Global ETD Search

1	Particle image velocimetry in practice / Green, Torbjörn M., January 2009 (has links) Lic.-avh. (sammanfattning) Luleå : Luleå tekniska university, 2009. / Härtill 3 uppsatser. Fluidmekanik.
2	Design principles for noise reduction in hydraulic piston pumps : simulation, optimisation and experimental verification / Johansson, Andreas, January 2005 (has links) (PDF) Diss. Linköping : Univ., 2005. Fluidmekanik. Vätskepumpar.
3	On valve controlled fluid power systems : flow amplifier and percussive rock drilling / Pettersson, Henrik, January 2002 (has links) (PDF) Diss. Linköping : Univ., 2002. Fluidmekanik. Hydraulik.
4	Optimal control of boundary layer transition / Högberg, Markus, January 1900 (has links) Diss. (sammanfattning) Stockholm : Tekn. högsk., 2001. / Härtill 7 uppsatser. Doktorsavhandlingar. Fluidmekanik.
5	Modellering av projektiler och skydd / Projectile and armor modeling Huss, Simon January 2020 (has links) The Walker-Anderson model has been proven to model the penetration of long rods into semi-infinite targets with great results. The equations of motion of the projectile are obtained by analytically integrating the conservation of momentum along the cylindrically symmetric axis of penetration. In this study, the original Walker-Anderson model is presented in detail and extended to include back surface bulging and breakout. To obtain the velocity in finite targets, the potential for the velocity in a semi-infinite target is multiplicatively blended with the potential for the velocity in an infinitely thin target. Different choices of these potentials are discussed. The extended model is capable of calculating the penetration history, as well as predicting the residual length and velocity of the projectile when the target fails. The implementation is primarily focused towards eroding projectiles, but a transition from eroding to rigid penetration is included.The extended model is compared to experimental data and agreement is relatively good, although more validations are needed. This study was made in collaboration with the Swedish Defence Research Agency, FOI, and is expected to lay the foundation for further generalizations of long-rod penetration. Pilprojektiler analytiska modeller fluidmekanik hållfasthetslära Engineering and Technology Teknik och teknologier
6	Materialmodellers applicerbarhet för multifasflöden med icke-Newtonska vätskor i Ansys CFX Wikström, Nils, Hovstadius, David January 2022 (has links) Material properties are very important to model correctly when calculating solutions for multiphase flows with non-Newtonian fluids. The models can make the solution converge or diverge depending on how it is chosen. This paper mainly focuses of the applicability of solid pressure and viscosity models in Ansys CFX. The main goal is to create a list of criterions that material properties must fullfill to ensure that the solution converges. Furthermore a test environment in MATLAB was made that verifies if the models satisfies the list of criterions. It was found that as long as the material properties has continous derivatives without removable singularities and are non imaginary on their domain they are applicable in Ansys CFX. It was also found that if there was a discontinuity in their domain the discontinuity could be moved outside of the domain using an assymetric model for the volume fraction. Ansys-CFX Fluidmekanik icke newtonska vätskor multifasflöden materialmodeller solidtryck Fluid Mechanics and Acoustics Strömningsmekanik och akustik
7	Principles for Diverting and Merging Viscous Flows : Evaluation and Visualisation / Principer för Delning och Sammnföring av Viskösa Flöden : Utvärdering och Visualisering Strese, Åke January 2017 (has links) In the chemistry branch of science is often a chromatograph usedto separate and purify substances in a solution. In achromatograph, different detectors are used to analyse the samplesconstituents. Some detectors destroy the sample during analysis.Because it is undesirable to destroy the entire flow of sample, asmall mass is transferred to a second flow by a flow splitter. Inthis report, four principles to divert a small mass from one flowto another are developed and evaluated. The basic principles todivert the flows is tested and principal mock-ups are designed andmanufactured. A brief survey of the market is conducted and aproblem related to flow spitting is investigated. The problem isthe influence on yield through a chromatograph due to flowretaining. Designing and testing of different retaining systems isalso included in this report. All four initial principles proved to be plausible splittingtechniques. However, only two principles appeared to be feasiblefor direct implementation in devices comparable withchromatographs. One of the less feasible principle is covered byseveral patents. The other is difficult to manufacture in order tomeet the strict requirements associated with e.g. chromatographs.The testing of different retaining systems showed that smallertube inner diameter and how the tube is winded can reduce theretaining system influence on the yield significantly. The splitting techniques in this report are all feasible splittingtechniques, and the report can be used as a solid foundation fordevelopment future laboratory instruments. / Inom kemin förekommer ofta kromatografer för att rena och separera kemiska substanser iett prov. De separerade substanserna kan detekteras och analyseras av olika detektorer, därvissa detektorer förstör provet i analysprocessen. Då det oftast är önskvärt att bevara såmycket som möjligt av ett prov, för vidare studier, avleds därför en liten mängd av deseparerade substanserna till detektorn då en förstörande detektor används. I denna studieutvecklades och undersöktes fyra principer för att avleda mycket små volymer från ett flödetill ett annat. Flödesdelning och sammanförning med de grundläggande flödesdelningsprincipernatestades, principiella modeller konstruerades och tillverkades. Enmarknadsundersökning samt en undersökning av ett flödesdelningsassocierat probleminkluderas också i rapporten. Problemet består i minskning av utbyte på grund avbandbreddning i flödesfördröjningssystem. Bandbreddning studerades således i olika formerav flödesfördröjningssystem. Alla fyra principer visade sig vara möjliga flödesdelningstekniker varav två av sådan karaktäratt de skulle kunna realiseras i ett instrument såsom en kromatograf. Av de två andra omfattasden ena av flertalet patent och den andra skulle vara tillverkningstekniks svår att förverkligamed vedertagna tillverkningstekniker. Tester på olika typer avflödesfördröjningssystemutformningar visade att slangdimension och hur slangen är lindadhar stor inverkan på bandbreddning. Det återstår en hel del konceptuell utveckling då principerna bara behandlats pågrundläggande nivå. Genom de principiella modellerna ges en bild av hur principerna skullekunna förverkligas, men vidare ställningstaganden måste tas till bland annat materialval samtmonitorering och anpassning av flöden. Rapporten ger en god grund för framtidaproduktutveckling. Flow splitter chromatography diversion dispersion laminar fluid mechanics MEMS mock-up design delayloop Mass rate attenuator (MRA) Flödessplitter flödesdelning kromatografi dispersion laminära flöden fluidmekanik MEMS mock-up delayloop kvarhållningssyste mass rate attenuator (MRA) Fluid Mechanics and Acoustics Strömningsmekanik och akustik Other Mechanical Engineering Annan maskinteknik Medicinsk laboratorie- och mätteknik
8	Validating results from the Molten Salt Reactor Experiment by use of turbulent CFD simulations : A study of a modified U-tube shell-and-tube primary heat exchanger and radiator with molten salts Akner, Malcolm January 2021 (has links) Background Nuclear reactors utilizing molten fuels rather than solid fuels show a massive advantage in energy yield, waste handling and safety features. The only successful reactor utilizing a molten fuel was called the ‘Molten Salt Reactor Experiment’ (MSRE), built and operated in the Oak Ridge national laboratory (ORNL) in Tennessee, U.S.A. during the 1960s. The molten salts in question are fluoride compounds under the name of “FLiBe”. In this thesis, the heat exchangers of the MSRE are modelled and simulated, with the aim to test whether current computational fluid dynamics (CFD) software and mathematical models can accurately predict molten salt heat transfer behaviour. Methods All programs used are open-source and/or free-access to facilitate open collaboration between researchers in this growing field. All models and findings produced in this thesis are free to use for future research. The program Onshape was used to draw CAD-models based on hand-drawn technical documents released by ORNL. Several programs, e.g., Simscale and Salome, were used to create high detailed meshes of the heat exchangers. The CFD software Simscale and OpenFOAM have been used to simulate the heat exchangers, using the 𝑘 − 𝜔 𝑆𝑆𝑇 Reynolds averaged Navier-Stokes (RANS) turbulence model to perform a multiregion conjugate heat transfer (CHT) analysis. The program Paraview has been used for all post-processing on the large datasets. Results A working toolchain with open-source programs for CFD has been identified. Highly detailed, full-scale and accurate CAD-drawings of the two heat exchangers have been produced. Models have been finely meshed, containing tens of millions of cells, with good quality measures. The simulations produced physically sound and valuable data: Great heat transfer predictive capability with high accuracy to the data presented by ORNL. Pressure data showed a consistent over-prediction with a factor of ~2. Possibility of error within the MSRE measurement. Conclusions CHT using modern turbulence methods work well for the intended purpose and can be used by industry to simulate molten salt heat transfer. Open-source programs perform well and can be used by researchers to share ideas and progress. Doubts around certain measurements from the MSRE, showing large uncertainties. Future projects have been outlined to continue the work performed in this thesis. Molten salt reactors show fantastic promise as an energy generation method and should be seriously considered for the future of clean, reliable energy. CFD MSRE CAD CHT experiment molten liquid salt fluid mechanics mechanics fluid LTU nuclear reactor nuclear reactor generation four generation IV copenhagen atomics copenhagen atomics space engineering space engineering aerospace thesis master's thesis master's Malcolm Akner Erik CFD MSRE CAD CHT flytande salt strömningslära strömningsmekanik fluid fluidmekanik LTU kärnreaktor generation fyra generation IV copenhagen atomics rymdteknik flygteknik ingenjör civilingenjör examensarbete Malcolm Akner Erik Aerospace Engineering Rymd- och flygteknik

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