To see the other types of publications on this topic, follow the link: Ocean and River Engineering.
Dissertations / Theses on the topic 'Ocean and River Engineering'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Ocean and River Engineering.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Swindale, Neil. "Numerical modelling of river rehabilitation schemes." Thesis, University of Nottingham, 1999. http://eprints.nottingham.ac.uk/29108/.
Full textAbstract:
This thesis is based on the application of hydraulic modelling techniques to the study of river rehabilitation schemes. River channelization and rehabilitation techniques are reviewed and the restoration of the River Idle is detailed. The rehabilitation of the Idle, consisting principally of the installation of a number of flow deflectors, forms the basis of the modelling work carried out. Open channel modelling techniques are reviewed and the packages ISIS, HEC-RAS, SSIIM and CFX are applied to the River Idle. Results from SSIIM (two dimensional) and CFX (three dimensional) are validated against site measured velocities. SSIIM predicted velocities calibrate poorly against site data whilst CFX results are considerably more encouraging. Reasons for the increased accuracy of the three dimensional results are discussed. The effect of the installation of the flow deflectors on aquatic habitat is simulated using the techniques underlying the Instream Flow Incremental Methodology (IFIM). The results from the one dimensional model ISIS and the three dimensional package CFX are used to make available habitat predictions. Results indicate an improvement in habitat for adult and spawning chub but a worsening of habitat for roach fry. However, habitat for roach fry can be expected to improve with time as the geomorphology of the river responds to the installation of the deflectors. The results from the habitat modelling exercise also indicate significant discrepancies between the results obtained by applying the one and three dimensional models. Greater improvements in habitat are indicated in the results from the three dimensional modelling approach. This can be attributed to a number of factors but most significantly the fact that the three dimensional model, in solving two further momentum balance equations, accurately simulates a plume of higher velocity which is produced by the narrowing of the channel width at the deflector. This plume of higher velocity is propagated downstream for some distance beyond the deflector and is associated with improved habitat suitability in the case of adult and spawning chub. The effect of the deflectors on the movement of sediments in the Idle is simulated using ISIS Sediment, a module of the ISIS package, and SHEAR. SHEAR is a FORTRAN program, written for this thesis, which calculates bed shear stresses from the vertical velocity distribution predicted by CFX. The predicted bed shear stresses are compared with a critical shear stress for erosion which is calculated from the Shields criteria. Deposition areas can be implied from zones of reduced bed shear stress. Thus, SHEAR is able to describe the spatial detail of erosion and deposition, for any given sediment particle size, at a specific discharge. Results from ISIS Sediment and SHEAR are compared qualitatively with site measurements of bed erosion that has taken place at a single deflector site. Results indicate that the programs have successfully reproduced the major features of the movement of sediments observed on site. These consist of the erosion of a scour pool adjacent to the deflector tip and deposition in the lee of the deflector leading to the development of a bank of sediment. Overall, significant benefits are indicated in a three dimensional approach over the more traditional one dimensional models. These are evident in both improved calibration with site measured velocities, better available habitat prediction and the ability to describe the spatial detail of erosion and deposition.
2
Morvan, Herve P. "Three-dimensional simulation of river flood flows." Thesis, University of Glasgow, 2001. http://theses.gla.ac.uk/6881/.
Full textAbstract:
This thesis describes the implementation of general Computational Fluid Dynamics (CFD) techniques to laboratory and natural channels under flood flow conditions. Two commercially available codes, TELEMAC and CFX4, have been used in this work. The assessment of CFD for the calculation of flooded channel flow dynamics is carried out by simulating one laboratory test case from the Flood Channel Facility (FCF) Series B. This test case is that of a meandering two-stage channel with a depth ratio of 25% on the flood plain. Results from a computer simulation of experiment B23 are presented with a detailed quantitative comparison of the measured velocity, turbulence and bed shear stress. It supports the conclusion that CFD is able to account for the different flow mechanisms arising from the interaction between inbank and overbank flows in meandering channels. The maximum error in the prediction of the velocity is 10% and the comparisons show the calculations of bed shear stress to be reasonably accurate as well. Numerical tests indicate that the numerical solution is relatively independent of the boundary conditions, and confirm that turbulence transport is of minor importance in the experiment simulated. Numerical results from the simulation of flood flow mechanisms in natural rivers are also presented. It is hoped that these are of value to practitioners. Two 1-km reaches on the River Severn and River Ribble are modelled. They permit the investigation of two-stage channel flow dynamics at a larger scale. The numerical verification process establishes that the scale and the complex nature of the geometry are limiting factors, particularly for the numerical discretization of the domain and the calculation of the variables at the walls. It is however possible to estimate a priori part of the error such constraints generate. Away from the walls, the flow main features seem well predicted. The parallel between the velocity fields observed in river flood flows and those observed in the FCF is evident. Validation against field data suggests that the models are able to reproduce the flow mechanisms and account for bed shear stress variations correctly. Yet a significant level of uncertainty remains when the model predictions are compared against measured point data; more validation work is therefore required.
3
Lee, Sang-Heon. "Numerical modelling of rapidly varied river flow." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/14377/.
Full textAbstract:
A new approach to solve shallow water flow problems over highly irregular geometry both correctly' and efficiently is presented in this thesis. Godunov-type schemes which are widely used with the finite volume technique cannot solve the shallow water equations correctly unless the source terms related to the bed slope and channel width variation are discretized properly, because Godunov-type schemes were developed on the basis of homogeneous governing equations which is not compatible with an inhomogeneous system. The main concept of the new approach is to avoid a fractional step method and transform the shallow water equations into homogeneous form equations. New definitions for the source terms which can be incorporated into the homogeneous form equations are also proposed in this thesis. The modification to the homogeneous form equations combines the source terms with the flux term and solves them by the same solution structure of the numerical scheme. As a result the source terms are automatically discretized to achieve perfect balance with the flux terms without any special treatment and the method does not introduce numerical errors. Another point considered to achieve well-balanced numerical schemes is that the channel geometry should be reconstructed in order to be compatible with the numerical flux term which is computed with piecewise constant initial data. In this thesis, the channel geometry has been changed to have constant state inside each cell and, consequently, each cell interface is considered as a discontinuity. The definition of the new flux related to the source terms has been obtained on the basis of the modified channel geometry. A simple and accurate algorithm to solve the moving boundary problem in two-dimensional modelling case has also been presented in this thesis. To solve the moving boundary condition, the locations of all the cell interfaces between the wet and dry cells have been detected first and the integrated numerical fluxes through the interfaces have been controlled according to the water surface level of the wet cells. The proposed techniques were applied to several well-known conservative schemes including Riemann solver based and verified against benchmark tests and natural river flow problems in the one and two dimensions. The numerical results shows good agreement with the analytical solutions, if available, and recorded data from other literature. The proposed approach features several advantages: 1) it can solve steady problems as well as highly unsteady ones over irregular channel geometry, 2) the numerical discretization of the source terms is always performed as the same way that the flux term is treated, 3) as a result, it shows strong applicability to various conservative numerical schemes, 4) it can solve the moving (wetting/drying) boundary problem correctly. The author believes that this new method can be a good option to simulate natural river flows over highly irregular geometries.
4
Fernandes, Sergio Alejandro. "Planning for future inland water transportation in the Parana-Paraguay River basin." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40578.
Full text
5
Reungoat, Anne Françoise Jeanne. "Classification of river networks for prediction in ungauged basins." Thesis, University of Glasgow, 2004. http://theses.gla.ac.uk/6331/.
Full textAbstract:
The majority of the world's river basins remain ungauged and, therefore, the triedand- tested empirical techniques for predicting floods and droughts cannot be applied. An alternative approach, which is currently receiving a great deal of attention from research hydrologists, is to develop continuous simulation models whose parameters pertain to physical or hydrological properties of the river basins. However, difficulties related to scale, heterogeneity and complexity of real river basins have made a priori estimation of such parameters impossible: their estimation has always required calibration using river flow data. Therefore, estimating hydrological model parameters in ungauged river basins is one of the greatest challenges currently facing research hydrologists. In this thesis research advances towards this goal have been made at three different levels. First, at a conceptual level, a novel method for classifying river basins according to their physical properties is proposed. It is specifically designed for transferring hydrological model parameters from gauged river basins, where calibration is possible, to ungauged river basins. This approach relies on recognising that river basins can be similar in parts of their hydrological cycle but not in others. Thus, basins go through three independent classifications, one relative to each of the major components of the land phase hydrological cycle: interaction of soil water/vegetation and atmosphere; surface flow; and groundwater flow. This requires the ability to characterise the response of the components of the hydrological cycle independently, which leads to a second conceptual advance; rather than relying entirely on measured river flow data, from which it is difficult to separate out the effects of the three components, classification rules are devised on the basis of synthetic data produced by comprehensive, distributed, physically-based models. This thesis focuses on the surface flow component, applying the methodology to the identification of the best classifiers for surface flow through river networks. This required simulating river flow through a large number of Scottish river basins, which led to more practical research advances; all available commercial flow routing models were too cumbersome and required an impractical level of detail to be applied in such a large study. Therefore, a new flow routing modelling system was developed that extracts river network detail from digital databases and numerically solves a distributed flow routing model. Finally, on a detailed scientific level, significant insights have been made into the relationship between river network geomorphologic structure and stream flow response. In particular, it is shown that: a downstream hydraulic geometry relationship exists for Scottish rivers; although channel conveyance is a key factor in dictating network response, the features of the response hydro graph - namely the percentage attenuation of the flood peak and the lag in time to peak - scale linearly with both roughness and hydraulic geometry coefficients; much publicised invariant power law scaling rules for flood peaks in fact vary as a function of storm duration; statistical multivariate analysis of the simulated network flow responses demonstrated the low capacity of the network descriptors commonly used in regionalisation studies for characterising flow response. Four variables are shown to have significantly higher classifying power than the majority of the commonly used classifiers. Of these, two are entirely new to this thesis.
6
Ji, Ming. "Integrated optimization and simulation model for resource acquisition and utilization : an application to ocean/river articulated tug/barge system." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43363.
Full text
7
Sichel, Alexander R. (Alexander Russell). "Supply chain security along the Columbia River : an analysis of maritime supply chain security with respect to communication between security experts." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33589.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.Includes bibliographical references (leaves 74-75).
The amount of cargo that enters the US border is at an all time high. Cargo containers and vessel shipments enter the US from all over the world. Tracking these shipments from their origin to destination requires professional expertise. Security organizations, such as the Regional Maritime Security Coalition of the Columbia River, realize the potential of these professionals, who track and coordinate cargo containers as they move through a supply chain, to enhance security of maritime cargo. In order to utilize these supply chain logistic professionals in a security coalition, proper training and certification would be required to comply with the US Federal Code on Liability Protection. This study examines the requirements that are necessary to certify supply chain logistic professionals as certified volunteers in an information sharing, security communication network to prevent terrorist activity, smuggling, theft, and to assist in general crisis mitigation. The thesis studies how the RMSC is currently developing its security communication system around supply chain logistic professionals, and the requirements and training that would be necessary to certify them under the US Federal Code.
by Alexander R. Sichel.
S.M.
8
Dangerfield, Stephen F. "The effects of sediment loading on morphology and flood risk in a lowland river system." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13659/.
Full textAbstract:
Diffuse sources of sediment may have important implications for flood risk management (FRM), especially as catchment sediment yields are predicted to increase in future. UK legislation requires FRM to work with natural processes wherever possible, including accounting for sediments. However, the importance of wash-material load to FRM has been under researched and both a robust evidence-base and practical sediment models are needed to identify, prioritise and justify sediment-related catchment management. Research addressing these issues was centred on the River Tone, a sub-catchment of the Parrett, in which features excessive inputs of sediment in its upper catchment combined with high potential for deposition in its lower reaches. Links between sediment sources, water and sediment runoff, and downstream sediment sinks were established and the research examined the role played by sediment, especially wash-material load, within the fluvial system. The greatest sediment-related threats to the functioning of this lowland river stem from either: a protracted, major reduction in wash-material load; or a significant increase in bed-material load. Imbalance in the Tone fluvial-sediment system may not significantly affect flood risk directly, but has implications for FRM operations, maintenance and monitoring. Impacts on land quality result from soil loss. For example, ~2.5 million tonnes of soil has been eroded from the Parrett catchment since WWII. Water quality issues include delivery of phosphate and other pollutants into the river, and potentially more frequent dredging that remobilises contaminants. The thesis defines the key sediment-related components of sustainable, integrated catchment management and provides an improved evidence-base upon which to engage stakeholders. It tests and benchmarks sediment assessment tools including the Sediment Impact Assessment Model (SIAM). An approach to catchment-scale sediment assessment for lowland rivers is recommended, which involves a nested-approach using routinely collected and project-specific field data, stream power screening and SIAM.
9
Chatzigiannakou, Maria Angeliki. "Efficiency evaluation of the offshore deployments of wave energy converters and marine substations." Licentiate thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-335184.
Full text
10
Ivansen, Anders. "Hydrauliska effekter av avbördade extremflöden : Fallstudie på en damm i Norrland." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231424.
Full textAbstract:
Flödesdimensionering är något som används världen över när det kommer till konstruktionen och hanteringen av byggnader i vattendrag. I Sverige har flödeskommitén, bestående av SMHI och intressenter från vattenkraftsindustrin, tagit fram flödesdimensioneringsriktlinjerna som blivit praxis för svenska dammägare. Utifrån dessa riktlinjer får dammar olika flödesdimensioneringsklassningar beroende på vad konsekvenserna blir av olika högflöden. Detta arbete bygger på en nyligt genomförd konsekvensutredning på en av Jämtkrafts dammar i mellersta Norrland. Dammen, som går under namnet Damm B i denna rapport, har tidigare haft flödesdimensioneringsklass II men bedöms nu tillhöra flödesdimensionerings klass I. Dammen ska utifrån detta kunna avbörda ett klass I-flöde på 1690 m3/s till skillnad från det tidigare kravet på 1035 m3/s (klass II-flöde). Syftet med denna rapport äratt undersöka vilka effekter den naturliga tillrinningen av dessa och mellanliggande flöden har på olika objekt och områden nedströms Damm B. Med modelleringsverktyget MIKE 11 konstrueras en en-dimensionell flödesmodell för flödessimuleringar och avläsning av vattennivåer. Simuleringarna visar att den största delen av nedströms undersökta objekt påverkas mellan flödena 1100 m3/s och det så kallade 1000-års flödet på 1376 m3/s där risken för människoliv börjar vid det senare. Redan under klass II-flödet sker viss översvämning på de strandnära vägarna i området. Mellan 1100 m3/s samt 1200 m3/s börjar den mindre dammen nedströms (Damm C) riskera att gå till brott för att sedan överströmmas vid 1400 m3/s. Uträkning av skjuvspänningen berättar att det finns erosionsrisker för korndiametrar på upp till ca 2 cm i vissa erosionsbenägna områden. Denna erosionsbenägenhet inträffar för flöden under 1300 m3/s innan dammbrott har skett i Damm C. Vattenytans lutning minskartill följd av en större motdämning vilket därefter orsakar att minskningen av skärspänningen sker snabbare än den ökning som uppkommer till följd av ett stigande vattendjup. Vattenytan stiger dock och berör områden som inte brukar ligga under vatten. Detta kan leda till kornfraktioner som inte har transporteras bort vid tidigare flöden nu riskerar göra detta vilket bland annat kan bilda drivgods. Flödesdimensioneringsriktlinjerna som har tagits fram i Sverige bygger på miljöbalkens allmänna hänsynsregler vilket gör dem till en bra mall för dammägare att följa. När funderingar dock finns att inte bygga ut avbördningskapaciteten helt behöver det funderas på hur mycket ett eventuellt dammbrott skulle påverka den egna anläggningen och förtroendet från myndigheter samt allmänheten. I fallet med Damm B kommer de flesta objekten som undersöks att beröras vid en naturlig tillrinning på 1400 m3/s. Det är därför av intresse att genomföra noggrannare dammbrotts simuleringar för att hitta ett flöde mellan 1400 m3/soch 1690 m3/s där inga större ytterligare konsekvenser från ett dammbrott uppstår. Till följd av de svårheter och osäkerheter som valetav en lägrea vbördningskapacitet medför motiverar denna rapport dock till en utökad kapacitet för ett klass I-flöde i Damm B och undersöka möjligheterna för ökad avbördning vid Damm C. Detta kan även kompletteras med en omfattande samordnad beredskapsplan längs med älven och ett utökat översvämnings-/erosionsskydd på utsatta områden.
11
Cheng, Yongming 1964. "Dynamic stiffness and transfer matrix analysis of marine riser vibration." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/107859.
Full text
12
Sin, Yongsik. "Ecosystem analysis of water column processes in the York River estuary, Virginia: Historical records, field studies and modeling analysis." W&M ScholarWorks, 1998. https://scholarworks.wm.edu/etd/1539616855.
Full textAbstract:
Analyses of EPA long-term datasets (1985--1994) combined with field studies and ecosystem model development were used to investigate phytoplankton and nutrient dynamics in the York River estuary. Analysis of the EPA dataset showed that algal blooms occurred during winter-spring followed by smaller summer blooms. Peak phytoplankton biomass during the winter-spring blooms occurred in the mid reach of the mesohaline zone whereas during the summer bloom it occurred in the tidal fresh-mesolialine transition zone. River discharge appears to be the major factor controlling the location and timing of the winter-spring blooms and the relative degree of potential nitrogen (N) and phosphorus (P) limitation. Phytoplankton biomass in tidal fresh water regions was limited by high flushing rates. Water residence time was less than cell doubling rate during seasons of high river flow. Positive correlations between PAR at 1m depth and chlorophyll a suggested light limitation of phytoplankton in the tidal fresh-mesohaline transition zone. A significant relationship between the delta of salinity between surface and bottom water and chlorophyll a distribution suggested the importance of tidal mixing for phytoplankton dynamics in the mesohaline zone. Accumulation of phytoplankton biomass in the mesohaline zone was generally controlled by N with the nutrient supply provided by benthic or bottom water remineralization. In general, phytoplankton dynamics appear controlled to a large extent by resource limitation (bottom-up control) rather than zooplankton grazing (top-down control). The dynamics of phytoplankton size structure were investigated in the freshwater, transitional and estuarine reaches of the York River over an annual cycle. The contribution of large cells (micro-plankton, >20 mum) to total biomass increased downstream during winter whereas that of small cells (nano-, 3--20 mum) pico-plankton, <3 mum) increased downstream during summer. I conclude from these studies that spatial and seasonal variations in size structure of phytoplankton observed on the estuarine scale are determined both by the different preferences of micro-, nano-, and picoplankton for nutrients and by their different light requirements. Analyses of phytoplankton size structure are, thus, necessary to better understand phytoplankton dynamics and to better manage water quality in estuarine systems. An ecosystem model was developed to integrate these data and to investigate mechanisms controlling the size-structured phytoplankton dynamics in the mesohaline zone of the York River estuary. The model developed in Fortran90 included 12 state variables describing the distribution of carbon and nutrients (nitrogen, phosphorus) in the surface mixed layer. Forcing functions included incident radiation, temperature, wind stress, mean flow and tide including advective transport and turbulent mixing. Model results supported the general view that phytoplankton dynamics are controlled by abiotic mechanisms (i.e. bottom-up control) rather than biotic, trophic interactions in the York River estuary. Model sensitivity tests showed that small cells (pico-, nano-sized) are more likely regulated by temperature and light whereas large cells (micro-sized) are regulated by physical processes such as advection, and tidal mixing. Microphytoplankton blooms during winter- pring resulted from a combination of longitudinal advection and vertical diffusion of phytoplankton cells rather than in-situ production.
13
Landry, Jennifer Jacobs. "Coastal Ocean Variability off the Coast of Taiwan in Response to Typhoon Morakot: River Forcing, Atmospheric Forcing, and Cold Dome Dynamics." Thesis, Massachusetts Institute of Technology (MIT), 2014. http://hdl.handle.net/10945/43427.
Full textAbstract:
CIVINSMultidisciplinary Simulation, Estimation, and Assimilation Systems, Reports in Ocean Science and Engineering, MSEAS-20
The ocean is a complex, constantly changing, highly dynamical system. Prediction capabilities are constantly being improved in order to better understand and forecast ocean properties for applications in science, industry, and maritime interests. Our overarching goal is to better predict the ocean environment in regions of complex topography with a continental shelf, shelfbreak, canyons and steep slopes using the MIT Multidisciplinary Simulation, Estimation and Assimilation Systems (MSEAS) primitive-equation ocean model. We did this by focusing on the complex region surrounding Taiwan, and the period of time immediately following the passage of Typhoon Morakot. This area and period were studied extensively as part of the intense observation period during August - September 2009 of the joint U.S. - Taiwan program Quantifying, Predicting, and Exploiting Uncertainty Department Research Initiative (QPE DRI). Typhoon Morakot brought an unprecedented amount of rainfall within a very short time period and in this research, we model and study the effects of this rainfall on Taiwan’s coastal oceans as a result of river discharge. We do this through the use of a river discharge model and a bulk river-ocean mixing model. We complete a sensitivity study of the primitive-equation ocean model simulations to the different parameters of these models. By varying the shape, size, and depth of the bulk mixing model footprint, and examining the resulting impacts on ocean salinity forecasts, we are able to determine an optimal combination of salinity relaxation factors for highest accuracy.
14
Donnelly, Jessica Mary. "A scatter diagram approach to the selection of design currents for prediction of marine riser vortex-induced vibration." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33425.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.Includes bibliographical references (leaf 25).
This paper describes a scatter diagram approach for the classification of large numbers of current profiles for use in the prediction of riser fatigue damage due to vortex-induced vibration. Scatter diagrams have long been used to characterize the probability of various combinations of wave height and period, which are then used to assess wave forces. To predict VIV fatigue damage the designer needs to know which current profiles have the combined property of long regions of relatively constant velocity and relatively high speed. A sorting algorithm is proposed which searches every current profile for long regions of relatively constant flow speed. The probability of each length and speed combination is assessed and the data is used to populate the bins of the scatter diagram. The designer need only select relatively few representative profiles for detailed VIV analysis from those bins that would account for the most damage. The method is tested by making comparison to a brute force approach in which each of many thousands of profiles is evaluated for fatigue damage by running it in the SHEAR7 VIV response prediction program.
by Jessica Mary Donnelly.
S.M.
15
Dingwall, James R. "The design of a deep water catenary riser." Thesis, University of Glasgow, 1997. http://theses.gla.ac.uk/1636/.
Full textAbstract:
The overall aim of this study is to propose and develop a cost effective production design concept suitable for oil reservoirs situated in deep (1500 m) water which can be quickly and safely installed in areas with limited weather windows. The proposed design is based upon a steel catenary riser which will connect an FPSO directly into either a wellhead or seabed pipeline system thereby eliminating both the connection complexes and high cost associated with a central manifold. The catenary geometry will ensure that the structure is inherently compliant whilst a carrier pipe arrangement will provide structural protection and buoyancy to a flowline bundle contained within. The interface between the riser and the surface production vessel is a critical part of any riser system and so for the purposes of this study two design arrangements are considered. The first is based upon a direct connection between an FPSO turret and riser whereas the second is a hybrid design in which the riser is supported by a sub-surface buoy which is hydraulically connected to an FPSO using flexible flowlines. This hybrid connection has the advantage of decoupling FPSO and riser motions. Design development is carried out by examining a range of critical areas.
16
von, Bahr Maximilian, and Bergström Ida Gomez. "Investigation of the origin of salt in coastal aquifers and assessment of metals in the aquatic environment : River Drin and River Vjosa, Albania." Thesis, KTH, Vatten- och miljöteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235421.
Full textAbstract:
The preservation of freshwater aquifers is one important task of managing natural resources today. Intrusion of saltwater from the sea into the groundwater might occur in coastal-near areas and can affect the freshwater quality negatively. One such risk area is the Adriatic coast line of Albania, a country predominantly rich in freshwater resources due to the numerous rivers flowing from the mountains in the east towards the sea. The coastal areas are mainly used for agricultural activities were groundwater is an important resource for irrigation purposes. This study was therefore partly conducted in Albania where samples of groundwater and river waters were collected from the river deltas of Drin and Vjosa in order to investigate the origin of the salt and to assess the bioavailable metal concentrations of nickel and zinc. Both on-site tests and off-site tests, in laboratories, were conducted. In the laboratory, the samples were analysed for oxygen and deuterium isotope data. The results were used to assess the origin of the oxygen content as the method of investigating the origin of the salt uses the oxygen isotope as a tracer. Anion and cation concentrations were analysed as well as the concentrations of metals. These were used as input data to Visual Minteq, a model used to calculate the metal speciation of waters, and a Biotic Ligand Model used to calculate the bioavailable concentrations and the HC5 concentrations. The isotope analysis yielded results similar to previous studies conducted in the nearby area indicating that the salt does not have oceanic origin but meteorological. The bioavailable concentrations were in most sample sites lower than the calculated HC5 concentrations indicating that there is a sufficient buffering system present even though there are several mining activities upstream of the sample sites that could have affected the water quality. This study concludes that the origin of salt is of meteoric origin and not from seawater intrusion. The bioavailable concentrations do not pose a threat as the concentrations are under the HC5 concentrations for all sites but one. In order to deepen the understanding and knowledge of the water qualities in these areas, future studies should focus on a continuous measuring period lasting for example over the whole year minimizing any seasonal variations of the sampled data. Other methods such as geophysical measures could also contribute to a wider analysis of the groundwater condition.Grundvatten är en av de viktigaste naturresurserna vilket innebär att för att säkerställa en långvarig försörjning krävs en god förvaltning av befintliga akvifärer. I kustnära områden kan intrång av saltvatten från havet till grundvattnet påverka sötvattenkvaliteten negativt. Ett sådant riskområde är den Adriatiska kustlinjen i Albanien, ett land som är övervägande rikt på sötvattenresurser tack vare de många floder som rinner från bergen i öst mot havet i väst. Kustområdena används huvudsakligen för jordbruksverksamhet, där grundvatten är en viktig resurs vid bevattning. Denna studie genomfördes därför delvis i Albanien där prov av grundvatten och flodvatten hämtades från Drins och Vjosas floddeltan för att undersöka saltets ursprung och för att bedöma de biotillgängliga metalkoncentrationerna av nickel och zink. Vattenprover togs på ett urval av platser och testades direkt för omgivningsberoende parametrar samt analyserades vidare i laboratorier. I laboratoriet analyserades proverna med avseende på fördelning av syre- och deuteriumisotoper. Resultaten användes för att bedöma syreinnehållets ursprung, eftersom metoden för att undersöka saltets ursprung använder syreisotopen som spårämne. Anjon- och katjonkoncentrationer analyserades såväl som koncentrationerna av metaller. Dessa användes som inmatningsdata till Visual Minteq, en modell som används för att beräkna metallsammansättningen i vatten och en Biotic ligand model som användes för att beräkna de biotillgängliga koncentrationerna samt HC5-koncentrationerna. Isotopanalysen gav resultat som liknar tidigare studier utförda i det närliggande området vilket indikerar att saltet inte har oceaniskt ursprung utan meteorologiskt. De biotillgängliga koncentrationerna av nickel och zink var i de flesta fall lägre än de beräknade HC5-koncentrationerna, vilket indikerar att det finns ett buffertsystem, trots att gruvaktiviteter uppströms provplatserna skulle kunna ha påverkat vattenkvaliteten negativt. Studien slutsats är att saltet i grundvattnet och flodvattnet är av meteoriskt ursprung och inte ett resultat av saltvatteninträngning från det Adriatiska havet. De biotillgängliga halterna av nickel och zink understiger HC5 halterna i samtliga fall utom ett. För att fördjupa förståelsen och kunskapen om vattenkvaliteten i dessa områden bör framtida studier fokusera på en kontinuerlig mätperiod som till exempel sträcker sig över hela året vilket skulle minimera eventuella säsongsvariationer av insamlad data. Andra metoder så som geofysiska mätningar kan också bidra till en bredare analys av tillståndet i grundvattnet.
17
Yang, Haiyan. "Development of a physics-based morphodynamic model and its application to braided rivers." Thesis, Cardiff University, 2013. http://orca.cf.ac.uk/56986/.
Full textAbstract:
An understanding of the interaction between flow, sediment and bed morphology is essential for dealing with engineering problems such as floods, river bank erosion and sedimentation in reservoirs. However, the morphodynamic processes in natural braided rivers are still not well understood due to difficulties in measurements in field. Numerical models provide a considerable assistance to investigate these complicated processes in natural rivers. In the present study, a physics-based two-dimensional model based on DIVAST with suspended load and bed load transport has been developed to simulate the braiding processes and morphodynamic changes in braided rivers. In this model, the hydrodynamic equations are solved using the ADI scheme and the advective-diffusion equations are solved using a modified ULTIMATE QUICKEST scheme. The TVD scheme has also been included to simulate trans-critical flows. Regarding sediment transport, a new module based on bed load transport theories has been developed. A module for suspended load transport based on energy theory has been improved. Secondary flow and slope effect are integrated into the model by altering the sediment transport rate. A multiple layer technique with a vertical sorting process has been applied including bank erosion. Graded sediment fractions are adopted to represent the coarsening and fining processes with sheltering effect. The model has been verified by solving a 2-D dam-break problem which worked well in predicting the water surface changes in trans-critical flow. It has also been tested by a sediment aggradation case and found to predict the flow and bed deformation effectively. The model has been applied to predict a laboratory river with bed load, with its prototype being the Sunwapta River, Canada. Braiding mechanisms and channel pattern responses to abruptly increased discharge have been investigated and compared with those of laboratory and natural rivers. Growth and relationship of active braiding intensity and total braiding intensity show similar trends to those of iii the laboratory river. The predicted river shows anisotropic scaling with periodical braiding morphology presented by sequential maximum scour depths. The model also simulates a large idealised braided river with suspended load transport. Its braiding mechanisms have been discussed and compared with the river with bed load and natural rivers. Important processes at bars and confluences have been investigated. Statistical characteristics of the river have been analysed with braiding indices, state-space plots and bar parameters. These findings have been compared with those from real rivers to assess the model simulating real braided rivers.
18
Al, Saleh Fatima. "Numerical Modeling Of Shoreline Changes Around Manavgat River Mouth." Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605705/index.pdf.
Full textAbstract:
River mouths are very active coastal regions. Continuous sediment supply by the river and the movement by wave action cause the shoreline to change in time and space. Modeling of shoreline changes is an essential step before the design of any coastal engineering project. This research aimed to develop a system of numerical models to present the shoreline changes around a river mouth. The system of numerical models has three components: 1) modeling of nearshore wave characteristics, 2) modeling of longshore sand transport rates using the results of the first component, 3) modeling of shoreline changes using the estimated sand transport rates. Thus, firstly, deep water wave characteristics including the annual wave rose affecting Manavgat River mouth have been obtained from the database of NATO TU-WAVES Project. Then REF/DIF1 and SWAN nearshore wave models have been used to find out nearshore wave conditions. Since the results obtained from REF/DIF1 wave model have been found to be more reasonable compared to SWAN&rsquos output, REF/DIF1 wave model has been used in preparing a time series nearshore reference wave file with three hours time interval. This reference file has been used to run GENESIS. Last step of the numerical shoreline change modelling of Manavgat River mouth was the calibration procedure in which the &ldquo
transport parameters&rdquo
k1 and k2 have been determined. As there is lack of measurements of shoreline positions that can be used in calibrating shoreline change model, k1 and k2 has been approximately found to be k1=0.516 and k2=0.9 by using an empirical sediment transport formula. As a future study, it is recommended that when the protection structure controlling the river mouth is finished, the measurements of shoreline position behind the structure should be used in verification of shoreline change model in order to get more accurate results.
19
Andersson, Elin, and Sofia Hietala. "Application of a new method to improve river cross sections derived from satellite images." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-242553.
Full textAbstract:
In hydrological and hydraulic modelling, river geometry is a crucial input data. Recent investigations have been looking at methods to improve the description of cross sections extracted by DEM derived by satellite images. SRTM derived DEM are often lacking precise information as the sensors cannot detect the submerged river parts, but, on the other hand, it is available on a global scale which makes it very attractive and useful, especially in data scarce regions. This study aims at applying the so called “slope break” method to improve river cross section geometry extracted from SRTM DEM. The report is divided into three parts: a) The making of a Matlab-code to improve cross sections geometry extracted by satellite derived DEM; b) an application of the code to real cross-sections from the river Po in Italy and c) hydraulic simulations with and without SRTM modified cross sections to test the performance of the method, in collaboration with senior colleagues. The Matlab successfully performs the slope break point and finds, when appropriate, the approximated lowest point zmin of the cross section below the water surface. The comparison of the river geometry of the modified SRTM cross sections versus LiDAR available cross sections show the good performance of the method in improving the river geometry description. This code can simplify the work and improve many SRTM river cross sections in an effective way. The hydraulic simulations performed with and without the modified cross sections show how the modified SRTM model improves when compared to LiDAR results
20
Hellmér, Elin. "Using eDNA to improve environmental monitoring for water bodies effected by hydropower in Sweden." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-235981.
Full textAbstract:
The aim of this report is to contribute to the base of knowledge on environmental monitoring by increasing understanding of how eDNA, electrofishing and sampling fishing may be used to examine fish biodiversity. It also aims at understanding if fish indexes developed within the Water Framework Directive reflect biodiversity, as well as the potential of eDNA data to serve as input to these indexes. This was done by using three different approaches. Firstly, in order to establish which of the methods eDNA, electrofishing and sampling fishing is more suitable to measure the different dimensions of biodiversity (species richness, species evenness and genetic diversity), a literature review comparing the different methods was carried out. It was found that eDNA yields a more detailed results for species richness, electrofishing yields better results for species evenness and sampling fishing is outperformed by eDNA and electrofishing alike. Both electrofishing and sampling fishing may collect data for genetic diversity analysis, however electrofishing outperforms sampling fishing with regards to amount of species caught, making electrofishing a more suitable data collection method. Secondly, in order to gain insight on practical usage of eDNA, a case study of Spjutmo (Dalarna county) was reviewed. It was established that eDNA generated more detailed information of species richness in the case of Spjutmo (as compared to electrofishing). The relative abundance data generated by the eDNA study might be seen as a measure of species evenness. However, electrofishing yielded data which may serve as input to species evenness indices. To the best knowledge of the author, none of the methods generated data on genetic diversity in this specific case. Officials from the energy company Fortum and the county board of Dalarna were also interviewed in order to get insight on what potential they see for eDNA to contribute to environmental monitoring. Both officials point at the ability to estimate abundance as a desired feature, hence a better understanding of what the relative abundance results indicates is wanted. The two interviews indicate that this understanding is an important feature to develop in order to make metabarcoding studies effective in current environmental monitoring. Thirdly, in order to understand if fish indexes developed within the Water Framework Directive reflect biodiversity, a literature review was performed. It was found that, all but one of the compared indexes incorporates or somewhat incorporates species richness. However, only five indexes are indicative or somewhat indicative of species richness. Species evenness is incorporated or somewhat incorporated by two indexes, which are also indicative or somewhat indicative of species evenness. None of the indexes incorporate or indicate genetic diversity. Within the third literature review, the potential of eDNA data to serve as input to current fish-based indexes developed within the Water Framework Directive, was studied. It was found that eDNA data may serve as input to only one index in its present form. However, five indexes also use proportional information (e.g. proportion of tolerant species), which possibly could be provided by eDNA data. The index where usage of eDNA data is currently possible uses presence-absence information.Målet med denna rapport är att bidra till kunskapsläget kring miljöövervakning genom att öka förståelsen för hur eDNA, elfiske och provfiske kan användas för att undersöka fisk biodiversitet. Målet är också att förstå om fisk-index utvecklade inom ramen för det Europeiska vattendirektivet reflekterar biodiversitet samt om data från eDNA kan utgöra input till dessa index. För att uppfylla dessa mål användes tre metoder. För att etablera vilken av metoderna eDNA, elfiske och provfiske är mer lämpad att mäta de olika dimensionerna av biodiversitet (artrikedom, distribution av arter och genetisk diversitet), genomfördes en litteraturstudie. Slutsatsen kunde dras att eDNA mäter artrikedom med högst noggrannhet, elfiske mäter distribution av arter mer detaljerat och att provfiske överträffas av både eDNA och elfiske i alla dimensioner. Både elfiske och provfiske kan samla data för analys av genetisk diversitet, men elfiske överträffar provfiske gällande hur många arter som fångas, vilket gör elfiske mer lämpligt som metod att samla in data för genetisk analys. För att få praktisk insikt i ett fall där eDNA använts, granskades en fallstudie från Spjutmo (i Dalarnas län). eDNA genererade mer detaljerad information om artrikedom än elfiske i detta fall. Datan genererad av eDNA kring relativ abundans mellan arter skulle kunna tolkas som ett mått på distribution av arter. Data genererad av elfiske kan å andra sidan användas som input till olika index för distribution av arter. Författaren veterligen, genererade varken eDNA eller elfiske mått på genetisk diversitet i detta specifika fall. Två personer, en från Fortum och en från länsstyrelsen Dalarna intervjuades också för att få insikt i deras syn på potentialen av att använda eDNA som ett miljöövervakningsverktyg. Båda intervjupersonerna pekade på att en bättre förståelse av de relativa abundansvärdena indikerar är önskad. Båda intervjupersonerna pekade på att det är en viktig aspekt för att metabarcoding studier ska vara effektiva i nuvarande miljöövervakning. För att förstå om fisk-index utvecklade för EU’s vattendirektiv reflekterar biodiversitet, genomfördes en komparativ litteraturstudie av index. Alla index förutom ett inkorporerar eller delvis inkorporerar artrikedom. Bara fem indikerar eller delvis indikerar artrikedom. Distribution av arter inkorporeras eller delvis inkorporeras av två index som också indikerar eller delvis indikerar distribution av arter. Inom den komparativa litteraturstudien av index, studerades även potential att fungera som input av data genererad av eDNA till indexen. Data genererad av eDNA kan i dagsläget fungera som input till ett av indexen. Fem index använder någon form av proportionell data (t.ex. proportion av toleranta arter), som möjligen skulle kunna ges av eDNA. Indexet till vilket det är möjligt att använda eDNA data använder närvarande-ej närvarande information som input.
21
Woodruff, Jonathan Dalrymple. "Sediment deposition in the lower Hudson River estuary." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80032.
Full textAbstract:
Thesis (S.M. in Civil and Environmental Engineering)--Joint Program in Applied Ocean Physics and Engineering (Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering; and the Woods Hole Oceanographic Institution), 1999.Includes bibliographical references (leaves 54-57).
by Jonathan Dalrymple Woodruff.
S.M.in Civil and Environmental Engineering
22
Ryu, Sangsoo. "Hull/Mooring/Riser coupled motion simulations of thruster-assisted moored platforms." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1621.
Full textAbstract:
To reduce large motion responses of moored platforms in a harsh environment in deep waters, a thruster-assisted position mooring system can be applied. By applying the system, global dynamic responses can be improved in terms of the mooring line/riser top tensions, operational radii, and the top and bottom angle of the production risers. Kalman filtering as an optimum observer and estimator for stochastic disturbances is implemented in the developed control algorithm to filter out wave frequency responses. Investigation of the performance of thruster-assisted moored offshore platforms was conducted in terms of six-degree-of-freedom motions and mooring line/riser top tensions by means of a fully coupled hull/mooring/riser dynamic analysis program in the time domain and a spectral analysis. The two cases, motion analyses of a platform with thrusters and without thrusters, are extensively compared. The numerical examples illustrate that for deepwater position-keeping of platforms a thruster-assisted moored platform can be an effective solution compared to a conventionally moored platform.
23
Johansson, Emilia, and Emma-Helena Ericsson. "Quantification for the Flow of Microplastic Particles in Urban Environment: A Case of the Chao Phraya River, Bangkok Thailand : A Minor Field Study." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-230990.
Full textAbstract:
Plastic, including microplastic, is a common product in the society today and is starting to be more common in oceans where it can stay for a long time. Microplastic is defined usually in the size range five millimeter and smaller and together with the important Chao Phraya river in Bangkok, Thailand, the main subject of this paper is described. More clearly, the aim of this paper is to provide a first-hand quantification of microplastics flowing into the Chao Phraya River. Samples were taken at upstream, middle and downstream locations in the river with a pump-system and were then analyzed in a lab. The result showed an increasing load of microplastic entering the river from Bangkok, for example the result for size range five to one millimeter showed a six times increase of microplastic between the upstream and downstream point.Plast, däribland mikroplaster, är en vanlig förekommande produkt i samhället idag och börjar bli allt vanligare i hav där det också kan stanna ett långt tag efter att det hamnat där. Mikroplaster definieras oftast med storleks intervallet fem millimeter och mindre och tillsammans med den viktiga floden Chao Phraya i Bangkok, Thailand, är huvudämnet för denna studie beskriven. Mer tydligt, målet för denna studie är att förse en första kvantifiering av mikroplaster som flödar in till Chao Phraya floden. Prover togs på platser som var uppströms, i mitten och nedströms på floden och sedan analyserades dessa prover i ett laboratorium. Resultatet som framkom visade på ökande belastning av mikroplaster i floden från Bangkok, exempelvis visade resultatet för storleks intervallet fem till en millimeter på en sex gånger ökning av mikroplaster mellan uppströms platsen och nedströms platsen. Ökningen som troligen kommer från innerstaden kan bero på olika faktorer såsom väder, stadens avfallshantering och användningen av engångsprodukter som är av plastmaterial. Således påvisar detta vikten av, bland annat, en fungerande avfallshantering.
24
Carpman, Nicole. "Marine Current Resource Assessment : Measurements and Characterization." Licentiate thesis, Uppsala universitet, Elektricitetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-266670.
Full textAbstract:
The increasing interest in converting energy from renewable resources into electricity has led to an increase in research covering the field of marine current energy, mainly concerning tidal currents and in-stream tidal turbines. Tides have the advantage of being predictable decades ahead. However, the tidal resource is intermittent and experiences local variations that affect the power output from a conversion system. The variability is mainly due to four aspects: the tidal regime, the tidal cycle, bathymetry at the site and weather effects. Each potential site is unique, the velocity flow field at tidal sites is highly influenced by local bathymetry and turbulence. Hence, characterizing the resource requires careful investigations and providing high quality velocity data from measurement surveys is of great importance. In this thesis, measurements of flow velocities have been performed at three kinds of sites. A tidal site has been investigated for its resource potential in one of all of the numerous fjords in Norway. Measurements have been performed to map the spatial and temporal variability of the resource. Results show that currents in the order of 2 m/s are present in the center of the channel. Furthermore, the flow is highly bi-directional between ebb and flood flows. The site thus have potential for in-stream energy conversion. A model is proposed that predicts peak current speed from information on tidal range at the site. A corresponding model can be set up and implemented at other similar sites affected by tides, i.e. fjord inlets connecting the ocean to a fjord or a basin. A river site serves as an experimental site for a marine current energy converter that has been designed at Uppsala University and deployed in Dalälven, Söderfors. The flow rate at the site is regulated by an upstream hydrokinetic power plant nearby, making the site suitable for experiments on the performance of the vertical axis turbine in its natural environment. The turbine has been run in uniform flow and measurements have been performed to characterize the extent of the wake. An ocean current site was a target of investigation for its potential for providing utilizable renewable energy. A measurement campaign was conducted, mapping the flow both spatially and temporally. However, the site was shown to not be suitable for energy conversion using present technique.Det ökande intresset för att producera elektricitet från förnybara energikällor har lett till en satsning på forskning inom området marin strömkraft, främst när det gäller tidvattenströmmar och tidvattenturbiner för fritt strömmande vatten. Tidvatten har fördelen att vara förutsägbar årtionden i förväg. Dock så är tidvattenresursen periodisk och varierar lokalt vilket påverkar effektuttaget från ett kraftverk. Variationerna beror till största delen på fyra aspekter: antal hög- och lågvatten per dag, tidvattencykeln, djupförhållanden på platsen (batymetri) och vädereffekter. Varje potentiell plats är unik, vattnets hastighetsfält påverkas i hög grad av lokal batymetri och turbulens. Därför krävs noggranna undersökningar för att karakterisera resursen. Att tillhandahålla hastighetsdata av hög kvalitet från mätningar är därför av stor betydelse. I denna avhandling har mätningar av flödeshastigheter utförts på tre typer av platser. En plats med tidvattenströmmar, belägen i en av alla fjordar längs Norges kust, har undersökts för sin resurspotential. Mätningar har utförts för att kartlägga resursens variation i både tid och rum. Resultaten visar att strömmar i storleksordningen 2 m/s återfinns i mitten av kanalen. Dessutom uppvisar flödet liten variation från huvudriktningen för både inkommande (flod) och utgående (ebb) flöden. Platsen har således potential för energiomvandling av fritt strömmande vatten. En modell föreslås som förutsäger strömmarnas maxhastighet från information om höjdskillnaden mellan ebb och flod och vice versa. En motsvarande modell kan ställas upp och användas på andra platser med liknande förhållanden som berörs av tidvatten, dvs. fjordinlopp som förbinder havet med en fjord eller en bassäng. En älv fungerar som en plats för experiment för ett marint strömkraftverk som har utvecklats vid Uppsala universitet och sjösatts i Dalälven, Söderfors. Flödeshastigheten på platsen regleras uppströms av ett närliggande vattenkraftverk, vilket gör platsen bra för att utföra experiment på prestandan av den vertikalaxlade turbinen i dess naturliga miljö. Turbinen har körts i jämnt flöde och mätningar har utförts för att karaktärisera vakens utbredning. En plats med havsströmmar var mål för en utredning av dess potential för att ge användbar förnybar energi. En mätningskampanj genomfördes för att kartlägga flödets variation både rumsligt och tidsmässigt. Emellertid visade sig platsen inte vara lämplig för energiomvandling utifrån användning av nuvarande teknik.
25
Wendin, Gustav. "Experimentell parameterstudie av bubbelridåer i syfte att avleda fisk." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-383082.
Full textAbstract:
Bubble curtains offer a potential solution for hindering downstream migrating fish from passing through the turbines of hydropower plants, by instead guiding them to a safe passage. Compared to the conventional method of using low-inclined bar racks close to the turbine intake, bubble curtains are considerably cheaper, especially for large scale hydropower plants. In this work bubble curtains are evaluated through an experimental parametric study, mainly regarding two quantities, defined here as the overall bubble coverage of the background, as well as the occurrence of large tears in the curtain. The examined parameters cover the design of the device that generates the bubbles, the positioning of the device, as well as the flow condition of the water. The bubble curtain was filmed with underwater cameras and image analysis was performed using image segmentation in MATLAB. Results indicate that the total air flow should be chosen high, around 200-500 nl/min/m. The number of holes the air is distributed across is of little importance, except in the area closest to the air outlets, where permanent tears may occur inbetween holes if the distance is to great. Smaller holes (<1mm) are preferable to larger holes (>1 mm), but the difference is small compared to the effect of the total air flow. In flowing water, a smaller angle of attack against the current is better based on the defined quantities, but it will also result in a longer and therefore more expensive device. The bubble curtain should not be placed where mean water velocities exceed 0,75 m/s, since it will result in an inclination with the current close to that of bar racks designed to guide fish towards the surface. Furthermore, at these water velocities some fish may have difficulties following the curtain, due to their limited swimming capabilities.
26
Redin, Sigrid Hjelm, and Sofia Lundholm. "Avskiljning av koppar och zink från vägdagvatten med filtermaterialet Polonite : Experiment och modellering." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297486.
Full textAbstract:
The number of hardened surfaces has increased as a result of urbanization, and thus also the amount of road stormwater. Road stormwater can transport pollutants that have been released on road areas to surrounding recipients. Two substances that are found in particularly high concentrations in road storm water are copper and zinc. At high concentrations of these substances, toxic effects occur which are particularly harmful to aquatic organisms. This report intends to investigate how well the filter material Polonite purifies road stormwater from copper and zinc. Polonite is a reactive filter material made of the sedimentary rock Opoka, which binds substances such as copper and zinc by adsorption. In this thesis, a laboratory experiment has been carried out where it has been investigated how well different amounts of Polonite adsorb copper and zinc during different time periods. The results show that the concentrations of copper and zinc generally decreased over time and with an increasing amount of Polonite. Furthermore, a simulation of how Polonite's purification capacity decreases over time has been created. The simulation showed that Polonite's ability to purify stormwater according to the guideline values ceases after 133 days for copper and 325 days for zinc. Data collected from a column experiment was then compared with the simulation. The comparison showed that the simulation for zinc was in good agreement with the data from the column experiment, while the data for copper were more different from the simulation. Conclusions drawn are that Polonite can be a good solution for sustainable road stormwater management as it can purify zinc and copper in accordance with the recommended guideline values. The results also show that Polonite has a better ability to purify zinc than copper and that it can purify zinc for a longer period of time. Moreover, other aspects such as economics need to be investigated in future studies to establish with certainty that Polonite is a good solution for the purification of road stormwater in large-scale treatment plants.Till följd av urbaniseringen ökar antalet hårdgjorda ytor, och därmed även mängden vägdagvatten. Vägdagvatten kan transportera föroreningar som uppkommit på vägområden till omgivande recipienter. Två ämnen som hittas i särskilt höga koncentrationer i vägdagvatten är koppar och zink. Vid höga koncentrationer av dessa ämnen uppstår toxiska effekter som är särskilt skadliga för vattenlevande organismer. Denna rapport ämnar att undersöka hur väl filtermaterialet Polonite renar vägdagvatten från koppar och zink. Polonite är ett reaktivt filtermaterial som genom adsorption kan rena vägdagvatten. I detta arbete har en laboration utförts där det har undersökts hur väl olika mängder Polonite adsorberar koppar och zink under olika tidsperioder. Resultatet visar att halterna koppar och zink generellt minskar med tiden samt med ökande mängd Polonite. Vidare skapades en simulering av hur Polonites reningsförmåga minskar med tiden. Slutsatser som dragits är att Polonite kan vara en god lösning för hållbar vägdagvattenhantering då det kan rena koppar och zink i enlighet med de rekommenderade riktvärdena. Resultatet visar även att Polonite har en bättre förmåga att rena zink än koppar samt att det kan rena zink under en längre tidsperiod. För att med säkerhet fastställa att Polonite är en bra lösning för rening av vägdagvatten i storskaliga reningsanläggningar behöver flera aspekter såsom ekonomi undersökas i framtida studier.
27
Molin, Gustav. "Bubble curtains with vertical tubes : A way to deter fish from hydro power intakes." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-161010.
Full textAbstract:
This project was performed on assigment of Vattenfall R&D in Älvkarleby. The project was a first step in evaluating whether bubble curtains with vertical tubes could be suitable for diverting fish from hydro power intakes into fish passages. To determine this, prototypes were constructed, where one was tested in still water and one in running water. The tests in still water were carried out in a large cylindrical tank and the tests in running water were carried out in Kungsr¨annan in ¨Alvkarleby. A number of test variables were developed to be able to vary the tests. These test variables were hole size, number of holes, tube center-to-center distance, air flow and water velocity. The tests were carried out without fish, but a number of indicators were developed to be able to compare and evaluate the tests. For the tests in still water, these indicators were the width of the bubble curtain created by a single tube and the horizontal movement of the air bubbles, to determine whether the hydrostatic pressure from the surrounding water had any effect on the appearance of the bubble curtain. For the tests in running water, the indicators were the bubble curtain density, the curvature of the tubes and the movement of the tubes. All experiments were documented using cameras and the results were then obtained through image processing in the software MATLAB. The results showed that the width of the bubble curtain created by a single tube varied between 12 and 34 cm for pressures between 0.5 and 2.0 bar. It was concluded that the hydrostatic pressure was of minimal significance for the appearance of the bubble curtain, at least for depths up to 1.95 m. For the tests in running water, the air flow rate and tube center-to-center distance was of the greatest importance for the bubble curtain density. The curvature of the tubes were most affected by the size of the holes and the movement of the tubes were most affected by the number of holes.Detta projekt utfördes på uppdrag av Vattenfall R&D i Älvkarleby. Projektet var ett första steg i att utvärdera om bubbelridåer med vertikala slangar skulle kunna lämpa sig för att avleda fisk från vattenkraftverk vidare mot fiskpassager. För att avgöra detta konstruerades prototyper, där en testades i stilla vatten och en i rinnande vatten. Testerna i stilla vatten utfördes i en stor cylindrisk tank och testerna i rinnande vatten utfördes i Kungsrännan i Älvkarleby. Ett antal testvariabler togs fram för att kunna variera testerna. Dessa testvariabler var hålstorlek, antal hål, avstånd mellan slangarnas centrum, luftflöde samt vattenhastighet. Testerna gjordes utan fisk, men ett antal indikatorer togs fram för att kunna jämföra och utvärdera testerna. För testerna i stilla vatten var dessa indikatorer bubbelridåns bredd skapad av en enskild slang samt luftbubblornas horisontella förflyttning, för att avgöra om det hydrostatiska trycket från omgivande vattnet hade någon effekt på bubbelridåns utseende. För testerna i rinnande vatten var indikatorerna bubbelridåns täthet, slangens krökning samt slangens rörelser. Alla experiment dokumenterades med hjälp av kameror och resultaten togs sedan fram genom bildhantering i programvaran MATLAB. Resultaten visade att bubbelridåns bredd skapad av en enskild slang varierade mellan 12 och 34 cm för tryck mellan 0,5 och 2,0 bar. Det bedömdes att det hydrostatiska trycket var av minimal betydelse för bubbelridåns utseende, åtminstone för djup upp till 1,95 m. För testerna i rinnande vatten visade resultaten att luftflödet och avståndet mellan slangarnas centrum var av störst betydelse förr bubbelridåns täthet. Slangens krökning påverkades mest av hålens storlek och slangens rörelser påverkades mest av antalet hål.
28
Skoglund, Anna, Maja Skotte, Alexander Fors, Stahl Fanny Jeppsson, Harald Löf, and Johanna Renberg. "Avsaltning av brackvatten som lösning för Ålands framtida vattenförsörjning." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-384460.
Full textAbstract:
Målet med detta projekt var att jämföra nuvarande dricksvattenproduktion på Åland med ett eventuellt kompletterande avsaltningsverk, samt undersöka om det är rimligt att uppföra ett sådant. Detta genomfördes genom informationsinsamling i en litteraturstudie och jämförelse mellan nuvarande vattenverk och ett eventuellt avsaltningsverk i en beslutsmatris. Kategorier som ansågs relevanta för jämförelsen identifierades och sedan utvecklades dessa genom att identifiera parametrar som byggde upp kategorierna. Den insamlade informationen användes sedan för att klassa de olika parametrarna inom kategorierna och en samlad bedömning gjordes. De kategorier som undersöktes var: dricksvattenkvalitet, miljökonsekvenser, energiförbrukning och kostnader samt tillräcklig och säker dricksvattentillgång. Det eventuella kompletterande avsaltningsverket ansågs kunna konkurrera med nuvarande vattenproduktion med avseende på alla dessa fyra kategorier och metoden bedömdes vara en bra grund för jämförelsen. För att utveckla projektet i framtiden rekommenderades modellering och en pilotstudie.
29
Mauriet, Sylvain. "Simulation d'un écoulement de jet de rive par une méthode VOF." Phd thesis, Université de Pau et des Pays de l'Adour, 2009. http://tel.archives-ouvertes.fr/tel-00463578.
Full textAbstract:
Les processus dynamiques présents en zone de swash ont un impact significatif sur l'évolution des zones côtières. Une part importante du transport sédimentaire cross-shore se produit dans cette zone, plus particulièrement dans cette zone où se produisent le run-up et le run-down. La zone située au-delà de la ligne de rivage au repos est le plus souvent décrite par des modèles intégrés sur la verticale. La décroissance des vagues est bien reproduite, cependant l'étude du transport sédimentaire impose une paramétrisation du frottement sur le fond. Nous présentons les résultats de simulations RANS de la propagation d'un mascaret (obtenu par un "lâcher de barrage") sur une plage en pente et le run-up et le run-down ainsi générés. Les résultats numériques sont comparés aux résultats expérimentaux de Yeh et al. (1989). Les simulations ont été réalisées avec le code Navier-Stokes diphasique AQUILON. Deux méthodes de suivi d'interface VOF (VOF TVD ET VOF PLIC) sont implémentées. La viscosité turbulente est calculée par un modèle V2-F (Durbin, 1991). Une estimation des grandeurs turbulentes k et epsilon basée sur la théorie des ondes longues pour la propagation d'un ressaut hydraulique est présentée. Une modélisation VOF-PLIC & V2-F est appliquée pour reproduire les caractéristiques macroscopiques du lâcher de barrage, qui comme on pouvait s'y attendre dépendent peu de la turbulence. Nous étudions aussi l'impact des conditions initiales sur k et epsilon sur l'établissement de l'écoulement turbulent. Après ces validations vis-à-vis de la turbulence, des simulations du cas décrit par Yeh et al. (1989) sont menées pour optimiser le choix des paramètres de calcul. La théorie de Whitham (1958), prédit un effondrement du mascaret au niveau de la ligne de rivage au repos. La théorie de Shen and Meyer (1963) est toujours à l'heure actuelle le modèle de référence. Les résultats expérimentaux de Yeh et al. (1989) montrent clairement un phénomène différent. L'utilisation conjointe de la technique VOF-TVD et du modèle de turbulence V2-F semble apporter les meilleurs résultats par rapport aux expériences de Yeh et al. (1989). Une étude de la transition mascaret/lame de swash est proposée. Nos résultats montrent que la théorie de Whitham décrit de façon assez précise le mécanisme de d'effondrement du mascaret. Les résultats de nos simulations sont utilisés pour décrire la transition entre l'effondrement du mascaret et l'écoulement du run-up. L'analyse des processus de frottement dans le jet de rive met en évidence une forte dissymétrie entre le run-up et le run-down avec cisaillement plus faible lors du run-down
30
Huh, Youngsook. "The fluvial geochemistry of the rivers of Eastern Siberia and implications for the effect of climate on weathering." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/55321.
Full textAbstract:
Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 1998.Includes bibliographical references.
by Youngsook Huh.
Ph.D.
31
Dahlstrand, Gustaf. "Konsekvenser av en avsänkning av Dragby kvarndamm i Björklingeån." Thesis, Uppsala universitet, Institutionen för ekologi och genetik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-453163.
Full textAbstract:
I Sverige finns i dagsläget närmare 10 000 dammar i våra vattendrag. Dammar som har varit en viktig del i den svenska historien men som nu utgör ett hot mot att uppsatta miljömål nås. Dammarna fragmenterar effektivt vattendragen då de utgör vandringshinder för fisk och andra vattenlevande organismer. På senare tid har problemen som dessa dammar skapat blivit högre prioriterat av myndigheter och beslutsfattare. För att uppnå EU:s miljökvalitetsnormer krävs åtgärder vid i stort sett samtliga av Sveriges dammar. Vid vissa av dessa får naturen kompromissa och fiskvägar av olika slag tas i anspråk. Total utrivning av dammar är i Sverige fortfarande en ovanlig åtgärd men som börjar få spridning. Utrivning har visat sig vara det mest ekonomiska alternativet samtidigt som det bästa för miljön då det återställer inte bara konnektiviteten utan även vattendragets naturliga geomorfologiska processer och flödesdynamik. I denna studie har konsekvenserna av en avsänkning av Dragby kvarndamm i Björklingeån undersökts. Studien har genomförts genom att sammanväga data från biotopkartering, elfiske samt en hydraulisk modellering i HEC-RAS. Den hydrauliska modelleringen visade hur flödesförhållanden och fallhöjd kommer fördela sig vid en potentiell avsänkning av Dragby kvarndamm. Tillsammans med övriga undersökningar kunde en sammanvävd bild av konsekvenserna av en avsänkning formas. Vid en avsänkning kommer vattenytan sänkas med 1-1,7 m och inga nya strömsträckor kommer att bildas. Trots detta tyder elfisket och biotopkarteringen på att en avsänkning kommer att gynna arter som till exempel lake. En avsänkning kan därav bidra till ökad ekologisk status i Björklingeån.Sweden is a country revolved around different types of water. With a coastline stretching around a big part of the country. The Baltic Sea which is fed with so much fresh water that it classifies as a brackish sea. The fresh water from Sweden originates from almost 100 000 lakes and nearly 30 000 rivers and streams. However, these different waterways are heavily impacted by approximately 10 000 artificial dams. Dams that for example block fish from migrating to their spawning grounds. In the last couple of years, the problems revolving around dams have been put higher up on the agenda of politicians and authorities. Significant efforts need to be made to be able to reach the goals of the European Water Framework Directive. Those efforts include building different kinds of fish passage solutions around dams, but also removing dams that no longer have a purpose. Dam removal is often the most cost-effective solution and at the same time the one with most ecological benefits. In this study, the consequences of a removal of the Dragby mill dam have been investigated. The study have been done by collecting and combining data from habitat assessment, electrofishing and hydraulic modeling in HEC-RAS. The hydraulic modelling showed that the water level upstream of the dam will decrease with approximately 1-1.5 m if the dam is removed. Simulated water velocities indicate that no rapids and stream habitat suitable for trout will immerse if the dam is to be removed. Nonetheless, the combined information suggests that a dam removal would most likely benefit other species such as the threatened burbot. Therefore, a removal of Dragby mill dam could result in a ecological boost for river Björklingeån.
32
Nygren, Astrid, and Robin Slättengren. "Analys och jämförelse av två pilotanläggningar med olika sammansättning av membran : Vid rening av processvatten från industri." Thesis, Linnéuniversitetet, Institutionen för byggd miljö och energiteknik (BET), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-65693.
Full textAbstract:
Vattentillgången på Öland har under en lång tid varit mycket ansträngd och har kommit till en punkt då det inte längre är hållbart. För att nå en mer långsiktig lösning planerar Mörbylånga kommun med hjälp av Norconsult att bygga ett vattenreningsverk. Detta kommer att rena bräckt vatten ifrån Kalmarsund samt processvatten ifrån Guldfågeln AB, som tillsammans kommer att fungera som ett komplement till det redan befintliga sötvattnet. Två pilotanläggningar som renar processvatten ifrån en industri, genom ultrafilter kombinerat med omvänd osmos, har utvärderats. En metod för att sammanställa de kostsamma driftparametrarna elförbrukning, förbrukning av kemikalier samt underhållsarbete vid drift och membranens inköpskostnad genom en LCC har tagits fram. Denna metod ger en ungefärlig totalkostnad per kubikmeter av det renade vattnet. Även vattenkvaliteten på ingående råvatten, vattnet mellan membranen samt det utgående vattnet har analyserats. Detta för att undersöka att processerna fungerar som den ska, samt ge en indikation på vilka mineraler som kommer att behöva tillsättas i efterhand. Pilot B blir ca fem kronor dyrare per kubikmeter jämfört med Pilot A. De totala kostnaderna, 9.70 – 10.79 kr/m3 för Pilot A och 15.19 – 15.28 kr/m3 för Pilot B, kan jämföras med den nuvarande kostnaden för en kubikmeter vatten i Mörbylånga, 15 kr/m3, samt den kostnad kommunen betalade sommaren 2016 för att frakta vatten i tankbilar, 70 kr/m3.
33
Simon, Peter. "Assessment of Embodied Energy and Carbon Emissions of the Swansea Bay Tidal Lagoon from a Life Cycle Perspective." Thesis, Mittuniversitetet, Avdelningen för ekoteknik och hållbart byggande, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-25145.
Full textAbstract:
In the pursuit of low-carbon, renewable energy sources one option with great potential in the UK is tidal energy. Specifically the proposed construction of the Swansea Bay Tidal Lagoon (SBTL) in South Wales has become one such discussed option. With a potential net annual output of 400 GWh and a 120-year lifetime the scheme represents a long-term and large-scale electricity production option. An assessment of carbon emissions and embodied energy (EE) of the lagoon’s life cycle was carried out. Total lifetime carbon emissions for the SBTL are in the region of 470,000 tCO2e and EE was found to be around 7,800 TJ. The assessment shows that the SBTL has significantly lower emissions per year than the existing National Grid mix and with emissions of around 0.01 kgCO2e/KWh is significantly lower than the UK emissions target of 0.07 kgCO2e/KWh. Energy payback of the SBTL was found to be in the region of 5.5 years. The use of dredged ballast infill sourced from within the area of the lagoon plays an important role in keeping emissions and energy use low; and is a key consideration when planning future tidal lagoon structures.
34
Sigfridson, Marcus. "Skyddsinfiltrationens influensområde för en fallstudie : - modellering och osäkerheter." Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-390702.
Full textAbstract:
För att uppskatta influensområdet till följd av skyddsinfiltartion finns ett antal analytiska modeller att tillämpa. Dessa modeller tar hänsyn till parametrar så som hydraulisk konduktivitet och magasinkoefficient, men de följer också med en rad antaganden som i praktiken inte kan uppfyllas. En alternativ tillvägagång för att bestämma influensområdet är därför med hjälp av numeriska modeller, som i större grad kan göras platsspecifika. Numeriska modeller är till följd av detta mer tidskrävande och behöver mer indata. I denna studie undersöktes vilken metod som är bäst lämpad för att bestämma skyddsinfiltrationens influensområden för en fallstudie i Bromstens industriområde, belägen cirka 15 km nordväst om Stockholm centrum. Två numeriska modeller med varierande underlag av platsspecifika data utvecklades över områdets geologi och grundvattenmagasin för att kunna simulera grundvattennivåer med och utan infiltration. Utöver detta beräknades influensområdet med fyra analytiska modeller. Modellerna testades sedan utifrån olika scenarion, där såväl dataupplösning som den platsspecifika kännedomen över området stegvis ökades. Platsspecifika data tillkom till följd av geotekniska undersökningar och hydrogeologiska tester. Studien ämnar även att besvara vilken data som är av störst vikt för att bestämma influensområdet med de analytiska respektive numeriska modellerna samt vilka skillnader som uppstår mellan analytiskt beräknade influensområden och numeriskt simulerade influensområden. Resultaten visar att de numeriska modellerna i huvudsak är känsligast med avseende på den hydrauliska konduktiviteten, samt att den enklare numeriska modellen är känslig för magasinkoefficienten, något som indikerar att denna modell inte uppnår jämvikt i enlighet med vad som observerats i fält. Utöver detta stod det klart att vattenavgivningstalet inte hade någon nämnvärd inverkan på resultaten. Bland de analytiska modellerna råder den största känsligheten i magasinkoefficienten, följt av konduktiviteten. För Sichardts formel, som inte tar hänsyn till magasinkoefficienten var konduktiviteten den känsligaste parametern. Akvifärens mäktighet, vilken reviderades mellan scenario 2 och 3, hade ingen betydande inverkan på de analytiska modellerna. Vidare visade infiltrationstestet på stora skillnader i skyddsinfiltrationens influensområde med avseende på de olika modellerna och dataunderlaget. Den minsta avvikelsen mätt i residualer observerades för den komplexa numeriska modellen under scenario 4, vilket motsvarar det scenario då dataunderlaget var som störst. Trots att detta scenario tillsammans med modell anses vara det dyraste fallet, anses detta vara det bästa och samtidigt mest tillförlitligt metoden för att uppskatta skyddsinfiltrationens influensområde.To evaluate the area of influence due to artificial infiltration several analytical models are available. Some of the parameters taken into account by these models are the hydraulic conductivity and storage coefficient, but with these models some assumptions, which in reality cannot be fulfilled, are made. An alternative approach to evaluate the area of influence is therefore with numerical models, which in a greater extent account for the site-specific conditions. Due to this, numerical models are more time consuming and require more input data. This project aims to investigate the most effective approaches to evaluate the area of influence due to artificial infiltration for a case study in Bromsten, located 15 kilometers northwest of Stockholm. Two numerical models, with different background data due to the extent of site knowledge, were developed to represent the site's geological settings and groundwater properties to simulate the groundwaterlevels with and without infiltration. Moreover the area of influence were calculated with four analytical models. All of the models were then applied on four different scenarios, in which the data resolution and the site knowledge increased. Site-specific data was added as a result of geological surveys and hydrogeological tests. The study also aims to answer which data is most important in order to determine the area of influence with analytical and numerical models and what differences there are between the analytical solutions compared with the numerical solutions. Among the methods investigated, constructing a more complex model with data from scenario 4, the scenario with the greatest data supply, resulted in the most reliable results and was therefore the best method and the method to choose for this case-study. Other results indicated that the numerical models first of all are sensitive to the conductivity and that the more simpel numerical model is sensitive to the storage coefficient as well. The last result shows that this model does not reach the steady state conditions as observed in field, which highlights the importance of goetechnical investigation for the numerical models. Moreover none of the numerical models were sensitive to the specific yield. Among the analytical models the storage coefficient was the most important followed by the conductivity. For one of the analytical models (Sichardts formula) the conductivity was the most sensitive parameter. The thickness of the aquifer had no significant impact on the analytical models.
35
Ludwig, Wolfgang. "Continental erosion and river transport of organic carbon to the world's oceans." Université Louis Pasteur (Strasbourg) (1971-2008), 1996. http://www.theses.fr/1996STR13246.
Full textAbstract:
L'objectif scientifique de cette etude est de quantifier a l'echelle globale les flux de carbone organique apportes chaque annees aux oceans, afin d'evaluer le role de ces flux dans le cycle global du carbone. Les flux de carbone organique concernent, de maniere a peu pres equivalente, le carbone organique dissous (cod) et le carbone organique particulaire (cop). Pour ces deux formes de carbone, les facteurs de controle sont identifies et des modeles empiriques sont etabli pour extrapoler les flux a l'echelle globale et regionale. Ces flux etant fortement associes aux flux d'eau (cod, cop) et de sediments (cop), une telle investigation n'est possible qu'avec un examen detaille des facteurs principaux de controle de ces deux parametres cles a l'echelle globale. L'approche de cette etude est basee sur un ensemble de 60 grands fleuves du monde. Les caracteristiques hydroclimatiques, biologiques, geomorphologiques et lithologiques des bassins versants de ces fleuves sont extraites d'un grand nombre de banques de donnees globales a partir des contours digitalises de ces bassins. Ensuite, ces caracteristiques sont utilisees pour des analyses statistiques avec les donnees de la litterature sur les flux de carbone, d'eau et des sediments dans ces fleuves. Lorsqu'on applique le modele de regression pour le cod a la surface totale des continents a partir de l'ensemble des donnees existantes, la quantite totale de carbone organique dissous exporte vers les oceans est estimee a environ 0,21 gigatonnes de carbone par an (gtc/an). Pour le cop, cette quantite est d'environ 0,16 gtc/an. Les flux correspondant d'eaux et de sediments sont respectivement de 44400 km#3/an et 16 gt/an. Pour tous ces transports fluviaux, des cartes globales representant la distribution spatiale des flux specifiques sur les continents sont ainsi presentees, et des bilans detailles sont proposes pour les differents continents, bassins oceaniques et type de climats. Finalement, la modelisation des transports fluviaux de carbone organique est couplee a une modelisation de carbone inorganique developpee par amiotte-suchet 1995
36
Jian, Jun. "Relationship between the Pacific Ocean SST Variability and the Ganges-Brahmaputra River Discharge." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6994.
Full textAbstract:
A simple correlation analysis was used to investigate the linear relationships between sea surface temperature (SST) and monthly flow of Ganges and Brahmaputra at the borders of Bangladesh and India using approximately 50 years of river discharge data. Strong correlations were found between the equatorial Pacific SST and boreal summer Ganges discharge from three-month lag to two-month lead times. The El Nio-Southern Oscillation (ENSO) explains Ganges flow variance exceeding 0.95 significance level using both the Nino 3.4 SST correlation and the composites made for El Nio (La Nina) periods.
The May SST of the southwest Pacific Ocean to the east of Australia continent has a strong correlation (>0.6) with early summer Ganges discharges. Using a lag correlation analysis of Ganges discharge and SST, we found a steady and continuous development in the Nino 3.4 SST relationship, and a strong correlation with the southwest Pacific SST which is most pronounced three-four months prior to the onset of Asian summer monsoon. These relationships mean that at least 25% of the interannual summer Ganges River discharge variability can be explained by antecedent equatorial and southwest Pacific SST. It provides a possible statistical method for linear forecasting two or three months in advance.
The Brahmaputra River discharge, on the other hand, shows weak relationships with tropical SST variability except for the Bay of Bengal and the higher northern latitudes of the Pacific.
37
Lai, Chiu-Mi. "River and ocean : the third-century verse of Pan Yue and Lu Ji /." Thesis, Connect to this title online; UW restricted, 1990. http://hdl.handle.net/1773/11102.
Full text
38
Soukup, Tyrel L. "Long lead-time streamflow forecasting of the North Platte River incorporating oceanic-atmospheric climate variability." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1594486091&sid=3&Fmt=2&clientId=18949&RQT=309&VName=PQD.
Full text
39
Swezey, Matthew Michael. "Ocean acoustic uncertainty for submarine applications." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104274.
Full textAbstract:
Thesis: S.M. in Naval Architecture and Marine Engineering, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Thesis: S.M. in Mechanical Engineering, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-125).
The focus of this research is to study the uncertainties forecast by multi-resolution ocean models and quantify how those uncertainties affect the pressure fields estimated by coupled ocean models. The quantified uncertainty can then be used to provide enhanced sonar performance predictions for tactical decision aides. High fidelity robust modeling of the oceans can resolve various scale processes from tidal shifts to mesoscale phenomena. These ocean models can be coupled with acoustic models that account for variations in the ocean environment and complex bathymetry to yield accurate acoustic field representations that are both range and time independent. Utilizing the MIT Multidisciplinary Environmental Assimilation System (MSEAS) implicit two-way nested primitive-equation ocean model and Error Subspace Statistical Estimation scheme (ESSE), coupled with three-dimensional-in-space (3D) parabolic equation acoustic models, we conduct a study to understand and determine the effects of ocean state uncertainty on the acoustic transmission loss. The region of study is focused on the ocean waters surrounding Taiwan in the East China Sea. This region contains complex ocean dynamics and topography along the critical shelf-break region where the ocean acoustic interaction is driven by several uncertainties. The resulting ocean acoustic uncertainty is modeled and analyzed to quantify sonar performance and uncertainty characteristics with respect to submarine counter detection. Utilizing cluster based data analysis techniques, the relationship between the resulting acoustic field and the uncertainty in the ocean model can be characterized. Furthermore, the dynamic transitioning between the clustered acoustic states can be modeled as Markov processes. This analysis can be used to enhance not only submarine counter detection aides, but it may also be used for several applications to enhance understanding of the capabilities and behavior of uncertainties of acoustic systems operating in the complex ocean environment.
by Matthew Michael Swezey.
S.M. in Naval Architecture and Marine Engineering
S.M. in Mechanical Engineering
40
Odriozola, Ana L. "On the color of the Orinoco River plume." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000565.
Full text
41
Farnsworth, Katherine L. "Controls on the delivery of fluvial sediment to the coastal ocean: The Salinas River, California." W&M ScholarWorks, 2003. https://scholarworks.wm.edu/etd/1539616643.
Full textAbstract:
To estimate delivery to the coastal ocean, a global river database was assembled. An estimated 35,000 km3 of freshwater, 4 * 10 6 tonnes of dissolved solids and 18.6 * 106 tonnes of suspended sediment are delivered annually. The global delivery of fluvial water and sediment, both suspended and dissolved, is dominated by Southeast Asia, due to the unique climatic, geologic and geomorphic character of the rivers in this region. Over 30% of the global freshwater and dissolved solid discharge, and an astounding 70% of the suspended sediment originate in this region. The Salinas River, central California, was the focus of an in-depth study on the controls on sediment delivery from a small, semi-arid watershed. This river discharges into the Monterey Bay an average of 0.4 km3 of water and 3.3 tonnes of sediment annually. Basin-scale control on the discharge of the river is dominated by the underlying geology as well as the anthropogenic changes to the watershed. Despite the altered nature of the Salinas River, the fluvial discharge is dominated by short-lived meteorological events. Large flood events on the Salinas River almost entirely correlate with El Nino events. However, not all El Nino years produce flood events. It was shown that the probability of a large flood on the Salinas River is determined not only by the presence of El Nino conditions, but also by the interaction between the Pacific Decadal Oscillation and the ENSO. The coinciding of warm phases of both of these large-scale phenomena produces significantly higher annual discharges than any other combination of the climatic phenomena. The Monterey Bay is bisected by a submarine canyon, restricting the shelf space and creating 2 separate sedimentary environments. The southern shelf bypasses most modern fluvial sediment to the canyon, whereas the northern shelf stores most of the sediment delivered. The estimate of Holocene sediment discharge from the rivers and creeks of the bay indicate that >60% of fluvially delivered sediment is lost to the canyon and deep ocean. The transport pathways of this removal are currently unknown, but hyperpycnal flow from the mouth of the Salinas River is hypothesized.
42
Terhaar, Jens. "Effects of river delivery of nutrients and carbon on the biogeochemistry of the Arctic Ocean." Doctoral thesis, Universite Libre de Bruxelles, 2019. https://dipot.ulb.ac.be/dspace/bitstream/2013/287713/3/Main.pdf.
Full textAbstract:
Coastal oceans play an important role in the carbon cycle and are hotspots of ocean primary production and ocean acidification. These coastal regions are strongly influenced by rives, especially in the Arctic. Despite the importance of the riverine delivery of carbon and nutrients, their effect on the Arctic Ocean is still poorly understood due to hostile conditions and the consequently low number of observations. This thesis aims at improving our understanding of the influence of Arctic riverine delivery of carbon and nutrients by using ocean biogeochemical models.The first part of the thesis evaluated the model skills of the ocean biogeochemical model NEMO-PISCES in the Arctic Ocean. By analyzing model results at different horizontal resolutions, the importance of lateral influx from the adjacent oceans for anthropogenic carbon cycle in the Arctic Ocean wasdemonstrated. These results were then used to adjust a previously published data-based estimate of anthropogenic carbon storage in the Arctic Ocean and the corresponding ocean acidification.In the second part, a pan-Arctic observation-based dataset of riverine carbon and nutrient fluxes was created. This dataset was then used to force the ocean biogeochemical model and the river fluxes were quantified. River fluxes have been shown to sustain up to 24% of Arctic Ocean primary production, to reduce the air-sea CO2 uptake by 20%, and to reduce surface ocean acidification seasonally. Eventually, idealized simulations were made to quantify the sensitivity of the Arctic Ocean biogeochemistry to future changes in riverine delivery of carbon and nutrients. Sensitivities are of small magnitude on a pan-Arctic scale, importance in the coastal areas, and the dominant factor close to river mouths.Doctorat en Sciences
info:eu-repo/semantics/nonPublished
43
Andrews, Matthew B. (Matthew Bryan) 1981. "Natural attenuation of organophosphates in river systems: Chattahoochee River case study." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/30138.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.Includes bibliographical references.
Three organophosphoric acid triesters, tributyl phosphate (TBP), tris(2-chloroethyl) phosphate (TCEP), and tris(2-butoxyethyl) phosphate (TBEP) have been detected in surface waters across the world, primarily the result of sewage treatment plant discharge. Despite concentrations as low as a few parts per trillion, there is growing concern over the potential impact these compounds can have on human and environmental health. This study is an attempt to identify the presence of natural removal processes for these three organophosphoric acid triesters within the Chattahoochee River near Atlanta, Georgia, USA. Samples were collected during the month of January at various sites along the Chattahoochee River. They were subsequently analyzed for concentration of all three organophosphoric acid triesters. These concentrations were then implemented in the construction of mass balances with the intention of identifying a sink term for each compound. A separate set of samples were collected and analyzed at various times over a 24-hour period. These results were used to calculate a biodegradation rate for each organophosphoric acid triester within the Chattahoochee River. The results demonstrate that these three compounds are persistent in the Chattahoochee River over the course of one day. This conclusion is specific to the time of year and location of sampling. Despite findings of no significant natural attenuation, this study should be used as a foundation for future research into the removal of low-level contaminants within the Chattahoochee River.
by Matthew B. Andrews.
M.Eng.
44
Rydholm, Björn. "Omlöp vid småskaliga vattenkraftverk, hållbarhet för både verk och miljö? : Mätning av effektförluster orsakade av omlöpet vid Åby vattenkraftverk i Växjö kommun." Thesis, Linnéuniversitetet, Sjöfartshögskolan (SJÖ), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-63792.
Full textAbstract:
I Sverige finns cirka 2000 vattenkraftverk men endast 10 procent har någon form av omlöp eller annan lösning (Risinger, 2012). Nya, strängare regler håller nu på att införas. Sedan 2014 finns en gemensam strategi från Energimyndigheten och Havs- och vattenmyndigheten för åtgärder i svensk vattenkraft (Risinger, 2014). En godkänd fiskväg är ett av kraven.Särskilt den småskaliga vattenkraften (energitillförsel under 10 MWh enligt Risinger (2012)) drabbas. Deras intäkter står många gånger i proportion till energiproduktionen och därmed saknas ofta de ekonomiska förutsättningarna för en fiskväg. Vidare kommer en del av vattnet, och därmed potentiella inkomster, att gå förlorade. Den här undersökningen syftar till att utröna vad ett omlöp får för konsekvenser i form av effektförluster. Det är naturligtvis omöjligt att komma fram till ett universellt svar. Istället mäts förlusterna hos ett specifikt mindre verk som redan har ett omlöp: Åby vattenkraftverk som ägs och drivs av Växjö kommun. Metoden som används är traversering i kombination med hydroskopisk flygel. Sedan tidigare finns beräknade värden från kommunen för flödet i omlöpet. Dessa jämförs med undersökningens uppmätta värden. Undersökningen visar att vid normalt vattenstånd (165,13 MÖH) flödar 167 ± 10 l/s vatten genom omlöpet. Detta är ett 70 l/s större flöde i jämförelse med kommunens beräknade värde. Förklaringar till den skillnaden ges av mätfel då djupet mättes och att inloppet hade byggts om mellan kommunens beräkningar och utförda mätningar. Även den formel som användes då de beräknade värdena togs fram föreslås som en tänkbar felkälla. 167 ± 10 l/s innebär ett bortfall om 4,2 ± 0,3 kW potentiell effekt.There are around 2000 hydropower plants in Sweden, but only 10 percent of them has a bio channel, fishway or equivalent solution (Risinger 2012). New, more strict rules are now about to be introduced. Since 2014 there is a mutual strategy from the two Swedish authorities ”Energimyndigheten” and ”Havs- och vattenmyndigheten”, which demands multiple actions from Swedish hydropower. (Risinger, 2014). An approved fishway is one of these.The small-scale hydropower plants (plants who produce less than 10 MWh according to Risinger (2012)) are especially affected from this. Their income is proportional to their production and therefore they’ll usually lack the economical ability to build a fishway. Furthermore, a part of the streaming water (which otherwise would equal income) will get lost. This study aims to decide the loss of effect a fishway causes. Of course, it is impossible to derive a universal answer. Instead the losses are measured at a specific smaller plant that already has a fishway: Åby hydropower plant that is owned and operated by Växjö municipality. Method being used is traversing in combination with a turbine flow meter. There are already calculated flows made by the municipality. These values will be compared with the measured values. The study shows that at a normal water level (165,13 m.a.sl) 167 ± 10 l/s of water is streaming through the fishway. This is a 70 l/s bigger flow in comparison with the municipality’s calculations. An explanation to this difference is given by measurement errors when the depth was measured, that the intake had been modified between when the calculations was being made and when the study’s measurements took place. Also, the formula being used for the calculated values is proposed as a possible source of error. 167 ± 10 l/s will result in a loss of 4,2 ± 0,3 kW potential effect.
45
Yttervik, Rune. "Ocean current Variability in Relation to Offshore Engineering." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-499.
Full textAbstract:
This work adresses ocean current variability in relation to offshore engineering.
The offshore oil and gas activity has up until recently taken place mainly on the continental shelves around the world. During the last few years, however, the industry has moved past the continental shelf edge and down the continental slope towards increasingly deeper waters. In deep water locations, marine structures may span large spaces, marine operations may become more complicated and require longer time for completion and the effect of the surface waves is diminished. Therefore, the spatial and temporal variability of the current is expected to become more important in design and planning than before.
The flow of water in the oceans of the world takes place on a wide variety of spatial scales, from the main forms of the global ocean circulation (~km), to the microstructure (~mm) of boundary layer turbulence. Similarly, the temporal variability is also large. In one end of the scale we find variations that take place over several decades, and in the other end we find small-scale turbulence (~seconds). Different features of the flow are driven by different mechanisms. Several processes and properties (stratification1, sloping boundary, Coriolis effect, friction, internal waves, etc.) interact on the continental slope to create a highly variable flow environment. Analysis of a set of observed data that were recorded close to the seabed on the continental slope west of Norway are presented. The data suggest that some strong and abrupt current events (changes in flow speed of ~0.4 m/s in just a couple of hours) were caused by motions of the deep pycnocline2, driven by variations in the surface wind field. This conjecture is partly supported by numerical simulations of an idealised continental slope and a two-layer ocean. The data also contains an event during which the flow direction at the sea bed changed very rapidly (within a few minutes) from down-slope to up-slope flow. The change in speed during this event was as high as 0.5 m/s.
Another data set has been analyzed in order to illustrate the spatial variation in the current that can sometimes be found. It is shown that the flow in the upper layer is virtually decoupled from the flow in the lower layer at a location west of Norway. This is either caused by bottom topography, stratification or both.
High variability of the current presents new requirements to the way that the current should be modelled by the offshore engineer. For instance, it is necessary to consider which type of operation/structure that is to be carried out or installed before selecting design current conditions. Reliable methods for obtaining design current conditions for a given deep water location have yet to be developed, only a brief discussion of this topic is given herein.
It is shown, through calculations of VIV-response and simulations of typical marine operations, that the variability of the current will sometimes have a significant effect on the response/operation.
1Vertical distribution of density. In a stratified ocean or flow, the density of the water varies in the vertical direction.
2pycnocline=density surface between water masses. The pycnocline between two water masses of different density is defined by the maximum of the density gradient.
46
Langlois, Gilles. "Diaphragm forming : innovation and application to ocean engineering." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37530.
Full text
47
Vaskov, Alex Kikeri. "Technological review of deep ocean manned submersibles." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74911.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis. Vita.
Includes bibliographical references (p. 63-65).
James Cameron's dive to the Challenger Deep in the Deepsea Challenger in March of 2012 marked the first time man had returned to the Mariana Trench since the Bathyscaphe Trieste's 1960 dive. Currently little is known about the geological processes and ecosystems of the deep ocean. The Deepsea Challenger is equipped with a plethora of instrumentation to collect scientific data and samples. The development of the Deepsea Challenger has sparked a renewed interest in manned exploration of the deep ocean. Due to the immense pressure at full ocean depth, a variety of advanced systems and materials are used on Cameron's dive craft. This paper provides an overview of the many novel features of the Deepsea Challenger as well as related features of past vehicles that have reached the Challenger Deep. Four key areas of innovation are identified: buoyancy materials, pilot sphere construction/instrument housings, lighting, and battery power. An in depth review of technological development in these areas is provided, as well as a glimpse into future manned submersibles and their technologies of choice.
by Alex Kikeri Vaskov.
S.B.
48
Balzola, Ricardo 1971. "Balancing container inventories for ocean carriers." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9494.
Full textAbstract:
Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.Includes bibliographical references (leaves 59-60).
Over the last twenty years the transportation industry has undergone a dramatic shift into container operations. The advantages of this mode of transportation are numerous, especially for the ocean carriers. The use of containers adds a high degree of versatility to their ships and increases the utilization of the vessels by means of a remarkable decrease in the loading and unloading operations time. However, the introduction of the containers adds, as well, a considerable investment cost to an industry that was already very capital intensive. The pressure of the high cost investment in equipment in addition to a remarkable competition in the sector forces every player in the industry to try to obtain the maximum efficiency in the utilization of its assets. Global trade is not in general balanced, and so the demand for containers at the different ports of the world varies greatly. As a result of this unbalanced situation, empty containers must be reallocated from mainly importing areas to those at which the overall outflow of freight is larger than the inflow. Managing the container inventory and the container reallocation, subject to the particular requirements of the industry and the present and future demand is known as the Container Allocation Problem. The purpose of this thesis is the development of a model for this problem so as to maximize the profit to be obtained from the management of a shipping line container inventory. The container avocation problem is modeled by the user of a large-scale, multi-stage stochastic network formulation that incorporates the uncertainty factor in the demand side of the problem. This network formulation captures the space-time dynamics of the reallocation process while using an objective function that minimizes the cost of the container operations in the long run. A continuous rolling horizon to limit the number of nodes in the network is used in the modeling of this system so as to make this problem tractable. Finally, a solution algorithm for this problem is proposed. The algorithm decomposes the initial non-linear network formulation into an iteration of successive linear approximations that can be solved via a classical linear programming method.
by Ricardo Balzola.
M.Eng.
49
Conroy, Brandon J. "Zooplankton Community Composition and Grazing in the Amazon River Plume and Western Tropical North Atlantic Ocean." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1477068157.
Full textAbstract:
Large river plumes and frontal zones are important physical features influencing plankton distribution in the marine environment. In the western tropical North Atlantic Ocean (WTNA) the Amazon River plume may extend over an area reaching 1.5 x 106 km2. The freshwater plume creates a low-density lens in the surface 25m and supplies silicon and phosphorus to the WTNA. These physical and chemical gradients create an ideal environment for large-scale blooms of diatom diazotroph associations (DDAs), a symbiotic relationship between nitrogen-fixing cyanobacteria and chain-forming diatoms. While the physical and chemical properties of the plume with regard to influences on phytoplankton have been reported, zooplankton distributions and the fate of enhanced primary production in the plume are largely unknown. I investigated mesozooplankton (>200 μm) composition and grazing in the Amazon River plume-influenced WTNA in spring (May-June 2010) and fall (Sept.-Oct. 2011). Changes in zooplankton distribution and grazing occurred over the sea surface salinity (SSS) gradient from low salinity and mesohaline plume waters to high salinity oceanic waters. Distinct communities were identified in each season along the salinity gradient with several taxa primarily constrained in the surface plume waters (e.g., Lucifer faxoni). The plume appears to function as an “extended estuary”, with a number of taxa (e.g., decapods, euphausiids, and fish larvae) utilizing the plume as a nursery habitat or dispersal mechanism for larval stages. Mesozooplankton grazing was elevated in plume waters compared to oceanic waters and was 2-3 times higher in the fall vs. spring. These patterns suggest a lag in the peak mesozooplankton abundance and grazing in response the observed spring DDA bloom, at least in low salinity plume waters. Comparison of micro- and mesozooplankton grazing along the SSS gradient supported a transition from an “export” food web in waters with SSS < 33 where mesozooplankton grazing dominated and potential for export via fecal pellet production is higher, to a “retention” food web at SSS above 33 where microzooplankton grazing was highest and recycling of nutrients in surface waters is predicted. Using molecular techniques to investigate feeding on DDAs and other N- fixers, I found that copepods consumed DDAs (Hemialus-Richelia and Rhizosolenia- Richelia, diatom-diazotroph respectively) as well as the colonial cyanobacterium Trichodesmium. Investigation of mesozooplankton grazing more broadly on other cyanobacteria with 16S rRNA sequencing revealed consumption of Synechococcus, Prochlorococcus, and the unicellular diazotroph UCYN-A Candidatus Atelocyanobacterium thalassa. Together, these results have important implications for our understanding of biogeochemical cycling in the WTNA, and other regions with abundant DDAs (e.g., the Mekong and Congo River plumes).
50
Lin, Steve S. (Steve Simpson) 1976. "A distributed interactive ocean visualization system." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80102.
Full textAbstract:
Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1999.Includes bibliographical references (leaf 47).
by Steve S. Lin.
S.B.and M.Eng.