Dissertations / Theses on the topic 'Gravity currents'
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Shin, Jonathan Oswald. "Colliding gravity currents." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/251821.
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Hang, Alice Thanh. "Intrusive gravity currents." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1461003.
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Thesis (M.S.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed February 6, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 61-63).
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Ross, Andrew Neil. "Gravity currents on slopes." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621127.
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Ahmed, Dhafar Ibrahim. "Experimental and numerical study of model gravity currents in coastal environment : bottom gravity currents." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0060/document.
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Le but de ce travail de recherche est de contribuer à une meilleure compréhension de la dynamique de propagation et de la miscibilité de jets gravitaires au-dessous d’un liquide ambiant. Des expériences ont été réalisées en laboratoire à l’aide d’une plateforme expérimentale constituée d’un bassin parallélépipédique contenant de l’eau douce et d’un canal d’injection de section rectangulaire de jets gravitaires de concentration constante initiale fixée. Les calculs mathématiques et numériques sont basés sur les modèles RANS (Reynolds-Averaged Navier Stokes equations), k-ε (K-epsilon) et DCE (Diffusion-Convective Equation) de la fraction volumique de l’eau salée pour décrire la propagation et le mélange du jet gravitaire. L’évolution du front du jet obtenue expérimentalement est utilisée pour valider le modèle numérique. Par ailleurs, la comparaison des résultats obtenus sur l’écoulement moyen (z⁄z0.5 =U/Umax) avec ceux des études 2D expérimentales et numériques antérieures ont montré des similarités. La simulation numérique des champs hydrodynamiques montre que la vitesse maximale est atteinte à la position 0.18 z0.5, où z0.5 est la hauteur d’eau pour laquelle la vitesse moyenne u est égale à la moitié de la vitesse maximale UmaxThe aim of this investigation is to contribute to a better understanding of the propagation dynamics and the mixing process of dense gravity currents. The Laboratory experiments proceeded with a fixed initial gravity current concentration in one experimental set-up. The gravity currents are injected using a rectangular injection channel into a rectangular basin containing the ambient lighter liquid. The injection studied is said in unsteady state volume, as the Reynolds number lies in the range 1111 - 3889. The experiments provided the evolution of the boundary interface of the jet, and it is used to validate the numerical model. The numerical model depends on the Reynolds-Averaged Navier Stokes equations (RANS). The k-ε (K-epsilon) and the Diffusion-Convective Equation (DCE) of the saline water volume fraction were used to model the mixing and the propagation of the gravity current jet. On the other hand, comparison of the mean flow (z⁄z0.5 =U/Umax) with previous two-dimensional numerical simulations and experimental measurements have shown similarities. The numerical simulations of the hydrodynamic fields indicate that the velocity maximum at 0.18 z0.5, where z0.5 is the height at which the mean velocity u is the half of the maximum velocity Umax
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Hacker, Jacob. "Gravity currents in rotating channels." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426506.
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Slim, Anja Catharina. "High Reynolds number gravity currents." Thesis, University of Cambridge, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.614096.
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Golding, Madeleine Jane. "Gravity currents in porous media." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608091.
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Zgheib, Nadim. "Gravity currents from non-axisymmetric releases." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/13941/1/zgheib.pdf.
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Gravity currents are buoyancy driven flows that appear in a variety of situations in nature as well as industrial applications. Typical examples include avalanches, oil spills, and turbidity currents. Most naturally occurring gravity currents are catastrophic in nature, and therefore there is a need to understand how these currents advance, the speeds they can attain, and the range they might cover. This dissertation will focus on the short and long term evolution of gravity currents initiated from a finite release. In particular, we will focus attention to hitherto unaddressed effect of the initial shape on the dynamics of gravity currents. A range of parameters is considered, which include the density ratio between the current and the ambient (heavy, light, and Boussinesq currents), the initial height aspect ratio (height/radius), different initial cross-sectional geometries (circular, rectangular, plus-shaped), a wide range of Reynolds numbers covering 4 orders of magnitude, as well as conservative scalar and non-conservative (particle-driven) currents. A large number of experiments have been conducted with the abovementioned parameters, some of these experiments were complemented with highly-resolved direct numerical simulations. The major outcome is that the shape of the spreading current, the speed of propagation, and the final deposition profile (for particle-driven currents) are significantly influenced by the initial geometry, displaying substantial azimuthal variation. Especially for the rectangular cases, the current propagates farther and deposits more particles along the initial minor axis of the rectangular cross section. This behavior pertaining to non-axisymmetric release is robust, in the sense that it is observed for the aforementioned range of parameters, but nonetheless cannot be predicted by current theoretical models such as the box model, which has been proven to work in the context of planar and axisymmetric releases. To that end, we put forth a simple analytical model (an extension to the classical box model), well suited for accurately capturing the evolution of finite volume gravity current releases with arbitrary initial shapes. We further investigate the dynamics of a gravity current resulting from a finite volume release on a sloping boundary where we observe some surprising features.
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Rachel, Zammett Rachel Zammett. "Gravity Currents on Earth and Mars." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491681.
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In this thesis we ~nvestigate three problems in the earth sciences where gravity currents play an important role. In the first part we consider two types of terrestrial gravity current: kata- . batic winds and submarine turbidity currents. We derive and solve the classical Prandtl model for katabatic wind flow in which the vertical wind profile is resolved. We show that this model breaks down when the slope becomes small, and pose a~ improved model which removes this singularity. Solutions of the improved model are compared with observations and output from a numerical model. We then investigate two layer-averaged models that are used to describe the flow of submarine turbidity currents. We find that both models predict that in some circumstances 'ignition' can occur, in which the current velocity becomes unbounded. We show that the only way this phenomenon can be prevented is by a decrease in the underlying slope. In the second part, we consider the unusual morphology of the Martian north polar ice cap. We use a model for the sublimation kinetics at the ice-atmosphere interface and include an explicit description of dust, both suspended in the atmosphere and frozen within the ice cap. Thansport of dust and ice are then included, and the model is investigated analytically and numerically. We find that this model can have multiple steady states, and that troughs may form during a transition between steady states. In this model, such a transition may be caused by obliquity-induced climate change.
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Montgomery, Patrick James. "Shallow-water models for gravity currents." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/NQ46888.pdf.
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Hoyes, James Russell. "Homogeneous and Particle-Driven Gravity Currents." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515344.
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Tanino, Yukie 1980. "Aquatic gravity currents through emergent vegetation." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/26712.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaves 109-112).
Differential heating and cooling can generate density-driven, lateral exchange flows in aquatic systems. Despite the ubiquity of wetlands and other types of aquatic canopies, few studies have examined the hydrodynamic effects of aquatic vegetation on these currents. This study investigates the dynamics of lock-exchange flows, a particular class of density currents, propagating through rigid emergent vegetation. First, previous mathematical formulation is extended to develop theoretical models of vegetated lock-exchange flows. The regime in which stem drag is inversely proportional to velocity is considered as a special case. Lock-exchange flows were generated in a laboratory flume with rigid cylindrical dowels as model vegetation. Experimental observations were consistent with the theory. Under high stem drag or low stem Reynolds number conditions, the interface deviated from the well-documented block profile associated with unobstructed lock-exchange flows and approached a linear profile. Criteria are developed to categorize all flow conditions as inertial or non-inertial and the interface profile as linear, transitional, or non-linear, respectively, based on (a) the evolution of the velocity of the leading edge of the undercurrent and (b) the interface shape. Finally, the present model is enhanced to account for wind forcing and bed friction to better describe conditions found in nature. The theory highlights the sensitivity of currents to wind forcing.
by Yukie Tanino.
S.M.
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Zhao, Benzhong. "Interface pinning of CO₂ gravity currents." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74498.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 41-43).
Carbon capture and storage (CCS) is widely regarded as a promising tool for reducing global atmospheric carbon dioxide (CO₂) emissions, while allowing continued use of fossil fuels in the 21st century. In CCS, CO₂ is captured at point sources such as coal power plants and injected deep underground in geological formations like saline aquifers for long-term storage. Given the large scale of CCS required to significantly reduce anthropogenic CO₂ emissions into the atmosphere, it is critical to understand the migration of CO₂ after injection, so that we can design effective injection strategies to minimize the leakage risks of CO₂ . Recent studies have demonstrated that simple models that incorporate the essential physics involved in CO₂ storage are able to make significant contributions in addressing important questions such as storage capacity and leakage risks in large scale CO₂ sequestration projects. Here, we study the impact of capillarity on the migration of CO₂ plume through exchange flow experiments of immiscible fluids. We show that capillarity leads to the development of striking features not present in miscible exchange flows, including a vertical pinned interface and sharp corners. We show that interface pinning is caused by capillary pressure hysteresis, and the amount of pinning scales with the relative strength of capillarity relative to gravity, as measured by the inverse of the Bond number. We demonstrate that capillary pressure hysteresis in porous media is caused by the fundamental difference in pore-scale invasion patterns between drainage and imbibition. In addition, we propose a sharp interface gravity current model that incorporates capillary pressure hysteresis and quantitatively explains the experimental observations, including the x ~ t1/2 spreading behavior at intermediate times and the fact that capillarity stops the spreading of a finite release current. These results suggest that interface pinning has important implications in the migration of CO₂ plume in deep saline aquifers.
by Benzhong Zhao.
S.M.
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Harris, Thomas Clive. "Homogeneous and particle-driven gravity currents." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624500.
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Li, Ming. "Models for gravity currents in stratified fluids." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291279.
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Sansom, Ahmos. "Spreading gravity currents with temperature-dependent viscosity." Thesis, University of Nottingham, 2000. http://eprints.nottingham.ac.uk/14140/.
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The spreading of a fluid under gravity has many important industrial and geophysical applications and has been the focus of much research. Variations in the thermal properties of the fluid have often been neglected. This thesis introduces a series of models incorporating fluids having temperature-dependent viscosity and vertical cross-sectional profile of small aspect ratio to show the important effects that cooling can have on the flow field. The numerical results show features that are commonly observed in experiment and lava dome growth, such as plateauing and fingering.
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Harichandran, Puveedran. "Propagating gravity currents in a turbulent fluid." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620514.
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Robinson, Tristan Oliver. "Gravity currents in the presence of water waves." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445076/.
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This thesis describes a laboratory study on the effect of free surface progressive waves on high Reynolds number gravity currents generated by instantaneous release of finite volumes of dense homogeneous fluid. The waves and gravity currents are studied as two-dimensional and the flows across the width of the flume are assumed to be constant. The engineering applications of this investigation will provide an insight into the processes by which dredging plumes are dispersed and flows propagate into estuaries at the coastline. This investigation examines the process at a fundamental level and gives a summary of the key characteristics and trends of the gravity current in the marine environment. This work has been carried out in the wave current flume at UCL using a number of advanced flow measuring techniques such as Laser Doppler Velocimetry to measure the orbital velocities of the waves and Particle Image Velocimetry to measure the internal dynamics of the gravity current. The position and density profiles of the gravity current were measured using digital images. In a static environment a gravity current spreading in two directions has symmetry in shape and distance from the point of release. In the presence of waves, the gravity current fronts propagate with and against the wave direction. The wave motion induces an asymmetry in the shape and rate of propagation of the gravity current fronts. Under certain wave conditions the overall length of the gravity current is found to be unchanged by the presence of the waves and the characteristics of the gravity current are similar to the case in static ambient water. However, in some cases the overall distance is severely modified by the wave motion. In addition to modifying the propagation rate of the gravity current the wave-induced mean flow modifies the profile of the gravity current head. The direction of the gravity current relative to the wave motion is vital in determining the rate of dispersion and the height of the density current.
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Barrass, Timothy Adam. "Dynamics and sedimentation from axisymmetric, polydisperse gravity currents." Thesis, University of Bristol, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288282.
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Samasiri, Peeradon. "Mixing in axisymmetric gravity currents and volcanic conduits." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/280120.
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The first part of this thesis investigates the mixing of ambient fluid into axisymmetric high Reynolds number gravity currents. A series of laboratory experiments were conducted in which small scale gravity currents travelled along a wedge shaped channel with an increasing width in the downstream direction. The channel was filled with fresh water and the current was generated using saline solution introduced either by a rapid release of a known finite volume from behind a lock gate or by pumping at a constant rate into the apex of the channel. The distribution and evolution of the density of the flow with distance downstream was measured using a light attenuation technique. Additional experiments were performed by injecting parcels of dye in different regions of the flow in order to visualise the motion of fluid in and surrounding the gravity current. Unlike currents introduced by the release of a finite volume of fluid, where most mixing occurs in the head of the flow, currents produced from a steady source develop a steady tail region behind the front which is also found to entrain a significant amount of ambient fluid. In both types of current, we estimate the fraction of displaced ambient fluid that is entrained into the flow. We then derive a new class of self-similar solutions for gravity currents produced from a finite volume release of fluid. The second part of this thesis develops the experimental method of measuring mixing using light attenuation to investigate the mixing of liquid in a vertical conduit which results from a continuous stream of high Reynolds number gas bubbles. The experiments identify that the mixing in the wake of the bubbles leads to a net dispersive transport along the conduit. The process provides an explanation for the heat transfer within a volcanic conduit in the case of a gas-slug flow regime as occurs in the near surface region of volcanic conduits connected to surface lava lakes. We derive a theoretical model to estimate the heat flux associated with such a system using the empirical law for the dispersive mixing. The predicted heat flux associated with the bubbles is found to be comparable to the heat loss at the surface of lava lakes associated with radiative and convective heat loss. Given values for the gas flux, the lake area and the temperature at the surface of the lake, the model enables new predictions for the size of the volcanic conduit.
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McBryde, J. D. "Experimental and numerical modelling of gravity currents preceding backdrafts /." Christchurch, N.Z. : Dept. of Civil Engineering, University of Canterbury, 2008. http://digital-library.canterbury.ac.nz/data/collection3/etd/adt-NZCU20080116.132247/.
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"A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering in Fire Engineering."Includes bibliographical references (p. 209-215). Also available via the World Wide Web.
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Ieong, Ka Kit. "Investigation on gravity currents with laser induced fluorescence technique." Thesis, University of Macau, 2005. http://umaclib3.umac.mo/record=b1445815.
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Gregorio, Sandy O. "Investigation on the dynamics of gravity-driven coastal currents." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/47656/.
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Numerical simulations of buoyant, gravity-driven coastal plumes are summarized and compared to the inviscid geostrophic theory of Thomas & Linden (2007) and to laboratory studies for plumes owing along a vertical-wall coastline (those of Thomas & Linden (2007) and additional experiments performed at Warwick University). In addition, results of two new laboratory studies with different scales for plumes owing along a more realistic inclined-wall coastline are presented and compared to an extended theoretical model from the geostrophic theory of Thomas & Linden (2007). The theoretical and experimental results for plumes flowing along inclined-wall coastlines are compared to the inclined-wall experimental studies of Avicola & Huq (2002), Whitehead & Chapman (1986) and Lentz & Helfrich (2002), to the inclined-wall scaling theory of Lentz & Helfrich (2002), and to oceanic observations. The lengths, widths and velocities of the buoyant gravity currents are studied. Agreement between the laboratory and numerical experiments, and the geostrophic theories for both vertical-wall and inclined-wall studies is found to depend mainly on one non-dimensional parameter which characterizes the strength of horizontal viscous forces (the horizontal Ekman number). The best agreement between the experiments and the geostrophic theories is found for plumes with low viscous forces. At large values of the horizontal Ekman number, laboratory and numerical experiments depart more significantly from theory (e.g., in the plume propagation velocity). At very low values of the horizontal Ekman number (obtained in the large-scale inclined-wall experimental study only), departures between experiments and theory are observed as well. Agreement between experiments and theory is also found to depend on the steepness of the plumes isopycnal interface for the vertical-wall study, and on the ratio between the isopycnal and coastline slopes for the inclined-wall study.
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McBryde, James David. "Experimental and Numerical Modelling of Gravity Currents Preceding Backdrafts." Thesis, University of Canterbury. Civil and Natural Resources Engineering, 2008. http://hdl.handle.net/10092/1219.
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This study investigates the turbulent mixing within gravity currents preceding backdrafts and validates the ability of the computational fluid dynamics (CFD) software Fire Dynamics Simulator version 4 (FDS) to simulate these flows. Backdrafts are rapid deflagrations, which occur after the introduction of oxygen into compartments containing unburned gaseous fuel. They may form large fireballs out of the compartment opening and present a significant hazard to the safety of fire-fighters. Gravity currents which precede backdrafts are responsible for the formation of flammable gas mixtures required for ignition. Scale saltwater modelling is used to generate Boussinesq, fully turbulent gravity currents for five different opening geometries, typical of fire compartments. Width-integrated concentration fields and two-dimensional velocity fields are generated using the non-intrusive light attenuation (LA) and particle tracking velocimetry (PTV) flow visualisation techniques respectively. Numerical simulations are carried out with FDS to replicate these flows. The experimental and numerical results are compared directly. Front velocities are shown to be governed directly by local buoyancy conditions, in the later stages of the flows, and therefore the initial conditions associated with the opening geometries only influence the front velocities indirectly. The internal concentration structure, internal velocity structure and location of potential flammable regions are found to be highly opening geometry dependent. In general, the results of the numerical simulations are quantitatively similar to those from experiment, which suggests that the numerical model realistically predicted the experimental flows. However, the numerical concentration fields appear slightly lumpier than those from the experiments, possibly due to unresolved turbulence on scales smaller than the numerical grid (0.01H, where H = compartment height).
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Corney, Ransome Kyle Tyrone. "Numerical, analytical & experimental modelling of channelised gravity currents." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426853.
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Mathunjwa, Jochonia S. "Self-similarity in inertial and porous media gravity currents." Thesis, University of Bristol, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414181.
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Ohata, Koji. "Formation conditions of bedforms under sediment-laden gravity currents." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263478.
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Anjum, Hafiz Junaid. "Numerical modelling of compositional and particle-driven turbulent gravity currents." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708453.
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Doyle, Emma EsmeÌ. "Analogue and numerical modelling of gravity currents and pyroclastic flows." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.443693.
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Tokyay, Talia Ekin. "A LES study on gravity currents propagating over roughness elements." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/610.
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Predicting the evolution of turbulent gravity currents is of great interest in many areas of geophysics and engineering, in particular due to their impact on the environment. In most practical applications in river, coastal and ocean engineering, gravity currents propagate over loose surfaces containing large scale bedforms (e.g., dunes). In others, arrays of obstacles (e.g., ribs) are often used as protective measures on hilly terrains to stop or slow down gravity currents in the form of powder-snow avalanches. To predict the capacity of a turbulent gravity current propagating over a loose bed to entrain, carry, and deposit sediment requires a detailed understanding of its structure and the role played by the large-scale instabilities present in the flow.
The present study uses high-resolution Large Eddy Simulation to study the physics of high Reynolds number compositional Boussinesq gravity currents with large and small volume of release in lock-exchange configurations and their dynamic effects on various obstacles (e.g., bedforms, flow retarding obstacles, submerged dams that are used to control sediment deposition in reservoirs). The study shows that gravity currents propagating over large-scale roughness elements reach a turbulent drag-dominated regime in which the front velocity decays proportional to t-1/2, similar to the case of gravity currents propagating within a porous medium. Though the establishment of a regime in which the flow evolution is mainly determined by the balance between the turbulent drag and the buoyancy force driving the flow was expected, the fact that the law of decay of the front velocity with time is identical for gravity currents propagating over roughness elements and in a porous medium of uniform porosity is not obvious.
The simulations provide detailed information on the temporal evolutions of the front velocity, energy balance, sediment entrainment capacity and the flow instabilities, and of the distributions of the density, velocity, local dissipation rate and bed shear stresses at different stages of the propagation of the gravity current. The study investigates of the effect of the shape and relative size of the obstacles, with respect to the current height, on the structure of the current and on the differences with the simpler, but much more widely studied case of a gravity current propagating over a flat smooth surface. For example, the simulation results are used to explain why gravity currents propagating over dunes have a much larger capacity to entrain sediment than gravity currents propagating over ribs of the same height and with similar spacing.
The accurate estimation of impact of gravity current on the structures over its path is very important from engineering point of view since many submerged cables over the ocean bottom or submerged dams in reservoirs are under the risk of such impacts. The simulations of gravity currents propagating past arrays of ribs or isolated dams are used to estimate the characteristic times and magnitudes of the hydrodynamic impact forces on these obstacles. This information is crucial for the proper design of these structures. The study shows the critical role played by flow disturbances (e.g., backward propagating hydraulic jumps) that form as a result of the interaction between the current and the large-scale obstacles. Finally, the study investigates scale effects between the Reynolds numbers at which most experimental investigations of gravity currents are conducted and Reynolds numbers at field scale.
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Flitton, Jonathan C. "Inertia dominated spreading of thin films." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369039.
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Holland, Dwight Allen. "Tidal gravity anomalies in southeastern North America." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/53101.
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Tidal variations of gravity were measured at fourteen sites in southeastern North America for periods of between 40 and 199 days. These measurements were used to obtain tidal gravity anomalies that indicate the geologic effect of the earth on tidal gravity. The tidal gravity anomaly is a vector quantity representing the difference between measured tidal gravity and the theoretical tidal gravity on a spherically symmetrical earth model subject to ocean tidal loading. The real part of the anomaly vectors include 8 values in the range of ±0.5 microgals, 4 values in the range of 0.5 to 1.5 microgals, 1 value of 1.5 to 2.5 microgals, and 1 other value in the range of -0.5 to -1.5 microgals, This grouping is consistent with a worldwide distribution of values from regions where the asthenosphere is at intermediate depth, the stress conditions are not excessive, and geothermal heat flow is approximately 60 mW/m².Master of Science
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Gerber, George. "Experimental measurement and numerical modelling of velocity, density and turbulence profiles of a gravity current." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/841.
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Trulsen, Karsten. "The influence of currents, long waves and wind on gravity-capilary." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36558.
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Jackson, Andrew. "Scaling for lobe and cleft patterns in particle-laden gravity currents." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14237/.
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Lobe and cleft patterns are frequently observed at the leading edge of gravity currents, including non-Boussinesq particle-laden currents such as powder snow avalanches. Despite the importance of the instability in driving air entrainment, little is known about its origin or the mechanisms behind its development. In this work we seek to gain a better understanding of these mechanisms from a laboratory scale model of powder snow avalanches using lightweight granular material. The instability mechanisms in these flows appear to be a combination of those found in both homogeneous Boussinesq gravity currents and unsuspended granular flows, with the size of the granular particles playing a central role in determining the wavelength of the lobe and cleft pattern. When scaled by particle diameter a relationship between Froude number and the wavelength of the lobe and cleft pattern is found, where the wavelength increases monotonically with Froude number. This relationship, in addition to Particle Image Velocimetry analysis, provides evidence for the existence of pairs of counter-rotating vortices at the leading edge of these currents, which play a key role in the development of the lobe and cleft pattern. The internal pressure of these flows is found to scale with the dynamics of the large vortex-like structure that is observed within the head of the current.
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Lingel, Sherrill Lee. "Scaling effects on the mixing processes of lock-exchange gravity currents /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/10149.
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Batt, Rachel Louise. "The influence of bed roughness on the dynamics of gravity currents." Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/11282/.
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To date the influence of bed roughness onl the propagation and dynamics of gravity currents has been largely neglected. A new physical modelling dataset has been compiled, which details the fundamental affects of several bed roughnesses on lock-release gravity currents. Five bed configurations were chosen encompassing 'grain' and 'form' type elements at a range of spacings. 1%, 5% and 10% initial density excesses were studied and the effect of removing the buoyant ambient fluid between the elements examined. Observations due to changing the current depth relative to the element height were also made. Ultrasonic Doppler velocimetry profiling (UDVP) and video capture techniques were used to analyse stream wise and vertical velocity structures and the affects on the front speed and distance travelled by the current. A 10 depth-averaged model solves modified 2-layer shallow water equations using the method of characteristics to obtain temporal velocity and depth evolution for a current under the influence of a general roughness quantity. 2D and 3D depth-resolved CFD simulations use the commercial software FLUENT to solve the RANS equations and transport of a scalar for the dense current with the RNG k - € turbulence model. The CFD predictions were well validated by the new experimental dataset and provide supplementary predictions of concentration, lateral motion and activity in the vicinity of the roughness elements. Comparison of 20 and 30 models resulted in the conclusion that the 3D model is vital for accurate simulation of internal dynamics of gravity current propagation over beam type bed roughness. In general general, the distance that the front travels decreases with any bed roughness present. This reduction increases with element spacing. The stream wise mean velocity profiles show a reduced velocity maximum further from the bed. Decreased entrainment results from breakdown of larger billows. Also observed is a thicker current, a rounder profile and a shorter, diluted head. Areas of increased vertical motion within the current. associated with decreased horizontal motion are observed, indicative of ejections of ambient fluid from between the elements. The presence of this fluid is found to contribute to ~ 50% of the current retardation. There are also similarities with the effects of bed roughness in open channel and pipe flows, most notably there is a critical element spacing (11'/ kr ~ 7) where the effects of roughness are greatest (where w is element spacing and kr is element height). The experimental and numerical results demonstrate that the application of existing models that rely on experimental validation with smooth beds to situations where a rough boundary is present may lead to significant errors.
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Matson, Gary Paul. "Low Reynolds number, gravity currents : Newtonian exchange and viscoplastic dam break flows." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437303.
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Ooi, Seng Keat. "High resolution numerical simulations of lock-exchange gravity-driven flows." Diss., University of Iowa, 2006. http://ir.uiowa.edu/etd/89.
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Fay, Gemma Louise. "Mathematical modelling of turbidity currents." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:62bb9382-1c50-47f3-8f59-66924cc31760.
Full textAbstract:
Turbidity currents are one of the primary means of transport of sediment in the ocean. They are fast-moving, destructive fluid flows which are able to entrain sediment from the seabed and accelerate downslope in a process known as `ignition'. In this thesis, we investigate one particular model for turbidity currents; the `Parker model' of Parker, Pantin and Fukushima (1986), which models the current as a continuous sediment stream and consists of four equations for the depth, velocity, sediment concentration and turbulent kinetic energy of the flow. We propose two reduced forms of the model; a one-equation velocity model and a two-equation shallow-water model. Both these models give an insight into the dynamics of a turbidity current propagating downstream and we find the slope profile to be particularly influential. Regions of supercritical and subcritical flow are identified and the model is solved through a combination of asymptotic approximations and numerical solutions. We next consider the dynamics of the four-equation model, which provides a particular focus on Parker's turbulent kinetic energy equation. This equation is found to fail catastrophically and predict complex-valued solutions when the sediment-induced stratification of the current becomes large. We propose a new `transition' model for turbulent kinetic energy which features a switch from an erosional, turbulent regime to a depositional, stably stratified regime. Finally, the transition model is solved for a series of case studies and a numerical parameter study is conducted in an attempt to answer the question `when does a turbidity current become extinct?'.
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Pritchard, David Thomas. "Some problems in two-phase flow : intertidal mudflats and low Reynolds number gravity currents." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391189.
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Poulin, Francis J. "Mesoscale gravity currents and cold-pools within a continuously stratified fluid overlying gently sloping topography." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq22654.pdf.
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Flynn, Morris R. "Buoyancy and stratification in Boussinesq flow with applications to natural ventilation and intrusive gravity currents." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2006. http://wwwlib.umi.com/cr/ucsd/fullcit?p3237381.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2006.Title from first page of PDF file (viewed December 8, 2006). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 158-164).
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Ilicak, Mehmet. "Development and Applications of Second-Order Turbulence Closures for Mixing in Overflows." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/225.
Full textAbstract:
Mixing between overflows and ambient water masses is a crucial problem of deep-water formation in the down-welling branch of the meridional overturning circulation of the ocean. In this dissertation work, performance of second-order turbulence closures in reproducing mixing of overflows is investigated within both hydrostatic and non-hydrostatic models. First, a 2D non-hydrostatic model is developed to simulate the Red Sea overflow in the northern channel. The model results are compared to the Red Sea Outflow Experiment. It is found that the experiments without sub-grid scale models cannot reproduce the basic structure of the overflow. The k-ε model yields unrealistically thick bottom layer (BL) and interfacial layer (IL). A new technique so-called very large eddy simulation (VLES) which allows the use of k-ε model in non-hydrostatic models is also employed. It is found that VLES results the most realistic reproduction of the observations. Furthermore, the non-hydrostatic model is improved by introducing laterally average terms, so the model can simulate the constrictions not only in the z-direction but also in the y-direction. Observational data from the Bosphorus Strait is employed to test the spatially average 2D non-hydrostatic model (SAM) in a realistic application. The simulations from SAM with a simple Smagorinsky type closure appear to be excessively diffusive and noisy. We show that SAM can benefit significantly from VLES turbulence closures. Second, the performance of different second-order turbulence closures is extensively tested in a hydrostatic model. Four different two-equation turbulence closures (k-&epsilon, k-&omega, Mellor-Yamada 2.5 (MY2.5) and a modified version of k- &epsilon) and K-Profile Parameterization (KPP) are selected for the comparison of 3D numerical simulations of the Red Sea overflow. All two-equation turbulence models are able to capture the vertical structure of the Red Sea overflow consisting of the BL and IL. MY2.5 with Galperin stability functions produce the largest salinity deviations from the observations along two sections across the overflow and the modified k-&epsilon exhibits the smallest deviations. The rest of the closures fall in between, showing deviations similar to one another. Four different closures (k- &epsilon, k-&omega, MY2.5KC and KPP) are also employed to simulate the Mediterranean outflow. The numerical results are compared with observational data obtained in the 1988 Gulf of Cadiz Expedition. The simulations with two-equation closures reproduce the observed properties of the overflow quite well, especially the evolution of temperature and salinity profiles. The vertically integrated turbulent salt flux displays that the overflow goes under significant mixing outside the west edge of the Strait of Gibraltar. The volume transport and water properties of the outflow are modified significantly in the first 50 km after the overflow exits the strait. The k-&epsilon and k-&omega cases show the best agreement with the observations. Finally, the interaction between the Red Sea overflow and Gulf of Aden (GOA) eddies has been investigated. It is found that the overflow is mainly transported by the undercurrent at the west side of the gulf. The transport of the overflow is episodic depending strength and location of GOA eddies. The most crucial finding is that the Red Sea overflow leaves the Gulf of Aden in patches rather than one steady current. Multiple GOA eddies induce lateral stirring, thus diapycnal mixing of the Red Sea outflow.
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Wells, Mathew Graeme, and mathew@inferno phys tue nl. "Convection, turbulent mixing and salt fingers." The Australian National University. Research School of Earth Sciences, 2001. http://thesis.anu.edu.au./public/adt-ANU20011212.103012.
Full textAbstract:
In this thesis I address several topics concerning the interaction of convection and density stratification in oceans and lakes. I present experimental and theoretical investigations of the
interaction between a localized buoyancy source and a heat flux through a horizontal boundary,
and of the interactions between salt fingers and intermittent turbulence or shear.
¶
An extensive series of laboratory experiments were used to quantify the stratification and circulation that result from the combined presence of a localized buoyancy source and a heat flux through a horizontal boundary. Previous studies found that convection in the form of a turbulent buoyant plume tends to produce a stable density stratification, whereas the distributed flux from a horizontal boundary tends to force vigorous overturning and to produce well-mixed layers. A new result of this thesis is that a steady density profile, consisting of a mixed layer and a stratified layer, can exist when the plume buoyancy flux is greater than the distributed flux. When the two fluxes originate from the same boundary, the steady state involves a balance between the rate at which the mixed layer deepens due to entrainment on the one hand and vertical advection of the stratified water far from the plume (due to the volume flux acquired by entrainment) on the other hand. There is a monotonic relationship between the normalized mixed layer depth and flux ratio R (boundary flux/plume flux) for 0 < R > 1, and the whole tank overturns for R > 1. The stable density gradient in the stratified region is primarily due to the buoyancy from the plume and for R > 0 there is a small increase in the gradient due to entrainment of buoyancy from the mixed layer. For the case of fluxes from a plume located at one boundary and a uniform heat flux from the opposite boundary the shape of the density
profile is that given by Baines & Turner (1969), with the gradient reduced by a factor (1 + R) due to the heating. Thus, when R < - 1 there is no stratified region and the whole water column
overturns. When 0 > R > - 1, the constant depth of the convecting layer is determined by the
Monin-Obukhov scale in the outflow from the plume.
¶
One application of these laboratory experiments is to surface cooling in lakes and reservoirs
that have shallow sidearms. During prolonged periods of atmospheric cooling, gravity currents can form in these sidearms and as the currents descend into the deeper waters they are analogous to isolated plumes. This can result in stratification at the base of a lake and an upwelling of cold water. Away from the shallow regions, surface cooling leads to a mixed surface layer. The depth of this layer will be steady when the rate of upwelling balances the rate at which the mixed layer deepens by turbulent entrainment. A series of laboratory experiments designed to model the depth distribution of a lake with a shallow sidearm showed that the steady depth of the mixed layer depended on the ratio of the area of the shallow region to the area of the deep region. Significant stratification resulted only when the reservoir had shallow regions that account for more than 50 % of the surface area. The depth of the surface mixed layer also depended on the ratio of the depths of the shallow and deep regions and no significant stratification forms if this ratio is greater than 0.5. These results are in good agreement with observations of circulation and stratification during long periods of winter cooling
from Chaffey reservoir, Australia. Theoretical time scales are also developed to predict the minimum duration of atmospheric cooling that can lead the development of stratification.
¶
In the second part of this thesis, I report a series of laboratory experiments which are designed to investigate the fine structure and buoyancy fluxes that result from salt finger convection in the presence of shear and intermittent turbulence. We find that, when salt finger convection in deep linear gradients is superposed with a depth-dependent spatially periodic shear, variations in the density profile develop on the same wavelength as the shear. The laboratory experiments presented in this thesis were carried out in a continuous density gradient with a spatially periodic shear produced by exciting a low-frequency baroclinic mode of vertical wavelength 60 mm. The density gradient consisted of opposing salt and sugar gradients favourable to salt fingers (an analogue to the oceanic heat/salt system). Where the shearing was large the salt finger buoyancy fluxes were small. Changes in salinity gradient due to the resulting flux divergence were self-amplifying until a steady state was reached in which the spatial variations in the ratio of salt and sugar gradients were such that the flux divergence vanished. Thus, along with reducing the mean salt finger buoyancy flux, a spatially varying shear can also lead to the formation of density structure.
¶
In the ocean intermittent turbulence can occur in isolated patches in salt finger-favourable
regions. I present new results from laboratory experiments in which a partially mixed patch
was produced in deep linear concentration gradients favourable to salt finger convection. Salt fingers give rise to an up gradient flux of buoyancy which can reduce the density gradient
in a partially mixed patch. This can then lead to overturning convection of the partially mixed
patch if a) the ratio of T and S gradients, R\rho =aTz/_ /betaSz, is near one, b) if turbulence results in
a nearly well-mixed patch and c) the patch thickness is large enough that convective eddies are
able to transport T and S faster than salt fingers. Once overturning occurs, subsequent turbulent
entrainment can lead to growth of the patch thickness. Experimental results agree well with
the theoretical prediction that h= \surd 8h B/N2 t, where h is the patch thickness, t is time, h is
the mixing efficiency of turbulent entrainment, B is the buoyancy flux of the salt fingers and N
is the buoyancy frequency of the ambient gradient region. This thickening is in contrast to the
collapse that a partially mixed patch would experience due to lateral intrusion in a very wide
tank. In regions of the ocean that contain salt fingers there is the possibility that, after a period
of initial collapse, an intrusion could enter a regime where the rate of collapse in the vertical is
balanced by the growth rate due to turbulent entrainment from the salt fingers buoyancy flux,
thus tending to maintain the rate of lateral spread.
¶
A further series of laboratory experiments quantified the buoyancy fluxes that result from
salt fingers and intermittent turbulence. A continuous density gradient, favourable to salt finger
convection, was stirred intermittently by an array of vertical rods that move horizontally back
and forth along the tank at a constant velocity. Previous experiments had found that continuous
turbulence destroys any salt fingers present because the dissipation of turbulent kinetic energy
occurs at scales that are generally smaller than salt fingers widths. However, when turbulence
is present only intermittently, the salt fingers may have time to grow between turbulent events
and so contribute to the vertical diffusivities of heat and salt. We conclude that the vertical
buoyancy flux of salt fingers is strongly dependent upon the intermittency of the turbulence,
and equilibrium fluxes are only achieved if the time between turbulent events is much greater
than the e-folding time of the salt fingers. When these results are applied to an oceanographic
setting, the effect of intermittent turbulence, occurring more 5% of the time, is to reduce the
effective eddy diffusivity due to salt fingers below equilibrium salt finger values, so that at
R\rho > > 2 the eddy diffusivity is due only to turbulence. The time averaged salt fingers fluxes are
not significantly reduced by intermittent turbulence when R\rho > 2 or if the intermittence occurs
less than 2% of the time, and so may contribute significant diapycnal fluxes in many parts of
the ocean.
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Ohiwa, Mitchihiro 1977. "An experimental study on mixing induced by gravity currents on a sloping bottom in a rotating fluid." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/55068.
Full textAbstract:
Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2002.Includes bibliographical references (p. 75-77).
Mixing induced by gravity currents on a sloping bottom was studied through laboratory experiments in a rotating fluid. The dense fluid on the sloping bottom formed a gravity current that could be in regimes where the flow was laminar or had waves. The mixing on a sloping bottom for gravity currents in the laminar and wave regimes was studied both qualitatively and quantitatively. The laboratory experiments were conducted on rotating tables in a tank with homogeneous ambient fluid. The slope angle, rotation rate, reduced gravity, and flow rate of the dense source water were changed for the experiments. The mixing was quantized by measuring the density of the ambient fluid, dense source water, and the bottom water collected at the end of the bottom slope and calculating the ratio of the source water in the bottom water. Comparing the mixing in the laminar regime and the wave regime by changing the slope angle and rotation rate showed that the waves in the gravity current increased the mixing due to the waves. Analysis of the ratio of source water based on the internal Froude number, the Ekman number, and the timescale of the experiments showed that diffusion was not the main mechanism for mixing. The Ekman layer solution was validated by the observation of a streak left by a grain of dye in the dense water layer. The values for the entrainment parameter for the laboratory experiments bracketed those calculated for the Denmark Strait overflow and the Mediterranean outflow, and the values based on observations in the ocean and those from the laboratory were similar for a nondimensional parameter defined using variables used in the laboratory experiments. This shows that the results from the experiments could be used to discuss the mixing in the ocean due to gravity currents along a slope in the ocean and that the waves observed in the laboratory might also be observed in the ocean.
by Mitchihiro Ohiwa.
S.M.
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Wobus, Fred. "The dynamics of dense water cascades : from laboratory scales to the Arctic Ocean." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/1610.
Full textAbstract:
The sinking of dense shelf waters down the continental slope (or “cascading”) contributes to oceanic water mass formation and carbon cycling. Cascading is therefore of significant importance for the global overturning circulation and thus climate. The occurrence of cascades is highly intermittent in space and time and observations of the process itself (rather than its outcomes) are scarce. Global climate models do not typically resolve cascading owing to numerical challenges concerning turbulence, mixing and faithful representation of bottom boundary layer dynamics. This work was motivated by the need to improve the representation of cascading in numerical ocean circulation models. Typical 3-D hydrostatic ocean circulation models are employed in a series of numerical experiments to investigate the process of dense water cascading in both idealised and realistic model setups. Cascading on steep bottom topography is modelled using POLCOMS, a 3-D ocean circulation model using a terrain-following s-coordinate system. The model setup is based on a laboratory experiment of a continuous dense water flow from a central source on a conical slope in a rotating tank. The descent of the dense flow as characterised by the length of the plume as a function of time is studied for a range of parameters, such as density difference, speed of rotation, flow rate and (in the model) diffusivity and viscosity. Very good agreement between the model and the laboratory results is shown in dimensional and non-dimensional variables. It is confirmed that a hydrostatic model is capable of reproducing the essential physics of cascading on a very steep slope if the model correctly resolves velocity veering in the bottom boundary layer. Experiments changing the height of the bottom Ekman layer (by changing viscosity) and modifying the plume from a 2-layer system to a stratified regime (by enhancing diapycnal diffusion) confirm previous theories, demonstrate their limitations and offer new insights into the dynamics of cascading outside of the controlled laboratory conditions. In further numerical experiments, the idealised geometry of the conical slope is retained but up-scaled to oceanic dimensions. The NEMO-SHELF model is used to study the fate of a dense water plume of similar properties to the overflow of brine-enriched shelf waters from the Storfjorden in Svalbard. The overflow plume, resulting from sea ice formation in the Storfjorden polynya, cascades into the ambient stratification resembling the predominant water masses of Fram Strait. At intermediate depths between 200-500m the plume encounters a layer of warm, saline AtlanticWater. In some years the plume ‘pierces’ the Atlantic Layer and sinks into the deep Fram Strait while in other years it remains ‘arrested’ at Atlantic Layer depths. It has been unclear what parameters control whether the plume pierces the Atlantic Layer or not. In a series of experiments we vary the salinity ‘S’ and the flow rate ‘Q’ of the simulated Storfjorden overflow to investigate both strong and weak cascading conditions. Results show that the cascading regime (piercing, arrested or ‘shaving’ - an intermediate case) can be predicted from the initial values of S and Q. In those model experiments where the initial density of the overflow water is considerably greater than of the deepest ambient water mass we find that a cascade with high initial S does not necessarily reach the bottom if Q is low. Conversely, cascades with an initial density just slightly higher than the deepest ambient layer may flow to the bottom if the flow rate Q is high. A functional relationship between S/Q and the final depth level of plume waters is explained by the flux of potential energy (arising from the introduction of dense water at shallow depth) which, in our idealised setting, represents the only energy source for downslope descent and mixing. Lastly, the influence of tides on the propagation of a dense water plume is investigated using a regional NEMO-SHELF model with realistic bathymetry, atmospheric forcing, open boundary conditions and tides. The model has 3 km horizontal resolution and 50 vertical levels in the sh-coordinate system which is specially designed to resolve bottom boundary layer processes. Tidal effects are isolated by comparing results from model runs with and without tides. A hotspot of tidally-induced horizontal diffusion leading to the lateral dispersion of the plume is identified at the southernmost headland of Spitsbergen which is in close proximity to the plume path. As a result the lighter fractions in the diluted upper layer of the plume are drawn into the shallow coastal current that carries Storfjorden water onto the Western Svalbard Shelf, while the dense bottom layer continues to sink down the slope. This bifurcation of the plume into a diluted shelf branch and a dense downslope branch is enhanced by tidally-induced shear dispersion at the headland. Tidal effects at the headland are shown to cause a net reduction in the downslope flux of Storfjorden water into deep Fram Strait. This finding contrasts previous results from observations of a dense plume on a different shelf without abrupt topography. The dispersive mechanism which is induced by the tides is identified as a mechanism by which tides may cause a relative reduction in downslope transport, thus adding to existing understanding of tidal effects on dense water overflows.
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Blomqvist, Claes. "Distribution of Ventilation Air and Heat by Buoyancy Forces inside Buildings : An Experimental Study." Doctoral thesis, Stockholm : Skolan för arkitektur och samhällsbyggnad, Kungliga tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10615.
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Cowton, Laurence Robert. "Monitoring sub-surface storage of carbon dioxide." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270308.
Full textAbstract:
Since 1996, super-critical CO$_2$ has been injected at a rate of $\sim$0.85~Mt~yr$^{-1}$ into a pristine, saline aquifer at the Sleipner carbon capture and storage project. A suite of time-lapse, three-dimensional seismic reflection surveys have been acquired over the injection site. This suite includes a pre-injection survey acquired in 1994 and seven post-injection surveys acquired between 1999 and 2010. Nine consistently bright reflections within the reservoir, mapped on all post-injection surveys, are interpreted to be thin layers of CO$_2$ trapped beneath mudstone horizons. The areal extents of these CO$_2$ layers are observed to either increase or remain constant with time. However, volume flux of CO$_2$ into these layers has proven difficult to measure accurately. In addition, the complex planform of the shallowest layer, Layer 9, has proven challenging to explain using reservoir simulations. In this dissertation, the spatial distribution of CO$_2$ in Layer~9 is measured in three dimensions using a combination of seismic reflection amplitudes and changes in two-way travel time between time-lapse seismic reflection surveys. The CO$_2$ volume in this layer is shown to be growing at an increasing rate through time. To investigate CO$_2$ flow within Layer~9, a numerical gravity current model that accounts for topographic gradients is developed. This vertically-integrated model is computationally efficient, allowing it to be inverted to find reservoir properties that minimise differences between measured and modelled CO$_2$ distributions. The best-fitting reservoir permeability agrees with measured values from nearby wells. Rapid northward migration of CO$_2$ in Layer~9 is explained by a high permeability channel, inferred from spectral decomposition of the seismic reflection surveys. This numerical model is found to be capable of forecasting CO$_2$ flow by comparing models calibrated on early seismic reflection surveys to observed CO$_2$ distributions from later surveys. Numerical and analytical models are then used to assess the effect of the proximity of an impermeable base on the flow of a buoyant fluid, motivated by the variable thickness of the uppermost reservoir. Spatial gradients in the confinement of the reservoir are found to direct the flow of CO$_2$ when the current is of comparable thickness to the reservoir. Finally, CO$_2$ volume in the second shallowest layer, Layer~8, is measured using structural analysis and numerical modelling. CO$_2$ in Layer~8 is estimated to have reached the spill point of its structural trap by 2010. CO$_2$ flux into the upper two layers is now $\sim$40\% of total CO$_2$ flux injected at the base of the reservoir, and is increasing with time. This estimate is supported by observations of decreasing areal growth rate of the lower layers. The uppermost layers are therefore expected to contribute significantly to the total reservoir storage capacity in the future. CO$_2$ flow within Layer~9 beyond 2010 is forecast to be predominantly directed towards a topographic dome located $\sim$3~km north of the injection point. This dissertation shows that advances in determining the spatial distribution and flow of CO$_2$ in the sub-surface can be made by a combination of careful seismic interpretation and numerical flow modelling.
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Leong, Chi Seng. "Gravity current around circular cylinder." Thesis, University of Macau, 2010. http://umaclib3.umac.mo/record=b2182938.
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