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1
Hsia, Chun-Hsiung. "Bifurcation and stability in fluid dynamics and geophysical fluid dynamics". [Bloomington, Ind.] : Indiana University, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3223038.
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Thesis (Ph.D.)--Indiana University, Dept. of Mathematics, 2006."Title from dissertation home page (viewed June 28, 2007)." Source: Dissertation Abstracts International, Volume: 67-06, Section: B, page: 3165. Adviser: Shouhong Wang.
2
Hussain, Muhammad Imtiaz. "Computational fluid dynamics". Thesis, Aberystwyth University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257607.
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3
Barran, Brian Arthur. "View dependent fluid dynamics". Texas A&M University, 2006. http://hdl.handle.net/1969.1/3827.
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This thesis presents a method for simulating fluids on a view dependent grid structure to
exploit level-of-detail with distance to the viewer. Current computer graphics techniques,
such as the Stable Fluid and Particle Level Set methods, are modified to support a nonuniform
simulation grid. In addition, infinite fluid boundary conditions are introduced that
allow fluid to flow freely into or out of the simulation domain to achieve the effect of
large, boundary free bodies of fluid. Finally, a physically based rendering method known
as photon mapping is used in conjunction with ray tracing to generate realistic images of
water with caustics. These methods were implemented as a C++ application framework
capable of simulating and rendering fluid in a variety of user-defined coordinate systems.
4
Acharya, Rutvika. "Fluid Dynamics of Phonation". Thesis, KTH, Mekanik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-149250.
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This thesis aims at presenting the studies conducted using computational modeling for understanding physiology of glottis and mechanism of phonation. The process of phonation occurs in the larynx, commonly called the voice box, due to the self-sustained vibrations induced in the vocal folds by the airflow. The physiology of glottis can be understood using fluid dynamics which is a vital process in developing and discovering voice disorder treatments. Simulations have been performed on a simplified two-dimensional version of the glottis to study the behavior of the vocal folds with help of fluid structure interaction. Fluid and structure interact in a two-way coupling and the flow is computed by solving 2D compressible Navier-Stokes equations. This report will present the modeling approach, solver characteristics and outcome of the three studies conducted; glottal gap study, Reynolds number study and elasticity study.
5
Glorioso, Paolo. "Fluid dynamics in action". Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107318.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.Cataloged 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.
6
Timmermans, Mary-Louise Elizabeth. "Studies in fluid dynamics". Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621995.
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Mokhtarian, Farzad. "Fluid dynamics of airfoils with moving surface boundary-layer control". Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/29026.
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The concept of moving surface boundary-layer control, as applied to the Joukowsky and NACA airfoils, is investigated through a planned experimental program complemented by theoretical and flow visualization studies. The moving surface was provided by one or two rotating cylinders located at the leading edge, the trailing edge, or the top surface of the airfoil. Three carefully designed two-dimensional models, which provided a wide range of single and twin cylinder configurations, were tested at a subcritical Reynolds number (Re = 4.62 x 10⁴ or Re — 2.31 x 10⁵) in a laminar-flow tunnel over a range of angles of attack and cylinder rotational speeds. The test results suggest that the concept is indeed quite promising and can provide a substantial increase in lift and a delay in stall.
The leading-edge rotating cylinder effectively extends the lift curve without substantially
affecting its slope. When used in conjunction with a second cylinder on the upper surface, further improvements in the maximum lift and stall angle are possible. The maximum coefficient of lift realized was around 2.22, approximately 2.6 times that of the base airfoil. The maximum delay in stall was to around 45°. In general, the performance improves with an increase in the ratio of cylinder surface speed (Uc) to the free stream speed (U). However, the additional benefit derived progressively diminishes with an increase in Uc/U and becomes virtually negligible for Uc/U > 5.
There appears to be an optimum location for the leading-edge-cylinder. Tests with the cylinder at the upper side of the leading edge gave quite promising results. Although the CLmax obtained was a little lower than the two-cylinder configuration (1.95 against 2.22), it offers a major advantage in terms of mechanical simplicity. Performance of the leading-edge-cylinder also depends on its geometry. A scooped configuration appears to improve performance at lower values of Uc/U (Uc/U ≤ 1). However, at higher rates of rotation the free stream is insensitive to the cylinder geometry and there is no particular advantage in using the scooped geometry.
A rotating trailing-edge-cylinder affects the airfoil characteristics in a fundamentally different manner. In contrast to the leading-edge-cylinder, it acts as a flap by shifting the CL vs. α plots to the left thus increasing the lift coefficient at smaller angles of attack before stall. For example, at α = 4°, it changed the lift coefficient from 0.35 to 1.5, an increase of 330%. Thus in conjunction with the leading-edge- cylinder, it can provide significant improvements in lift over the entire range of small to moderately high angles of incidence (α ≤ 18°).
On the theoretical side, to start with, the simple conformal transformation approach
is used to obtain a closed form potential-flow solution for the leading-edge-cylinder configuration. Though highly approximate, the solution does predict correct trends and can be used at a relatively small angle of attack. This is followed by an extensive numerical study of the problem using:
• the surface singularity approach including wall confinement and separated flow effects;
• a finite-difference boundary-layer scheme to account for viscous corrections; and
• an iteration procedure to construct an equivalent airfoil, in accordance with the local displacement thickness of the boundary layer, and to arrive at an estimate for the pressure distribution.
Effect of the cylinder is considered either through the concept of slip velocity or a pair of counter-rotating vortices located below the leading edge. This significantly
improves the correlation. However, discrepancies between experimental and numerical results do remain. Although the numerical model generally predicts CLmax with a reasonable accuracy, the stall estimate is often off because of an error in the slope of the lift curve. This is partly attributed to the spanwise flow at the model during the wind tunnel tests due to gaps in the tunnel floor and ceiling required for the connections to the externally located model support and cylinder drive motor. However, the main reason is the complex character of the unsteady flow with separation and reattachment, resulting in a bubble, which the present numerical
procedure does not model adequately. It is expected that better modelling of the cylinder rotation with the slip velocity depending on a dissipation function, rotation, and angle of attack should considerably improve the situation.
Finally, a flow visualization study substantiates, rather spectacularly, effectiveness
of the moving surface boundary-layer control and qualitatively confirms complex
character of the flow as predicted by the experimental data.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
8
Ellam, Darren John. "Modelling smart fluid devices using computational fluid dynamics". Thesis, University of Sheffield, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398597.
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Durazzo, Gerardo. "Simulation of supply chains dynamics using fluid-dynamic models". Doctoral thesis, Universita degli studi di Salerno, 2013. http://hdl.handle.net/10556/887.
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2011 - 2012The aim of thesis is to present some macroscopic models for supply chains and networks able to reproduce the goods dynamics, successively to show, via simulations, some phenomena appearing in planning and managing such systems and, finally, to dead with optimization problems... [edited by author]
XI n.s.
10
Thillaisundaram, Ashok. "Aspects of fluid dynamics and the fluid/gravity correspondence". Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/267097.
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This thesis considers various extensions to the fluid/gravity correspondence as well as problems fundamental to the study of fluid dynamics. The fluid/gravity correspondence is a map between the solutions of the Navier-Stokes equations of fluid dynamics and the solutions of the Einstein equations in one higher spatial dimension. This map arose within the context of string theory and holography and is a specific realisation of a much wider class of dualities known as the Anti de Sitter/Conformal Field Theory (AdS/CFT) correspondence. The first chapter is an introduction; the second chapter reviews the fluid/gravity correspondence. The next two chapters extend existing work on the fluid/gravity map. Our first result concerns the fluid/gravity map for forced fluid dynamics in arbitrary spacetime dimensions. Forced fluid flows are of particular interest as they are known to demonstrate turbulent behaviour. For the case of a fluid with a dilaton-dependent forcing term, we present explicit expressions for the dual bulk metric, the fluid dynamical stress tensor and Lagrangian to second order in boundary spacetime derivatives. Our second result concerns fluid flows with multiple anomalous currents in the presence of external electromagnetic fields. It has recently been shown using thermodynamic arguments that the entropy current for such anomalous fluids contains additional first order terms proportional to the vorticity and magnetic field. Using the fluid/gravity map, we replicate this result using gravitational methods. The final two chapters consider questions related to the equations of fluid dynamics themselves; these chapters do not involve the fluid/gravity correspondence. The first of these chapters is a review of the various constraints that must be satisfied by the transport coefficients. In the final chapter, we derive the constraints obtained by requiring that the equilibrium fluid configurations are linearly stable to small perturbations. The inequalities that we obtain here are slightly weaker than those found by demanding that the divergence of the entropy current is non-negative.
11
Hajghayesh, Mergen. "Dynamics of fluid-conveying pipes". Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114479.
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This thesis studies the linear and nonlinear dynamics of pipes conveying fluid. It consists of four peer-reviewed journal papers, three published and one submitted for publication. The aim is to investigate aspects of the dynamical behaviour of extensible and inextensible pipes conveying fluid, both theoretically and experimentally.In particular, (i) the three-dimensional nonlinear dynamics of a pipe conveying fluid, constrained by an array of four springs attached at a point along its length is examined from the theoretical and experimental perspectives; (ii) the three-dimensional dynamical behaviour of a fluid-conveying cantilevered pipe fitted with an end-mass and additional intra-span spring support is investigated, both theoretically and experimentally; (iii) the nonlinear planar dynamics of a cantilevered extensible pipe conveying fluid is investigated theoretically via two different numerical techniques; (iv) the phase-shift along the length of the measuring pipe of a Coriolis mass-flowmeter is developed (and thus mass-flow rate is determined) analytically by means of a perturbation technique and confirmed numerically. In the theoretical analyses, the Galerkin method and Lagrange equations for systems containing non-material volumes are employed to obtain a set of nonlinear second-order ordinary differential equations. These equations are solved by means of Houbolt's finite difference scheme, the pseudo-arclength continuation technique, and direct time integration via a modified Rosenbrock technique. The method of multiple timescales, an approximate analytical technique, is also used to predict the phase-shift along the length of the measuring pipe of a Coriolis mass-flowmeter.A series of experiments were conducted with silicone rubber pipes conveying water, and thereby the theoretical models have been broadly validated.Cette thèse traite de la dynamique linéaire et non linéaire de tuyaux parcourus par un fluide. Composée de quatre articles scientifiques ayant fait l'objet d'un examen critique, trois publiés dans des revues techniques et un soumis pour publication, l'objectif étant d'étudier certains aspects du comportement dynamique des conduits extensibles et inextensibles transportant du fluide, de manière théorique et expérimentale.En particulier, (i) la dynamique tridimensionnelle non linéaire d'un tuyau de transport de fluide, contraint par un réseau de quatre ressorts attachés entre les deux bouts est examinée d'un point de vue théorique ainsi qu'expérimental; (ii) le comportement dynamique tridimensionnel d'un tuyau aux extrémités encastrées-libres avec une masse additionnelle au bout libre et un support flexible (ressort) supplémentaire, est également étudié; (iii) la dynamique non linéaire plane d'un tuyau extensible encastre-libre transportant du fluide est étudiée théoriquement par deux méthodes numériques différentes; (iv) le calcul du déphasage sur la longueur du conduit de mesure d'un débitmètre à effet Coriolis (et donc, du débit massique) est mis au point analytiquement au moyen d'une technique de perturbation et est confirmé numériquement. Lors des analyses théoriques, la méthode de Galerkin et les équations de Lagrange pour les systèmes contenant des volumes vides sont utilisés pour obtenir un ensemble d'équations différentielles ordinaires non-linéaires du second ordre. Ces équations sont résolues grâce à un schéma de différences finies de Houbolt, la technique de continuation à pseudo-longueur d'arc, et l'intégration temporelle directe par l'intermédiaire d'une technique de Rosenbrock modifiée. La méthode des délais multiples (dite "multiple scale method"), une technique analytique approximative, est également utilisée pour prédire le déphasage le long du tuyau de mesure d'un débitmètre à effet Coriolis.Une série d'expériences ont été réalisées à l'aide de tuyaux en silicone transportant de l'eau afin de pouvoir vérifier de manière concluante la validité des modèles théoriques.
12
Heslop, S. E. "Aspects of volcanic fluid dynamics". Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383570.
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Shaw, G. J. "Multigrid methods in fluid dynamics". Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371582.
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14
Ogilvy, Iver. "Fluid dynamics of underwater explosions". Thesis, University of Birmingham, 2010. http://etheses.bham.ac.uk//id/eprint/8840/.
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The detonation of an explosive in water leads to a complex set of chemical and physical phenomena. When the detonation wave reaches the surface of the explosive it reacts violently with the water, producing a shock wave propagating outwards and also a nearly spherical gaseous bubble of detonation products. The fact that the characteristic time scales of these two phenomena differ by approximately two orders of magnitude has often been exploited by utilising independent models to describe the shock and the bubble. In this thesis both the shock and the bubble are examined using a range of methods from a differential equation solver approach through to full hydrocode simulation. With the increasing use of the hydrocode approach for the underwater explosion (UNDEX) problem and the subsequent loading of a structure, then a verification and validation process is required to ensure its accuracy. In this study the capability of the hydrocode to model the shock and the bubble and also their interaction with a rigid structure and with a flexible structure, has been assessed. This has been done computationally, by using faster running purpose built codes, and also by comparison with experimental data. A familiarisation work-up of the boundary integral code for the incompressible bubble flow, which included incorporating modifications into the code in order to investigate the pathlines swept out by the particles in the fluid during the expansion and collapse of the bubble. The boundary integral code was also used to provide a comparison with the Kelvin impulse method with respect to the computation of the zones of explosion bubble collapse direction in a shallow water environment. The validation and verification work carried out and the comparisons of the various computational approaches, make this multifaceted study a useful reference for research workers in the field of UNDEX phenomena.
15
Khan, Sharon. "Studies in geophysical fluid dynamics". Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620035.
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Ziegenhein, Thomas. "Fluid dynamics of bubbly flows". Helmholtz-Zentrum Dresden - Rossendorf, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-213581.
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Bubbly flows can be found in many applications in chemical, biological and power engineering. Reliable simulation tools of such flows that allow the design of new processes and optimization of existing one are therefore highly desirable. CFD-simulations applying the multi-fluid approach are very promising to provide such a design tool for complete facilities. In the multi-fluid approach, however, closure models have to be formulated to model the interaction between the continuous and dispersed phase. Due to the complex nature of bubbly flows, different phenomena have to be taken into account and for every phenomenon different closure models exist. Therefore, reliable predictions of unknown bubbly flows are not yet possible with the multi-fluid approach.
A strategy to overcome this problem is to define a baseline model in which the closure models including the model constants are fixed so that the limitations of the modeling can be evaluated by validating it on different experiments. Afterwards, the shortcomings are identified so that the baseline model can be stepwise improved without losing the validity for the already validated cases. This development of a baseline model is done in the present work by validating the baseline model developed at the Helmholtz-Zentrum Dresden-Rossendorf mainly basing on experimental data for bubbly pipe flows to bubble columns, bubble plumes and airlift reactors that are relevant in chemical and biological engineering applications.
In the present work, a large variety of such setups is used for validation. The buoyancy driven bubbly flows showed thereby a transient behavior on the scale of the facility. Since such large scales are characterized by the geometry of the facility, turbulence models cannot describe them. Therefore, the transient simulation of bubbly flows with two equation models based on the unsteady Reynolds-averaged Navier–Stokes equations is investigated. In combination with the before mentioned baseline model these transient simulations can reproduce many experimental setups without fitting any model. Nevertheless, shortcomings are identified that need to be further investigated to improve the baseline model.
For a validation of models, experiments that describe as far as possible all relevant phenomena of bubbly flows are needed. Since such data are rare in the literature, CFD-grade experiments in an airlift reactor were conducted in the present work. Concepts to measure the bubble size distribution and liquid velocities are developed for this purpose. In particular, the liquid velocity measurements are difficult; a sampling bias that was not yet described in the literature is identified. To overcome this error, a hold processor is developed.
The closure models are usually formulated based on single bubble experiments in simplified conditions. In particular, the lift force was not yet measured in low Morton number systems under turbulent conditions. A new experimental method is developed in the present work to determine the lift force coefficient in such flow conditions without the aid of moving parts so that the lift force can be measured in any chemical system easily.
17
Furtak-Cole, Eden. "Three Environmental Fluid Dynamics Papers". DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/6913.
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Three papers are presented, applying computational fluid dynamics methods to fluid flows in the geosciences. In the first paper, a numerical method is developed for single phase potential flow in the subsurface. For a class of monotonically advancing flows, the method provides a computational savings as compared to classical methods and can be applied to problems such as forced groundwater recharge. The second paper investigates the shear stress reducing action of an erosion control roughness array. Incompressible Naiver-Stokes simulations are performed for multiple wind angles to understand the changing aerodynamics of individual and grouped roughness elements. In the third paper, a 1D analytical flow model is compared with multiphase Navier-Stokes simulations in a parabolic fissure. Sampling the numerical results allows the isolation of flow factors such as surface tension, which are difficult to measure in physical experiments.
18
Zhang, Junfang. "Computer simulation of nanorheology for inhomogenous fluids". Australasian Digital Thesis Program, 2005. http://adt.lib.swin.edu.au/public/adt-VSWT20050620.095154.
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Thesis (PhD) - Swinburne University of Technology, School of Information Technology, Centre for Molecular Simulation - 2005.A thesis submitted in fulfilment of requirements for the degree of Doctor of Philosophy, Centre for Molecular Simulation, School of Information Technology, Swinburne University of Technology - 2005. Typescript. Bibliography: p. 164-170.
19
Da, Ronch Andrea. "On the calculation of dynamic derivatives using computational fluid dynamics". Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/5513/.
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In this thesis, the exploitation of computational fluid dynamics (CFD) methods for the flight dynamics of manoeuvring aircraft is investigated. It is demonstrated that CFD can now be used in a reasonably routine fashion to generate stability and control databases. Different strategies to create CFD-derived simulation models across the flight envelope are explored, ranging from combined low-fidelity/high-fidelity methods to reduced-order modelling. For the representation of the unsteady aerodynamic loads, a model based on aerodynamic derivatives is considered. Static contributions are obtained from steady-state CFD calculations in a routine manner. To more fully account for the aircraft motion, dynamic derivatives are used to update the steady-state predictions with additional contributions. These terms are extracted from small-amplitude oscillatory tests. The numerical simulation of the flow around a moving airframe for the prediction of dynamic derivatives is a computationally expensive task. Results presented are in good agreement with available experimental data for complex geometries. A generic fighter configuration and a transonic cruiser wind tunnel model are the test cases. In the presence of aerodynamic non-linearities, dynamic derivatives exhibit significant dependency on flow and motion parameters, which cannot be reconciled with the model formulation. An approach to evaluate the sensitivity of the non-linear flight simulation model to variations in dynamic derivatives is described. The use of reduced models, based on the manipulation of the full-order model to reduce the cost of calculations, is discussed for the fast prediction of dynamic derivatives. A linearized solution of the unsteady problem, with an attendant loss of generality, is inadequate for studies of flight dynamics because the aircraft may experience large excursions from the reference point. The harmonic balance technique, which approximates the flow solution in a Fourier series sense, retains a more general validity. The model truncation, resolving only a small subset of frequencies typically restricted to include one Fourier mode at the frequency at which dynamic derivatives are desired, provides accurate predictions over a range of two- and three-dimensional test cases. While retaining the high fidelity of the full-order model, the cost of calculations is a fraction of the cost for solving the original unsteady problem. An important consideration is the limitation of the conventional model based on aerodynamic derivatives when applied to conditions of practical interest (transonic speeds and high angles of attack). There is a definite need for models with more realism to be used in flight dynamics. To address this demand, various reduced models based on system-identification methods are investigated for a model case. A non-linear model based on aerodynamic derivatives, a multi-input discrete-time Volterra model, a surrogate-based recurrence-framework model, linear indicial functions and radial basis functions trained with neural networks are evaluated. For the flow conditions considered, predictions based on the conventional model are the least accurate. While requiring similar computational resources, improved predictions are achieved using the alternative models investigated. Furthermore, an approach for the automatic generation of aerodynamic tables using CFD is described. To efficiently reduce the number of high-fidelity (physics-based) analyses required, a kriging-based surrogate model is used. The framework is applied to a variety of test cases, and it is illustrated that the approach proposed can handle changes in aircraft geometry. The aerodynamic tables can also be used in real-time to fly the aircraft through the database. This is representative of the role played by CFD simulations and the potential impact that high-fidelity analyses might have to reduce overall costs and design cycle time.
20
Or, Chun-ming, e 柯雋銘. "Flow development in the initial region of a submerged round jet in a moving environment". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B42664512.
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Andersson, Tomas. "Controlling the fluid dynamics : an analysis of the workflow of fluids". Thesis, University of Gävle, Department of Mathematics, Natural and Computer Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-155.
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A scene containing dynamic fluids can be created in a number of ways. There are two approaches that will highlight the problems and obstacles that might occur. Today’s leading fluid simulator, RealFlow, simulates the fluid dynamics. A comparison between the two approaches will be made and are analyzed. Through experimentation, one of the approaches fails to produce the set requirements in the experiment and furthermore the two approaches differ in efficiency.
22
Pagliuca, Giampaolo. "Model reduction for flight dynamics using computational fluid dynamics". Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3029018/.
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The coupling of computational fluid dynamics and rigid body dynamics promises enhanced multidisciplinary simulation capability for aircraft design and certification. Industrial application of such coupled simulations is limited however by computational cost. In this context, model reduction can retain the fidelity of the underlying model while decreasing the overall computational effort. Thus, investigation of such coupled model reduction is presented in this thesis. The technique described herein relies on an expansion of the full order non-linear residual function in a truncated Taylor series and subsequent projection onto a small modal basis. Two procedures are outlined to obtain modes for the projection. First, flight dynamics eigenmodes are obtained with an operator-based identification procedure which is capable of calculating the global modes of the coupled Jacobian matrix related to flight dynamics without computing all the modes of the system. Secondly, proper orthogonal decomposition is used as a data-based method to obtain modes representing the coupled system subject to external disturbances such as gusts. Benefits and limitations of the two methods are investigated by analysing results for both initial and external disturbance simulations. Three test cases of increasing complexity are presented. First, an aerofoil, free to translate vertically and rotate, is investigated with aerodynamics based on the Euler equations. Secondly, a two-dimensional wing-tail configuration is studied for longitudinal dynamics. Aerodynamics is modelled with Reynolds-averaged Navier-Stokes equations and Spalart-Allmaras turbulence model. Thirdly, a three-dimensional industrial use case, which concerns a large civil aircraft, is investigated and longitudinal as well as lateral dynamics are both taken into account. Overall, reduced order models relying on both operator-based and data-based identifications are able to retain the accuracy of the high-fidelity tools to predict accurately flight dynamics responses and loads while reducing the computational cost by up to two orders of magnitude. If adopted, these techniques are expected to speed-up aircraft design and lowering certification costs with the final aim of reduced expense for airlines and, as a consequence, for flying passengers.
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Barker, Shaun, e sbarker@eos ubc ca. "Dynamics of fluid flow and fluid chemistry during crustal shortening". The Australian National University. Research School of Earth Sciences, 2007. http://thesis.anu.edu.au./public/adt-ANU20090711.074630.
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In this thesis, an integrated structural and chemical approach has been used to investigate the spatial and temporal evolution of fluid chemistry, and fluid flow pathways, during crustal shortening. The Taemas Vein Swarm is hosted in a limestone-shale sequence, the Murrumbidgee Group, in the Eastern Belt of the Lachlan Orogen, in New South Wales, Australia. The Taemas Vein Swarm (TVS) is composed of calcite ± quartz veins, hosted in a series of faults and fractures, which extends over an area of approximately 20 km2. The Murrumbidgee Group is composed of several formations, comprising massive grey micritic limestones, redbed sandstones and shales,and thinly interbedded (1020 cm scale) limestones and shales.
¶
The sedimentary sequence has been folded into a series of upright, open to close
folds, and was probably deformed during either mid-late Devonian, or early Carboniferous, crustal shortening. To the east, the Murrumbidgee Group is overthrust
by a Silurian volcanic sedimentary sequence along the Deakin-Warroo Fault System.
Crosscutting and overprinting relationships demonstrate that vein growth was synchronous with folding, with different vein types related to different fold mechanisms
at various stages of fold growth.
¶
Flexural slip folding led to the development of bedding-concordant veins (hereafter
called bedding-parallel veins). Flexural flow in semicompetent to incompetent beds
caused en echelon extension vein arrays to grow. Decoupling between beds, and
dilatancy at fold hinges led to significant vein growth. In addition, fold lock-up led to
limb-parallel stretching, and the growth of bedding-orthogonal extension fractures.
¶
Vein growth is inferred to have occurred in a compressional tectonic regime (i.e.
sigma3=vertical). Oxygen isotope quartz-calcite thermometry suggests that veins formed at temperatures of 100200 oC. The depth of vein formation may have been between
about 5 and 8 km. Vein textures indicate that growth of veins occurred during
multiple cycles of permeability enhancement and destruction. Subhorizontal extension
fractures, and faults at unfavourable angles for reactivation, imply that fluid
pressures exceeded lithostatic levels during the growth of some veins. Coexisting
extension and shear fractures imply that differential stress levels varied over time.
¶
Flexural slip continued throughout folding at Taemas, despite some fold limbs
being at angles extremely unfavourable for reactivation ( > 60). As folds approached
frictional lock-up, flexural slip continued to occur when supralithostatic fluid pressures were developed. Therefore, large, bedding-discordant faults were not
developed to accommodate strain during folding, explaining a deficiency of larger
faults in the TVS.
¶
Infiltration of overpressured fluids occurred into the base of the Murrumbidgee
Group, and was channelled into a distributed mesh of small faults and fractures.
At the point that a connected backbone flow network developed in the TVS, highpressure
fluids would no longer be available to allow continuing flexural slip on fold
limbs approaching lockup. Thereafter, larger faults would develop, which would
adjust the fault population in the TVS to a more typical displacement-frequency
distribution. This had not occurred in the Taemas area by the time crustal shortening
ceased. An abundance of small faults, and fracturing driven by invasion of
overpressured fluid, implies that the TVS formed via an earthquake swarm process.
¶
Modern analytical techniques, utilising laser ablation sampling technology, allow
high-spatial resolution chemical data to be collected from syntectonic veins. Insights
into the role that fluid-mineral interface processes may have on the chemistry of minerals grown in syntectonic veins were provided by an experimental study. Moderate sized ( < 1−5 mm) synthetic calcite crystals were successfully grown to investigate the uptake of rare earth elements (REE) into calcite. Changes in crystal morphology are linked to variable solution chemistry, which has important implications for the interpretation of hydrothermal vein textures. High-spatial resolution chemical analyses of synthetic calcite crystals demonstrate significant fluctuations in REE concentrations over distances of < 200 μm within calcite crystals. Time-equivalent regions on different crystal faces have significantly different REE concentrations,
indicating that fluctuations in calcite trace element composition cannot be interpreted
exclusively in terms of changing bulk fluid composition. Rare earth element
anomalies (Eu/Eu* and Ce/Ce*) are not significantly influenced by compositional
zoning, and may be robust indicators of changes in solution bulk chemistry and fluid
oxidation state.
¶
Changes in isotopic ratios (13C, 18O and 87Sr/86Sr), and trace element concentrations in veins from the TVS are related to variations in fluid source, flow pathways and chemical conditions (e.g. trace element complexation, precipitation rate, fluid oxidation) during hydrothermal fluid flow. This integrated structural, textural and chemical approach has direct application to the examination of hydrothermal veins
in fracture-hosted ore deposits, and may allow the fluid source and/or chemical
conditions conducive to the formation of high-grade ore to be discerned.
¶
Vein 18O compositions systematically increase upwards through the Murrumbidgee
Group, caused by progressive reaction of an externally derived, low-18O fluid (of
probable meteoric origin) with host limestones. Vein 18O and 87Sr/86Sr compositions vary spatially and temporally within the same outcrop, and within individual veins, which is inferred to be caused by the ascent of packages of fluid along constantly changing flow pathways. Fluid-buffered oxygen isotope ratios at the earliest stages of deformation imply that the TVS formed via an invasion percolation process. Fluid pathways are inferred to have changed constantly, with fractures toggleswitching between high-permeability and low-permeability states, due to repeated
fracture opening and sealing events.
24
Paton, Jonathan. "Computational fluid dynamics and fluid structure interaction of yacht sails". Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/14036/.
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This thesis focuses on the numerical simulation of yacht sails using both computational fluid dynamics (CFD) and fluid structure interaction (FSI) modelling. The modelling of yacht sails using RANS based CFD and the SST turbulence model is justified with validation against wind tunnel studies (Collie, 2005; Wilkinson, 1983). The CFD method is found to perform well, with the ability to predict flow separation, velocity and pressure profiles satisfactorily. This work is extended to look into multiple sail interaction and the impact of the mast upon performance. A FSI solution is proposed next, coupling viscous RANS based CFD and a structural code capable of modelling anistropic laminate sails (RELAX, 2009). The aim of this FSI solution is to offer the ability to investigate sails' performance and flying shapes more accurately than with current methods. The FSI solution is validated with the comparison to flying shapes of offwind sails from a bespoke wind tunnel experiment carried out at the University of Nottingham. The method predicted offwind flying shapes to a greater level of accuracy than previous methods. Finally the CFD and FSI solution described here above is showcased and used to model a full scale Volvo Open 70 racing yacht, including multiple offwind laminate sails, mast, hull, deck and twisted wind profile. The model is used to demonstrate the potential of viscous CFD and FSI to predict performance and aid in the design of high performance sails and yachts. The method predicted flying shapes and performance through a range of realistic sail trims providing valuable data for crews, naval architects and sail designers.
25
Molale, Dimpho Millicent. "A computational evaluation of flow through porous media". Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/686.
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Van, Ke Sum. "Dynamics and stability of curved pipes conveying fluid". Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66108.
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Cardillo, Giulia. "Fluid Dynamic Modeling of Biological Fluids : From the Cerebrospinal Fluid to Blood Thrombosis". Thesis, Institut polytechnique de Paris, 2020. http://www.theses.fr/2020IPPAX110.
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Dans cette thèse, trois modèles mathématiques ont été proposés, avec l’objectif de modéliser autant d’aspects complexes de la biomédecine, dans lesquels la dynamique des fluides du système joue un rôle fondamental: i) les interactions fluide-structure entre la pulsatilité du liquide céphalo-rachidien et la moelle épinière (modélisation analytique); ii) dispersion efficace d’un médicament dans l’espace sous-arachnoïdien (modélisation numérique); et iii) la formation et l’évolution d’un thrombus au sein du système cardiovasculaire (modélisation numérique).Le liquide céphalorachidien est un fluide aqueux qui entoure le cerveau et la moelle épinière afin de les protéger. Une connaissance détaillée de la circulation du liquide céphalorachidien et de son interaction avec les tissus peut être importante dans l’étude de la pathogenèse de maladies neurologiques graves, telles que la syringomyélie, un trouble qui implique la formation de cavités remplies de liquide (seringues) dans la moelle épinière.Par ailleurs, dans certains cas, des analgésiques - ainsi que des médicaments pour le traitement de maladies graves telles que les tumeurs et les infections du liquide céphalorachidien - doivent être administrés directement dans le liquide céphalorachidien. L’importance de connaître et de décrire l’écoulement du liquide céphalorachidien, ses interactions avec les tissus environnants et les phénomènes de transport qui y sont liés devient claire. Dans ce contexte, nous avons proposé: un modèle capable de décrire les interactions du liquide céphalo-rachidien avec la moelle épinière, considérant cela, pour la première fois, comme un milieu poreux imprégné de différents fluides (sang capillaire et veineux et liquide céphalo-rachidien); et un modèle capable d’évaluer le transport d’un médicament dans l’espace sousarachnoïdien, une cavité annulaire remplie de liquide céphalo-rachidien qui entoure la moelle épinière.Avec le troisième modèle proposé, nous entrons dans le système cardiovasculaire.Dans le monde entière, les maladies cardiovasculaires sont la cause principale de mortalité. Parmi ceux-ci, nous trouvons la thrombose, une condition qui implique la formation d’un caillot à l’intérieur d’un vaisseau sanguin, qui peut causer sa occlusion. À cet égard, un modèle numérique a été développé qui étudie la formation et l’évolution des thrombus, en considérant simultanément les aspects chimico-biomécaniques et dynamiques des fluides du problème. Dans le modèle proposé pour la première fois, l'importance du rôle joué par les gradients de contrainte de cisaillement dans le processus de thrombogenèse est pris en compte.Les modèles sélectionnés ont fourni des résultats intéressants. Tout d’abord, l’étude des interactions fluide-structure entre le liquide céphalo-rachidien et la moelle épinière a mis en évidence es conditions pouvant induire l’apparition de la syringomyélie. Il a été observé comment la déviation des valeurs physiologiques du module d’Young de la moelle épinière, les pressions capillaires dans l’interface moelle-espace sousarachnoïdien et la perméabilité des compartiments capillaire et veineux, conduisent à la formation de seringues.Le modèle de calcul pour l’évaluation de la dispersion pharmacologique dans l’espace sousarachnoïdien a permis une estimation quantitatif de la diffusivité effective du médicament, une quantité qui peut aider à l’optimisation des protocoles d’injections intrathécales.Le modèle de thrombogenèse a fourni un instrument capable d’étudier quantitativement l’évolution des dépôts de plaquettes dans la circulation sanguine. En particulier, les résultats ont fourni des informations importantes sur la nécessité de considérer le rôle de l’activation mécanique et de l’agrégation des plaquettes aux côtés de la substance chimiqueIn the present thesis, three mathematical models are described. Three different biomedical issues, where fluid dynamical aspects are of paramount importance, are modeled: i) Fluid-structure interactions between cerebro-spinal fluid pulsatility and the spinal cord (analytical modeling); ii) Enhanced dispersion of a drug in the subarachnoid space (numerical modeling); and iii) Thrombus formation and evolution in the cardiovascular system (numerical modeling).The cerebrospinal fluid (CSF) is a liquid that surrounds and protects the brain and the spinal cord. Insights into the functioning of cerebrospinal fluid are expected to reveal the pathogenesis of severe neurological diseases, such as syringomyelia that involves the formation of fluid-filled cavities (syrinxes) in the spinal cord.Furthermore, in some cases, analgesic drugs -- as well drugs for treatments of serious diseases such as cancers and cerebrospinal fluid infections -- need to be delivered directly into the cerebrospinal fluid. This underscores the importance of knowing and describing cerebrospinal fluid flow, its interactions with the surrounding tissues and the transport phenomena related to it. In this framework, we have proposed: a model that describes the interactions of the cerebrospinal fluid with the spinal cord that is considered, for the first time, as a porous medium permeated by different fluids (capillary and venous blood and cerebrospinal fluid); and a model that evaluates drug transport within the cerebrospinal fluid-filled space around the spinal cord --namely the subarachnoid space--.The third model deals with the cardiovascular system. Cardiovascular diseases are the leading cause of death worldwide, among these diseases, thrombosis is a condition that involves the formation of a blood clot inside a blood vessel. A computational model that studies thrombus formation and evolution is developed, considering the chemical, bio-mechanical and fluid dynamical aspects of the problem in the same computational framework. In this model, the primary novelty is the introduction of the role of shear micro-gradients into the process of thrombogenesis.The developed models have provided several outcomes. First, the study of the fluid-structure interactions between cerebro-spinal fluid and the spinal cord has shed light on scenarios that may induce the occurrence of Syringomyelia. It was seen how the deviation from the physiological values of the Young modulus of the spinal cord, the capillary pressures at the SC-SAS interface and the permeability of blood networks can lead to syrinx formation.The computational model of the drug dispersion has allowed to quantitatively estimate the drug effective diffusivity, a feature that can aid the tuning of intrathecal delivery protocols.The comprehensive thrombus formation model has provided a quantification tool of the thrombotic deposition evolution in a blood vessel. In particular, the results have given insight into the importance of considering both mechanical and chemical activation and aggregation of platelets
28
Petrus, Ryan Curtis. "Dynamics of fluid-conveying Timoshenko pipes". Texas A&M University, 2006. http://hdl.handle.net/1969.1/3822.
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Structures conveying mass lose stability once the mass exceeds a certain critical
velocity. The type of instability observed depends on the nature of the supports that the
structure has. If the structure (beam or pipe) is cantilevered (thereby deeming it a nonconservative
system), Âgarden-hose-like flutter instability is observed once a critical
velocity is exceeded. When studying the flutter instability of a cantilevered pipe
(including shear deformation) by strictly a linear theory, it has been demonstrated
through numerical integration that the values of the critical velocity are only valid for
small values of the mass ratio (mass of the fluid divided by the total mass)
(approximately 0.1 β< ). This fact is also true if shear deformation is neglected. Also,
linear theory predicts the pipe to oscillate unboundedly as time progresses, which is
physically impossible. Therefore, shortly after the pipe goes unstable, the linear theory
is no longer applicable. If non-linear terms are taken into account from the beginning, it
can be shown that the pipe oscillates into a limit cycle.
29
Williams, A. G. "The fluid dynamics of radio sources". Thesis, University of Cambridge, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373717.
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Davidson, Jonathan. "Dynamics of semi-discretised fluid flow". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364471.
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Valluri, Prashant. "Multiphase fluid dynamics in structured packings". Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415894.
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Palapanidis, Konstantinos. "Relativistic fluid dynamics and electromagnetic media". Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/427364/.
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In this thesis we describe fluid media with electromagnetic properties in the context of general relativity. Using the variational principle we derive the Einstein equations from the Einstein-Hilbert action, the Euler-Lagrange equations for a multicomponent fluid and the Maxwell equations. We provide a covariant description of linear electromagnetic media and we also discuss media with non linear electromagnetic properties. We also provide a formula that generalises the expression for the Lagrangian of linear media, to that of non linear media and we discuss a set of constraints for linear electromagnetic media in terms of the material derivative. We discuss a model for a multifluid with general electromagnetic properties. We also derive the limit for the single fluid ideal magnetohydrodynamics in general relativistic context. In the final part we look into the linear stability of specific systems using the geometric optics method along with the notion of "fast" and "slow" variables. Employing this method we reproduce a number of results in Newtonian context, building gradually to the derivation of the magnetorotational instability. Additionally, we discuss the vanishing magnetic field of this configuration. Subsequently, considering an unperturbed background spacetime we derive the characteristic equations describing the relativistic inertial waves, the relativistic Rayleigh shearing instability and the relativistic magnetorotational instability. Finally, by assuming a low velocity and flat metric limit of the relativistic equations we reproduce the Newtonian characteristic equations.
33
Chelghoum, Abdelkrim. "Dynamics of structures including fluid interaction". Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/37966.
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Fernando, Bothalage D. R. "Fluid dynamics of rotor-stator cavities". Thesis, University of Leicester, 2018. http://hdl.handle.net/2381/43057.
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This investigation is of mass, momentum and heat transfer applications of the idealised rotor-stator cavities using Computational Fluid Dynamics (CFD). This approach is based on previous literature that provides a fundamental view of the subject. However, this research is more focused on the development and simulation of high-fidelity computational models to refine the understanding of rotor-stator flow problems in engineering. An open source CFD toolbox, OpenFOAM, is used to solve Navier-Stokes equations and turbulence is modelled using Large eddy simulation (LES) approaches. The rotor boundary layer roughness is modelled by the parametric force approach, which is an ideal method to represent real-world roughness. Different types of rough wall conditions are imposed on the rotor. The roughness of the rotor wall affected the mean velocity profiles and turbulence intensity at the rotor. Increasing the roughness height transmits these effects to the stator wall. The outer wall of the rotor-stator cavity provides a passage to transport the roughness induced disturbances to the stator side, which tends to an unsteady flow even at minor roughness levels. The nanofluid heat transfer in the rotor-stator cavities is investigated using single-phase and two-phase transport models. Both models result in enhanced heat transfer rate by using different volume fractions of nanoparticles. The two-phase models provide additional information on the relative slip in the nanoparticle phase due to the Brownian and thermophoresis effects. Near the hot stator, particles are displaced away from the surface, which results in a mild reduction of heat transfer rates. The final section studies the Lagrangian particle dynamics and deposition in a Rotating Disk Chemical Vapour Deposition (RCVD) chamber. Here, the rotating effects of the disk highly agitate the particle phase, which enhances the deposition efficiencies on the rotor. Apart from that, carrier phase turbulence and thermophoretic forces are important factors in particle dynamics.
35
Wang, Xiaohan. "Fluid dynamics of hot gas ingress". Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.698954.
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The gas turbine engine, as an adaptable source of power, has been used extensively for electric power generation, mechanical drive and jet propulsion. Driven by competition within the industry, gas turbine engine manufactures strive to produce ever more efficient products that also comply with emission regulations. The overall efficiency, as a crucial parameter governing engine performance and life cycle operating costs, depends on a high turbine inlet temperature, as well as an appropriately high pressure ratio across the compressor. The turbine components operating at elevated temperatures could experience serious problems, such as unwanted creep, oxidation or thermal fatigue, which compromise the integrity and reduce lifespan. In modern gas turbine engines, cooling air bled from the compressor is used to prevent overheating of the turbine, through the secondary air system. As much as 25% of the compressor air bypasses combustion to be used for cooling and sealing purposes. Hot gas ingress is one of the most important and intricate problems of the secondary air system faced by engine designers. Ingress occurs when the hot gas from the mainstream is ingested into the wheel space, formed by the turbine disc and its adjacent casing. A rim seal is fitted at the periphery of the wheel-space, and a sealing flow of coolant is used to purge the cavity reducing or preventing ingress. Sufficient sealing flow is required, but an excessive use of coolant decreases overall engine efficiency. Therefore, from engine designers’ perspective the use of sealing air must be minimised. Optimisation of the rim-seal design is a crucial approach to fulfil the purpose. The double-clearance rim seal is widely employed in gas turbines, which consists of an outer-seal at the periphery of the wheel-space and an inner-seal located radially inboard. The annular cavity formed between the double-seal arrangement is known to predominantly confine the ingested hot gases, thus significantly reducing ingestion inboard of the inner seal. In order to study how double-clearance seals operate in depth, this thesis describes a new single stage turbine research facility, designed for conducting extensive and comprehensive experimental studies on ingress for different rim-seal configurations. Experimental study conducted with the new facility is reported for a variety of generic but engine-representative double-clearance seal configurations, to gain insights into the sealing effectiveness and fluid dynamics associated with different rim-seal design features. Besides being adaptable for various rim-seal configurations, the research facility was also designed to be highly versatile in respect of wheel-space geometries and gas path blading, in order to investigate the impact on ingress from the aerodynamics both inboard and outboard of the rim seal. Extensive instrumentation was incorporated into the turbine stage for the measurements of pressure, swirl velocities, gas concentration and temperature. Additionally, the facility is capable of modelling leakage flow paths found in actual gas turbines to explore novel techniques that could reduce ingress by utilising the leakage air. A parametric study is presented for a range of double-clearance rim seal configurations, characterised by various design features both on the stator side and rotor side of the turbine disc system. Gas concentration measurements were made for each configuration to assess the relative sealing performance. The sealing effectiveness was determined both in the outer wheel-space between the double clearances, and in the inner wheel-space radially inboard of the inner-seal. These measurements constitute a research database that will support the design approach at Siemens, in conjunction with the theoretical model previously developed at Bath, which treats the seal clearance as an orifice ring and uses adapted Bernoulli’s equation to correlate sealing flow rate and pressure difference across the seal. The sealing effectiveness is correlated with pressure and swirl ratio in the wheel-space to study the fluid dynamics associated with different rim-seal features, in support of rim-seal design and optimisations for secondary air systems.
36
Onslow, Roland James. "Fluid-particle transport dynamics of sandwaves". Thesis, University of Birmingham, 1995. http://etheses.bham.ac.uk//id/eprint/4533/.
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The local dynamics of sandwaves and their crest-shedding turbulent flows has received little mechanistic attention, unlike recent advances in allied fields such as bubbly shear flows. One main purpose of the present project is to address these questions of particle engagement and transport by transient large eddies in the free shear layer over sandwaves. Experimental studies were conducted on the trajectories of model particles over suitably scaled fixed bedforms in a purpose built flume. Three important results emerged. Firstly, trajectories of particles jetted over the crest fell into seven primary modes from short paths beyond the crest to extended downstream transport. Secondly, the vertical profiles of particle concentration exhibited peaks at crest elevation over the trough, comparing with recent field observations by (Soulsby, 1989). Thirdly, flapping excursions of the shear layer were found to enhance lee slope scour and probably account for the sediment clouds observed in Soulsby's field study, here further conjectured to result in sandwave washout at high flow velocities. Favourable comparisons with previous studies are described.
37
Sun, Mingqiu. "Molecular dynamics simulation of fluid systems /". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487849696964891.
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Gay, Etienne. "Coherent interferometric imaging in fluid dynamics". Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7029.
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La présente recherche vise à développer des algorithmes d’imagerie par interférométrie cohérente (CINT) pour localiser des sources et des réflecteurs dans des applications impliquant des écoulements. L’imagerie CINT s’est avérée efficace et statistiquement stable dans des milieux inhomogènes au repos, où les techniques classiques d’imagerie, telles que la migration de Kirchhoff (KM), peuvent éventuellement échouer en raison de leur manque de robustesse statistique. Nous visons à étendre ces méthodes aux milieux en mouvement inhomogènes, car elles concernent l’aéroacoustique, l’acoustique atmosphérique et sous-marine, la propagation des infrasons, voire l’astrophysique. Dans ce rapport de thèse, nous abordons à la fois le problème direct de la modélisation de la propagation des ondes acoustiques dans un écoulement ambiant hétérogène et aléatoire, et le problème inverse de la recherche de la position de sources ou de réflecteurs par l'algorithme CINT mis en œuvre avec les traces des ondes acoustiques qui ont traversé l’écoulementThe present research is aimed at developing coherent interferometric (CINT) imaging algorithms to localize sources and reflectors in applications involving fluid flows. CINT imaging has been shown to be efficient and statistically stable in quiescent cluttered media where classical imaging techniques, such as Kirchhoff’s migration (KM), may possibly fail due to their lack of statistical robustness. We aim at extending these methods to inhomogeneous moving media, for it has relevance to aero-acoustics, atmospheric and underwater acoustics, infrasound propagation, or even astrophysics. In this thesis report we address both the direct problem of modeling the propagation of acoustic waves in a randomly heterogeneous ambient flow, and the inverse problem of finding the position of sources or reflectors by the CINT algorithm implemented with the traces of the acoustic waves that have travelled through the flow
39
Katz, Aaron Jon. "Meshless methods for computational fluid dynamics /". May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Sahasrabudhe, Mandar. "Neural network applications in fluid dynamics". Thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-08112002-221615.
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Hunton, B. J. "Vortex dynamics". Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259909.
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Chambers, Steven B. "Investigation of combustive flows and dynamic meshing in computational fluid dynamics". Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1324.
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Computational Fluid Dynamics (CFD) is a field that is constantly advancing. Its advances in terms of capabilities are a result of new theories, faster computers, and new numerical methods. In this thesis, advances in the computational fluid dynamic modeling of moving bodies and combustive flows are investigated. Thus, the basic theory behind CFD is being extended to solve a new class of problems that are generally more complex. The first chapter that investigates some of the results, chapter IV, discusses a technique developed to model unsteady aerodynamics with moving boundaries such as flapping winged flight. This will include mesh deformation and fluid dynamics theory needed to solve such a complex system. Chapter V will examine the numerical modeling of a combustive flow. A three dimensional single vane burner combustion chamber is numerically modeled. Species balance equations along with rates of reactions are introduced when modeling combustive flows and these expressions are discussed. A reaction mechanism is validated for use with in situ reheat simulations. Chapter VI compares numerical results with a laminar methane flame experiment to further investigate the capabilities of CFD to simulate a combustive flow. A new method of examining a combustive flow is introduced by looking at the solutions ability to satisfy the second law of thermodynamics. All laminar flame simulations are found to be in violation of the entropy inequality.
43
Kachani, Soulaymane, e Georgia Perakis. "Modeling Travel Times in Dynamic Transportation Networks; A Fluid Dynamics Approach". Massachusetts Institute of Technology, Operations Research Center, 2001. http://hdl.handle.net/1721.1/5224.
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In this paper, we take a fluid dynamics approach to determine the travel time in traversing a network's link. We propose a general model for travel time functions that utilizes fluid dynamics laws for compressible flow to capture a variety of flow patterns such as the formation and dissipation of queues, drivers' response to upstream congestion or decongestion and drivers' reaction time. We examine two variants of the model, in the case of separable velocity functions, which gives rise to two families of travel time functions for the problem; a polynomial and an exponential family. We analyze these travel time functions and examine several special cases. Our investigation also extends to the case of non-separable velocity functions starting with an analysis of the interaction between two links, and then extending it to the general case of acyclic networks.
44
Liu, Li. "Computational fluid dynamics modelling of complex fluid flow in stirred vessels". Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/4753/.
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Fluid mixing in stirred vessels is widely encountered in a number of industries. In this work, different experimental techniques and the CFD modelling approach are used to measure the mixing of a wide range of fluids in stirred vessels. As the detailed validation is essential for CFD modelling, CFD predictions are compared in detail with different experimental measurements. The capability of CFD modelling of the 3D spatial distribution of velocity and solid concentration within opaque concentrated solid-liquid suspensions with the mean solid concentration up to 40 wt% is assessed by comparing with the experimental data obtained from positron emission particle tracking (PEPT) measurements. Because the impeller configuration is of significant importance to the flow pattern, the performance of different impellers for single-phase mixing of Newtonian and non-Newtonian fluids in stirred vessels is compared. CFD predictions of flow fields generated from different impellers are compared with those measured by the well-established particle image velocimetry (PIV) technique. The capability of CFD modelling of different mixing features of non-Newtonian fluids in stirred vessels are verified by comparing with experimental data obtained from PIV, PEPT, and planar laser induced fluorescence (PLIF) measurements.
45
Ichinose, Matthew Hiroki. "Fluid Agitation Studies for Drug Product Containers using Computational Fluid Dynamics". DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1980.
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At Amgen, the Automated Vision Inspection (AVI) systems capture the movement of unwanted particles in Amgen's drug product containers. For quality inspection, the AVI system must detect these undesired particles using a high speed spin-stop agitation process. To better understand the fluid movements to swirl the particles away from the walls, Computational Fluid Dynamics (CFD) is used to analyze the nature of the two phase flow of air and a liquid solution.
Several 2-D and 3-D models were developed using Fluent to create simulations of Amgen's drug product containers for a 1 mL syringe, 2.25 mL syringe, and a 5 mL cartridge. Fluid motion and potential bubble formations were studied within the liquid/gas domain inside the container by varying parameters such as viscosity, angular velocity, and surface tension. Experiments were conducted using Amgen's own equipment to capture the images of the spin-stop process and validate the models created in Fluent. Observations were made to see the effects of bubble formation or splashing during spin-down to rest.
The numerical and experimental results showed favorable comparison when measuring the meniscus height or the surface profile between the air and liquid. Also, at high angular velocity and dynamic viscosity, the container experiences instabilities and bubble formations. These studies indicate that CFD can be used as an useful and important tool to study fluid movement during agitation and observe any undesirable results for quality inspection.
46
Holland, David M. "Nano-scale computational fluid dynamics with molecular dynamics pre-simulations". Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/72851/.
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A procedure for using Molecular Dynamics (MD) simulations to provide essential fl uid and interface properties for subsequent use in Computational Fluid Dynamics (CFD) calculations of nano-scale fluid fl ows is presented. The MD presimulations enable an equation of state, constitutive relations, and boundary conditions to be obtained for any given fl uid/solid combination, in a form that can be conveniently implemented within an otherwise conventional Navier-Stokes solver. The results presented demonstrate that these enhanced CFD simulations are capable of providing good fl ow field results in a range of complex geometries at the nano-scale. Comparison for validation is with full-scale MD simulations here, but the computational cost of the enhanced CFD is negligible in comparison with the MD. It is shown that this enhanced CFD can predict unsteady nano-scale ows in non-trivial geometries. A converging-diverging nano-scale channel is modelled where the fl uid fl ow is driven by a time-varying body force. The time-dependent mass fl ow rate predicted by the enhanced CFD agrees well with a MD simulation of the same configuration. Conventional CFD predictions of the same case are wholly inadequate. It is demonstrated that accurate predictions can be obtained in geometries that are more complex than the planar MD pre-simulation geometry that provides the nano-scale fl uid properties. The robustness of the enhanced CFD is tested by application to water fl ow along a (15,15) carbon nanotube (CNT) and it is found that useful fl ow information can be obtained. The enhnaced CFD model is applied as a design optimisation tool on a bifurcating two-dimensional channel, with the target of maximising mass fl ow rate for a fixed total volume and applied pressure. At macro scales the optimised geometry agrees well with Murray's law for optimal branching of vascular networks; however, at the nano-scale, the optimum result deviates from Murray's law, and a corrected equation is presented. However, it is found that as the mass flow rate increases through the channel high pressure losses occur at the junction of the network. These high pressure losses also have an impact on the optimal design of a network.
47
Georgeton, Gus Konstantinos. "Group contribution equations of state for complex fluid mixtures". Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/11772.
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Hester, Eric William. "Modelling fluid-solid interactions". Thesis, The University of Sydney, 2021. https://hdl.handle.net/2123/25114.
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Fluid-solid interactions have wide-ranging implications for science, engineering, and the global climate. This thesis combines mathematical analysis, computational algorithms, and laboratory experiments to understand fluid-solid interactions, providing new insights on the influence of shape on iceberg melting, and mysterious boat drag in the dead-water effect.
The discontinuous interfaces of fluid-solid interactions are challenging to simulate. We develop improved diffuse-domain methods that allow straightforward algorithms to simulate fluid-solid interactions. Diffuse-domain methods are simple to implement because they replace complicated boundary conditions with smooth source terms. But the smoothing induces a boundary layer of size ε between the fluid and solid. Previous diffuse-domain methods incurred errors of this size—corresponding to first order numerical accuracy.
The first part of the thesis develops an asymptotic framework to derive second-order accurate diffuse-domain methods. In chapter 2, we exploit the signed distance function to simplify vector calculus around boundary layers in arbitrary smooth geometries. In chapter 3 we apply this machinery to optimise the volume-penalty method for fluid-solid interactions. In chapter 4 we then derive higher-order phase-field models for coupled melting, dissolution, and convection. We verify these corrections in extensive numerical benchmarks. We also explore techniques for fourth order convergence in ε using Richardson extrapolation, and spectral accuracy simulations via coordinate remapping. These improved methods provide powerful tools to simulate and understand real-world fluid-solid interactions.
In chapter 5, we apply these methods to investigate how iceberg shape affects melting. Icebergs vary in shape and size, and iceberg melting determines their influence on the climate. Our laboratory experiments reveal previous models underestimate melting and ignore large differences between sides. The improved phase-field model reproduces experimental melt rates and explains observed patterns. Simulations show that non-uniform basal melt rates stem from upwelling during vortex generation. We outline the geophysical implications of our findings and discuss improvements to current melting parameterisations that account for iceberg geometry.
Then in chapter 6, we use these techniques to examine the dead-water effect—extreme boat drag in density-stratified waters. Walfrid Ekman showed in 1904 that sub-surface internal waves cause dead water. Boats moving near the internal wave speed generate large internal waves which steal energy from the boat. We perform the first direct numerical simulation of dead water. In contrast to previous potential flow models, we find that vorticity generated throughout the domain plays an important role in the effect. The vorticity coalesces into large, previously unnoticed eddies. These robust eddies interfere with the boat-wave interaction, and may suggest new strategies to mitigate the effect.
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Shen, Jihua. "Formation and characteristics of sprays from annular viscous liquid jet breakup". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32723.pdf.
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Azouz, Idir. "Numerical simulation of laminar and turbulent flows of wellbore fluids in annular passages of arbitrary cross-section /". Access abstract and link to full text, 1994. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9500702.
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