Dissertations / Theses on the topic 'Free Surface Flow'
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陳彤{272b21} and Tong Chen. "Numerical computations on free-surface flow." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31238245.
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Chen, Tong. "Numerical computations on free-surface flow /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21020292.
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Sellar, Alistair Alexander. "Free-surface rapid granular flows." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274642.
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Jesuthasan, Nirmalakanth. "Optical measurements of a free-surface granular flow." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=83869.
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The experimental investigation described in this thesis is primarily aimed at acquiring digital particle-tracking velocimetry (DPTV) measurements of a free-surface granular flow down the upper inclined surface of a wedge-shaped static pile of the same material, contained in a narrow channel between two parallel vertical glass plates. The glass plates are 610 mm long and 350 mm high. Three different values of the normal separation distance between them were investigated: 25.4 mm, 38.1 mm, and 50.8 mm. For each of these separation distances, the following three values (nominal) of the mass flow rate per unit width were considered: 0.81 kg/s-m, 1.85 kg/s-m, and 3.33 kg/s-m. The granular material used in this work consists of slightly polydisperse, almost spherical, ceramic (zirconium silicate) beads: mean effective diameter of 1.59 mm and mass density of 4071 kg/m3. For these ranges of dimensional parameters, statistically-steady fully developed flows were established in a reliable and repeatable manner. A high-speed camera system was used to acquire digital images of the granular flows of interest in the fully developed region. Image processing and a commercial PTV software package (DiaTrackPro 2.3) were used to obtain the particle trajectories. Special routines were written in Matlab to obtain the corresponding instantaneous and ensemble-averaged velocity distributions. These results were then used to compute the corresponding distributions of granular temperature and a related dimensionless parameter that is commonly referred to as the Savage-Jeffrey parameter. The aforementioned PTV and data processing procedures, the results in dimensional and dimensionless forms, and the applicability of some recently proposed scaling laws are discussed in this thesis.
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Robertson, Iain. "Free surface flow simulations using high order algorithms." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342294.
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Tome, Murilo Francisco. "GENSMAC : a multiple free surface fluid flow solver." Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.689607.
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Collins, Justin Andrew. "Velocity and free surface measurements of free plane jets." Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/17888.
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Gutiérrez-Matus, Pablo. "Effects on the free surface of a turbulent flow." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/92/19/54/PDF/PGutierrez-PhdThesis20131219.pdf.
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Nous nous intéressons aux effets en surface induits par un écoulement turbulent, en utilisant une approche expérimentale. Nous étudions un écoulement turbulent de faible épaisseur avec une surface libre. L'écoulement est produit dans un métal liquide à l'aide d'une force électromagnétique. Il présente des tourbillons, des bandes de cisaillement et des ondes, dépendent des conditions de forçage. Trois aspects ont été considérées: la déformation de surface engendré par la turbulence; les effets de la turbulence sur la propagation des ondes; et les effets de la turbulence sur des particules qui flottent à la surface. Concernant la déformation de surface : à mesure que l'on augmente l'intensité du forçage, l'écart type de la déformation augmente de façon linéaire, jusqu'à atteindre le 10% de l'épaisseur du fluide. Les déformations extrêmes peuvent atteindre la moitié de l'épaisseur. A faible forçage, la déformation de surface est principalement liée à la présence des tourbillons, impliquant une distribution de l'hauteur avec un facteur d'asymétrie négatif. Cette observation contraste avec la turbulence d'onde, où une asymétrie est aussi observée, mais avec un facteur d'asymétrie positif, notamment à cause des crêtes pointues dans les ondes de gravité. Le spectre en fréquence de la déformation présente une loi de puissance avec un exposant -5, similaire au spectre de singularité de Phillips. Ainsi, nous avons présenté les empreintes statistiques des tourbillons. Deuxièmement, nous avons considéré un autre aspect de la relation onde-écoulement turbulent : nous avons induit mécaniquement des ondes monochromatiques à la surface de l'écoulement. Lorsque l'écoulement deviens plus intense, nous avons mesure la décroissance et l'élargissement du mode associé à l'onde. Nous avons calculé une moyenne cohérente que souligne l'onde para rapport aux fluctuations turbulentes. Ceci nous permet d'observer la décroissance spatial de l'onde lorsque l'écoulement deviens plus intense. Ces analyses nous ont permit de quantifier une augmentation de l'atténuation des ondes à cause de la turbulence. Si l'on considère des particules qui flottent à la surface du liquide, on s'aperçoit qu'elles ont tendance à former des amas. Ce phénomène est confirmé par une analyse statistique des aires définies par la position des trois particules voisines. Ce faisant, on peut identifier clairement les particules qui appartiennent aux amas. De plus, ces particules présentent une corrélation très forte des vitesses et d'orientation angulaire. Plusieurs mécanismes physiques peuvent induire cette formation des amas: (i) l'inertie des particules ; (ii) des mouvements verticaux secondaires et ; (iii) la déformation de surface. Nous avons construit des quantités pour corréler les effets de concentration de particules avec ses mécanismes. Les corrélations plus importantes sont celles que concernent les mouvements verticaux secondaires, qui l'on interprète comme le mécanisme responsable des effets de concentrationWe study surface manifestations of a turbulent flow from an experimental point of view. Specifically we study a turbulent flow in a thin layer of fluid (a liquid metal) with free surface. The flow is generated with an electromagnetic force. It exhibits interacting vortices, shear bands and waves, depending on the forcing conditions. We explored three consequences of the horizontal turbulent motion as observed on the surface: Surface deformation itself; the effects on propagating waves; and the effects on floating particles. Concerning the surface deformation: when the forcing strength is increased, we observe a linear increase of the surface level r. M. S. Fluctuations up to 10% of the liquid layer thickness. Largest deformations, however, can reach a half of the layer thickness. Surface deformation is mainly produced by vortices, thus it is asymmetric through values under the mean. This contrast with observations in random sea waves and wave turbulence, were an asymmetry appears as well --this time through values above the mean--, as a consequence of sharp crests in steep gravity waves. The frequency spectrum of the deformation follows a power-law with an exponent close to -5, similar to the singularity spectrum of Phillips. Thus, we presented the statistical signature of vortical motion. We considered another aspect of the wave-turbulence relation: we mechanically induced a monochromatic wave over the turbulent flow. We measure a reduction and widening of the wave spectral peak that happens when turbulent motion is increased. Also, we computed coherent averages to emphasize the wavy part of the signal. We observe a spatial decay in wave content when turbulent motion is increased. Therefore, we quantified the enhancement of wave attenuation due to turbulence, and we observed its non trivial dependence on the wave frequency. Concerning dynamics of floating particles: We observe that particles have the tendency to form clusters, and we confirm this observation by developing a statistical method based on the areas defined by the position of three nearest neighbors. This tool allows us to clearly identify particles belonging to a cluster. Indeed, clustered particles exhibit much stronger velocity and angular correlations than the unconditioned case. Several mechanisms are susceptible to induce clustering of floating particles. We identify (i) particles' inertia, (ii) upwelling/downwelling flows and (iii) surface tension. For each mechanism we construct suitable quantities, which we correlate with the cumulated concentration of particles. These correlations suggest upwelling and downwelling motions as responsible for particles clustering
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Reichl, Paul 1973. "Flow past a cylinder close to a free surface." Monash University, Dept. of Mechanical Engineering, 2001. http://arrow.monash.edu.au/hdl/1959.1/9212.
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Lee, Haegyun. "Level-set finite element simulation of free-surface flow." Diss., University of Iowa, 2007. http://ir.uiowa.edu/etd/168.
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Gao, Feng. "An efficient finite element technique for free surface flow." Thesis, University of Brighton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275077.
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Poles, Richard R. "Free-surface flow in a shallow laterally heated cavity." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363313.
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Aybar, Akin. "Computational Modelling Of Free Surface Flow In Intake Structures Using Flow 3d Software." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614377/index.pdf.
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Intakes are inlet structures where fluid is accelerated to a certain flow velocity to provide required amount of water into a hydraulic system. Intake size and geometry affects the formation of flow patterns, which can be influential for hydraulic performance of the whole system. An experimental study is conducted by measuring velocity field in the hydraulic model of the head pond of a hydropower plant to investigate vortex formation. Vortex strength based on potential flow theory is calculated from the measured velocity field. It was shown that vortex strength increases with the submergence Froude number. The free surface flow in the head pond is simulated using Flow-3D software. Vortex strength calculations are repeated using the computational velocity distributions and compared to experimentally obtained values. Similar computations were carried on with some idealized pond geometries such as rectangular and circular.
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Andersson, Anders G. "Simulations and measurements of free surface flow in regulated rivers." Licentiate thesis, Luleå tekniska universitet, Strömningslära och experimentell mekanik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18022.
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Open channel flow near hydropower stations is of interest for both engineering and environmental applications. In this research project Computational Fluid Dynamics simulations of free surface flow in regulated rivers were applied with both fish migration and validation of numerical simulations in focus. In the first paper, numerical simulations has been used to evaluate the flow downstream a hydropower plant with regards to upstream migrating fish. Field measurements with an Acoustic Doppler Current Profiler were performed and the measurements were used to validate the simulations. In the second paper ,simulations on the spilling from a dam were performed and compared to experimental results from a physical scale model. The third paper deals with more in depth analysis of field measurements where the variations in the flow downstream a hydropower plant was examined.Godkänd; 2010; 20101028 (aneane); LICENTIATSEMINARIUM Ämnesområde: Strömningslära/Fluid Mechanics Examinator: Professor Staffan Lundström, Luleå tekniska universitet Diskutant: Teknologie doktor Mats Billstein, Vattenfall Research and Development AB, Älvkarleby Tid: Fredag den 3 december 2010 kl 10.30 Plats: A109, Luleå tekniska universitet
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Chan, Johnson Lap-Kay. "Numerical procedure for potential flow problems with a free surface." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/28637.
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A numerical procedure based upon a boundary integral method for gravity wave making problems is studied in the time domain. The free-surface boundary conditions are combined and expressed in a Lagrangian notation to follow the free-surface particle's motion in time. The corresponding material derivative term is approximated by a finite difference expression, and the velocity terms are extrapolated in time for the completion of the formulations. The fluid-body intersection position at the free surface is predicted by an interpolation function that requires information from both the free surface and the submerged surface conditions. Solutions corresponding to a linear free-surface condition and to a non-linear free-surface condition are obtained at small time increment values. Numerical modelling of surface wave problems is studied in two dimensions and in three dimensions. Comparisons are made to linear analytical solutions as well as to published experimental results. Good agreement between the numerical solutions and measured values is found. For the modelling of a three dimensional wave diffraction problem, results at high wave amplitude are restricted because of the use of quadrilateral elements. The near cylinder region of the free surface is not considered to be well represented because of the coarse element size. Wave forces calculated on the vertical cylinder are found to be affected by the modelled tank length. When the simulated wave length is comparable to the wave tank's dimension, numerical results are found to be less than the experimental measurements. However, when the wave length is shorter than the tank's length, solutions are obtained with very good precision.Applied Science, Faculty of
Mechanical Engineering, Department of
Graduate
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Ebrahimi, Kumars. "Development of an integrated free surface and groundwater flow model." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/55912/.
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An integrated novel, two-dimensional, numerical groundwater-surface flow model has been developed to simulate hydro-environmental interactions between wetland areas, the neighbouring coastal waters and the groundwater passages. The main target in this research was to prepare a general linked model, which could be applied to different applications. For free surface flow modelling, an existing widely used two-dimensional, unsteady mathematical model, named the DIVAST model (Depth Integrated Velocities And Solute Transport model, developed originally by Falconer 1976) has been refined. However, in order to simulate the flow and solute transport in porous media, a two-dimensional model namely the GWK (Ground Water Key) has been developed to include an aquifer influenced by tidal currents. The GWK model is based on the transient flow Boussinesq equation as the governing equation for groundwater flow, and the advection-diffusion equation is used as the governing equation for contaminant transport. The model predicts the water table, the velocity components in the horizontal plane, the recharge/discharge levels for source/sink on the water table and solute tracer levels across the domain. The finite difference scheme used in this model is based upon the Alternating Direction Implicit (ADI) technique and using orthogonal grids. The structure of the GWK model is based on having a good relationship with the free surface flow model. The two sub-models (DIVAST-GWK) are linked by an interface, and flow and pollutants are able to pass across the interface in both directions, depending on the relative height of the water levels. A physical scale model has been constructed to provide experimental data of the groundwater transport between an idealised wetland and the adjacent coastal waters. However, in the dimensional analysis and designing of the physical model the Fleet Lagoon and adjacent coastal waters, in Dorset just west of Weymouth and the Isle of Portland UK, was chosen as a typical prototype. In the physical model the aim has been to study seepage behavior through the sand embankment by recording water levels on both sides of the sand, point velocity measurements, and the studies of a conservative dye tracer for constant water levels on one side of the embankment while running tidal cycle on the other side of the sand ridge. The integrated model has been verified using the laboratory data. Comparison between the experimental data and the simulated physical model, involving numerical linked model, showed that the integrated model was capable of simulating both phenomena, groundwater and free surface water, with a high level of accuracy.
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Parkinson, Steven. "Modelling free-surface flow with bathymetry variation using spectral methods." Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570859.
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Generation of electricity, by harnessing tidal currents with turbines, has the potential to contribute to a more sustainable future. However, knowledge of the fluid velocity, at a certain depth, is required in order to predict the available energy resource. Therefore, a modelling framework is described, which is computationally efficient, with only a few tunable parameters, and yields good results in comparison to experimental work and computational fluid dynamics. Existing approximate analysis methods, which describe fluid flow over varying topography are discussed. It is found that these theories are incapable of satisfying our objective. From field measurements of a tidal channel, a model is developed that describes turbulent free-surface flow over varying bathymetry. The flow is modelled using the steady incompressible two- dimensional shallow water equations. Turbulence closure is achieved using the eddy-viscosity model. The equations are solved using spectral methods. Convergence of the method is tested by varying the number of modes and the mixing parameterisation. A comparison with experimental work and a regional scale ocean circulation model, for free-surface flow over a ridge, is made. Close agreement is found using pseudo spectral methods. The Galerkin method does not achieve the same level of accuracy. In addition, numerical instability is found to occur on the downstream face of the ridge. However, provided the bathymetry gradients are sufficiently shallow, the solution procedure performs well. A three-dimensional model is achieved by calculating the two-dimensional depth-averaged flow through a tidal channel. Upon calculation of the streamlines from the depth-averaged flow solution, the vertical structure of the flow is calculated. The full flow profile can be obtained by piecing together outputs from each streamline. This is then compared to a one-dimensional hydraulic model where good agreement is found. Finally, flow for a real channel is computed.
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Abdalla, Ayad A. "Bilayer channel and free-surface thin film flow over topography." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/8819/.
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The work presented in this thesis focuses on gravity driven bilayer flow over a functional surface containing topography, with both liquids taken to be perfectly immiscible. Two such problems are considered and investigated systematically: (i) when the flow is confined between two rigid surfaces ("channel flow"); (ii) for the case of free-surface film flow down an inclined plane ("free-surface flow"). Both problems are underpinned by rigorous and comprehensive mathematical derivations, and the governing equation sets, resulting from application of the long-wave approximation, solved numerically using efficient and accurate finite difference algorithms programmed in C++. Such problems have received scant attention to-date. The channel flow work begins by revisiting the problem investigated by Lenz and Kumar (2007) and Zhou and Kumar (2012), to explore bilayer flow for the particular case of one Newtonian liquid lying above another and confined by rigid surfaces aligned parallel to each other, the lower one containing a steep-sided topographical feature. The investigation carried out serves a number of important purposes, the first being to establish the validity of the modelling and numerical approaches adopted, with the mesh independent results obtained found to be in excellent agreement with earlier work. In addition, the depth-averaged equation set derived in the thesis enables solutions to be obtained when the Reynolds number is non-zero, in contrast to the work of others which achieved only partial success. Finally, the situation when the upper wall of the channel is allowed to move horizontally with a constant speed, inducing a shear flow, is investigated for the first time. Bilayer free surface film flow over steep-sided topography, solutions to which have not been reported in the literature hitherto, is similarly investigated; comparisons having to be drawn for consistency and verification purposes with the case of single layer flow, Decré and Baret (2003), Gaskell et al. (2004), Veremieiev et al. (2010). Both zero and non-zero Reynolds number flow are considered and the governing equation sets and finite difference expressions re-derived to accommodate non-Newtonian behaviour, for the particular case of power-law liquids; it is found that for the latter case the associated depth-averaged equation set as formulated cannot be solved unless additional simplifications are adopted. In addition, for the case of Newtonian liquids, it is shown that the work can be extended to embody the more practical situation of three-dimensional bilayer film flow over topography. The mathematical model for this same film flow problem is extended to accommodate N layers, for the case when the Reynolds number is zero, with the derivation provided for completeness.
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McKibben, John Ferney. "A Computational fluid dynamics model for transient three-dimensional free surface flows." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/5790.
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Battista, Thomas Andrew. "Lagrangian Mechanics Modeling of Free Surface-Affected Marine Craft." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/82928.
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Although ships have been used for thousands of years, modeling the dynamics of marine craft has historically been restricted by the complex nature of the hydrodynamics. The principal challenge is that the vehicle motion is coupled to the ambient fluid motion, effectively requiring one to solve an infinite dimensional set of equations to predict the hydrodynamic forces and moments acting on a marine vehicle. Additional challenges arise in parametric modeling, where one approximates the fluid behavior using reduced-order ordinary differential equations. Parametric models are typically required for model-based state estimation and feedback control design, while also supporting other applications including vehicle design and submarine operator training.
In this dissertation, Lagrangian mechanics is used to derive nonlinear, parametric motion models for marine craft operating in the presence of a free surface. In Lagrangian mechanics, one constructs the equations of motion for a dynamic system using a system Lagrangian, a scalar energy-like function canonically defined as the system kinetic energy minus the system potential energies. The Lagrangian functions are identified under ideal flow assumptions and are used to derive two sets of equations. The first set of equations neglects hydrodynamic forces due to exogenous fluid motions and may be interpreted as a nonlinear calm water maneuvering model. The second set of equations incorporates effects due to exogenous fluid motion, and may be interpreted as a nonlinear, unified maneuvering and seakeeping model. Having identified the state- and time-dependent model parameters, one may use these models to rapidly simulate surface-affected marine craft maneuvers, enabling model-based control design and state estimation algorithms.Ph. D.
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Satheesh, Sukruth. "Hydrodynamics of flat plates in cross-flow near the free surface." Doctoral thesis, Universitat Rovira i Virgili, 2019. http://hdl.handle.net/10803/667080.
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Aquesta tesi presenta els resultats d'un estudi realitzat per comprendre l'efecte de la superfície lliure sobre les forces generades per una placa plana que es mou en un fluid estacionari, de manera que la superfície de la placa és perpendicular a la direcció d’empenta. El treball es basa en un estudi paramètric que inclou la relació d'aspecte, el nombre de Reynolds i la profunditat d'immersió mesurada com la distància entre la superfície lliure i la vora superior de la placa. S'han utilitzat mesures de força i tècniques de visualització quantitativa de flux. S'ha demostrat que les forces d'arrossegament augmenten bruscament just sota de la superfície lliure, essent l'augment més destacat en les plaques de baixa relació d'aspecte. L'augment abrupte en el coeficient d'arrossegament es deu a l'existència del flux que apareix entre la placa i la superfície lliure i que resulta en la formació d'una zona de recirculació prop de la base de la placa. En general, les tendències són independents del número de Reynolds, excepte quan les relacions d'aspecte estan en el rang de 0,75 a 1,33, amb la placa a prop de la superfície lliure.
Sukruth Satheesh
A més, s'han investigat dues configuracions de plaques diferents. En primer lloc, plaques rígides amb porositat en diferents ubicacions i, en segon lloc, flexibilitat estructural. Ambdós conceptes han resultat en una reducció significativa del coeficient d'arrossegament, especialment a prop de la superfície lliure. S'ha demostrat que el mecanisme de reducció d'arrossegament en models porosos es deu a la interacció entre els dolls formats en els orificis, les capes de cisalla i el flux que apareix entre la placa i la superfície lliure. Amb flexibilitat estructural, la reconfiguració de la plaça implica la reducció de l'arrossegament.Esta tesis presenta los resultados de un estudio realizado para comprender el efecto de la superficie libre sobre las fuerzas generadas por una placa plana que se mueve en el seno de un fluido estacionario, de manera que la superficie de la placa es perpendicular a la dirección de empuje. El trabajo se basa en un estudio paramétrico que incluye la relación de aspecto, el número de Reynolds y la profundidad de inmersión medida como la distancia entre la superficie libre y el borde superior de la placa. Se han usado medidas de fuerza y técnicas de visualización cuantitativa de flujo. Se ha demostrado que las fuerzas de arrastre aumentan bruscamente justo debajo de la superficie libre, siendo el aumento más prominente en las placas de baja relación de aspecto. El aumento abrupto en el coeficiente de arrastre se debe a la existencia de un flujo encauzado entre la placa y la superficie libre que resulta en la formación de una zona de recirculación cerca de la base de la placa. En general, las tendencias son independientes del número de Reynolds, excepto cuando las relaciones de aspecto están en el rango de 0.75 a 1.33, con la placa cerca de la superficie libre. Además, se han investigado dos configuraciones de placa diferentes. Primero, placas rígidas con porosidad en distintas ubicaciones y, en segundo lugar, flexibilidad estructural. Ambos conceptos han resultado en una reducción significativa del coeficiente de arrastre, especialmente cerca de la superficie libre. Se ha demostrado que el mecanismo de reducción de arrastre en modelos porosos se debe a la interacción entre los chorros formados en los orificios, las capas de cizalladura y el flujo que aparece entre la placa y la superficie libre. Con flexibilidad estructural, la reconfiguración de la placa implica la reducción del arrastre.
This thesis presents the results of a study conducted to understand the effect of free surface on forces generated by a flat plate being towed in a quiescent fluid, with the plate surface being normal to the towing direction. The work is based on a parametric study involving aspect ratio, Reynolds number and submergence depth, with the depth always being measured as the distance between free surface and the upper edge of the plate. Force and quantitative flow visualization techniques have been employed to understand the flow physics. It was found that the drag increases abruptly prior subsiding with increasing submergence depth, with this jump in drag being more prominent in low aspect ratio plates. The abrupt rise in the drag is due to the existence of a gap-flow at the free surface resulting in the formation of a recirculating flow in close proximity to the base region of plate. Overall, the trends are Reynolds number independent, except when the aspect ratios are in the range from 0.75 to 1.33, and the plate was near the free surface. Furthermore, two different plate configurations have been investigated. First, rigid plates with porosity at distinct locations and secondly structural flexibility. Both concepts have resulted in significant drag reduction, especially near the free surface. The mechanism of drag reduction for porous models has been shown to be due to the interaction between the jets formed at the holes, the shear layers and the gap-flow. With structural flexibility, reconfiguration leads to drag reduction.
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Kainyek, George Philip. "The simulation of three dimensional free surface flow around river structures." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422069.
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D'Agostino, Silvia. "Particle segregation and mixing in a dry free surface granular flow." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/317018.
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Geophysical massive flows as snow avalanches and debris flows are characterized by a wide grain size distribution. The interactions between particles among the granulometric classes are a consequent of a such large distribution. However, most of the studies on the geophysical massive flows assume the simplifying hypothesis of a constant granulometry. The aim of this work is studying the coexistence of two granulometric classes in statistically stationary and homogeneous conditions and investigating the physical processes responsible for the particles transfer. Experimental investigations using two different grain size classes were conducted to reproduce the two-phases mixture. The granular material was recirculated in a close system and the experiments were carried out in a laboratory flume having a loose two size
granular bed. A proper optical technique was innovatively improved to obtain the average and instantaneous values of the velocity and concentration from the side-walls. Through these values, the average particle profiles of velocity, concentration and granular temperature of the two solid fractions were computed. Moreover, the instantaneous values provide the average profiles of the second order correlation of the variables, such as the component of the granular temperature and the fluctuating components of the velocity and the concentration. The average distribution profiles in time of velocity and concentration prove the statistically stationary and homogeneous condition in a stretch sufficiently long of the running flow. Moreover, two types of regimes were identified: in case of low and intermediate discharges, the frictional regime nearly prevails at the free surface; for high discharges there is a coexistence across the flow depth of two regimes, the frictional regime in the intermediate flow-depth region and the collisional regime in the free surface. The existence of a vertical velocity component of both phases brings to hypothesize the presence of secondary circulations in the flow.
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D'Agostino, Silvia. "Particle segregation and mixing in a dry free surface granular flow." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/317018.
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Geophysical massive flows as snow avalanches and debris flows are characterized by a wide grain size distribution. The interactions between particles among the granulometric classes are a consequent of a such large distribution. However, most of the studies on the geophysical massive flows assume the simplifying hypothesis of a constant granulometry. The aim of this work is studying the coexistence of two granulometric classes in statistically stationary and homogeneous conditions and investigating the physical processes responsible for the particles transfer. Experimental investigations using two different grain size classes were conducted to reproduce the two-phases mixture. The granular material was recirculated in a close system and the experiments were carried out in a laboratory flume having a loose two size
granular bed. A proper optical technique was innovatively improved to obtain the average and instantaneous values of the velocity and concentration from the side-walls. Through these values, the average particle profiles of velocity, concentration and granular temperature of the two solid fractions were computed. Moreover, the instantaneous values provide the average profiles of the second order correlation of the variables, such as the component of the granular temperature and the fluctuating components of the velocity and the concentration. The average distribution profiles in time of velocity and concentration prove the statistically stationary and homogeneous condition in a stretch sufficiently long of the running flow. Moreover, two types of regimes were identified: in case of low and intermediate discharges, the frictional regime nearly prevails at the free surface; for high discharges there is a coexistence across the flow depth of two regimes, the frictional regime in the intermediate flow-depth region and the collisional regime in the free surface. The existence of a vertical velocity component of both phases brings to hypothesize the presence of secondary circulations in the flow.
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Wright, Alexander Mitchell. "Automated adaptation of spatial grids for flow solutions around marine bodies of complex geometry." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326861.
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Khyyer, Abbas. "Improved Particle Methods by Refined Differential Operator Models for Free-Surface Fluid Flows." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/66215.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第14147号
工博第2981号
新制||工||1442(附属図書館)
26453
UT51-2008-N464
京都大学大学院工学研究科都市環境工学専攻
(主査)教授 後藤 仁志, 教授 細田 尚, 准教授 牛島 省
学位規則第4条第1項該当
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Timberlake, Brian D. (Brian Davis). "Free-surface film flow of a suspension and a related concentration instability." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5145.
Full textAbstract:
Film flow of a suspension has been investigated both experimentally and theoretically. Gravity-driven free-surface inclined plane flow of a suspension of neutrally buoyant particles has been investigated using a stereoscopic particle imaging velocimetry technique. Particles have been shown to migrate away from the solid surface, and the film thickness has been shown to
decrease as the fluid moves down the inclined plane. The free surface has been characterized using a light reflection technique, which shows that surface topography is affected by the inclination angle, and the particle concentration.
This flow has been modeled based on a suspension normal stress approach. A boundary condition at the free surface has been examined, and model predictions have been compared with experimental results. The model predicts that the film thickness, relative to its initial value, will decrease with the bulk particle concentration.
The thin film flow over the inner cylinder in partially filled Couette flow of a suspension has been experimentally investigated as well as modeled. Concentration bands have been shown to form under a variety of different fill fractions, bulk particle concentrations, inclination angles, ratio of inner to outer cylinder, and rotation rates of the inner cylinder. The banding phenomena ranges from a regime where bands are small, mobile and relatively similar in concentration to the bulk, to a regime where
the concentration bands are larger, stationary, and where the space between them is completely devoid of particles.
The role of the film thickness in the band formation process has been investigated, and has led to a model for the band formation process based on a difference in the rate that fluid can drain from height fluctuations relative to the particles.
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Yilmaz, Burak. "Development And Validation Of Two-dimensional Depth-averaged Free Surface Flow Solver." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1089523/index.pdf.
Full textAbstract:
A numerical solution algorithm based on finite volume method is developed for
unsteady, two-dimensional, depth-averaged shallow water flow equations. The model
is verified using test cases from the literature and free surface data obtained from
measurements in a laboratory flume. Experiments are carried out in a horizontal,
rectangular channel with vertical solid boxes attached on the sidewalls to obtain freesurface
data set in flows where three-dimensionality is significant. Experimental data
contain both subcritical and supercritical states. The shallow water equations are
solved on a structured, rectangular grid system. Godunov type solution procedure
evaluates the interface fluxes using an upwind method with an exact Riemann solver.
The numerical solution reproduces analytical solutions for the test cases successfully.
Comparison of the numerical results with the experimental two-dimensional free
surface data is used to illustrate the limitations of the shallow water equations and
improvements necessary for better simulation of such cases.
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Lok, Tak-Shun Lawrence. "Analysis of smoothed particle hydrodynamics method for 2D free-surface flow applications." Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.599578.
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Norris, Stuart Edward. "A Parallel Navier Stokes Solver for Natural Convection and Free Surface Flow." University of Sydney. Engineering, 2001. http://hdl.handle.net/2123/376.
Full textAbstract:
A parallel numerical method has been implemented for solving the Navier Stokes equations on Cartesian and non-orthogonal meshes. To ensure the accuracy of the code first, second and third order differencing schemes, with and without flux-limiters, have been implemented and tested. The most computationally expensive task in the code is the solution of linear equations, and a number of linear solvers have been tested to determine the most efficient. Krylov space, incomplete factorisation, and other iterative and direct solvers from the literature have been implemented, and have been compared with a novel black-box multigrid linear solver that has been developed both as a solver and as a preconditioner for the Krylov space methods. To further reduce execution time the code was parallelised, after a series of experiments comparing the suitability of different parallelisation techniques and computer architectures for the Navier Stokes solver. The code has been applied to the solution of two classes of problem. Two natural convection flows were studied, with an initial study of two dimensional Rayleigh Benard convection being followed by a study of a transient three dimensional flow, in both cases the results being compared with experiment. The second class of problems modelled were free surface flows. A two dimensional free surface driven cavity, and a two dimensional flume flow were modelled, the latter being compared with analytic theory. Finally a three dimensional ship flow was modelled, with the flow about a Wigley hull being simulated for a range of Reynolds and Froude numbers.
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Wang, Jr-Ping. "Viscous free surface flow modelling using interface capturing methods on adaptive grids." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270183.
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Zhang, Yong. "Numerical Modelling of Layered Free Surface Flow Using the Finite Volume Method." Thesis, Manchester Metropolitan University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503739.
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Grandison, Scott. "Boundary integral equation techniques in protein electrostatics and free surface flow problems." Thesis, University of East Anglia, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410096.
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Norris, S. E. "A parallel Navier-Stokes solver for natural convection and free surface flow." Connect to full text, 2000. http://hdl.handle.net/2123/376.
Full textAbstract:
Thesis (Ph. D.)--University of Sydney, 2000.Title from title screen (viewed Apr. 23, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Dept. of Mechanical Engineering, Faculty of Engineering. Includes bibliography. Also available in print form.
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Timberlake, Brian D. "Free-surface film flow of a suspension and a related concentration instability." Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-03312004-220050/unrestricted/timberlake%5Fbrian%5Fd%5F200405%5Fphd.pdf.
Full textAbstract:
Thesis (Ph. D.)--Chemical Engineering, Georgia Institute of Technology, 2004.Ludovice, Peter, Committee Chair; Lee, Jay, Committee Member; Meredith, Carson, Committee Member; Morris, Jeff, Committee Member; Neitzel, Paul, Committee Member. Vita. Includes bibliographical references (leaves 120-123).
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Holmes, Rachel. "Disturbances to the uniform stream flow of a fluid with free surface." Thesis, Holmes, Rachel (2014) Disturbances to the uniform stream flow of a fluid with free surface. PhD thesis, Murdoch University, 2014. https://researchrepository.murdoch.edu.au/id/eprint/27338/.
Full textAbstract:
We consider two main problems involving disturbances to uniform stream flow. In the first part of the thesis we examine flow over topography with particular interest in obtaining subcritical solutions with no downstream waves. Solutions to the linearised, fully nonlinear and weakly nonlinear problem are computed for two different types of topography. An array of waveless solutions corresponding to one or more trapped waves are computed at a range of different Froude numbers and are shown to provide a rather elaborate mosaic of solution curves in parameter space. The free surface is shown to evolve into different shapes as we track these waveless contours through parameter space. In addition, for one type of bottom topography, certain values of the dimensionless flow rate and obstruction height are shown to have waveless solutions for almost all obstruction separation distances greater than some particular value. In the second part of the thesis we examine the flow past a line sink. We consider the fully nonlinear problem with the inclusion of surface tension and investigate the maximum sink strength for a given stream flow, before examining non-unique solutions. The addition of surface tension allows for a more thorough investigation into the characteristics of the solutions and produces some interesting results. The breakdown of steady solutions with surface tension appears to be caused by a curvature singularity as the flow rate approaches the maximum. The non-uniqueness in solutions is shown to occur for a range of parameter values in all cases with non-zero surface tension. The work involved in this thesis has application in design of submerged structures and water quality management in reservoirs.
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Lu, Dongqiang, and 盧東強. "Unsteady free-surface waves generated by bodies in a viscous fluid." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B29750787.
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Ali, Babar. "Finite Element Modelling of free-surface viscoelastic flow : theory and sample case studies." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/35282.
Full textAbstract:
In this thesis the development of a general finite element model for free surface viscoelastic flow is presented. The model uses the weighted residual finite element technique in conjunction with the VOF (volume of fluid) method in Arbitrary Lagrangian–Eulerian (ALE) and Eulerian frameworks for tracking free surface boundaries. Application of the developed model to two different case studies and obtained results are discussed and the capabilities of the model are demonstrated. The first case study is based on the simulation of an injection moulding process. The second case study is based on the modelling of a de-vulcanisation process used for recycling of rubber products.
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Doro, Emmanuel O. "Computational modeling of falling liquid film free surface evaporation." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44812.
Full textAbstract:
A computational model is developed to investigate fundamental flow physics and transport phenomena of evaporating wavy-laminar falling liquid films of water and black liquor. The computational model is formulated from first principles based on the conservation laws for mass, momentum, energy and species in addition to a phase transport equation for capturing interface deformation and evolution. Free surface waves are generated by monochromatic perturbation of velocity. Continuum models for interfacial evaporation define source terms for liquid vaporization and species enrichment in the conservation laws. A phenomenological crystallization model is derived to account for species depletion due to salt precipitation during black liquor falling film evaporation. Using highly resolved numerical grids on parallel computers, the computational model is implemented to analyze the dynamics of capillary separation eddies in low Reynolds number falling films, investigate the dominant mechanisms of heat transfer enhancement in falling films at moderately high Reynolds numbers and study the fundamental wave structures and wave induced transport in black liquor falling films on flat and cylindrical walls. From simulation results, a theory based on the dynamics of wavefront streamwise pressure gradient is proposed to explain interfacial waves interaction that give rise to multiple backflow regions in films dominated by solitary-capillary waves. The study shows that the mechanism of heat transfer enhancement in moderately high Reynolds number films follows from relatively lower conduction thermal resistance and higher crosswise convective transport at newly formed intermediate wavefronts. Interfacial phenomena such as wave-breaking and vapor entrainment observed in black liquor falling films is explained in terms of a mechanistic theory based on evolution of secondary instabilities and large amplitude wave force imbalances.
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Brocchini, Maurizio. "Flows with freely moving boundaries : the swash zone and turbulence at a free surface." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336872.
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You, Soyoung Ph D. Massachusetts Institute of Technology. "Finite element solution of interface and free surface three-dimensional fluid flow problems using flow-condition-based interpolation." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97845.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 103-106).
The necessity for a highly accurate simulation scheme of free surface flows is emphasized in various industrial and scientific applications. To obtain an accurate response prediction, mass conservation must be satisfied. Due to a continuously moving fluid domain, however, it is a challenge to maintain the volume of the fluid while calculating the dynamic responses of free surfaces, especially when seeking solutions for long time durations. This thesis describes how the difficulty can be overcome by proper employment of an Arbitrary Lagrangian Eulerian (ALE) method derived from the Reynolds transport theorem to compute unsteady Newtonian flows including fluid interfaces and free surfaces. The proposed method conserves mass very accurately and obtains stable and accurate results with very large solution steps and even coarse meshes. The continuum mechanics equations are formulated, and the Navier-Stokes equations are solved using a 'flow-condition-based interpolation' (FCBI) scheme. The FCBI method uses exponential interpolations derived from the analytical solution of the 1-dimensional advection-diffusion equation. The thesis revisits the 2-dimensional FCBI method with special focus on the application to flow problems in highly nonlinear moving domains with interfaces and free surfaces, and develops an effective 3-D FCBI tetrahedral element for such applications. The newly developed 3-D FCBI solution scheme can solve flow problems of a wide range since it can handle highly nonlinear and unsteady flow conditions, even when large mesh distortions occur. Various example solutions are given to show the effectiveness of the developed solution schemes.
by Soyoung You.
Ph. D.
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Carmona, Vasquez Leonardo R. "Numerical Modeling of Lifting Flows in the Presence of a Free Surface." ScholarWorks@UNO, 2012. http://scholarworks.uno.edu/td/1426.
Full textAbstract:
This thesis work started as an attempt to create a computational tool to model hydrodynamics problems involving lifting flows. The method employed to solve the problem is potential flow theory.
Despite the fast evolution of computers and the latest developments in Navier-Stokes solvers, such as the Ranse methods; potential flow theory offers the possibility to create or use existing computational tools, which allow us modeling hydrodynamics problems in a simpler manner. Navier-Stokes solver can be very expensive from the computational point of view, and require a high level of expertise in order to achieve reliable models.
Based on the above, we have developed a lifting flow modeling tool that we hope can serve as the starting point of a more elaborated method, and a valuable alternative, for the solution of different hydrodynamics problems.
Key words highlighting important concepts related to this thesis work are: Vortex, circulation, potential flow, panel methods, Sources, doublets.
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Buttle, Nicholas. "An efficient numerical scheme for free-surface flow over a three-dimensional bottom topography." Thesis, Queensland University of Technology, 2018. https://eprints.qut.edu.au/117145/1/Nicholas_Buttle_Thesis.pdf.
Full textAbstract:
This thesis uses mathematical and computational modelling to explore water wave patterns that form on the surface of a stream when subject to some sort of wave-making disturbance. While a range of geometries are considered, the focus is on flow over a bottom topography that involves localised bumps. From a computational perspective, the key challenge is to solve the full governing equations using a sufficiently fine mesh to provide accurate solutions. To this end, we use a boundary integral approach together with a technique called a Jacobian-free Newton Krylov method. We present a range of numerical results and highlight the role of nonlinearity in three-dimensional water waves patterns.
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Mead, Ryan M. "Analysis of Flow in a Spray Nozzle With Emphasis on Exiting Jet Free Surface." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000138.
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Rouse, Victoria J. "Comparison of heat transfer and fluid flow characteristics between submerged and free surface jet impingement for two-phase flow." Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1546428292091476.
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Koski, Samuel Robert. "Free Surface Penetration of Inverted Right Circular Cones at Low Froude Number." Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/77036.
Full textAbstract:
In this thesis the impact of inverted cones on a liquid surface is studied. It is known that with the right combination of velocity, geometry, and surface treatment, a cavity of air can be formed behind an impacting body and extended for a considerable distance. Other investigators have shown that the time and depth of the cone when this cavity collapses and seals follows a different power law for flat objects such as disks, then it does for slender objects such as cylinders. Intuitively it can be expected that a more slender body will have less drag and that the streamlined shape will not push the fluid out of it's way at impact to the same extent as a more blunt body, therefore forming a smaller cavity behind it. With a smaller initial cavity, the time and depth of it's eventual collapse can be expected to be less than that of a much more blunt object, such as a flat disk.
To study this, a numerical model has been developed to simulate cones with the same base radius but different angles impacting on a liquid surface over a range of velocities, showing how the seal depth, time at cavity seal, and drag forces change. In order to ensure the numerical model is accurate, it is compared with experimental data including high speed video and measurements made of the force with time.
It is expected that the results will fall inside the power law exponents reported by other authors for very blunt objects such as disks on one end of the spectrum, and long slender cylinders on the other. Furthermore, we expect that the drag force exerted on the cones will become lower as the L/D of the cone is increased.Master of Science
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Chung, Peter Mang-Yu. "An experimental investigation of free-surface structures in turbulent channel flow at low Reynolds numbers." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0013/MQ40904.pdf.
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Stavrev, Atanas [Verfasser]. "NURBS-Enhanced Geometry Handling for Free-Surface Flow Problems and Immersed Boundary Methods / Atanas Stavrev." München : Verlag Dr. Hut, 2016. http://d-nb.info/1113335335/34.
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King, A. C. "Application of a generalised Schwarz-Christoffel transformation of some problems of steady free surface flow." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233284.
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Ikram, Zaheer. "Numerical investigation of the effects of free-surface flow past submerged bluff and streamlined bodies." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8477.
Full textAbstract:
The last decade has been marked by a continuous growth in computational power, which has allowed for elaborate modelling techniques like LES and DES applied at engineering scales which generally imply a Reynolds number in excess of 1×106. One field that has seen a rapid growth in use of numerical methods in design and performance analysis is the naval sector, especially in the design of submarines where the free-surface boundary plays an important role. This thesis is devoted to the study of free-surface flow past submerged bodies, with the objective of numerically studying free-surface flow past a submarine fairwater at periscope depth near actual operating conditions. This work is motivated by DSTL, who have reported that near periscope depth submarines exhibit an increased drag (private communication). In this work both LES and DES modelling approaches are also utilized, while the submerged body is accounted through the use of an immersed boundary method and the free-surface is through the use of a part moving mesh. The thesis is split in two main parts. The first part of the thesis focuses on low and moderate Reynolds number flow about a submerged cube (bluff body) for various submergence depths. Two configurations are examined one being that of a single cube in a uniform flow, while the other is that of a matrix of equally spaced cubes. Results show that for both cases a reduction in submergence depth causes the forces, the fluctuation in the forces and shedding frequencies to alter, while the level of interaction between vortices and free-surface to increase. The second part of this thesis focuses on the main study of free-surface flow past a submerged fairwater at a high and near operating Reynolds number. It is found that for both Reynolds numbers the flow behaviour shows little change, while the effects of reducing submergence depth results in the forces, the force variation and shedding frequency to increase. Surface waves are found to disperse by an angle of up to 40° for all submergence depth and are of the Kelvin wave kind. No direct interaction between vortical structures shed from the fairwater and free-surface are found, whilst the increases in forces acting on the fairwater are directly attributed due to wave motion.