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Tesi sul tema "Hydrodynamics"
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1
Merriam, Susan Carol. "Direct demonstration of self-similarity in a hydrodynamic treatment of polymer self-diffusion". Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0501102-142449.
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2
Ulrich, Christian [Verfasser], e Thomas [Akademischer Betreuer] Rung. "Smoothed-particle-hydrodynamics simulation of port hydrodynamic problems / Christian Ulrich. Betreuer: Thomas Rung". Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2013. http://d-nb.info/1048574903/34.
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3
Ulrich, Christian Verfasser], e Thomas [Akademischer Betreuer] [Rung. "Smoothed-particle-hydrodynamics simulation of port hydrodynamic problems / Christian Ulrich. Betreuer: Thomas Rung". Hamburg-Harburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2013. http://nbn-resolving.de/urn:nbn:de:gbv:830-tubdok-12458.
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4
Renick, Dirk H. "Unsteady propeller hydrodynamics". Thesis, Springfield, Va. : Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA393206.
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5
Xavier, Patricia Anne. "Floodplain woodland hydrodynamics". Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54961/.
Testo completoAbstract (sommario):
Floodplain woodlands are valuable environments, providing a diverse habitat for many riparian and land-based species. It is now recognised that the continual loss of floodplain woodland has impoverished the national biodiversity of riparian environments, and measures have been brought in both nationally and through the European Commission to halt the decline. This has however, highlighted a deficiency that has existed for many years in the field of river hydraulics. The representation of complex riparian vegetation environments within river models remains an area not adequately addressed. This research presents experimental investigations into floodplain woodland vegetation, with a view to improving the representation of these vegetations within numerical models. Floodplain woodland hydrodynamics were explored with scaled-down (1:8) stag gered arrays of single stem and multi-stem model trees at planting densities of 8.8, 19.8 and 80.6 plants per m 2. The planting densities investigated correspond to the recommended planting densities cited by the Forestry Commission UK. Roughness factors, including Manning's n, the Darcy-Weisbach friction factor / and the bulk drag coefficient Ca were computed for the different model tree and planting density combinations. Velocity measurements within the arrays were investigated, and a study to determine the optimum sampling strategy was carried out to obtain representative velocity and turbulent kinetic energy measurements within the model tree arrays. The optimum sampling locations for streamwise velocity appeared to be clustered around 0.3 s and 0.7 s, where s is the lateral or longitudinal spacing between the model trees, while for turbulent kinetic energy the optimum location was 0.5 s. Full scale drag force versus velocity tests of floodplain woodland trees were carried out and a drag area parameter CdA.Uo derived. The trees experienced little to no bending at low velocities, with force varying linearly with the square of velocity, while considerable deflection was observed at higher velocities, with force varying linearly with the velocity. Physical parameters including height, diameter, mass and volume of the wood are compared against the drag area parameter, with mass and volume showing a stronger correlation than height or diameter. The increase in the drag area parameter due to the presence of foliage was also investigated. The numerical incorporation of floodplain woodland vegetation is presented with respect to two-dimensional depth-averaged numerical modelling. A reach of the River Laver in North Yorkshire, England was modelled to assess the hydraulic impact of the conversion of arable land to floodplain woodland.
6
Hawke, I. "Computational ultrarelativistic hydrodynamics". Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603857.
Testo completoAbstract (sommario):
This thesis studies critical collapse in the early universe as modelled by a Friedman-Robertson-Walker (FRW) spacetime. This differs from most previous studies of critical collapse as the spacetime is not asymptotically flat or approximately stationary. This study allows us to look at the formation of black holes in the early universe. In order to perform this study we consider in depth the numerical methods necessary to study the collapse of an ultrarelativistic fluid. The general solution of the Riemann problem with the ultrarelativistic equation of state is derived, along with previous results. The efficiency and accuracy of different exact and approximate Riemann solvers is compared. The Riemann solvers are then used to implement and test a number of High Resolution Shock Capturing methods. A variety of high order methods are compared using a wide variety of test. The stability, accuracy and efficiency of the methods are the focus of this part of the thesis. These methods are combined with different gridding strategies. The Adaptive Mesh Refinement algorithm is described, together with simpler methods such as an uneven grid. The Adaptive Mesh algorithm is found to have some unexpected problems when the system of equations is not hyperbolic. Finally we look at the behaviour of the collapse of a density perturbation in a FRW spacetime. It is shown that it does not conform to the standard critical collapse scenario. Various explanations for this are discussed, together with the implications for primordial black hole formation.
7
Ren, Qilong. "Hydrodynamics of ammonoids". Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760977.
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8
Tajima, Yoshimitsu 1972. "Surf zone hydrodynamics". Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84236.
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9
Lin, Feng Ying. "Smoothed particle hydrodynamics". Mémoire, Université de Sherbrooke, 2005. http://savoirs.usherbrooke.ca/handle/11143/4654.
Testo completoAbstract (sommario):
Since its introduction in the late 1970s by Lucy [11] and Gingold and Monaghan [4], smoothed particle hydrodynamics (SPH) has been used in many areas. It has grown into a widely-recognized technique with many practical applications. In this thesis, we present a new application of the SPH method: a new algorithm for computing a null divergence velocity field using SPH for incompressible flow - a pure SPH solution of the Helmholtz-Hodge decomposition. Also, a new version of the Laplacian for SPH is proposed and the advantages and disadvantages of different gradient and Laplacian approximation formulas used in SPH are also discussed. A new treatment of boundary conditions is proposed for the whole solution procedure. Throughout the thesis, a brief historical overview is presented, along with some fundamental notions about SPH and computational fluid dynamics.
10
Parameswaran, Gopalkrishnan. "Smoothed Particle Hydrodynamics studies of heap leaching hydrodynamics and thermal transport". Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/39879.
Testo completoAbstract (sommario):
This thesis is concerned with the development and application of Smoothed Particle Hydrodynamics (SPH) models for studying multiphase flows such as those relevant to the analysis of the hydrodynamics and thermal transport involved in heap leaching. The improvements made here to the modelling aspects of multiphase SPH are seen to bring about measurable improvements to solution quality. A relative density formulation and a 'compressibility-matching' method for handling interfaces eliminate what would otherwise be significant obstacles to obtaining stable and smooth pressure fields. The convergence properties of the formulation are seen to approach the theoretically expected value in SPH. Convergence is also seen to strongly depend on the smoothing length factor used. A factor found to influence error magnitudes that nevertheless does not affect convergence rates is the extent of initial particle disorder. The simplified cases representative of heap leaching hydrodynamics studied through 2D simulations allow an understanding of flow at the particle scale. The significant dependence of mean flow rates in these systems on particle sizes, saturation and contact angle is shown. In 3D, saturated flows through packed beds of spherical particles are presented. Steady-state superficial velocities obtained through simulations, compared with analytical relationships given by Cozeny-Karman and Ergun relations are illustrative of the ability of SPH to reproduce packed bed flows satisfactorily. Subsequently unsaturated regimes encountered at the channel scale are studied qualitatively for saturation values typical of real heaps. A heat transfer model based on a formulation for single-phase SPH developed by Szewc et al. is implemented. The model's performance (in terms of Rayleigh numbers indicative of transition to unsteady convection in differentially heated cavities (DHCs)) is satisfactory when compared with the established single-phase results of Le Quere. Its application to an idealised unsaturated scenario demonstrates its useability for multiphase studies. Finally, an extension is made to the model to account for turbulent regime heat transport. This extension, deriving from one used for finite elements by Chatelain et al. is novel in the SPH context and lets the loss of stratification seen in DHCs at high Rayleigh numbers be predicted with reasonable accuracy.
11
Allen, Leanne. "Modelling dolphin hydrodynamics : the numerical analysis and hydrodynamic stability of flow past compliant surfaces". Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844005/.
Testo completoAbstract (sommario):
Historical numerical methods for solving stiff ordinary differential equations are investigated and a new numerical framework developed and applied to a variety of hydrodynamic stability problems where the effects of passive wall compliance are investigated. The compound matrix method is set in a general coordinate free framework using exterior algebra, and is considered to be the most accurate and easy to implement method for complex systems. The effect of passive wall compliance on the Blasius boundary layer flow is studied. The linear stability of the mean flow state is considered using the new numerical framework and shooting technique. A Newton algorithm is implemented to converge the eigenvalue such that the boundary condition at the surface is satisfied. Curves of neutral stability are produced in the Re-alpha plane for various degrees of compliance, damping and tension parameters. Three dimensionality is incorporated first by a simple introduction of rotation in the flow leading to the investigation of the Ekman boundary layer problem where a Coriolis force instability mechanism (type-2) produces streamwise rolls at modest Reynolds numbers. The linear stability of the Ekman mean flow state is considered using an extension of the new numerical framework for use on the vector space Lambda(3)(C6). Curves of neutral stability are produced in the E-gamma plane for constant values of the Reynolds number and in the Re-gamma plane for a selection of constant angle of orientation, E. This work is extended to consider the effects of wall compliance on the type-2 viscous instability mechanism, with the type-1 mode of instability briefly discussed. Three-dimensionality is then used for a direct application to the dolphin. The stability of the attachment-line boundary layer is investigated on flows past swept wings, relating directly to the dolphins swept-back fins. Wall compliance, modelling the dolphins skin, is included for analysis of its effect on the attachment-line instability.
12
Akinci, Nadir [Verfasser], e Matthias [Akademischer Betreuer] Teschner. "Interface handling in smoothed particle hydrodynamics = Interface-Handhabung in Smoothed Particle Hydrodynamics". Freiburg : Universität, 2014. http://d-nb.info/1114829331/34.
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13
Steinfurt, Stephan. "Generalisations of holographic hydrodynamics". Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-175251.
Testo completoAbstract (sommario):
In der vorliegenden Dissertation werden Eigenschaften stark gekoppelter hydrodynamischer Theorien untersucht, die mittels einer dualen Beschreibung als höherdimensionale gravitative Systeme aufgefasst werden können. Besonderes Augenmerk liegt hierbei auf der Berechnung physikalischer Größen wie Viskositäten oder Diffusionskonstanten. Diese werden hinsichtlich der Frage betrachtet, ob sie allgemeingültigen, universellen Gesetzmäßigkeiten folgen, die man aus der Beschreibung mittels einer Gravitationstheorie ableiten kann.
Die theoretische Grundlage bildet hierbei die Dualität konformer Quantenfeldtheorien im Minkowski Raum und höherdimensionaler Stringtheorien im Anti-de Sitter Raum, die AdS/CFT Korrespondenz. Einen besonders interessanten Grenzfall stellt der Limes starker Kopplung und hoher Anzahl von Freiheitsgraden der konformen Feldtheorie dar, in dem sich die duale Beschreibung zu klassischer Gravitationstheorie im AdS Raum vereinfacht. Mittels störungstheoretischer Betrachtung der Fluktuationen von Schwarzen Loch Lösungen der Gravitationstheorie lassen sich universelle hydrodynamische Eigenschaften der stark gekoppelten Feldtheorie beschreiben.
Eines der Hauptergebnisse dieses Forschungsgebietes ist der Nachweis, dass Fluide, die durch eine einfache duale Gravitationstheorie mit ungebrochener Rotationsinvarianz beschrieben werden können, ein universelles Verhältnis aus Scherviskosität und Entropiedichte besitzen. Erstaunlicherweise stimmt dieses Verhältnis parametrisch mit dem gemessenen Wert des stark gekoppelten Quark-Gluonen-Plasmas überein, ohne dass eine direkte Beschreibung dieser QCD Phase momentan möglich ist.
In der vorliegenden Arbeit wird die Konstruktion eines ähnlichen, universellen Zusammenhangs beschrieben. In der hydrodynamischen Beschreibung supersymmetrischen Feldtheorien existiert eine Diffusionskonstante, die, ähnlich der Scherviskosität, den spurfreien Teil der Konstitutivgleichung des Supersymmetriestroms beschreibt. Wir berechnen diese Konstante in supersymmetrischen Theorien allgemeiner Dimension mittels verschiedener unabhängiger Rechnungen. Dazu betrachten wir als duale Gravitationstheorie eine generische Supergravitationstheorie. Die Bewegungsgleichung des zum Supersymmetriestrom dualen Gravitinos in Schwarzen Loch Hintergründen wird gelöst und erlaubt die Berechnung der retardierten Greenschen Funktion des Supersymmetriestroms der Feldtheorie. Diese besitzt einen Pol, der die charakteristische Schalldispersionsrelation des Phoninos beschreibt, des Goldstonefermions spontan gebrochener Supersymmetrie aufgrund endlicher Temperatur. In dieser Dispersionsrelation findet sich die besagte Diffusionskonstante, die sich auch mittels einer neuartigen Kubo-Formel direkt aus der Greenschen Funktion berechnen lässt.
Das Hauptergebnis der Arbeit bildet hierbei die Etablierung eines Zusammenhangs dieser Diffusionskonstante und eines universell gültigen Absorptionsquerschnitts auf der dualen Seite der Gravitationstheorie, der die Absorption von Spinoren von einem Schwarzen Loch Hintergrund beschreibt.
Eine weitere bedeutende Entwicklung besteht in der Entdeckung eines neuartigen Transportkoeffizienten, der einen beobachtbaren induzierten Strom aufgrund der Vortizität eines Fluids beschreibt. Dieser stellt die klassische Manifestation eines quantenmechanischen Effektes dar, der entsteht, wenn die zugrunde liegende mikroskopische Theorie eine quantenmechanische chirale Anomalie aufweist.
Wir untersuchen diesen Effekt mithilfe eines theoretischen Ansatzes, der verschiedene Zugänge zum Verhältnis von Hydrodynamik und Gravitation miteinander vereint. Dazu werden rotierende D3-Branen effektiv als asymptotisch flache Verallgemeinerungen von fünf-dimensionalen AdS Reissner-Nordström Schwarzen Löchern beschrieben. Die Fluktuationen dieses Hintergrundes beschreiben nun eine effektive hydrodynamische Theorie auf einer Fläche in festem Abstand zur Singularität des Schwarzen Lochs, auf der die Fluktuationen Dirichlet Randbedingungen annehmen.
Diese Herangehensweise erlaubt es uns den erwähnten Quanteneffekt nicht nur am Rand des AdS Raums zu betrachten, sondern auch am Horizont des Schwarzen Lochs, auf jeder Fläche mit konstantem Radius dazwischen oder sogar im asymptotisch flachen Raum.In the present thesis we study properties of strongly coupled hydrodynamic theories which may be described in terms of a dual higher dimensional gravitational system. Particular attention is given to the computation of physical quantities like the theories' viscosities and diffusion constants. These are analysed with regard to the question of whether they follow generally applicable, universal laws which may be derived from the description in terms of a gravitational theory. The theoretical foundation for this is laid by the duality between conformal quantum field theories in Minkowski space and higher-dimensional string theories on Anti-de Sitter space, the AdS/CFT correspondence. A particularly interesting simplification is given by the limit of strong coupling and large number of degrees of freedom of the conformal field theory in which the dual description reduces to a classical theory of gravity on AdS space. By using a perturbative treatment of fluctuations of the gravitational theory's black hole solutions one may describe universal hydrodynamic properties of the strongly coupled field theory. One of the main results within this area of research is the proof that fluids which may be described by a simple dual gravitational theory with unbroken rotational invariance possess a universal ratio of shear viscosity and entropy density. Astonishingly, this ratio parametrically agrees with the value measured for the strongly-coupled quark gluon plasma, although a direct treatment of this QCD phase is at present not available. In the following work we describe the construction of a similar, universal relation. In the hydrodynamic description of supersymmetric field theories there exists a further diffusion constant which, similarly to the shear viscosity, appears in the traceless part of the constitutive relation of the supersymmetry current. We compute this constant in supersymmetric theories of arbitrary dimension via different independent calculations. For doing so we look at a generic supergravity theory as the gravitational dual. The equation of motion of a gravitino, which is the dual field to the supersymmetry current, is solved in a black hole background and allows for the computation of retarded Green's functions of the field theory's supersymmetry current. This has a pole which describes the characteristic sound dispersion relation of the phonino, the Goldstone fermion of spontaneously broken supersymmetry due to finite temperature. In this dispersion relation we find the aforementioned diffusion constant which we also obtain directly from the correlator via a new Kubo formula. The main result of this project is the establishment of a relation of the supersound diffusion constant and a universally applicable absorption cross section on the dual gravitational side which describes the absorption of spinors by a black hole. A further important development is the discovery of a new transport coefficient which describes the observable current that is induced by the vorticity of a fluid. This illustrates the classical manifestation of a quantum mechanical effect which appears when the underlying microscopic theory possesses a quantum mechanical chiral anomaly. We investigate this effect within a theoretical framework which unifies several different approaches at the interplay of hydrodynamics and gravitational physics. We effectively describe rotating D3-branes as asymptotically flat generalisations of five-dimensional AdS Reissner-Nordström black holes. The fluctuations of this background describe an effective hydrodynamical theory on a surface at a finite distance from the black hole's singularity, on which the fluctuations satisfy Dirichlet boundary conditions. This approach allows us to study the mentioned quantum effect not only at the boundary of AdS space, but also at the black hole's horizon, at a surface in between at finite radius, or even in asymptotically flat space.
14
Brumley, Douglas Richard. "Hydrodynamics of swimming microorganisms". Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608174.
Testo completo
15
Stewart, Kelley Christine. "Hydrodynamics of Cardiac Diastole". Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/26837.
Testo completoAbstract (sommario):
Left ventricular diastole (filling) is a complex process with many features and coupled compensatory mechanisms which coordinate to maintain optimal filling and ejection of the left ventricle. Diastolic filling is controlled by the left ventricular recoil, relaxation, and compliance as well as atrial and ventricular pressures making left ventricular diastolic dysfunction very difficult to understand and diagnose. An improved understanding of these unique flows is important to both the fundamental mechanics of the cardiac diastolic filling as well as the development of novel and accurate diagnostic techniques.
This work includes studies of in-vivo and in-vitro vortex rings. Vortex rings created in the left ventricle past the mitral valve during diastole are produced in a confined domain and are influenced by the left ventricular walls. Therefore, an in-vitro analysis of the formation and decay of vortex rings within confined cylindrical domains using particle image velocimetry was conducted. Varying mechanisms of vortex ring breakdown were observed over a wide range of Reynolds numbers, and an analytical model for vortex ring circulation decay of laminar vortex rings was developed. Also, in this work a novel method for analyzing color M-mode echocardiography data using a newly developed automated algorithm is introduced which examines the pressure gradients and velocities within the left ventricle. From this analysis, a new diagnostic filling parameter is introduced which displays a greater probability of detection of diastolic dysfunction over the conventionally used diagnostic parameter.Ph. D.
16
Muscutt, Luke Edward. "The hydrodynamics of plesiosaurs". Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/412255/.
Testo completoAbstract (sommario):
When the dinosaurs were walking on the earth, there was a marine reptile called a plesiosaur that was swimming in the seas. Plesiosaurs are unique in the animal kingdom because they had four large flippers with which they used to swim, but exactly how they used them has been controversial for almost 200 years. Debate has included 1) whether plesiosaurs use all four flippers for propulsion, or use the fore flippers for propulsion and the hind flippers for manoeuvring, and 2) if plesiosaurs use all four flippers, what phase did they flap with? i.e. did both the fore and hind flippers flap up and down together, did one go up as the other goes down, or was it something in between? This thesis helps to answer these questions by providing the first quantitative experimental data ever collected on the swimming method of plesiosaurs. By using a combination of flume-tank experiments, numerical simulations, and mathematical models, I show that 1) the hind flippers of plesiosaurs would experience large increases in thrust and efficiency, and it is therefore likely that they indeed used all four flippers for propulsion, 2) that the performance of the hind flipper is increased when it weaves in between the primary vortices that have been shed from the fore flipper. This flipper/vortex interaction is dependant on the phase, flipper spacing, flow speed, and flapping frequency. Therefore there would not be one phase that is optimum for all plesiosaurs under all conditions, and the optimum phase at for each plesiosaur at each instance in time would vary depending on the swimming conditions, and 3) that the tandem-flipper arrangement of the plesiosaur reduces the unsteady loads experienced by the body and therefore provides a smoother movement than would be achieved by only two flippers.
17
Jarkova, Elena. "Hydrodynamics of ferronematics and ferrogels". [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969961405.
Testo completo
18
Ozer, Ceren. "Tsunami Hydrodynamics In Coastal Zones". Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614343/index.pdf.
Testo completoAbstract (sommario):
This study analyzes the parameter &ldquohydrodynamic demand&rdquo
that is also defined by the square of Froude Number representing the damage of tsunami waves on structures and coastlines, and other hydrodynamic parameters, i.e., the distribution of instantaneous flow depths, runup values and the direction of maximum currents, occurred during tsunami inundation by using advanced numerical modeling. The analyses are performed on regular-shaped basins with different bottom slopes and real-shaped topographies using different wave shapes, wave periods and types. Various orientation and amount of coastal and land structures are used in simulations to have results for many different cases. This study provides the opportunity to define the damage of level in residential areas and to test the performance of coastal protection structures. The behavior of tsunami hydrodynamic parameters in shallow and inundation zone is investigated and a correlation is obtained between the average maximum values of square of Froude Number with the wave characteristics and sea bottom slope. After determining hydrodynamic parameters in regular shaped basins, a case study is applied by modeling the March 11, 2011 Great East Japan Tsunami with finer resolution in nested domains. The determination of hydrodynamic parameters in inundation zone during 2011 Japan event is performed in one of the most damaged coastal city Kamaishi.
19
Hess, Steffen. "Particle hydrodynamics with tessellation techniques". Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-131613.
Testo completo
20
Roshanzamir, Alireza. "Hydrodynamics of blade gap formers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0016/NQ56608.pdf.
Testo completo
21
Zhang, Jing 1961. "System identification of bladder hydrodynamics". Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26440.
Testo completoAbstract (sommario):
Understanding bladder mechanics and the changes caused by bladder outlet obstruction is an important task in urology. In this work, bladder mechanics are examined in terms of bladder hydrodynamics: the relation between a perturbing volume applied to the bladder and the evoked pressure change. A PC-based experimental system was built which can generate a computer-controlled perturbation volume and measure volume and pressure signals.The bladders of six minipigs, three normal and three obstructed, were subjected to stochastic volume perturbations about different average volume levels and evoked pressure changes were measured. The hydrodynamic stiffness transfer function relating volume and pressure was calculated and described by a second-order, lumped parametric model having inertial, viscous and elastic terms. Estimates of the elastic constant (K) increased linearly with volume in both normal and obstructed animals. The rate of increase was substantially greater in the obstructed animals than in the normals. Consequently, this approach shows promise for distinguishing normal and obstructed bladder mechanics.
22
Baran, Oleh. "Numerical studies of thermal hydrodynamics". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36873.
Testo completoAbstract (sommario):
We introduce and study new lattice gas models of hydrodynamics to simulate thermal fluids in non-equilibrium. The new approach consists in modifying the conventional Lattice Gas Cellular Automata method for fluids by removing the constraints of the Fermi exclusion principle and by introducing internal potential energy levels for the particles. These modifications allow the effective employment of Monte-Carlo dynamics for the evolution of the models, so that the temperature is defined in a natural way, and the introduction of interactions becomes straightforward.Because the transport properties of fluids determine their behavior in non-equilibrium, we study in detail the effect of our modifications on transport coefficients. We derive expressions for these coefficients in two ways: from Chapman-Enskog expansions and from linear response theory. Because of the potential energy, the transport properties are more similar to those of real fluids than are conventional LGCA models with kinetic energy only: the bulk viscosity is non-zero and thermal diffusion is well defined over a range of densities and temperatures.
We construct several models to illustrate the advantages and implications of our approach. One model is used to study the local temperature distribution in a simulation of Rayleigh Benard convection. Another is used to introduce interactions between particles and to simulate the 1st order phase separation of a fluid into the regions of low and high density. This latter model is also used to study the dynamics of interfaces between the phases. We observe the effects of inertia at the interface and demonstrate that the mean square width of an initially flat interface scales as t3/2 for late times t.
23
Hughes, Paul Edward. "The hydrodynamics of arterial prostheses". Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316892.
Testo completo
24
Jain, Akash. "A universal framework for hydrodynamics". Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12707/.
Testo completoAbstract (sommario):
In this thesis, we present a universal framework for hydrodynamics starting from the fundamental considerations of symmetries and the second law of thermodynamics, while allowing for additional gapless modes in the low-energy spectrum. Examples of such fluids include superfluids and fluids with surfaces. Typically, additional dynamical modes in hydrodynamics also need to be supplied with their own equations of motion by hand, like the Josephson equation for superfluids and the Young-Laplace equation for fluid surfaces. However, we argue that these equations can be derived within the hydrodynamic framework by a careful off-shell generalisation of the second law. This potentially provides a universal framework for a large class of hydrodynamic theories, based on their underlying symmetries and gapless modes. Motivated by this newly found universality, we present an all-order analysis of the second law of thermodynamics and propose a classification scheme for the allowed hydrodynamic transport, including arbitrary gapless modes, independent spin current, and background torsion. In the second half of this thesis, we look at the construction of null fluids which are a new viewpoint of Galilean fluids. These are essentially fluids coupled to spacetime backgrounds carrying a covariantly constant null isometry, but with additional constraints imposed on the background gauge field and affine connection to reproduce the correct Galilean degrees of freedom. We discuss the Galilean version of quantum anomalies and their effect on hydrodynamics. Finally, we follow our relativistic discussion to allow for arbitrary gapless modes in Galilean hydrodynamics and present a classification scheme for the second law abiding hydrodynamic transport at all orders in the derivative expansion. We apply these abstract ideas to review the theory of ordinary relativistic/Galilean hydrodynamics and provide novel constructions for relativistic/Galilean (non-Abelian) superfluid dynamics and surface transport. We also comment on the possible application to the theory of magnetohydrodynamics.
25
Sequeira, Carl Luís. "Hydrodynamics of tidal stream turbines". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708759.
Testo completo
26
Overby, Darryl Ray 1974. "Hydrodynamics of aqueous humor outflow". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/89882.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2002.Includes bibliographical references (p. 277-286).
Primary open-angle glaucoma (POAG) is a leading cause of irreversible blindness resulting from elevated intraocular pressure caused by a pathologic increase in the resistance to aqueous humor outflow from the eye. Currently, the physiological and ultrastructural bases for the generation of aqueous humor outflow resistance remain unclear in both the normal and glaucomatous eye, although experimental evidence suggests that the extracellular matrix within the juxtacanalicular connective tissue (JCT) is the principle resistive element. Johnson, Shapiro et al. (1992) have postulated that the resistance of the JCT is further increased by a hydrodynamic "funneling" interaction whereby the available area for aqueous flow through the JCT is reduced by the constraint that aqueous must cross the inner wall endothelium of Schlemm's canal through discrete pores. In this study, we focus on uncovering the role of the JCT in the generation of aqueous humor outflow resistance in the non-glaucomatous eye. Quick-freeze/deep-etch (QF/DE) electron microscopy was used to visualize the extracellular matrix within the JCT. A novel stereologic theory was developed to relate the two-dimensional void area and perimeter observed on a micrograph to the three-dimensional tissue porosity and specific surface, allowing the hydraulic resistance of an extracellular matrix to be estimated from a QF/DE micrograph. Extensive numerical studies were conducted to validate the predictions of the stereologic theory. To investigate the funneling effect,
(cont.) morphologic changes that would disrupt funneling were proposed and investigated to determine their role in the "washout" phenomenon (the progressive decrease in aqueous outflow resistance measured during experimental perfusion of non-human eyes). QF/DE revealed the presence of empty space devoid of extracellular matrix within the JCT. Washout was found to act through a reversible separation of the JCT from the basal lamina of the inner wall endothelium that was proposed to eliminate funneling. These results challenge the belief that aqueous outflow resistance is generated by extracellular matrix within the JCT. This study also suggests that the molecular components responsible for tethering the inner wall to the JCT are important regulators of aqueous humor outflow resistance in the normal eye and thereby represent potential targets for treatment of POAG.
by Darryl Ray Overby.
Ph.D.
27
Sit, Arthur John. "Hydrodynamics of aqueous humour outflow". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11499.
Testo completo
28
DePaoli, Laura L. (Laura Lynn) 1975. "Numerical modeling of wetland hydrodynamics". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80587.
Testo completo
29
Quintella, Cristina M. A. L. T. Mata H. "Liquids : a molecular hydrodynamics perspective". Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332794.
Testo completoAbstract (sommario):
New insights into the kinetic and molecular dynamics of liquids are presented through two distinct experimental studies. The kinetics and dynamics of cold 12 molecules scattered off liquid polydimethylsiloxane are studied. Time resolved LIF spectra give number densities and quantum state populations throughout both the inelastic scattering and the trapping/ desorption processes. The vibrational cooling of inelastically scattered molecules indicates different mechanisms for the trapping and desorption processes. Surface temperature dependence yields desorption enthalpy 23 - 30 kJ moZ-1 and frequency factor 108 - 1010 Hz, thus suggesting predesorption diffusion. Dynamical behaviour indicates more than one mechanism for activation of trapped species, i.e., conversion of internal energy into translation and energising via interaction with liquid molecules. The molecular dynamics of vertical liquid jets produced by slit nozzles was determined. The alignment of rhodamine 6G molecules, seeded in ethylene glycol jets, is evaluated through polarised laser induced fluorescence (PLF). Computational fitting and integration produce the corresponding liquid velocity distributions. Different streams within the jets are identified. The study is extended to the alignment inside the nozzle. An asymmetric nozzle flow is studied in order to verify the conclusions drawn. An interpretation of the lobed jet kinetics and molecular dynamics is proposed by relating the velocity distributions with the jet horizontal sections.
30
Millmore, Stephen Timothy. "Interfaces in numerical relativistic hydrodynamics". Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/170233/.
Testo completoAbstract (sommario):
This thesis investigates numerical techniques for modelling sharp interfaces between relativistic fluids. The motivation for this work lies in obtaining accurate models of neutron star interiors for use in multidimensional simulations in general relativity. The interior structure of a neutron star is believed to contain several regions, often separated by sharp transition layers. These layers are too thin to be explicitly incorporated in a numerical simulation of the entire star. We investigate how techniques can be developed to model these layers as sharp interfaces, across which the matter model can change, with the microphysical behaviour of the transition layer described through some appropriate boundary conditions. The physical situations in which strong, detectable, gravitational waves are produced are, by their nature, violent events. As a result, we expect that large non-linear features, such as shock waves, will be formed. Therefore it is essential that the techniques developed to incorporate these sharp interfaces allow for their interaction with non-linear features in a stable manner numerically. The techniques required for modelling sharp interfaces between two fluid components has not previously been considered in relativity. However, in Newtonian computational fluid dynamics, the boundary conditions required for stable, accurate behaviour across a sharp interface between two fluids, modelled using level set methods, have been developed. These techniques lend themselves naturally to an extension to the relativistic situations we wish to consider. In this thesis we start from the Ghost Fluid Method of Fedkiw et al. We first investigate whether it can be extended to simple relativistic situations, hence use special relativity in 1+1 dimensions. In order to use this method in neutron star simulations, however, full general relativity is required. We therefore extend these initial results to a spherically symmetric self-gravitating body in 1+1 dimensional general relativity. Finally, since gravitational wave production requires a fully asymmetric system, we show that our method extends to multidimensional relativistic situations. To this end, the final chapter presents results using 2+1 dimensional special relativistic simulations.
31
Trigg, Mark Adam. "Amazon River and floodplain hydrodynamics". Thesis, University of Bristol, 2010. http://hdl.handle.net/1983/a11db296-b2d8-4c75-95e4-7c94816345c0.
Testo completoAbstract (sommario):
The annual monomodal flood pulse of the Amazon River is a key driver for this globally important hydrological system. Understanding the behaviour and characteristics of this flood wave and its influence on the dynamics of river and floodplain interaction is important to many studies attempting to quantify processes dependent upon it, including estimates of carbon fluxes from the wetlands and sediment movement to the ocean. The main aim of the research presented in this thesis was to investigate the hydrodynamic behaviour of the Amazon River and its floodplain, in order to better understand its components and processes. The key scientific question underpinning this aim is: How do the floodplain storage and fluxes affect the passage of the Amazon flood wave and in turn how does the passage of the flood wave control the dynamics on the floodplain? Research was carried out using a synthesis of hydraulic characterisation, numerical modelling, spatial analysis of remote sensing data and field surveys. In combination with information from published floodplain studies, these results were then used to inform the development of a conceptual hydrodynamics framework for the Amazon floodplain. Hydraulic characterisation of the Amazon flood wave was undertaken showing that it is subcritical and diffusive in nature with dominating backwater effects. Experiments with the main channel using hydraulic models showed that main channel water levels were relatively insensitive (0.5 m error on a 12 m flood wave amplitude) to the geometric representation of the channel and that simplified bathymetry is adequate for calibrated predictions, provided the mean cross sectional area can be reasonably well approximated. Hydraulic model results compare well with observed data despite explicit exclusion of the floodplain, indicating that the storage volume of the floodplain has a minimal affect on the passage of the Amazon flood wave for this reach. The spatial analysis of Landsat TM images shows a total of 1,762 floodplain channels in the study area with a mean width of 47 m. Shuttle radar topography mission data has difficulty in resolving many of these floodplain channels due to 96% of the channels having a width less than the SRTM spatial resolution of 90 m. Comparing floodplain channel widths with their frequency reveals a power law relationship, showing patterns of structure that are self-similar over many orders of magnitude. Analysis of the floodplain channel network connectivity showed that the complex floodplain can be divided into floodplain hydrologic units (FHU) and that each unit type has different geomorphic characteristics resulting from a different mixture of water inputs, with each unit isolated from other units for much of the flood cycle by sediment barriers. A field survey of the floodplain channels was conducted in order to measure and characterise their morphology. The findings of this survey together with numerical connectivity experiments, demonstrate that floodplain channels could be playing a much more significant role in the floodplain hydrodynamics then previously acknowledged. Floodplain channels were grouped into three types by depth: (i) for channels carrying only river flood water, depth was strongly correlated with the flood wave’s mean annual range of 11.4 m; (ii) for channels which carried river flood water and local runoff, the mean depth was substantially deeper at 15.9 m; and, (iii) main river island channels were deeper again, with a mean depth of 17.7 m. Finally, a coherent, evidence based, conceptual floodplain hydrodynamics framework was developed to inform a broad range of future Amazon wetland research. The framework represents an extension to the macro level understanding available in the scientific literature and provides an important link between the macro and detailed level study scale.
32
Williams, Alicia M. "The Hydrodynamics of Ferrofluid Aggregates". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/29446.
Testo completoAbstract (sommario):
Ferrofluids are comprised of subdomain particles of magnetite or iron oxide material that can become magnetized in the presence of a magnetic field. These unique liquids are being incorporated into many new applications due to the ability to control them at a distance using magnetic fields. However, although our understanding of the dynamics of ferrofluids has evolved, many aspects of ferrohydrodynamics remain largely unexplored, especially experimentally.
This study is the first to characterize the stability and internal dynamics of accumulating or dispersing ferrofluid aggregates spanning the stable, low Reynolds number behavior to unstable, higher Reynolds numbers. The dynamics of ferrofluid aggregates are governed by the interaction between the bulk flow shear stresses acting to wash away the aggregate and magnetic body forces acting to retain them at the magnet location. This interaction results in different aggregate dynamics, including the stretching and coagulation of the aggregate to Kelvin-Helmholtz shedding from the aggregate interface as identified by focused shadowgraphs.
Using TRDPIV, the first time-resolved flow field measurements conducted in ferrofluids reveal the presence of a three-stage process by which the ferrofluid interacts with a pulsatile bulk flow. An expanded parametric study of the effect of Reynolds number, magnetic field strength, and flow unsteadiness reveals that the increased field results can result in the lifting and wash away of the aggregate by means of vortex strengthening. In pulsatile flow, different forms of the three-stage interaction occur based on magnetic field, flow rate, and Reynolds number.Ph. D.
33
Brady, Michael Richard. "Multiphase Hydrodynamics in Flotation Systems". Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28860.
Testo completoAbstract (sommario):
Flotation is a complex, multiphase process used to separate minerals. Four problems central to the fundamentals of the flotation process were studied. A multiphase grid turbulence experiment was conducted to verify particle collision models. The slip velocities of solid particles and bubbles were measured using Digital Particle Image Velocimetry (DPIV). The experimental results were compared with the predictions from empirical and theoretical collision models.
Time-resolved DPIV was used to measure the turbulent velocity field in a Rushton turbine around the impeller region. The turbulence quantities were found by removing the periodic component from the blade passing, which is a dominant part of the measured velocities near the impeller. We provide evidence that larger, biased dissipation and turbulent kinetic energy values are estimated in the vicinity of the impeller due to the periodic component of the blade passage. The flow was found to be anisotropic close to the impeller. Vortex detection revealed that the tip vortices travel in a nearly radial direction from the impeller for small Reynolds numbers and with a wider distribution for higher Reynolds numbers.
The rise of a buoyant bubble and its interaction with a free liquid surface was experimentally investigated using Time-Resolved Digital Particle Image Velocimetry as a function of bubble size, and surfactant concentration of the fluid medium. It is shown that the presence of a surfactant significantly affected the characteristics of the velocity field during the rise and interaction with the free surface. This difference is attributed to the adsorption coverage of the surfactant at the bubble-fluid interface. Wake profiles were compared. The presence of large vortices were observed and found to play a significant role.
Finally, Numerical and experimental results of stable and unstable foams are presented by comparing liquid fractions and bubble sizes. There was good agreement between the experiments and numerical modeling in free drainage and forced drainage experiments. In addition, foam coarsening was measured and characterized experimentally.
Each of the problems investigated have added to the understanding in the underlying physics of the flotation process and can lead to more accurate modeling. The ultimate goal of this work is to contribute to the design of more effective and efficient flotation machines.Ph. D.
34
Liu, David. "Flow through Rigid Vegetation Hydrodynamics". Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35068.
Testo completoAbstract (sommario):
Better understanding of the role of vegetation in the transport of fluid and pollutants requires improved knowledge of the detailed flow structure within the vegetation. Instead of spatial averaging, this study uses discrete measurements at multiple locations within the canopy to develop velocity and turbulence intensity profiles and observe the changes in the flow characteristics as water travels through a vegetation array simulated by rigid dowels. Velocity data were collected with a one dimensional laser Doppler velocimeter (LDV) under single layer emergent and submerged flow conditions, and through two layers of vegetation. The effects of dowel arrangement, density, and roughness are also examined under the single layer experiments. The results show that the velocity within the vegetation array is constant with depth and the velocity profile is logarithmic above it. The region immediately behind a dowel, where the vorticity and turbulence intensity are highest, is characterized by a velocity spike near the bed and an inflection point near the top of the dowel arrays. With two dowel layers, the velocity profile in the region behind a tall dowel exhibits multiple inflection points and the highest turbulence intensities are found there.Master of Science
35
Evans, Ashley D. "Hydrodynamics of mine impact burial". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2002. http://library.nps.navy.mil/uhtbin/hyperion-image/02sep%5FEvans.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, September 2002.Thesis advisor(s): Peter Chu, Peter Fleischer. Includes bibliographical references (p. 443-444). Also available online.
36
Agrawal, Vaibhav. "Hydrodynamics of Bubbling Fluidized Bed". Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/76113.
Testo completoAbstract (sommario):
Computational fluid dynamic (CFD) simulations and electrical capacitance volume tomography (ECVT) experiments were conducted to study the gas-solid hydrodynamics in bubbling fluidized beds having mono- and bi-dispersed solids. The major contributions of this thesis are investigations of (i) gas-solid drag models to improve CFD-DEM (discrete element model) predictions, (ii) initial bed condition on mixing of bi-dispersed solids, and (iii) ECVT measurements of bubble properties.
37
Gale, Emma Jane. "The hydrodynamics of intermittently closing and opening lakes and lagoons". University of Western Australia. School of Environmental Systems Engineering, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0025.
Testo completoAbstract (sommario):
[Truncated abstract] Coastal lagoons play an important role in the transport of materials between the coastal zone and the ocean. Understanding the dynamics associated with the movement of waters between and within these systems is therefore significant in defining the ecological health of the system. An important sub category of lagoons is Intermittently Closing and Opening Lakes and Lagoons (ICOLLs). These systems lack any significant river inflow; have a restricted sill type inlet and experience intermittent exchange with the ocean, making them susceptible to the retention of nutrients and pollutants from the catchment. The duration and frequency of an opening event may vary from weeks to months between each ICOLL, and inter and intra annually, respectively, and during an opening event, there are appreciable fluctuations in water level (1-3m range) accompanied by large changes in salinity (7 30ppt) within a short timeframe (hours). . . Regardless of the processes complete oceanic flushing was still predicted for each system, by the end of their respective opening events. The modelling work successfully reproduced the spring tidal setup in water level and exchange, using real bathymetry and meteorological forcing and defined the spring tidal set-up as the key predictable process in the exchange of water and salt between the larger ICOLL and the ocean. It was also shown that strong winds had the capacity to influence the magnitude of the exchange. The overall outcomes of this research therefore include the identification of key physical processes associated with the variability of the hydrodynamics within and between ICOLLs, which will aid in the future management of these highly dynamic systems.
38
Mokos, Athanasios Dorotheos. "Multi-phase modelling of violent hydrodynamics using Smoothed Particle Hydrodynamics (SPH) on Graphics Processing Units (GPUs)". Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/multiphase-modelling-of-violent-hydrodynamics-using-smoothed-particle-hydrodynamics-sph-on-graphics-processing-units-gpus(a82b8187-f81a-400b-8bd2-9a74c502a953).html.
Testo completoAbstract (sommario):
This thesis investigates violent air-water flows in two and three dimensions using a smoothed particle hydrodynamics (SPH) model accelerated using the parallel architecture of graphics processing units (GPUs). SPH is a meshless Lagrangian technique for CFD simulations, whose major advantage for multi-phase flows is that the highly nonlinear behaviour of the motion of the interface can be implicitly captured with a sharp interface. However, prior to this thesis performing multi-phase simulations of large scale air-water flows has been prohibitive due to the inherent high computational cost. The open source code DualSPHysics, a hybrid central processing unit (CPU) and GPU code, is heavily modified in order to be able to handle flows with multiple fluids by implementing a weakly compressible multi-phase model that is simple to implement on GPUs. The computational runtime shows a clear improvement over a conventional serial code for both two- and three dimensional cases enabling simulations with millions of particles. An investigation into different GPU algorithms focuses on optimising the multi-phase SPH implementation for the first time, leading to speedups of up to two orders of magnitude compared to a CPU-only simulation. Detailed comparison of different GPU algorithms reveals a further 12% improvement on the computational runtime. Enabling the modelling of cases with millions of fluid particles demonstrates some previously unreported problems regarding the simulation of the air phase. A new particle shifting algorithm has been proposed for multi-phase flows enabling the air, initially simulated as a highly compressible liquid, to expand rapidly as a gas and prevent the formation of unphysical voids. The new shifting algorithm is validated using dam break flows over a dry bed where good agreement is obtained with experimental data and reference solutions published in the literature. An improvement over a corresponding single-phase SPH simulation is also shown. Results for dam break flows over a wet bed are shown for different resolutions performing simulations that were unfeasible prior to the GPU multi-phase SPH code. Good agreement with the experimental results and a clear improvement over the single-phase model are obtained with the higher resolution showing closer agreement with the experimental results. Sloshing inside a rolling tank was also examined and was found to be heavily dependent on the viscosity model and the speed of sound of the phases. A sensitivity analysis was performed for a range of different values comparing the results to experimental data with the emphasis on the pressure impact on the wall. Finally, a 3-D gravity-driven flow where water is impacting an obstacle was studied comparing results with published experimental data. The height of the water at different points in the domain and the pressure on the side of the obstacle are compared to a state-of-the-art single-phase GPU SPH simulation. The results obtained were generally in good agreement with the experiment with closer results obtained for higher resolutions and showing an improvement on the single-phase model.
39
Qamar, Shamsul. "Kinetic schemes for the relativistic hydrodynamics". [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975630040.
Testo completo
40
Yapici, Kerim. "Numerical Investigation Of Stirred Tank Hydrodynamics". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1302140/index.pdf.
Testo completoAbstract (sommario):
A theoretical study on the hydrodynamics of mixing processes in stirred tanks is described. The primary objective of this study is to investigate flow field and power consumption generated by the six blades Rushton turbine impeller in baffled, flat-bottom cylindrical tank both at laminar and turbulent flow regime both qualitatively and quantitatively. Experimental techniques are expensive and time consuming in characterizing mixing processes. For these reasons, computational fluid dynamics (CFD) has been considered as an alternative method. In this study, the velocity field and power requirement are obtained using FASTEST, which is a CFD package. It employs a fully conservative second order finite volume method for the solution of Navier-Stokes equations. The inherently time-dependent geometry of stirred vessel is simulated by a multiple frame of reference approach. The flow field obtained numerically agrees well with those published experimental measurements. It is shown that Rushton turbine impeller creates predominantly radial jet flow pattern and produces two main recirculation flows one above and the other below the impeller plane. Throughout the tank impeller plane dimensionless radial velocity is not affected significantly by the increasing impeller speed and almost decreases linearly with increase in radial distance. Effect of the baffling on the radial and tangential velocities is also investigated. It is seen that tangential velocity is larger than radial velocity at the same radial position in unbaffled system. An overall impeller performance characteristic like power number is also found to be in agreement with the published experimental data. Also power number is mainly affected by the baffle length and increase with increase in baffle length. It is concluded that multiple frame of reference approach is suitable for the prediction of flow pattern and power number in stirred tank.
41
Hodgkinson, Derek Anthony Martin. "Computer graphics applications in offshore hydrodynamics". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26705.
Testo completoAbstract (sommario):
The results of hydrodynamic analyses of two problems involving offshore structures are displayed graphically. This form of presentation of the results and the liberal use of colour have been found to significantly help the ease in which the results are interpreted.
For the transformation of waves around an artificial island, a time history of the evolution of the regular, unidirectional wave field around an artificial island is obtained. Through the use of colour, regions in which wave breaking occurs have been clearly defined. The numerical technique used is based on the finite element method using eight noded isoparametric elements. The determination of the transformed wave field takes wave breaking, wave refraction, diffraction, reflection and shoaling into account. The graphical display is achieved by using a plotting program developed for the output of finite element analyses.
The motions of a semi-submersible rig are computed from the RAO curves of the rig, used to obtain its' small response in a random sea. The numerical technique used in the analysis assumes that the vertical members are slender and may be analysed using the Morison equation whereas the hulls are treated as large members which are discretised and analysed using diffraction theory. The discretisation of the cylinders and hulls together with the time history of the rig's motions are displayed graphically. Once again, the graphical display is plotted using a program developed for the output of finite element analyses for four noded elements. In this case, a finite element technique has not been employed but the results were ordered to act as though this is the case. The slender members (cylinders) and large members (hulls) are clearly distinguishable by using different colours. The elements used in the analysis are also clearly shown.
The VAX 11/730 system was used to obtain the results shown. A video tape, using the results of a time stepping procedure, was made by successively recording the hardcopies produced by the VAX printer. The time stepping could also be seen, in real time, on the IRIS.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
42
Klindt, Gary. "Hydrodynamics of flagellar swimming and synchronization". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-231897.
Testo completoAbstract (sommario):
What is flagellar swimming? Cilia and flagella are whip-like cell appendages that can exhibit regular bending waves. This active process emerges from the non-equilibrium dynamics of molecular motors distributed along the length of cilia and flagella. Eukaryotic cells can possess many cilia and flagella that beat in a coordinated fashion, thus transporting fluids, as in mammalian airways or the ventricular system inside the brain. Many unicellular organisms posses just one or two flagella, rendering them microswimmers that are propelled through fluids by the flagellar beat including sperm cells and the biflagellate green alga Chlamydomonas.
Objectives. In this thesis in theoretical biological physics, we seek to understand the nonlinear dynamics of flagellar swimming and synchronization. We investigate the flow fields induced by beating flagella and how in turn external hydrodynamic flows change speed and shape of the flagellar beat. This flagellar load-response is a prerequisite for flagellar synchronization. We want to find the physical principals underlying stable synchronization of the two flagella of Chlamydomonas cells.
Results. First, we employed realistic hydrodynamic simulations of flagellar swimming based on experimentally measured beat patterns. For this, we developed analysis tools to extract flagellar shapes from high-speed videoscopy data. Flow-signatures of flagellated swimmers are analysed and their effect on a neighboring swimmer is compared to the effect of active noise of the flagellar beat. We were able to estimate a chemomechanical energy efficiency of the flagellar beat and determine its waveform compliance by comparing findings from experiments, in which a clamped Chlamydomonas is exposed to external flow, to predictions from an effective theory that we designed. These mechanical properties have interesting consequences for the synchronization dynamics of Chlamydomonas, which are revealed by computer simulations. We propose that direct elastic coupling between the two flagella of Chlamydomonas, as suggested by recent experiments, in combination with waveform compliance is crucial to facilitate in-phase synchronization of the two flagella of Chlamydomonas.
43
Reeve, Glen M. D. "Sedimentation And Hydrodynamics of Whitianga Estuary". The University of Waikato, 2008. http://hdl.handle.net/10289/2344.
Testo completoAbstract (sommario):
Whitianga Estuary is a bayhead barrier type estuary located on the east of the Coromandel Peninsula, North Island, New Zealand. The catchment has undergone many land-use changes since pre-European settlement. In some areas of the catchment land-use has changed from native forest to grasslands to forestry and back to pasture. These changes in catchment land-use all contribute to increased sedimentation into the estuary. Development of the estuary itself has also occurred in recent times. Much growth has been focussed around the estuary due to Whitianga town-ship having a large boating community, and includes a 170 berth marina and wharf situated at the tidal inlet entrance to the estuary. These, and the extensive canal development engineering works can have substantial impacts on the sedimentation regime, and may modify tidal circulation, flushing, and sediment deposition within the estuary. The principle aim of this research is to assess hydrodynamics and sedimentation of the estuary for future management and development purposes, and also to model different scenarios in order to determine the most cost effective, and least obtrusive design for a proposed boat-ramp and approach channel near the marina. To determine sedimentation rates, sediment cores from four locations were collected to depths of 1 m. Coring locations were chosen based on preliminary model run results, selecting areas that appeared to be long-term sediment sinks of a stable nature. Cores were divided into 10 mm sections and prepared for 210Pb dating and heavy metal analysis, to make an assessment of the vertical sedimentation rates. Recent sedimentation rates were found to be as high as 9 mm/yr post-1950s and past sedimentation rates as high as 30 mm/yr pre-1950s. The use of heavy metal analysis for dating proved difficult as the background levels of the conservative elements used to normalise results varied, making the geochemical analysis approach inappropriate. As bathymetry is one of the most important aspects of modelling, a large amount of surveying was undertaken for this study. LiDAR, singlebeam data, and recent rectified aerial photographs were interpreted for the creation of a bathymetric grid file to be used for hydrodynamic modelling of the estuary. The 3DD numerical model was used to determine tidal flows and current velocities. From this initial hydrodynamic model a particle-tracking model was created to determine sediment transport pathways within the estuary. From the initial 20 m model it was then possible to create a number of nested model grids for the purpose of determining the best practice scenario for the creation of a proposed boat ramp and associated approach channel near the harbour entrance. Hydrodynamic results suggest that residual circulation in Whitianga Estuary is nearly in balance, with a low ebb tidal domination present. Particle tracking results suggest that sediment entrained and carried into and within the estuary will accumulate on the intertidal flats. Sediment transport modelling indicates that the impact of a proposed boat-ramp will result in sedimentation of the dredged approach channel due to reductions in residual and tidal velocities.
44
Alonso-Romero, Sergio. "Metering film hydrodynamics in film coating". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ60928.pdf.
Testo completo
45
Ide, Kym Martin. "Bubble hydrodynamics in gas fluidized beds /". Title page, contents and abstract only, 1989. http://web4.library.adelaide.edu.au/theses/09ENS/09ensi19.pdf.
Testo completo
46
Choi, Eunwoo. "Numerical Hydrodynamics of Relativistic Extragalactic Jets". Digital Archive @ GSU, 2007. http://digitalarchive.gsu.edu/phy_astr_diss/13.
Testo completoAbstract (sommario):
This dissertation describes a multidimensional relativistic hydrodynamic code which solves the special relativistic hydrodynamic equations as a hyperbolic system of conservation laws based on the total variation diminishing (TVD) scheme. Several standard tests and test simulations are presented to demonstrate the accuracy, robustness and flexibility of the code. Using this code we have studied three-dimensional hydrodynamic interactions of relativistic extragalactic jets with two-phase ambient media. The deflection angle of the jet is influenced more by the density contrast of the cloud than by the beam Mach number of the jet, and a relativistic jet with low relativistic beam Mach number can eventually be slightly bent after it crosses the dense cloud. Relativistic jet impacts on dense clouds do not necessarily destroy the clouds completely, and much of the cloud body can survive as a coherent blob due to the combination of the geometric influence of off-axis collisions and the lower rate of cloud fragmentation through the Kelvin-Helmholtz instability for relativistic flows. We find that relativistic jets interacting with clouds can produce synchrotron emission knots similar to structures observed in many VLBI-scale radio sources and the synchrotron emission peaks right before the jet passes through the cloud.
47
Harris, Benjamin James. "The hydrodynamics of circulating fluidized beds". Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385331.
Testo completo
48
Anderson, Malcolm Ringland. "The hydrodynamics of rotating accretion flows". Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304202.
Testo completo
49
Shanehsazzadeh, Ahmad. "Swash zone hydrodynamics and sediment transport". Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406464.
Testo completo
50
Kikuchi, Norio. "A mesoscale model for polymer hydrodynamics". Thesis, University of Oxford, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289276.
Testo completo