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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Data extraction in holographic particle image velocimetry

Yang, Hui January 2004 (has links)
Holographic Particle Image Velocimetry (HPIV) is potentially the best technique to obtain instantaneous, three-dimensional, flow field information. Several researchers have presented their experimental results to demonstrate the power of HPIV technique. However, the challenge to find an economical and automatic means to extract and process the immense amount of data from the holograms still remains. This thesis reports on the development of complex amplitude correlation as a means of data extraction. At the same time, three-dimensional quantitative measurements for a micro scale flow is of increasing importance in the design of microfluidic devices. This thesis also reports the investigation of HPIV in micro-scale fluid flow. The author has re-examined complex amplitude correlation using a formulation of scalar diffraction in three-dimensional vector space.
52

Modelling vortex motion with a stream function subdivision finite element

Fisher, Alex John January 2007 (has links)
This thesis develops an approach for discretising and solving the Navier-Stokes equations characterising viscous fluid flow. This subject of describing partial differential equations Is approached through the analogous field of computeraided geometric design. Recent developments in efficient techniques for surface definition used in computational design and computer animation are presented.
53

Characterization of flow dynamics in vessels with complex geometry using Doppler optical coherence tomography

Bonesi, Marco January 2008 (has links)
The study of flow dynamics in complex geometry vessels is highly important in many biomedical applications where the knowledge of the mechanic interactions between the moving fluid and the housing media plays a key role for the determination of the parameters of interest, including the effect of blood flow on the possible rupture of atherosclerotic plaques. Doppler Optical Coherence Tomography (DOCT) is an optic, non-contact, non-invasive technique able to achieve detailed analysis of the flow/vessel interactions, allowing simultaneously high resolution imaging of the morphology and composition of the vessel and of the flow velocity distribution along the measured cross-section. DOCT system was developed to image high-resolution one-dimensional and multi-dimensional velocity distribution profiles of Newtonian and non-Newtonian fluids flowing in vessels with complex geometry, including Y-shaped and T-shaped vessels, vessels with aneurism, bifurcated vessels with deployed stent and scaffolds. The phantoms were built to study the interaction of the flow dynamics with different channel geometries and to map the related velocity profiles at several inlet volume flow rates. Feasibility studies for quantitative observation of the turbulence of flows arising within the complex geometry vessels are discussed. In addition, optical clearing of skin tissues has been utilized to achieve DOCT imaging of human blood vessels in vivo, at a depth up to 1.7 mm. Two-dimensional OCT images of complex flow velocity profiles in blood vessel phantom and in vivo subcutaneous human skin tissues are presented. The effect of optical clearing on in vivo images is demonstrated and discussed. DOCT was also applied for imaging scaffold structures and for mapping flow distributions within the scaffold.
54

Modelling smart fluid devices using computational fluid dynamics

Ellam, Darren John January 2003 (has links)
No description available.
55

Instabilities in low pressure boiling systems

Pickering, Paul Frederick January 1994 (has links)
No description available.
56

Transient one-dimensional modelling of multiphase slug flows

Bonizzi, Marco January 2003 (has links)
No description available.
57

Oscillatory wave induced boundary layer flow over a rippled bed

Ourmières, Yann January 2003 (has links)
No description available.
58

Large eddy simulation of reacting and non-reacting turbulent flows

Di Mare, F. January 2002 (has links)
No description available.
59

An investigation of larger scale coherent structures in fully developed turbulent boundary layers

Hutchins, Nick January 2003 (has links)
No description available.
60

Transport phenomena in porous media

Kilchherr, Rudolf January 2003 (has links)
Non-Newtonian flow in heterogeneous media is of enormous theoretical and industrial importance. This phenomenon is studied to reveal macroscopic effects that arise due to the interaction between the non-linear flow behaviour and the spatial variation of the medium through which it is forced to move. The heterogeneity is achieved by using porous granular media, which is naturally non-homogeneous. The non-Newtonian properties of the fluid may have many causes and is an intrinsic property of the fluid that is used: One way of achieving it is by studying dense slurries of neutral particles or naturally occurring magmatic flows. Another way is to study the case where the flow is dominated by its ionic content and where the double layer thickness (the effective size of the ionic entities) is of the order of magnitude of the pore size. All cases studied in this thesis pertain to slow flow (low Reynolds number), though the fluid may be compressible. The variations in the flow are calculated in first order and these turn out to be coupled to the spatial variations in the porous medium. In this way structure formation is predicted. The structures may be either aligned with or may be perpendicular to the mean flow direction. 'Experiments to decide on which regime is relevant have been conducted. The genesis of structure formation is studied as a temporal development by considering a compressible flow. The constitutive equation that is required to couple the compressibility to the flow parameters is investigated. Two possible mechanisms have been identified: compressibility coupled to the pressure field and compressibility associated with the fluctuations in the flow. Using linear analysis the structure formation patterns associated with these two mechanisms are established for the steady state. Flow of ionically laden fluids has also been studied. Experiments done at Loughborough University (Department of Chemical Engineering) on electrowashing of filter cakes has been used to prove a major macroscopic effect. This effect takes place when the ionic diameter (which is approximately twice the double layer thickness) is of the order of magnitude of the pore size. A phenomenological set of transport equations has been set up. These contain coefficients, such as transition probabilities and mean ionic flow rates, that can be obtained from experiments by doing a first order solution of the equations for short times. A more involved numerical solution is also supplied and confirms the initial analytical estimates.

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