under en hastighet på 80 km/h. Venturitunnel designen har visat sig ge en förbättring på 29% nedåtkraft jämfört med en konventionell platt design, med starkare längsgående virvlar och lägre, mer utbredd, minimitryckfördelning. De viktigaste aspekterna som påverkar nedåtkraft i underredes designen dras som slutsats till att vara diffuser utloppets höjd, upphöjning vinkeln och fordonets markfrigång. Inga specifika aerodynamiska fördelar med att ha en konvergerande avsmalning av tunnelns tvärsnitt obververades, vilket innebär att underredet kan antas endast bestå av en expanderande diffuser. Tunneldesignen anser ge lovande bantestresultat och vara en gnista för ytterliga innovativa idéer inom aerodynamisk design för både bil- och racingindustrin.
25
Dall'Olio, Giacomo. "CFD study of electric motor's cooling". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Cerca il testo completoAbstract (sommario):
Nowadays electrification is one of the leading fields of engineering as it is seen as one of the key factors that can reduce environmental impact of human activities by reducing theirs polluting emissions. Mobility is the sector in which electric driven systems are diffusing the most. The search for performance in one of its main component, the electric motor, is therefore of fundamental importance in terms of efficiency and reliability of every electric driven applications. The optimization of thermal aspects covers a primary role and highly affect power consumption and lifetime of components. With this intent the use of CFD, Computational Fluid Dynamics, allows to exploit most of heat transfer aspects which concurs on thermal behavior both for design phase and performance estimations.
The work of this thesis investigates the cooling performances of the motor driving an electric vehicle made by Engines Engineering -EE- which is a company that projects motorbikes for thirds and is recently going to expand in the field of electric mobility. Beside the specific case studied, the methods can be extended to any component which require a thermal management as CFD tools are fundamental in a very wide spectrum of application in engineering.
26
Farstad, Øyvind. "CFD av strømningskarakteristikker i hydrauliske motorer". Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10525.
Testo completoAbstract (sommario):
CFD-vertøy er i dagens industri et mye brukt redskap for analyse av komplekse strømningsdynamiske problemstillinger. Dette gjelder også hos Rolls-Royce Marine Deckmachinery i Brattvåg. Her blir CFD brukt på hydrauliske komponenter som ventiler og motorer. Målet med denne oppgaven er å studere muligheten for å modellere og analysere motorene til nettopp Rolls-Royce med CFD. Motoren som blir brukt i denne oppgaven er av typen MX6300, som er en hydraulisk vingemotor. Dette arbeidet bestod i å bearbeide en CAD-modell av motoren slik at den ble hensiktsmessig for CFD-analyse i programmet Fluent 6.3.26. Denne bearbeidingen gikk i å forenkle modellen på en slik måte at de viktigste strømningsegenskapene til motoren ikke gikk tapt. En ny metode for spaltesimulering ble testet ut. Denne gikk ut på å erstatte tynne spalter med en porøs sone, som har en definert strømningsmotstand som gir samme trykktap som over den tynne spalten. Dette vil gi en forenklet geometri, og dermed redusere antall celler i meshet. For å kunne verifisere resultatene fra CFD-analysen, har det blitt utført eksperimentelle virkningsgradsmålinger på den virkelige motoren. Målingene ble utført ved en teststand hos Rolls-Royce i Brattvåg. Resultatene fra CFD-analysen var lovende. En fikk gode indikasjoner på at implementering av en porøs sone i stedet for spalter i en avansert modell, fungerer på en god måte. Det totale strømningsbildet viste imidlertid avvik fra et realistisk bilde. Det er forventet at en stor forbedring vil skje dersom et finere mesh benyttes. Dette vil også kreve mer dataressurser.
27
Krepper, Eckhard, e Dirk Lucas. "CFD models for polydispersed bubbly flows". Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28052.
Testo completoAbstract (sommario):
Many flow regimes in Nuclear Reactor Safety Research are characterized by multiphase flows, with one phase being a continuous liquid and the other phase consisting of gas or vapour of the liquid phase. In dependence on the void fraction of the gaseous phase the flow regimes e.g. in vertical pipes are varying from bubbly flows with low and higher volume fraction of bubbles to slug flow, churn turbulent flow, annular flow and finally to droplet flow. In the regime of bubbly and slug flow the multiphase flow shows a spectrum of different bubble sizes. While disperse bubbly flows with low gas volume fraction are mostly mono-disperse, an increase of the gas volume fraction leads to a broader bubble size distribution due to breakup and coalescence of bubbles. Bubbles of different sizes are subject to lateral migration due to forces acting in lateral direction different from the main drag force direction. The bubble lift force was found to change the sign dependent on the bubble size. Consequently this lateral migration leads to a de-mixing of small and large bubbles and to further coalescence of large bubbles migrating towards the pipe center into even larger Taylor bubbles or slugs. An adequate modeling has to consider all these phenomena. A Multi Bubble Size Class Test Solver has been developed to investigate these effects and test the influence of different model approaches. Basing on the results of these investigations a generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework has been proposed and was finally implemented into the CFD code CFX. Within this model the dispersed gaseous phase is divided into N inhomogeneous velocity groups (phases) and each of these groups is subdivided into Mj bubble size classes. Bubble breakup and coalescence processes between all bubble size classes Mj are taken into account by appropriate models. The inhomogeneous MUSIG model has been validated against experimental data from the TOPFLOW test facility.
28
Barstad, Lorentz Fjellanger. "CFD Analysis of a Pelton Turbine". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18598.
Testo completoAbstract (sommario):
A Pelton design software is currently being developed at the Waterpower laboratory at NTNU. The motivation behind this software is to streamline the parametric design process for Pelton turbines. A numerical flow model is a cornerstone in this application, but the lack of a bucket geometry and model runner has prevented the development of such a model. DynaVec, a turbine producer who specializes on sediment erosion and corrosion problems, offered to help by providing a bucket geometry and a model runner.The objective of this Master's thesis was to develop and validate a CFD model that predicts the torque applied to a non-stationary Pelton bucket, subject to a high-speed water jet. The numerical model was based on a method proposed by DynaVec, and the bucket geometry used in the simulations was identical (1:1) to the model runner.Numerous simulations were conducted, testing mesh dependency and different operational points (e.g. head). Mesh independence occurred at approximately 4.5 million elements. Furthermore, simulations of varying heads showed that the model may be independent of the head (40-80m), but this was not verified properly.Experiments showed that the numerical prediction was fairly accurate. A comparison of the numerical and experimental measurements showed that the CFD model over-predicts the torque by approximately 1.5%. This prediction was validated for the specific geometry used in the simulations, and a head of 75m.Overall, the results suggest that the numerical model is promising as a parametric design tool, but further development is required to obtain a true validation of the model.Task three and four were changed in agreement with Ole Gunnar Dahlhaug, because Solemslie's design program was delayed. In essence, the parametric study proceeded in favor of the development of a CFD model. To ensure that this work would benefit future research, especially students at the Waterpower laboratory, a detailed procedure for the CAD modeling, meshing and physical setup was included in the Appendix.
29
Thelin, Fredrik. "A CFD Analysis of Cyclodial Propellers". Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-144535.
Testo completoAbstract (sommario):
The quest for more efficient machines is always ongoing in the engineering world. This project is no different. ABB are investigating a new type of propeller that seems to offer increased efficiency compared to normal screw propellers. That is a so called foil wheel propeller. The foil move in a circular pattern with the fluid stream moving in the radial direction of the propeller instead of the axial as in a screw propeller. If the propeller is placed and modeled correctly it can also be used as a thrust vectoring device. This report focuses on the fluid physics of the foil wheel propeller, or as it is called in this report radial flow propeller. First of all the movements and interactions of the blades must be understood. Both to keep the efficiency high to compete with screw propellers, but also to foresee any problems that may occur with such a new device. A scaled down version of the propeller have been commissioned by ABB and will be tested in some time after the work within this report is completed. The effects associated to this will also be analyzed. The tool to compute the flow physics of the radial flow propeller will be computational fluid dynamics. Computational fluid dynamics uses a numerical method to compute the entire fluid field in space and time. The flow around the propeller is highly complex so a detailed analysis is needed if a well functioning control system is to be constructed for instance. The differences between the downscale and the full-scale are great, even when the non dimensional coefficients are considered. The down-scale case will be less efficient, it will be difficulties predicting the performance of the full-scale since the downscale flow is much less powerful than the full-scale case. The interaction between the blades has a large effect. There is a strong relation between angle of attack and the number of blades. The forces that are large change by about 30\% so it must definitely be considered if a model is to be used for a control system.
30
Walker, Patrick Gareth Chemical Engineering & Industrial Chemistry UNSW. "CFD modeling of heat exchange fouling". Awarded by:University of New South Wales. Chemical Engineering & Industrial Chemistry, 2005. http://handle.unsw.edu.au/1959.4/22385.
Testo completoAbstract (sommario):
Heat exchanger fouling is the deposition of material onto the heat transfer surface causing a reduction in thermal efficiency. A study using Computational Fluid Dynamics (CFD) was conducted to increase understanding of key aspects of fouling in desalination processes. Fouling is a complex phenomenon and therefore this numerical model was developed in stages. Each stage required a critical assessment of each fouling process in order to design physical models to describe the process???s intricate kinetic and thermodynamic behaviour. The completed physical models were incorporated into the simulations through employing extra transport equations, and coding additional subroutines depicting the behaviour of the aqueous phase involved in the fouling phenomena prominent in crystalline streams. The research objectives of creating a CFD model to predict fouling behaviour and assess the influence of key operating parameters were achieved. The completed model of the key crystallisation fouling processes monitors the temporal variation of the fouling resistance. The fouling rates predicted from these results revealed that the numerical model satisfactorily reproduced the phenomenon observed experimentally. Inspection of the CFD results at a local level indicated that the interface temperature was the most influential operating parameter. The research also examined the likelihood that the crystallisation and particulate fouling mechanisms coexist. It was found that the distribution of velocity increased the likelihood of the particulate phase forming within the boundary layer, thus emphasizing the importance of differentiating between behaviour within the bulk and the boundary layer. These numerical results also implied that the probability of this composite fouling was greater in turbulent flow. Finally, supersaturation was confirmed as the key parameter when precipitation occurred within the bulk/boundary layer. This investigation demonstrated the advantages of using CFD to assess heat exchanger fouling. It produced additional physical models which when incorporated into the CFD code adequately modeled key aspects of the crystallisation and particulate fouling mechanisms. These innovative modelling ideas should encourage extensive use of CFD in future fouling investigations. It is recommended that further work include detailed experimental data to assist in defining the key kinetic and thermodynamic parameters to extend the scope of the required physical models.
31
Lowe, C. "CFD modelling of solid propellant ignition". Thesis, Cranfield University, 1996. http://hdl.handle.net/1826/3921.
Testo completoAbstract (sommario):
Solid propellant is the highly energetic fuel burnt in the combustion chamber
of ballistic weapons. It is manufactured, for this purpose, in either granular
or stick form. Internal ballistics describes the behavior within the combustion
chamber throughout the ballistic cycle upto projectile exit from the muzzle of
the gun barrel. Over the last twenty years this has been achieved by modelling
the process using two-phase flow equations.
The solid granules or sticks constitute the first phase, which can be assumed
to be incompressible over typical pressure ranges within the chamber. The
gas-phase is composed of both the original ambient gas contained around the
propellant and additional gas produced by the propellant gasifying on heating.
Equations can be derived that describe the conservation of mass, momentum
and energy in terms of average flow variables. The equations are a highly
non-linear system of partial-differential- equations. High-speed flow features
are observed in internal ballistics and ordinary fini te- difference methods are
unsuitable numerical methods due to inaccurate prediction of discontinuous
flow features. Modern shock-capturing methods are employed, which solve the
system of equations in conservation form, with the ability to capture shocks
and contact discontinuities.
However, although the numerical solutions compare well with experiment
over the bulk of the combustion chamber, the ignition models used in internal
ballistics are unreliable. These are based on either gas or solid-surface temperature
achieving some empirically measured 'ignition temperature' after which
the propellant burns according to an empirical pressure dependent burning
law. Observations indicate that this is not an adequate representation of ignition.
Time differences between first solid gasification and ignition imply two
distinct processes occurring. ]Further, ignition occurring in gas-only regions
indicates that ignition is controlled by a gas-phase reaction.
This thesis develops simple ideas to describe possible mechanisms for these
physical observations. The aim is to provide an improved model of the ignition
of solid propellant. A two stage reaction process is described involving
endothermic gasification of the solid, to produce a source of reactant gas, followed
by a very exothermic gas-phase ignition reaction.
Firstly the gas-phase ignition is considered. A very simple reaction is suggested
which is assumed to control the combustion of reactant gas, produced
by solid gasification. Ignition is, by definition, the initiation of this exothermic
reaction. Chemical kinetics are included in the gas-phase flow equations to explore the evolution of the reactant gas that is subject to changes in temperature
and pressure. By assuming spatial uniformity, analytical solutions of the
problem are deduced. The physical interpretation of the solution is discussed,
in particular, the relationship between temperature, reactant concentration
and ignition is explored.
Numerical methods are required to solve the one-dimensional flow equations.
Development of suitable CFD methods provides a method of solution.
Finite-volume schemes, based on the original work by Godunov, are used to
solve the conservation form of the equations. A simple test problem is considered
whereby reactant gas is injected into a cylindrical combustion chamber.
By examining the resulting flow histories, valuable information is gathered
about the complicated coupling of chemistry and flow.
Chemistry is included into a system of two-phase flow equations. By using
standard averaging methods along with an equation for gas-phase species,
equations are derived that describe the rate of change of average flo%v variables
for both gas and particle phases. Numerical schemes are developed and
some of the difficulties involved in two-phase flow systems, that are not an
issue in single-phase flow, are presented. An internal ballistics application is
considered as a test case and the solution discussed.
The other important reaction involved in the combustion cycle, solid gasification,
is explored. The model is based on detailed description of interphase
mass and energy transfer at the solid-gas interface. This involves the solution
of the heat conduction equation with a moving boundary that divides the
solid and gas regions. Similar numerical schemes are constructed to solve the
equations. Finally, this model is coupled with the equations of gas-phase reaction.
This describes the complete cycle whereby increases in gas temperature
cause the solid to increase in temperature and gasify. Subsequent gas-phase
combustion of the reactant gases produces heat-transfer between the solid and
gas and continues to accelerate gasification. Eventually this results in selfsustained
combustion of the solid propellant.
32
Juretic, Franjo. "Error analysis in finite volume CFD". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420616.
Testo completo
33
Heide, Jakob, e Patrik Lans. "CFD investigation of a fin keel". Thesis, KTH, Mekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148816.
Testo completoAbstract (sommario):
This thesis aims to help sailboat owners to decide a preferable NACA profile. A CFD comparison in terms of drag and lift coefficients between two NACA profiles have been applied on a typical fin keel. Each profile has been computed with different angles of attack to investigate the impact of small direction changes. ANSYS Fluent 13.0 is used to model the flow according to RANS k-epsilon model. The conclusion is that NACA65 series gives lower drag while NACA64 series gives higher lift.Syftet med det här examensarbetet är att undersöka skillnaderna för olika NACA-kölprofiler med avseende på tryckkoefficienter Arbetet strävar även efter att ge båtägare en tydligare bild av en fördelaktig NACA-profil. Varje kölprofil har beräknats med olika anfallsvinklar för att undersöka effekten av små vinkeländringar. ANSYS Fluent 13.0 har använts för att modellera flödet enligt k-epsilon-modellen. Slutsatsen är NACA65-serien ger en lägre motståndskoefficient medan NACA64-serien ger en högre lyftkoefficient.
34
Johansson, Christopher. "Optimization of wall parameters using CFD". Thesis, KTH, Aerodynamik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159875.
Testo completoAbstract (sommario):
Computational Fluid Dynamics (CFD) is commonly used to calculate the pressure drop in systems with internal ow. To get accurate results the physics of the ow must be well dened together with the right material parameters of the considered geometry. The mate- rial parameter considered in this report is the wall roughness, or sand-grain roughness, and during the thesis work it has been investigated how dierent wall roughnesses aects the pressure drop. It has also been investigated how to set up a CFD simulation to accurately calculate the pressure drop. When setting up a simulation, a good mesh is essential to get accurate results, while using a turbulence model and wall function that is correct for the geometry and physics involved. Pressure drop measurements and the corresponding CAD geometries were available at the start of the thesis work. The simulations were adapted to these to nd the sand-grain roughness for the dierent materials. The main conclusions is that the pressure drop can be accurately calculated when the sand-grain roughness is known and the CFD simulation is well dened. It was found from the mesh sensitivity study that it is essential that the rst cell size is at least twice the size of the sand-grain roughness and that at least two cell layers are used to resolve the turbulent boundary layer.
35
Spentzos, Agis. "CFD analysis of 3D dynamic stall". Thesis, University of Glasgow, 2005. http://theses.gla.ac.uk/1855/.
Testo completoAbstract (sommario):
Focusing on helicopter aerodynamics, it is known that the aerodynamic performance of the retreating side of a rotor disk is mainly dictated by the stall characteristics of the blade. Stall under dynamic conditions (Dynamic Stall) is the dominant phenomenon encountered on heavily loaded fast-flying rotors, resulting in an extra lift and excessive pitching moments. Dynamic stall (DS) can be idealised as the pitching motion of a finite wing and this is the focus of the present work which includes three main stages. At first, comparisons between available experimental data with CFD simulations were performed for 3D DS cases. This work is the first detailed CFD study of 3D Dynamic Stall and has produced results indicating that DS can be predicted and analysed using CFD. The CFD results were validated against all known experimental investigations. In addition, a comprehensive set of CFD results was generated and used to enhance our understanding of 3D DS. Straight, tapered and swept-tip wings of various aspect ratios were used at a range of Reynolds and Mach numbers and flow conditions. For all cases where experimental data were available effort was put to obtain the original data and process these in exactly the same ways as the CFD results. Special care was put to represent exactly the motion of the lifting surfaces, its geometry and the boundary conditions of the problem. Secondly, the evolution of the Ω-shaped DS vortex observed in experimental works as well as its interaction with the tip vortices were investigated. Both pitching and pitching/rotating blade conditions were considered. Finally, the potential of training a Neural network as a model for DS was assessed in an attempt to reduce the required CPU time for modelling 3D DS. Neural networks have a proven track record in applications involving pattern recognition but so far have seen little application in unsteady aerodynamics. In this work, two different NN models were developed and assessed in a variety of conditions involving DS. Both experimental and CFD data were used during these investigations. The dependence of the quality of the predictions of the NN on the choice of the training data was then assessed and thoughts towards the correct strategy behind this choice were laid out.
36
Macpherson, Iain. "A CFD investigation of synthetic jets". Thesis, University of Glasgow, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404494.
Testo completo
37
Kokkonen, Toni. "CFD analysis of stepped planing vessels". Thesis, KTH, Mekanik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-250023.
Testo completoAbstract (sommario):
High speed planing hulls are currently widely used for example in recreational and emergency vessel applications. However, very little CFD research has been done for planing vessels, especially for those with stepped hulls. A validated CFD method for planing stepped hulls could be a valuable improvement for the design phase of such hulls. In this thesis, a CFD method for stepped hulls, with a primary focus on two-step hulls, is developed using STAR-CCM+. As a secondary objective, porpoising instability of two-step hulls is investigated. The simulations are divided into two parts: In the first part a method is developed and validated with existing experimental and numerical data for a simple model scale planing hull with one step. In the second part the method is applied for two two-step hulls provided with Hydrolift AS. A maximum two degrees of freedom, trim and heave, are used, as well as RANS based k-w SST turbulence model and Volume of Fluid (VOF) as a free surface model. The results for the one-step hull mostly corresponded well with the validation data. For the two-step hulls, validation data did not exists and they were first simulated with a fixed trim and sinkage and compered between each other. In the simulations with free trim and heave both hulls experienced unstable porpoising behavior.
38
Modiano, David. "Visualization of three dimensional CFD results". Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/41238.
Testo completo
39
Denton, G. S. "CFD simulation of highly transient flows". Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18693/.
Testo completoAbstract (sommario):
This thesis describes the fundamental extension and extensive testing of a robust CFD model for predicting outflow following the failure of pressurised hydrocarbon pipelines. The main thrust of the study involves the extension of the basic outflow model to account for complex pipeline systems, improvements of the theoretical basis and numerical stability. The basic model, based on the numerical solution of conservation equations using the method of characteristics, incorporates a suitable equation of state to deal with pipelines containing pressurised multi-component hydrocarbon mixtures. It utilises the homogeneous equilibrium flow (HEM) assumption, where the constituent phases in a two-phase mixture are assumed to be at thermal and mechanical equilibrium. The first part of the study focuses on the development of an outflow model to simulate the failure of multi-segment pipelines incorporating valves and fittings passing through terrains of different inclinations. In the absence of real data, the numerical accuracy of the model is assessed based on the calculation of a mass conservation index. The results of a case study involving the comparison of the simulated outflow data based on the failure of a multi-segment pipeline as opposed to an equivalent single segment pipeline containing gas, liquid or two-phase inventories are used to highlight the impact of pipeline complexity on the simulated data. The development and extensive testing of two models, namely the Hybrid Model and the Modified Homogeneous Equilibrium Model (MHEM) each addressing a principal limitation of the HEM are presented next. The Hybrid Model deals with the failure of the HEM in predicting post-depressurisation outflow for inclined pipelines containing two-phase mixtures or liquids through its coupling with a hydraulic flow model. The MHEM on the other hand addresses the failure of the HEM to accurately predict the discharge rates of flashing/ two-phase fluids discharging through an orifice. Finally, the dilemma of the appropriate choice of the size and duration of the numerical discritisation steps expressed in terms of the Courant, Friedrichs and Lewy (CFL) criterion on the stability and computational workload of the pipeline failure model is investigated for different classes of hydrocarbon inventories. These include gas, liquid (flashing and incompressible) and two-phase mixtures.
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Gomez-Iradi, Sugoi. "CFD for Horizontal Axis Wind Turbines". Thesis, University of Liverpool, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511051.
Testo completo
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Abhishek, Chintagunta. "Performance of CFD solver on GPU". Thesis, University of Surrey, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616889.
Testo completoAbstract (sommario):
The advances in multi-core architecture for general-purpose computing in the past decade have tremendously increased the available raw computing power. The two major architectures are the central processing unit (CPU) and the graphics processing unit (CPU). CPUs have been developed recently as general purpose processors. The present work is focused on the performance of unstructured CFD solvers on the CPU. For this purpose an explicit and implicit solvers were developed. The explicit solver for the CPU and the multicore CPU were generated using the OPlus 2 library. This was achieved by implementing minimal extensions to the sequential code. The explicit solver achieved a speedup of an order of magnitude on the CPU, compared to the multi-core CPU code. For the explicit solver the CPU is a cost effective option compared to the CPU. On the other hand, the implicit solver using the Jacobi linear solver was implemented in two variants. The first using the OPlus 2 library and the second using NVIDIA library. The manufacturer library performed better than the OPlus 2 implementation. This was due to the inefficient implementation of the OPlus 2 version. The NVIDIA library gave a speedup of 27x compared to the sequential version. Hence, for the implicit solver the CPU might not be a viable option.
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Ghate, Devendra. "Inexpensive uncertainty analysis for CFD applications". Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:6be44a1d-6e2f-4bf9-b1e5-1468f92e21e3.
Testo completoAbstract (sommario):
The work presented in this thesis aims to provide various tools to be used during design process to make maximum use of the increasing availability of accurate engine blade measurement data for high fidelity fluid mechanic simulations at a reasonable computational expense. A new method for uncertainty propagation for geometric error has been proposed for fluid mechanics codes using adjoint error correction. Inexpensive Monte Carlo (IMC) method targets small uncertainties and provides complete probability distribution for the objective function at a significantly reduced computational cost. A brief literature survey of the existing methods is followed by the formulation of IMC. An example algebraic model is used to demonstrate the IMC method. The IMC method is extended to fluid mechanic applications using Principal Component Analysis (PCA) for reduced order modelling. Implementation details for the IMC method are discussed using an example airfoil code. Finally, the IMC method has been implemented and validated for an industrial fluid mechanic code HYDRA. A consistent methodology has been developed for the automatic generation of the linear and adjoint codes by selective use of automatic differentiation (AD) technique. The method has the advantage of keeping the linear and the adjoint codes in-sync with the changes in the underlying nonlinear fluid mechanic solver. The use of various consistency checks have been demonstrated to ease the development and maintenance process of the linear and the adjoint codes. The use of AD has been extended for the calculation of the complete Hessian using forward-on-forward approach. The complete mathematical formulation for Hessian calculation using the linear and the adjoint solutions has been outlined for fluid mechanic solvers. An efficient implementation for the Hessian calculation is demonstrated using the airfoil code. A new application of the Independent Component Analysis (ICA) is proposed for manufacturing uncertainty source identification. The mathematical formulation is outlined followed by an example application of ICA for artificially generated uncertainty for the NACA0012 airfoil.
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Cai, Liping. "CFD modelling of chalcopyrite heap leaching". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/44559.
Testo completoAbstract (sommario):
Heap leaching is widely applied to recover metals from ore. The behaviour of the fluid and chemical species inside heaps, which involves many coupled physico-chemical phenomena, are highly variable and complex. Computational Fluid Dynamics (CFD) simulation can provide an efficient approach to investigate these phenomena and offer guidelines to improve heap design. Stagnant zones exist in the packed bed with multiphase flow, however, the conventional advection-dispersion model (ADE) failed to capture this phenomenon, therefore, the mobile immobile model (MIM) is employed to model the mass transport and heat transfer instead of the conventional ADE. For predicting the mineral dissolution in heap leaching, we developed a new semi-empirical model which is an alternative to the traditional shrinking core model (SCM), but is more flexible in ability to fit with various dissolution kinetics profiles. The key assumption of this semi-empirical model is validated, and it is calibrated with experiments for chalcopyrite leaching. The software Fluidity, which is an unstructured mesh based finite element/control finite volume modelling, is further developed to implement the reactive mass transport and heat transfer simulation for heap leaching. The numerical schemes for multiphase flow models are control volume finite element method (CVFEM) for spacial discretization and the implicit pressure explicit saturation algorithm (IMPES) for temporal discretization. The mass transport and heat transfer equations are solved implicitly by using the control volume method.\ Before the implementation of various heap leaching simulations, the MIM is validated by experiments and the liquid-solid phase heat transfer models are verified by method of manufactured solution (MMS). Then the reactive transport model for chalcopyrite leaching, which includes the semi-empirical model for predictions of mineral dissolution, is validated by three separate experiments. Various heap leaching simulations are implemented to analyse the leaching performance and efficiency. Four groups of 1D simulations are implemented to evaluate the effects of the bacterial activity, the form of the mass transport model, solution temperature, Fe^(3+) concentrations and solution pH on the leaching system. The large scale 2D simulations for leaching with a heap of trapezoid shape were implemented to evaluate the effects of oblique walls on the leaching performance. There different wall slopes, which are 30°, 45° and 60°, are investigated in the 2D simulations. The main contribution of this project is that a new semi-empirical model and the mobile immobile model are developed and integrated into a chalcopyrite leaching simulator, the simulation results of those models approach to the real physical world better than the conventional models. In conclusion, an improved numerical scheme is provided in this project to investigate and optimise the process of chalcopyrite leaching for industrial purpose.
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Krepper, Eckhard, e Dirk Lucas. "CFD models for polydispersed bubbly flows". Forschungszentrum Dresden-Rossendorf, 2007. https://hzdr.qucosa.de/id/qucosa%3A21632.
Testo completoAbstract (sommario):
Many flow regimes in Nuclear Reactor Safety Research are characterized by multiphase flows, with one phase being a continuous liquid and the other phase consisting of gas or vapour of the liquid phase. In dependence on the void fraction of the gaseous phase the flow regimes e.g. in vertical pipes are varying from bubbly flows with low and higher volume fraction of bubbles to slug flow, churn turbulent flow, annular flow and finally to droplet flow. In the regime of bubbly and slug flow the multiphase flow shows a spectrum of different bubble sizes. While disperse bubbly flows with low gas volume fraction are mostly mono-disperse, an increase of the gas volume fraction leads to a broader bubble size distribution due to breakup and coalescence of bubbles. Bubbles of different sizes are subject to lateral migration due to forces acting in lateral direction different from the main drag force direction. The bubble lift force was found to change the sign dependent on the bubble size. Consequently this lateral migration leads to a de-mixing of small and large bubbles and to further coalescence of large bubbles migrating towards the pipe center into even larger Taylor bubbles or slugs. An adequate modeling has to consider all these phenomena. A Multi Bubble Size Class Test Solver has been developed to investigate these effects and test the influence of different model approaches. Basing on the results of these investigations a generalized inhomogeneous Multiple Size Group (MUSIG) Model based on the Eulerian modeling framework has been proposed and was finally implemented into the CFD code CFX. Within this model the dispersed gaseous phase is divided into N inhomogeneous velocity groups (phases) and each of these groups is subdivided into Mj bubble size classes. Bubble breakup and coalescence processes between all bubble size classes Mj are taken into account by appropriate models. The inhomogeneous MUSIG model has been validated against experimental data from the TOPFLOW test facility.
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Drdla, Adam. "CFD simulace proudění rozváděcím mechanismem turbodmychadla". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229246.
Testo completoAbstract (sommario):
The aim of this thesis is to provide research into turbocharger regulation, and analyze the force load of vanes in the VNT mechanism of Garrett turbocharger by CFD simulation. In the thesis there is one model with two different mesh densities. It describes the relevance of supercharging vehicle engines and the kinds of supercharging aggregates in the introduction. Then, the thesis is divided into two chapters. The first chapter provides research, describing primary principle of supercharging, turbocharger construction and kinds of air regulation. The practical part of the thesis solves the force load of VNT mechanisms. It was necessary to optimalize the 3D Garrett turbocharger model, create two meshes with different element densities, specify boundary conditions and analyse the results of both cases. A general description of solved problems, comparison of results of force load vanes and propose simplifying and verifying the CFD calculation are included in the conclusion.
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Przeczek, Jan. "CFD analýza vstupního kanálu turbovrtulového motoru". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229454.
Testo completoAbstract (sommario):
This diploma thesis is focused on CFD analysis of M-601 turboprop engine nacelle mounted on L-410 commuter aircraft. Calibrating exercise is performed at the beginning of the thesis in order to be more familiar with CFD problems. Next parts of the thesis are chronologically divided with respect to project progress, namely suitable geometrical model creation, mesh creation in order to obtain computational model, calculation using CFD methods, results evaluation and proposal of possible construction transformation at the conclusion.
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Pavlíček, David. "CFD modelování mísení kapalin v potrubí". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-387733.
Testo completoAbstract (sommario):
This work is focused on computational modelling of mixing fluids in pipeline with static mixers. Main objective is to analyze several selected static mixers in a particular industrial application, namely dosing of the aluminium sulphate solution in the clarification process for potable water treatment. The analysis focuses on the degree of mixedness and pressure loss of individual mixers. Further, the aim of this work is to process the search of available types of static mixers. The benefit of this work is at least an effort to motivate the reader to deeper understanding of the mixing fluids, especially by static mixers.
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Sušovský, Martin. "Parametrická studie výměníku tepla pomocí CFD". Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417779.
Testo completoAbstract (sommario):
In this paper is carried out basic design and calculation of tube heat exchanger with a straight tube bundle with installed systém of disk and doughnut baffles. The calculation included pressure losses and heat transfer coefficient of tubular space and shell side. Then CFD model was made for parametric study, which was focused on influence of change of the baffles geometry on the heat output of the exchanger and the pressure loses on the shell side.
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Appa, Harish. "Multiphase CFD modelling of stirred tanks". Master's thesis, University of Cape Town, 2007. http://hdl.handle.net/11427/5548.
Testo completoAbstract (sommario):
Includes bibliographical references (p. 67-70).Stirred tanks agitated with Rushton turbines are commonly used in industry, for instance mixing processes and flotation systems. The need for more efficient systems in industries has led to the study of fluid flow within the tanks upon agitation; so that a better understanding of the phenomena can help in the optimisation of the tanks. In the recent years, efforts have been made towards the development of predictive methods using computational fluid dynamics (CFD). Among the various numerical works presented, emphasis was laid mainly on single phase systems. However, due to the various processes involving gas-liquid systems, the need for multiphase modelling of stirred tanks became increasingly important. This has led to more research studies involving multiphase flows. Most of the work reported showed good prediction of the velocity data and the power draw, reasonable turbulence parameters. But, the prediction of the gas hold-up was rarely well established. Therefore, the aim of this thesis, based on the numerical work presented by Engelbrecht (2006), is to investigate the discrepancies reported and to develop a multiphase model of a stirred tank agitated by a Rushton turbine. The commercially available CFD code FLUENT@ was used to model the agitated gas-liquid system. The results were validated with the numerical work of Engelbrecht (2006) and the experimental work presented by Deglon (1998). Two main cases were investigated, with a steady state and a transient approach. The QUICK scheme was used for the discretisation of the volume fraction and momentum and the first order upwind scheme for the discretisation of the turbulent kinetic energy and dissipation rate. The standard k - E turbulence model was used to account for the turbulent flow regime. A steady state MRF model was used for the investigation of the discrepancy reported by Engelbrecht (2006). The author reported that no convergence was achieved with such models. Solving the problem would have resulted in a good modelling approach for the prediction of gas dispersion, since steady state models are not computationally intensive. Three different boundary conditions, namely, a pressure outlet, an outflow and a velocity inlet, were used to model the outlet of the tank. The Euler-Euler multiphase model was used to simulate the gas-liquid system for the steady state model.
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Kern, Simon. "Sensitivity Analysis in 3D Turbine CFD". Thesis, KTH, Mekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210821.
Testo completoAbstract (sommario):
A better understanding of turbine performance and its sensitivity to variations in the inletboundary conditions is crucial in the quest of further improving the efficiency of aero engines.Within the research efforts to reach this goal, a high-pressure turbine test rig has been designedby Rolls-Royce Deutschland in cooperation with the Deutsches Zentrum für Luft- und Raumfahrt(DLR), the German Aerospace Center. The scope of the test rig is high-precision measurement ofaerodynamic efficiency including the effects of film cooling and secondary air flows as well as theimprovement of numerical prediction tools, especially 3D Computational Fluid Dynamics (CFD).A sensitivity analysis of the test rig based on detailed 3D CFD computations was carried outwith the aim to quantify the influence of inlet boundary condition variations occurring in the testrig on the outlet capacity of the first stage nozzle guide vane (NGV) and the turbine efficiency.The analysis considered variations of the cooling and rimseal leakage mass flow rates as well asfluctuations in the inlet distributions of total temperature and pressure. The influence of anincreased rotor tip clearance was also studied.This thesis covers the creation, calibration and validation of the steady state 3D CFD modelof the full turbine domain. All relevant geometrical details of the blades, walls and the rimsealcavities are included with the exception of the film cooling holes that are replaced by a volumesource term based cooling strip model to reduce the computational cost of the analysis. Thehigh-fidelity CFD computation is run only on a sample of parameter combinations spread overthe entire input parameter space determined using the optimal latin hypercube technique. Thesubsequent sensitivity analysis is based on a Kriging response surface model fit to the sampledata. The results are discussed with regard to the planned experimental campaign on the test rigand general conclusions concerning the impacts of the studied parameters on turbine performanceare deduced.