Rozprawy doktorskie na temat „Fluid physics”
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Osman, S. M. "Theoretical studies of the fluid-fluid interface". Thesis, University of East Anglia, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382833.
Pełny tekst źródłaGlorioso, Paolo. "Fluid dynamics in action". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107318.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 207-213).
In this thesis we formulate an effective field theory for nonlinear dissipative fluid dynamics. The formalism incorporates an action principle for the classical equations of motion as well as a systematic approach to thermal and quantum fluctuations around the classical motion of fluids. The dynamical degrees of freedom are Stuckelberg-like fields associated with diffeomorphisms and gauge transformations, and are related to the conservation of the stress tensor and a U(1) current if the fluid possesses a charge. This inherently geometric construction gives rise to an emergent "fluid space-time", similar to the Lagrangian description of fluids. We develop the variational formulation based on symmetry principles defined on such fluid space-time. Through a prescribed correspondence, the dynamical fields are mapped to the standard fluid variables, such as temperature, chemical potential and velocity. This allows to recover the standard equations of fluid dynamics in the limit where fluctuations are negligible. Demanding the action to be invariant under a discrete transformation, which we call local KMS, guarantees that the correlators of the stress tensor and the current satisfy the fluctuation-dissipation theorem. Local KMS invariance also automatically ensures that the constitutive relations of the conserved quantities satisfy the standard constraints implied e.g. by the second law of thermodynamics, and leads to a new set of constraints which we call generalized Onsager relations. Requiring the above properties to hold beyond tree-level leads to introducing fermionic partners of the original degrees of freedom, and to an emergent supersymmetry. We also outline a procedure for obtaining the effective field theory for fluid dynamics by applying the holographic Wilsonian renormalization group to systems with a gravity dual.
by Paolo Glorioso.
Ph. D.
Feudel, Fred, Norbert Seehafer i Olaf Schmidtmann. "Fluid helicity and dynamo bifurcations". Universität Potsdam, 1995. http://opus.kobv.de/ubp/volltexte/2007/1388/.
Pełny tekst źródłaMoe, John Einar. "Near and far-field acoustic scattering through and from two dimensional fluid-fluid rough interfaces /". Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/6019.
Pełny tekst źródłaSun, Mingqiu. "Molecular dynamics simulation of fluid systems /". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849696964891.
Pełny tekst źródłaCrossley, Michael James. "An action principle for dissipative fluid dynamics". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103242.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 193-199).
Fluid dynamics is the universal theory of low-energy excitations around equilibrium states, governing the physics of long-lived modes associated with conserved charges. Historically, fluid dynamics has been formulated at the level of equations of motion, in terms of a local fluid velocity and thermodynamic quantities. In this thesis, we describe a new formulation of fluid dynamics in terms of a path integral, which systematically encodes the effects of thermal and quantum fluctuations. In our formulation, the dynamical degrees of freedom are Stuckelberg-type fields associated to the conserved quantities, which are subject to natural symmetry considerations, and the time evolution of the path integral is along the closed-time contour. Our formulation recovers the standard hydrodynamics, including the expected constraints from thermodynamics and the fluctuation-dissipation theorem, as well as an additional non-linear generalization of the Onsager relations. We demonstrate an emergent supersymmetry in the "classical statistical" limit of our theory. For the non-linear fluid, the formalism is encoded in a non-trivial differential geometric structure, with a non vanishing torsion tensor required to recover the correct physics of the most general fluid. Finally, we discuss progress in obtaining a holographic derivation of the action formulation at the ideal level, in which the low energy degrees of freedom emerge naturally as the relative embedding of the boundary and horizon hypersurfaces.
by Michael James Crossley.
Ph. D.
麥民光 i Man-kwong Mak. "The relativistic static charged fluid sphere and viscous fluid cosmological model". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31237526.
Pełny tekst źródłaMak, Man-kwong. "The relativistic static charged fluid sphere and viscous fluid cosmological model /". Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19324352.
Pełny tekst źródłaSandin, Patrik. "The asymptotic states of perfect fluid cosmological models". Licentiate thesis, Karlstad : Faculty of Technology and Science, Physics, Karlstads universitet, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4713.
Pełny tekst źródłaDegen, Michael Merle. "Time-dependent pattern formation in fluid dynamical systems /". The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu148794815862621.
Pełny tekst źródłaPerin, Maxime. "Hamiltonian fluid reductions of kinetic equations in plasma physics". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4050/document.
Pełny tekst źródłaFluid reduction of kinetic equations is a ubiquitous procedure in plasma physics which aims to replace the distribution function defined in phase space with more concrete fluid quantities defined solely in configuration space such as the density, the fluid velocity and the pressure. This reduction lowers the complexity of the initial system, leading to a gain of physical insight into the phenomena under investigation as well as a significant decrease of the cost of numerical simulations. On the other hand, in order for the fluid reduction to be complete, one needs to perform a closure on the higher order fluid moments. The choice of the closure usually relies on some ad hoc physical arguments (e.g., conserved quantities, existence of an H-theorem, ...). In this manuscript, we present a reduction procedure that preserves the Hamiltonian structure of the parent kinetic model. This is important in order to ensure that no non-physical dissipation is introduced in the resulting fluid model, providing it with a geometric structure that can be traced back to the microscopic dynamics of the particles. We use this procedure to derive non-adiabatic fluid models for the first three fluid moments of the distribution function of the one dimensional Vlasov-Poisson equation, namely the density, the fluid velocity and the pressure. The results are extended to include the dynamics of the heat-flux by considering a closure based on dimensional analysis. For an arbitrary number of fields, we demonstrate the relationship with the water-bags model. Finally, the extension to higher dimensions is investigated through the drift-kinetic equation and the three dimensional Vlasov-Poisson equation
Slone, Avril Kay. "A finite volume unstructured mesh approach to dynamic fluid structure interaction between fluids and linear elastic solids". Thesis, University of Greenwich, 2000. http://gala.gre.ac.uk/6303/.
Pełny tekst źródłaHall, Christopher David. "Neutron diffraction and molecular dynamics studies of fluid halocarbons". Thesis, University of Liverpool, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316495.
Pełny tekst źródłaArcher, Andrew John. "Statistical mechanics of soft core fluid mixtures". Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288269.
Pełny tekst źródłaCourts, Samuel Scott. "Superfluid turbulence in two-fluid flow of helium II /". The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu148759165817599.
Pełny tekst źródłaFeudel, Fred, i Norbert Seehafer. "Bifurcations and pattern formation in a 2D Navier-Stokes fluid". Universität Potsdam, 1995. http://opus.kobv.de/ubp/volltexte/2007/1390/.
Pełny tekst źródłaBenjamin, Nathan S. "Numerical implementations of holographic duality via the fluid/gravity correspondence". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/83815.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 65-66).
The fluid/gravity correspondence describes an map from relativistic fluid dynamics to general relativity in an anti de Sitter (AdS) background in one more dimension. This is a specific example of a more general principle known as holographic duality, in which a quantum field theory (QFT) is dual to a gravitational theory with the QFT defined on the boundary. Since we can regard hydrodynamics as a low-energy description of many QFTs, the fluid/gravity correspondence lets us probe holographic duality for QFTs at low energy. In this thesis, we will discuss holographic duality, hydrodynamic theory and turbulence, numerical implementations of hydrodynamics, black branes in AdS, the fluid/gravity correspondence, and numerically testing the fluid/gravity correspondence.
by Nathan S. Benjamin.
S.B.
Paleo, Cageao Paloma. "Fluid-particle interaction in geophysical flows : debris flow". Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/27808/.
Pełny tekst źródłaAsbell, Jessica Lee. "Non-radial fluid pulsation modes of compact stars". Thesis, California State University, Long Beach, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10150591.
Pełny tekst źródłaThe observation of gravitational waves from compact stars (neutron and quark stars) is a promising method of determining their internal composition. This research presents the details and results for calculations of some of the principal modes of compact star oscillations, by which they radiate gravitational waves. These are: the f-modes, p-modes, and g-modes. We find that for the same stellar mass, the f-modes for quark stars are higher in frequency than for neutron stars. The p-mode frequency of quark stars decrease with stellar mass, displaying an opposite trend to that of neutron stars. Two-component models were also considered. A core-ocean model was examined for a neutron star, using a polytropic equation of state (EOS), and a core-crust model for a quark star, using a bag model EOS. We find that g-mode oscillations in neutron star oceans depend on the dominant chemical species of the ocean as well as the mass of the underlying core. The addition of a solid crust onto a quark star increases the frequencies, attributable to shear stresses between the core and crust. These results pave the way to model and contrast the gravitational wave signals emitted by oscillating compact stars.
Law, Adam Daniel. "Structure and interactions of colloidal particles at fluid interfaces". Thesis, University of Hull, 2011. http://hydra.hull.ac.uk/resources/hull:4716.
Pełny tekst źródłaMoreau, Filip. "Physics-Based, Real-Time Simulation of Fluid-Immersed Rigid Bodies". Thesis, Malmö universitet, Fakulteten för teknik och samhälle (TS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-43343.
Pełny tekst źródłaSörensson, Christian. "Cost efficient fluid sensor : Master’s Thesis project in Engineering Physics". Thesis, Uppsala universitet, Mikrosystemteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-317792.
Pełny tekst źródłaCastonguay, Francois. "Increasing the quality factor of microcantilevers in a fluid environment". Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96942.
Pełny tekst źródłaLe besoin criant d'augmenter le facteur de qualité de micros-levier immergée dans un fluide utilisé en microscopie de force atomique a été démontré a mainte reprise, plus particulièrement dans le cas ou les échantillons devais être dans leur environnent liquide naturelle. C'est pour cette raison qu'une série de micro-levier ont été crée sur une basse de paramètre prédéfini et avec un dépôt de nitrure de silicium chimique en phase vapeur sous pression réduite. Chaque micros-leviers a une aire de surface de 5600μm2, pouvant ainsi être comparé avec le micro-levier de référence ayant pour dimension 140μm par 40μm. Une procédure pour fabriquer c'est micros-leviers dans un environnent de salle blanche, ainsi que les méthodes utiliser pour contrevenir aux problèmes encourus durant la fabrication, sont expliqués en détail. Chaque prise de mesure a été effectué sur notre appareil fait maison ayant comment composante principale un laser focalisé, un porte échantillon et une photodiode divisée. Les résultats obtenu n'ont pas été a la hauteur de nos attentes, néanmoins certain micros-leviers ont démontrés une réduction significative de leur facteur de qualité, nous aidant donc à diriger le travail futur sur le sujet. Un microlevier (#9), a par contre démontré une performance équivalente par rapport au micro-levier de référence augmentant même le ratio de facteur de qualité pour le 2e mode d'opération.
Wang, Huamin. "Practical water animation using physics". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31745.
Pełny tekst źródłaCommittee Chair: Greg Turk; Committee Member: C. Karen Liu; Committee Member: Irfan Essa; Committee Member: Jarek Rossignac; Committee Member: Peter J. Mucha. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Kim, Yootai. "Control of physics-based fluid animation using a velocity-matching method". Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149087881.
Pełny tekst źródłaColovas, Peter William. "The Formation of Time Dependent Patterns in Non-Equilibrium Fluid Dynamical Systems /". The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487933648648833.
Pełny tekst źródłaRimstad, Kjartan. "Bayesian Seismic Lithology/Fluid Inversion Constrained by Rock Physics Depth Trends". Thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9772.
Pełny tekst źródłaIn this study we consider 2D seismic lithology/fluid inversion constrained by rock physics depth trends and a prior lithology/fluid Markov random field. A stochastic relation from porosity and lithology/fluid to seismic observations is established. The inversion is done in a Bayesian framework with an approximate posterior distribution. Block Gibbs samplers are used to estimate the approximate posterior distribution. Two different inversion algorithms are established, one with the support of well observations and one without. Both inversion algorithms are tested on a synthetic reservoir and the algorithm with well observations is also tested on a data set from the North Sea. The classification results with both algorithms are good. Without the support of well observations it is problematic to estimate the level of the porosity trends, however the classification results are approximately translation invariant with respect to porosity trends.
Pouliot, Dominique. "Models of binary fluid phase separation in the inertial regime". Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94930.
Pełny tekst źródłaCette thèse présente une analyse théorique de la cinétique tardive de séparation de phase dans un fluide binaire. On utilise les idées et les techniques du groupe de renormalisation (RG) à enveloppe d'impulsion pour étudier les propriétés du système de fluides, pour des distances et des temps très longs. La description non-linéaire effective à un fluide de Sain et Grant est généralisée, dans le but d'inclure des effets de mémoire, grâce à la construction de deux corrélateurs de bruit non-Markoviens, et l'équation complète de Navier-Stokes (NSE) pour un fluide incompressible est considérée. La structure des corrélateurs non-Markoviens est justifiée de façon heuristique, et l'exposant du facteur de decroissance en puissance de t est obtenu en utilisant une équation d'énergie et le théorème de Novikov. Il y a trois motivations principales à cette étude. Le but premier est d'obtenir une meilleure compréhension de la façon de modéliser de tels systèmes fluides binaires, en utilisant un nombre minimal d'éléments clés, grâce à l'approche du groupe de renormalisation (RG). Le deuxième objectif est d'obtenir de l'information dynamique sur le taux de croissance en puissance de t du rayon R des gouttelettes, à travers le calcul d'un intervalle de valeurs permises pour l'exposant, et le critère de decroissance du nombre de Reynolds , Re, en puissance de L. L'exposant dynamique du nombre de Reynolds résulte du calcul de renormalisation, et L est l'échelle de longueur à laquelle les phénomènes sont observés. Ceci mène à la considération de la classe d'universalité (pour les transitions de phase du premier ordre) associée à ce processus cinétique. Le troisième objectif est d'estimer une échelle de grandeur des vitesses dans le fluide, au moyen d'un autre résultat du processus de renormalisation, l'exposant dynamique z. Les résultats des deux modèles, MI et MII, sont en bon accord avec les donné
Wilson, James W. "Development and optimisation of supercritical fluid deposition of semiconductor films". Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/167623/.
Pełny tekst źródłaKruse, Matthew Thomas 1964. "Smooth, cusped, and discontinuous traveling waves in the periodic fluid resonance equation". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282759.
Pełny tekst źródłaSmith, Katherine Margaret. "Effects of Submesoscale Turbulence on Reactive Tracers in the Upper Ocean". Thesis, University of Colorado at Boulder, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10623667.
Pełny tekst źródłaIn this dissertation, Large Eddy Simulations (LES) are used to model the coupled turbulence-reactive tracer dynamics within the upper mixed layer of the ocean. Prior work has shown that LES works well over the spatial and time scales relevant to both turbulence and reactive biogeochemistry. Additionally, the code intended for use is able to carry an arbitrary number of tracer equations, allowing for easy expansion of the species reactions. Research in this dissertation includes a study of 15 idealized non-reactive tracers within an evolving large-scale temperature front in order determine and understand the fundamental dynamics underlying turbulence-tracer interaction in the absence of reactions. The focus of this study, in particular, was on understanding the evolution of biogeochemically-relevant, non-reactive tracers in the presence of both large (~5 km) submesoscale eddies and smallscale (~100 m) wave-driven Langmuir turbulence. The 15 tracers studied have different initial, boundary, and source conditions and significant differences are seen in their distributions depending on these conditions. Differences are also seen between regions where submesoscale eddies and small-scale Langmuir turbulence are both present, and in regions with only Langmuir turbulence. A second study focuses on the examination of Langmuir turbulence effects on upper ocean carbonate chemistry. Langmuir mixing time scales are similar to those of chemical reactions, resulting in potentially strong tracer-flow coupling effects. The strength of the Langmuir turbulence is varied, from no wave-driven turbulence (i.e., only shear-driven turbulence), to Langmuir turbulence that is much stronger than that found in typical upper ocean conditions. Three different carbonate chemistry models are also used in this study: time-dependent chemistry, equilibrium chemistry, and no-chemistry (i.e., non-reactive tracers). The third and final study described in this dissertation details the development of a reduced-order biogeochemical model with 17 state equations that can accurately reproduce the Bermuda Atlantic Time-series Study (BATS) ecosystem behavior, but that can also be integrated within high-resolution LES.
Kawai, Risa. "Analysis of the swimming-to-crawling transition of Caenorhabditis elegans in viscous fluid". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44763.
Pełny tekst źródłaIncludes bibliographical references (leaves 26-27).
The locomotory behavior of the nematode Caenorhabditis elegans is often characterized by two distinct gaits - swimming when in fluids and crawling when on surfaces. Swimming is characterized by about a twice greater wavelength and about four time greater frequency of undulatory waves, compared with the crawling gait. These mechanisms which generate these gaits are not well-understood but have been suggested to be controlled by two separate neural circuits of central pattern generators. Here we studied the locomotion of young adult C. elegans in viscous fluids ranging from 0.001-1000 Pa s to determine whether there is a sharp or continuous transition between swimming and crawling. We characterized the locomotion by two parameters: the wavelength and the frequency of the undulating gaits. Our results for both parameters show a smooth transition, which suggests that there is only one neural circuit controlling forward locomotion which is modulated by the mechanical loading of the environment.
by Risa Kawai.
S.B.
Tourbier, Dietmar 1964. "Numerical investigation of transitional and turbulent compressible axisymmetric wakes". Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282242.
Pełny tekst źródłaShala, Mehmet. "Unstructured staggered mesh discretisation methods for computational fluid dynamics". Thesis, University of Greenwich, 2007. http://gala.gre.ac.uk/6297/.
Pełny tekst źródłaCooper, Jason. "Numerical Modeling of Fluid Flow in a Porous Media Using Python". Thesis, University of Louisiana at Lafayette, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10682421.
Pełny tekst źródłaThis project numerically modeled a simplified version of a fault system complete with a shear zone, similar to that of the fault zones in the Sierra Nevada, purely in Python to compare to that of one using ABAQUS. Modeling fluid flow in this system can help explain or predict where water is coming to the surface in places like the Sierra Nevada. The model took into account fluid flow based on Darcy’s law, which explains how fluid flows through a porous media, and applied it to the background diffusivities and pressures that it was given. This gave fluid velocities off initial pressure gradients and perturbations. After testing several initial pressure fields in the model against the previous models, it was found that, with Test 3, it was possible to match the “black box” of ABAQUS using the freeware of Python. This result opens up opportunities to explore further this system by refining the model and adding new parameters that were just not possible to do with ABAQUS.
Richardson, Philip Jarvis. "Magnetoconductivity of a two dimensional electron fluid on liquid helium". Thesis, Royal Holloway, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265881.
Pełny tekst źródłaPollard, Jeremy David. "Optical excitation of surface plasmons at metal/organic fluid boundaries". Thesis, University of Exeter, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253622.
Pełny tekst źródłaWah, Darren M. "Turbulence in binary fluid flow systems: A lattice Boltzmann approach". W&M ScholarWorks, 1999. https://scholarworks.wm.edu/etd/1539623963.
Pełny tekst źródłaBarnes, Caleb J. "Unsteady Physics and Aeroelastic Response of Streamwise Vortex-Surface Interactions". Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1431937866.
Pełny tekst źródłaFrom, Christopher. "High-order lattice Boltzmann for nonideal fluid mixtures". Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/200190/1/Christopher_From_Thesis.pdf.
Pełny tekst źródłaLiu, Minghua. "Lattice Boltzmann study of fluid flow and heat transfer in random porous media". Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/55219/.
Pełny tekst źródłaMellema, Garfield Richard. "Subcritical acoustic scattering across a rough fluid-solid interface /". Thesis, Connect to this title online; UW restricted, 1999. http://hdl.handle.net/1773/6098.
Pełny tekst źródłaNixon, Grant Ian. "Entropic trapping and polymer dynamics in static, quasi-periodic arrays of obstacles in two dimensional media". Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26307.
Pełny tekst źródłaLayer, Brian David. "Structured plasma waveguides and deep EUV generation enabled by intense laser-cluster interactions". Thesis, University of Maryland, College Park, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3557663.
Pełny tekst źródłaUsing the unique properties of the interaction between intense, short-pulse lasers and nanometer scale van-der-Waals bonded aggregates (or 'clusters'), modulated waveguides in hydrogen, argon and nitrogen plasmas were produced and extreme ultraviolet (EUV) light was generated in deeply ionized nitrogen plasmas. A jet of clusters behaves as an array of mass-limited, solid-density targets with the average density of a gas.
Two highly versatile experimental techniques are demonstrated for making preformed plasma waveguides with periodic structure within a laser-ionized cluster jet. The propagation of ultra-intense femtosecond laser pulses with intensities up to 2 x1017 W/cm2 has been experimentally demonstrated in waveguides generated using both methods, limited by available laser energy. The first uses a 'ring grating' to impose radial intensity modulations on the channel-generating laser pulse, which leads to axial intensity modulations at the laser focus within the cluster jet target. This creates a waveguide with axial modulations in diameter with a period between 35 μm and 2 mm, determined by the choice of ring grating. The second method creates modulated waveguides by focusing a uniform laser pulse within a jet of clusters with ow that has been modulated by periodically spaced wire obstructions. These wires make sharp, stable voids as short as 50 μm with a period as small as 200 μm within waveguides of hydrogen, nitrogen, and argon plasma. The gaps persist as the plasma expands for the full lifetime of the waveguide. This technique is useful for quasi-phase matching applications where index-modulated guides are superior to diameter modulated guides. Simulations show that these 'slow wave' guiding structures could allow direct laser acceleration of electrons, achieving gradients of 80 MV/cm and 10 MV/cm for laser pulse powers of 1.9 TW and 30 GW, respectively.
Results are also presented from experiments in which a nitrogen cluster jet from a cryogenically cooled gas valve was irradiated with relativistically intense (up to 2 x 1018 W/cm2) femtosecond laser pulses. The original purpose of these experiments was to create a transient recombination-pumped nitrogen soft x-ray laser on the 2p3/2 → 1s1/2 (λ = 24.779 Å) and 2p1/2 → 1 s1/2 (λ = 24.785 Å) transitions in H-like nitrogen (N 6+). Although no amplification was observed, trends in EUV emission from H-like, He-like and Li-like nitrogen ions in the 15 –150 Åspectral range were measured as a function of laser intensity and cluster size. These results were compared with calculations run in a 1-D fluid laser-cluster interaction code to study the time-dependent ionization, recombination, and evolution of nitrogen cluster plasmas.
Ohia, Obioma Ogonna Chinyerem. "Two-fluid simulations of magnetic reconnection with a kinetic closure for the electron pressure anisotropy". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/95854.
Pełny tekst źródłaCataloged from PDF version of thesis.
Includes bibliographical references (pages 189-206).
Magnetic reconnection is a rapid rearrangement of magnetic line topology in a plasma that can allow magnetic energy to heat, drive macroscopic flows, or accelerate particles in space and laboratory plasmas. Though reconnection affects global plasma dynamics, it depends intimately on small-scale electron physics. In weakly-collisional plasmas, electron pressure anisotropy resulting from the electric and magnetic trapping of electrons strongly affects the structure surrounding the electron diffusion region and the electron current layer. Previous fluid models and simulations fail to account for this anisotropy. In this thesis, new equations of state that accurately describe the electron pressure anisotropy in cases of sufficiently strong guide magnetic field are implemented in fluid simulations and are compared to previous fluid models and kinetic simulations. Elongated current layers in the reconnection region, driven, in part, by this pressure anisotropy, appear as part of a self-regulating mechanism of electron pressure anisotropy. The structure depends on plasma parameters, with low guide fields yielding longer layers.
by Obioma Ogonna Chinyerem Ohia.
Ph. D.
Lipscombe, Trevor. "The role of helicity in turbulent fluid dynamics". Thesis, University of Oxford, 1986. http://ora.ox.ac.uk/objects/uuid:e60f1258-5398-4ce7-b1ff-a1fe6b848595.
Pełny tekst źródłaTahmassebi, Amirhessam. "Fluid Flow Through Carbon Nanotubes And Graphene Based Nanostructures". University of Akron / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=akron1436545689.
Pełny tekst źródłaJacobson, Craig Michael. "Electron transport in plasmas with lithium-coated plasma-facing components". Thesis, Princeton University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3615076.
Pełny tekst źródłaThe Lithium Tokamak Experiment (LTX) is a spherical tokamak designed to study the lowrecycling regime through the use of lithium-coated shells conformal to the last closed flux surface (LCFS). A lowered recycling rate is expected to flatten core Te profiles, raise edge Te, strongly affect n e profiles, and enhance confinement.
To study these unique plasmas, a Thomson scattering diagnostic uses a ≤ 20 J, 30 ns FWHM pulsed ruby laser to measure Te and ne at 11 radial points on the horizontal midplane, spaced from the magnetic axis to the outer edge at a single temporal point for each discharge. Scattered light is imaged through a spectrometer onto an intensified CCD. The diagnostic is absolutely calibrated using a precision light source and Raman scattering. Measurements of n e are compared with line integrated density measurements from a microwave interferometer. Adequate signal to noise is obtained with ne ≥ 2 ×10 18 m–3.
Thomson profiles of plasmas following evaporation of lithium onto room-temperature plasmafacing components (PFCs) are used in conjunction with magnetic equilibria as input for TRANSP modeling runs. Neoclassical calculations are used to determine Ti profiles, which have levels that agree with passive charge exchange recombination spectroscopy (CHERS) measurements. TRANSP results for confinement times and stored energies agree with diamagnetic loop measurements. Results of χe result in values as low as 7 m2/s near the core, which rise to around 100 m2/s near the edge. These are the first measurements of χe in LTX, or its predecessor, the Current Drive Experiment-Upgrade (CDX-U), with lithium PFCs.
Chun-Lin, Louis Chang. "High Intensity Mirror-Free Nanosecond Ytterbium Fiber Laser System in Master Oscillator Power Amplification". Thesis, National Taiwan University (Taiwan), 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3583082.
Pełny tekst źródłaRare-earth-doped fiber lasers and amplifiers are relatively easy to efficiently produce a stable and high quality laser beam in a compact, robust, and alignment-free configuration. Recently, high power fiber laser systems have facilitated wide spread applications in academics, industries, and militaries in replacement of bulk solid-state laser systems. The master oscillator power amplifier (MOPA) composed of a highly-controlled seed, high-gain preamplifiers, and high-efficiency power amplifiers are typically utilized to scale up the pulse energy, peak power, or average power. Furthermore, a direct-current-modulated nanosecond diode laser in single transverse mode can simply provide a compact and highly-controlled seed to result in the flexible output parameters, such as repetition rate, pulse duration, and even temporal pulse shape. However, when scaling up the peak power for high intensity applications, such a versatile diode-seeded nanosecond MOPA laser system using rare-earth-doped fibers is unable to completely save its own advantages compared to bulk laser systems. Without a strong seeding among the amplifiers, the guided amplified spontaneous amplification is easy to become dominant during the amplification, leading to the harmful self-lasing or pulsing effects, and the difficulty of the quantitative numerical comparison. In this dissertation, we study a high-efficiency and intense nanosecond ytterbium fiber MOPA system with good beam quality and stability for high intensity applications. The all-PM-fiber structure is achieved with the output extinction ratio of >12 dB by optimizing the interconnection of high power optical fibers.
The diode-seeded MOPA configuration without parasitic stimulated amplification (PAS) is implemented using the double-pass scheme to extract energy efficiently for scaling peak power. The broadband PAS was studied experimentally, which matches well with our numerical simulation. The 1064-nm nanosecond seed was a direct-current-modulated Fabry-Pérot diode laser associated with a weak and pulsed noise spanning from 1045 to 1063 nm. Even though the contribution of input noise pulse is only <5%, it becomes a significant transient spike during amplification. The blue-shifted pulsed noise may be caused by band filling effect for quantum-well seed laser driven by high peak current. The study helps the development of adaptive pulse shaping for scaling peak power or energy at high efficiency. On the other hand, the broadband spike with a 3-dB bandwidth of 8.8 nm can support pulses to seed the amplifier for sub-nanosecond giant pulse generation.
Because of the very weak seed laser, the design of high-gain preamplifier becomes critical. The utilization of single-mode core-pumped fiber preamplifier can not only improve the mode contrast without fiber coiling effect but also significantly suppress the fiber nonlinearity. The double-pass scheme was therefore studied both numerically and experimentally to improve energy extraction efficiency for the lack of attainable seed and core-pumped power. As a result, a record-high peak power of > 30 kW and energy of > 0.23 mJ was successfully achieved to the best of our knowledge from the output of clad-pumped power amplifier with a beam quality of M2 ∼1.1 in a diode-seeded 15-µm-core fiber MOPA system. After the power amplifier, the MOPA conversion efficiency can be dramatically improved to >56% for an energy gain of >63 dB at a moderate repetition rate of 20 kHz with a beam quality of M 2 <1.5. The output energy of >1.1 mJ with a pulse duration of ∼6.1 ns can result in a peak power up to >116 kW which is limited by fiber fuse in long-term operation. Such a condition able to generate the on-target laser intensity of > 60 GW/cm2 for applications is qualified to preliminarily create a laser-plasma light source. Moreover, the related simulation results also reveal the double-passed power amplifier can further simplify MOPA.
Such an intense clad-pumped power amplifier can further become a nonlinear fiber amplifier in all-normal dispersion instead of a nonlinear passive fiber. The combination of laser amplification and nonlinear conversion together can therefore overcome the significant pump depletion during the propagation along the passive fiber for power scaling. As a result, an intense spectrum spanning from 980 to 1600 nm as a high-power nanosecond supercontinuum source can be successfully generated with a conversion efficiency of >65% and a record-high peak power of >116 kW to the best of our knowledge. Because of MOPA structure, the influence of input parameters of nonlinear fiber amplifier on supercontinuum parameters can also be studied. The onset and interplay of fiber nonlinearities can be revealed stage by stage. Such an unique and linearly-polarized light source composed of an intense pump and broad sideband seed is beneficial for efficiently driving the broadband tunable optical parametric amplification free from the bulkiness and timing jitter.
Keywords: High power fiber laser and amplifier, ytterbium fiber, master oscillator power amplification, parasitic stimulated amplification, multi-pass fiber amplification, peak power/pulse energy scaling, fiber nonlinear optics, supercontinuum generation.
Bray, David Jonathan. "Statistical properties of a randomly excited granular fluid". Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11041/.
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