Дисертації з теми "Pipelines Hydrodynamics Mathematical models"
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1
Yeow, Kervin. "Three dimensional scour along offshore pipelines." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0008.
Повний текст джерелаАнотація:
Three-dimensional scour propagation along offshore pipelines is a major reason to pipeline failures in an offshore environment. Although the research on scour in both numerical and experimental aspect has been extensive over the last three decades, the focus of the investigation has been limited to the two-dimensional aspect. The knowledge on three-dimensional scour is still limited. This dissertation presents the results of an experimental investigation on threedimensional scour along offshore pipelines in (1) steady currents (2) waves only and (3) combined waves and current. The major emphasis of the investigation is to investigate the propagation of the scour hole along the pipeline after the initiation of scour. Physical experiments conducted were used to quantify the effects of various parameters on scour propagation velocities along the pipeline. The problem of monitoring real time scour below a pipeline was solved by using specifically developed conductivity scour probes. Effects of various parameters such as pipeline embedment depth, incoming flow Shields parameter, Keuglegan- Carpenter (KC) number and flow incident angle to the pipeline on scour propagation velocities along the pipeline were investigated. The investigations clearly reveal that scour propagation velocities generally increase with the increase of flow but decrease with the increase of the pipeline embedment depth. A general predictive formula for scour propagation velocities is proposed and validated against the experimental results. There are still some common issues related to pipeline scour that is lacking in the literature to date. One of these issues is the effects of Reynolds number on two-dimensional scour beneath pipelines. A numerical approach was adopted to investigate the Reynolds-number dependence of two-dimensional scour beneath offshore pipelines in steady currents. A novel wall function is proposed in calculating the suspended sediment transport rate in the model. The effects of Reynolds number were investigated by simulating the same undisturbed Shields parameters in both model and prototype but with different values of Reynolds number in two separate calculations. The results revealed that scour depths for prototype pipelines are about 10~15% smaller than those for model pipelines. The normalized time scales was found to be approximately the same, and the simulated scour profiles for the model pipelines agree well with the experimental results from an independent study. The backfilling of pipeline trenches is also an important issue to the design and management of offshore pipelines. A numerical model is developed to simulate the self-burial of a pipeline trench. Morphological evolutions of a pipeline trench under steady-current or oscillatory-flow conditions are simulated with/without a pipeline inside the trench. The two-dimensional Reynolds-averaged continuity and Navier-Stokes equations with the standard k-e turbulence closure, as well as the sediment transport equations, are solved using finite difference method in a curvilinear coordinate system. Different time-marching schemes are employed for the morphological computation under unidirectional and oscillatory conditions. It is found that vortex motions within the trench play an important role in the trench development.
2
Brumley, Douglas Richard. "Hydrodynamics of swimming microorganisms." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608174.
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3
蔡景華 and King-wah Choi. "Finite difference modelling of estuarine hydrodynamics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1985. http://hub.hku.hk/bib/B30425153.
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4
Tsang, Suk-chong, and 曾淑莊. "A numerical study of coupled nonlinear Schrödinger equations arising in hydrodynamics and optics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2003. http://hub.hku.hk/bib/B26652651.
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5
McTaggart, Kevin Andrew. "Hydrodynamics and risk analysis of iceberg impacts with offshore structures." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/30733.
Повний текст джерелаАнотація:
The evaluation of design iceberg impact loads for offshore structures and the influence
of hydrodynamic effects on impact loads are examined. Important hydrodynamic effects include iceberg added mass, wave-induced oscillatory iceberg motions, and the influence of a large structure on the surrounding flow field and subsequent velocities of approaching icebergs. The significance of these phenomena has been investigated using a two-body numerical diffraction model and through a series of experiments modelling the drift of various sized icebergs driven by waves and currents approaching a large offshore structure. Relevant findings from the hydrodynamic studies have been incorporated into two probabilistic models which can be used to determine design iceberg collision events with a structure based on either iceberg kinetic energy upon impact or global sliding force acting on the structure. Load exceedence probabilities from the kinetic energy and sliding force models are evaluated using the second-order reliability method. Output from the probabilistic models can be used to determine design collision parameters and to assess whether more sophisticated modelling of various impact processes is required. The influence of the structure on velocities of approaching icebergs is shown to be significant
when the structure horizontal dimension is greater than twice the iceberg dimension. As expected, wave-induced oscillatory motions dominate the collision velocity for smaller icebergs but have a negligible effect on velocity for larger icebergs.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
6
Ye, Feng. "Derivation of a two-layer non-hydrostatic shallow water model." Thesis, Water Resources Research Center, University of Hawaii at Manoa, 1995. http://hdl.handle.net/10125/21919.
Повний текст джерелаАнотація:
A theoretical non-hydrostatic model is developed to describe the dynamics of a two-layer shallow water system in the presence of viscous and Coriolis effects. The Navier-Stokes equations are integrated over the water depth in each layer to obtain the layer-mean equations. To close the resulting equation set, perturbation expansions of the vertical momentum equation are used and the dynamic pressures are solved in terms of wave elevations and horizontal velocities. A preliminary analysis is also carried out and a result for the quasigeostrophic problems is given based on an previous study. Our final model is of the Bousinesq class which is nonlinear and dispersive, and includes the effects of surface wind stress, bottom friction, eddy diffusion and earth rotation. It is shown that our new model can be readily reduced to previous inviscid non-hydrostatic models. Our model can be used in numerical simulations to study real ocean problems such as hurricane generated waves, tidal induced current, and interactions among surface waves, internal waves and variable topographies.Thesis (M. S.)--University of Hawaii at Manoa, 1995.
Includes bibliographical references (leaves 55-59).
UHM: Has both book and microform.
U.S. Geological Survey; project no. 06; grant agreement no. 14-08-0001-G2015
7
Marchand, Philippe 1972. "Hydrodynamic modeling of shallow basins." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20274.
Повний текст джерелаАнотація:
A two-dimensional hydrodynamic model is used to simulate the flow field and the concentration distribution of a conservative tracer in shallow basins. A series of numerical test are performed to evaluate different numerical schemes and problems which arise for the use of the Second Moment Method (SMM) in diffusion dominated flows are reported. The results of the basin simulations are compared with experimental data. The model predicts the location and the size of the dead zones, bypassing, recirculation, and local concentrations within the basin. The positioning of the inlet and outlet, and the presence of baffles are important parameters for the location and size of dead zones. The model gives results which are in agreement with the experimental data. The results show that the hydrodynamic model is quite powerful in terms of predicting correctly the residence time distribution for ponds of various dimensions and shapes.
8
Muir, Stuart. "A relativisitic, 3-dimensional smoothed particle hydrodynamics (SPH) algorithm and its applications." Monash University, School of Mathematical Sciences, 2003. http://arrow.monash.edu.au/hdl/1959.1/9513.
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9
Song, Charlotte Kathryn Cody. "Hydrodynamic stability of confined shear-driven flows." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/17662.
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10
吳家鳴 and Jiaming Wu. "Simulation of a two-part underwater towed system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31239481.
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11
Jung, Kyung Tae. "On three-dimensional hydrodynamic numerical modelling of wind induced flows in stably stratified waters : a Galerkin-finite difference approach." Title page, contents and summary only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09phj95.pdf.
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12
Hudson, Dominic A. "A validation study on mathematical models of speed and frequency dependence in seakeeping of high speed craft." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299687.
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13
孫仁 and Ren Sun. "Hydrodynamic interaction between two bodies with rotation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31239304.
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14
Kurz, Günter. "Hydrodynamics of defects in nematic liquid crystal films." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313591.
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15
Al-Zubaidi, Hussein Ali Mahdi. "3D Hydrodynamic, Temperature, and Water Quality Numerical Model for Surface Waterbodies: Development, Verification, and Field Case Studies." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4500.
Повний текст джерелаАнотація:
Numerical modeling has become a major tool for managing water quality in surface waterbodies such as rivers, lakes, reservoirs, and estuaries. Since the two-dimensional longitudinal/vertical model CE-QUAL-W2 is a well-known model and it has been applied to thousands of waterbodies around the world successfully, its numerical scheme was adapted to develop a new three-dimensional numerical model for simulating hydrodynamics, temperature, and water quality in surface waterbodies. Finite difference approximations were used to solve the fluid dynamic governing equations of continuity, free water surface, momentums, and mass transport. No coordinate transformations were performed and the z-coordinate system has been used. Higher-order schemes (QUICK, QUICKEST, and ULTIMATE QUICKEST) in addition to the UPWIND scheme were used for the advective temperature and mass transport. A novel numerical approach was used for the numerical formulation of the three-dimensional scheme. This approach forced the numerical solution of the free surface equation to be a tri-diagonal matrix form rather than a more computationally intensive penta-diagonal matrix solution. This new approach was done by linking a method called line-by-line with the free water surface numerical solution. Another new approach was that the three-dimensional numerical scheme involved a simultaneous solution of hydrodynamics, temperature, and water quality at every model time level instead of saving the hydrodynamic results to be used later for water quality simulation. Hence, this scheme allowed feedback between the hydrodynamics and water quality every time step. In addition, various unique numerical algorithms were employed from CE-QUAL-W2 such as the W2 turbulence model, selective withdrawal theory, surface heat fluxes, and water quality sources and sinks, making the three-dimensional model built on well-tested algorithms.
To test the model structure and assumptions, an analytical verification was performed by comparing model predictions to known analytical exact solutions test cases. Good agreement was showed by the model for all of these tests. A computation of the volume balance over the simulation period was also incorporated within the model to assess how well the code performed. Sensitivity tests were also made varying bed and wind shear.
The model was also applied to three reservoirs in the USA as field case studies: Lake Chaplain in WA, Laurance Lake in OR, and Cooper Creek Reservoir in OR. The model was validated by comparing the model predictions of water levels, velocities, vertical temperature profiles, and dissolved oxygen with field data. Through these real applications, the numerical predictions of the 3D model showed good agreement with field data based on error statistics. The model results of each field case study were discussed separately. In the Lake Chaplain model application, the study was focused on the importance of the higher-order schemes compared to the first-order UPWIND scheme. The model predictions of temperature were determined by using the UPWIND, QUICK, and QUICKEST scheme and compared with field data. The Error statistics of the model predictions compared to field data were an absolute mean error (AME) of 0.065 m for the water level predictions and an overall AME of 1.62 °C, 1.09 °C, and 1.23 °C for the temperature predictions by using the UPWIND, QUICK, and QUICKEST scheme, respectively. In the Laurance Lake model application, a comparison was performed between the present 3D model and the 2D CE-QUAL-W2. Since the 3D model was build based on CE-QUAL-W2, differences between the two models were evaluated. Error statistics between the model predictions of water level and temperature compared to field data showed that both models were in good agreement with field data. However, the 3D model AME (0.30 m for the water level predictions and 0.48 °C for the temperature predictions) was higher than the 2D model (0.03 m for the water level predictions and 0.42 °C for the temperature predictions). Finally, the Cooper Creek Reservoir case study was done to show the model predictions of temperature and dissolved oxygen. In this application, vertical temperature profiles were covered the entire simulation period in order to show how the model transfer heat between stratification and non- stratification conditions. The model showed good agreement with field data (0.12 m AME for the water level predictions, 1.00 °C overall AME for the temperature predictions, and 1.32 g/m3 overall AME for the dissolved oxygen predictions).
Finally, comparisons were made between CE-QUAL-W2 and the 3D model. The 2D model generally performed better in the tests cases if the model user is unconcerned about lateral impacts. The 3D model is important to use when lateral currents and variation in the lateral dimension are important.
16
Seaid, Mohammed [Verfasser]. "Mathematical Models and Numerical Methods for Radiation Hydrodynamics: : Relaxation Schemes and Multilevel Algorithms / Mohammed Seaid." Aachen : Shaker, 2004. http://d-nb.info/1172611831/34.
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17
Barlow, Andrew. "An adaptive multi-material Arbitrary Lagrangian Eulerian algorithm for computational shock hydrodynamics." Thesis, Swansea University, 2002. https://cronfa.swan.ac.uk/Record/cronfa43081.
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18
Shek, Cheuk-man Edmond, and 石焯文. "The continuous and discrete extended Korteweg-de Vries equations and their applications in hydrodynamics and lattice dynamics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B36925585.
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19
Pinilla, Camilo Ernesto. "Numerical simulation of shear instability in shallow shear flows." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115697.
Повний текст джерелаАнотація:
The instabilities of shallow shear flows are analyzed to study exchanges processes across shear flows in inland and coastal waters, coastal and ocean currents, and winds across the thermal-and-moisture fronts. These shear flows observed in nature are driven by gravity and governed by the shallow water equations (SWE). A highly accurate, and robust, computational scheme has been developed to solve these SWE. Time integration of the SWE was carried out using the fourth-order Runge-Kutta scheme. A third-order upwind bias finite difference approximation known as QUICK (Quadratic Upstream Interpolation of Convective Kinematics) was employed for the spatial discretization. The numerical oscillations were controlled using flux limiters for Total Variation Diminishing (TVD). Direct numerical simulations (DNS) were conducted for the base flow with the TANH velocity profile, and the base flow in the form of a jet with the SECH velocity profile. The depth across the base flows was selected for the' balance of the driving forces. In the rotating flow simulation, the Coriolis force in the lateral direction was perfectly in balance with the pressure gradient across the shear flow during the simulation. The development of instabilities in the shear flows was considered for a range of convective Froude number, friction number, and Rossby number. The DNS of the SWE has produced linear results that are consistent with classical stability analyses based on the normal mode approach, and new results that had not been determined by the classical method. The formation of eddies, and the generation of shocklets subsequent to the linear instabilities were computed as part of the DNS. Without modelling the small scales, the simulation was able to produce the correct turbulent spreading rate in agreement with the experimental observations. The simulations have identified radiation damping, in addition to friction damping, as a primary factor of influence on the instability of the shear flows admissible to waves. A convective Froude number correlated the energy lost due to radiation damping. The friction number determined the energy lost due to friction. A significant fraction of available energy produced by the shear flow is lost due the radiation of waves at high convective Froude number. This radiation of gravity waves in shallow gravity-stratified shear flow, and its dependence on the convective Froude number, is shown to be analogous to the Mach-number effect in compressible flow. Furthermore, and most significantly, is the discovery from the simulation the crucial role of the radiation damping in the development of shear flows in the rotating earth. Rings and eddies were produced by the rotating-flow simulations in a range of Rossby numbers, as they were observed in the Gulf Stream of the Atlantic, Jet Stream in the atmosphere, and various fronts across currents in coastal waters.
20
Xu, Wenwei. "Development of a Steady-State River Hydrodynamic and Temperature Model Based on CE-QUAL-W2." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1619.
Повний текст джерелаАнотація:
CE-QUAL-W2 is a 2-D hydrodynamic and water quality model that has been applied to reservoirs, lakes, river systems, and estuaries throughout the world. However, when this model is applied for shallow systems, this model requires a long calculation time to maintain numerical stability, compared to applications of reservoirs or deeper river systems.
To solve this problem, a new hydrodynamic and temperature model was built based on the framework of CE-QUAL-W2 but that allows for steady-state hydrodynamic computations. By calculating the hydrodynamics at steady-state, the time step for stability is relaxed and simulations can proceed at much higher time steps. The rest of the model framework is still used for water quality state variables, in this case, temperature. The algorithm used for computing the water surface elevation is Manning's equation.
This thesis study is one part of the Willamette Water 2100 project (Santelmann et al., 2012), which examines hydrological, ecological, and human factors affecting water scarcity in the Willamette River Basin. This study included three stages: (1) Convert six existing CE-QUAL-W2 V3.1 models into a newer version: CE-QUAL-W2 V3.7. (2) Develop the steady-state model code in FORTRAN. (3) Test the steady-state model on three river systems in the Willamette River Basin at Year 2001 and 2002.
The result proved that the steady-state model could reduce the computing time by 90% for river applications, while predicting dynamic river temperature with high accuracy at a two-minute time scale. This new model will be employed to simulate the future of the Willamette River System at a decadal or centennial timescales, addressing river temperature concerns and fish habitat issues.
21
Snyman, M. F. "Numerical modelling of an offshore pipeline laid from a barge." Master's thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21804.
Повний текст джерелаАнотація:
Bibliography: pages 81-85.This thesis addresses some of the issues involved in using numerical methods to simulate the laying of an offshore pipeline, the objective being to contribute to the expertise of the South African offshore technology. Of particular interest is the prediction of the stresses in the pipe during such an event. The thesis concentrates on the use and suitability of the finite element method to simulate the important aspects of the pipelaying problem. ABAQUS, a nonlinear general purpose finite element code, was chosen as numerical tool, and nonlinear effects such as geometry and drag, as well as contact and lift-off at the boundaries, are included in the models. The analysis is performed in two parts: in the static analysis the displaced equilibrium position of the pipeline under self weight, buoyancy and barge tension is sought, whilst the response due to wave action and barge motion is of interest in the dynamic analysis. Numerical experiments show the suitability of ABAQUS to model the behaviour of slender structures under both static loads and dynamic excitations.
22
Husain, Sarhang Mustafa. "Computational investigation of skimming flow on stepped spillways using the smoothed particle hydrodynamics method." Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa43038.
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23
Wilms, Josefine. "On the hydrodynamic permeability of foamlike media." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1316.
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24
Virtanen, M. (Markku). "Mathematical modelling of flow and transport as link to impacts in multidiscipline environments." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514292002.
Повний текст джерелаАнотація:
Abstract
Examples of numerical modelling of surface water hydrodynamics and water quality are presented. Their meaning for the development of the EIA 3D model system is analyzed from the almost 70 tracer studies (mainly 1971–1974) until the 3-dimensional (3D) solutions which became dominant since 1982. Up to summer 2008, the number of 3D applications has increased to almost 230 while the number of all applications exceeds 300.
The specific applications considered are from: Porttipahta reservoir in Northern Finland (I), Porttipahta and Lokka reservoirs (II), combination of reservoirs, lake, river sections, Kemi estuary and the sea (III), Kemi estuary and other coastal applications in the Gulf of Bothnia (IV), Lake Haukivesi in Eastern Finland (V), Lake Näsiselkä in South-West Central Finland (VI), and Kymi River and Kotka estuary in Southern Finland (VII).
A detailed description of the 3D model system is given in the application of Näsiselkä (VI). It is completed with drastically changing water levels, drying and wetting of immersed areas, characteristics of pulsing system, and internal loading in the application of Porttipahta (I). The application of the Kymi River and Kotka estuary (VII) shows the sensitivity of tracers as transport indicators and the validity of the transport model. In Lokka and Porttipahta (II) the methods of validity tests are extended to include field tests, laboratory experiments, and comparisons with expert evaluations and analytical solutions.
A strong indication of model validity is obtained in Näsiselkä (VI). When the loading after the model work was changed according to a plan included in the computation, the observed changes of water quality corresponded closely with those predicted by the model. Another severe indication of the model validity is from Porttipahta and Lokka (I, II). With the parameter values based on data from 1967–1986, a recent application indicated a close agreement with the observed data from 2000–2006. In Haukivesi (V) and Näsiselkä (VI) the agreement between the model and observed results is extended to the biological indicators of the algal biomass.
The integrated application to the network of a planned and two existing reservoirs, a strongly regulated lake, river sections, Kemi estuary and the sea (III) shows the usability of the model system to all types of water bodies. As a practical result it highlights the decay of the effects of a new impoundment with time and distance, including fast dilution in the estuary and the sea.
25
Shojaei, Nasim. "Automatic Calibration of Water Quality and Hydrodynamic Model (CE-QUAL-W2)." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1942.
Повний текст джерелаАнотація:
One of the most important purposes of surface water resource management is to develop predictive models to assist in identifying and evaluating operational and structural measures for improving water quality. To better understand the effects of external and internal nutrient and organic loading and the effects of reservoir operation, a model is often developed, calibrated, and used for sensitivity and management simulations. The importance of modeling and simulation in the scientific community has drawn interest towards methods for automated calibration. This study addresses using an automatic technique to calibrate the water quality model CE-QUAL-W2 (Cole and Wells, 2013). CE-QUAL-W2 is a two-dimensional (2D) longitudinal/vertical hydrodynamic and water quality model for surface water bodies, modeling eutrophication processes such as temperature-nutrient-algae-dissolved oxygen-organic matter and sediment relationships. The numerical method used for calibration in this study is the particle swarm optimization method developed by Kennedy and Eberhart (1995) and inspired by the paradigm of birds flocking. The objective of this calibration procedure is to choose model parameters and coefficients affecting temperature, chlorophyll a, dissolved oxygen, and nutrients (such as NH4, NO3, and PO4). A case study is presented for the Karkheh Reservoir in Iran with a capacity of more than 5 billion cubic meters that is the largest dam in Iran with both agricultural and drinking water usages. This algorithm is shown to perform very well for determining model parameters for the reservoir water quality and hydrodynamic model. Implications of the use of this procedure for other water quality models are also shown.
26
Clark, Paul Campbell. "The onset of gravitational collapse in molecular clouds." Thesis, University of St Andrews, 2005. http://hdl.handle.net/10023/12945.
Повний текст джерелаАнотація:
We conduct an investigation into the role that turbulence plays in the formation of stars. In small clouds, with masses of ~ 30 Mʘ and where the turbulence is only injected at the start, we find that the turbulence does not trigger star formation. Instead, the dissipation of the kinetic energy allows the mean Jeans mass of the cloud to control the formation of stars. The equipartition of the kinetic and thermal energies in the final stages before star formation, allows the pre-protostellar clumps to fragment. Binary and multiple systems are thus a natural product of star formation in a turbulent environment. We find that globally unbound clouds can be the sites of star formation. Furthermore the star formation efficiency is naturally less than 100%, thus in part providing an explanation for the low efficiency in star forming regions. Globally unbound GMCs not only form stars, and naturally disperse, within a few crossing times, but also provide a mechanism for the formation of OB associations.
27
Johnson, David. "The spatial and temporal variability of nearshore currents." University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0067.
Повний текст джерелаАнотація:
The nearshore current field, defined here as the residual horizontal flow after averaging over the incident wave period, exhibits variability at a range of time and space scales. Some of the variable currents are low frequency gravity wave motions. However, variable, rotational (in the sense of possessing vertical vorticity) flow can also exist as part of the overall nearshore current field. A field and numerical modelling investigation of these variable rotational currents has been carried out. Drifters, which were developed for surfzone use, enabled measurement of the nearshore current structure; the design and testing of these new instruments is described. Two sets of field measurements, using the new drifters and Eulerian instruments were carried out for conditions with swell perpendicular to a plane beach and in strong longshore currents. In the perpendicular swell conditions, an interesting and well-defined feature of the measured trajectories was the development of transient rip currents. Discrete vortices were also observed. In the longshore current case, trajectories with the longshore current displacement removed had complex meandering paths. Lagrangian data were used to make estimates of length scales and dispersion, both of which provide strong evidence that the current field cannot be due to low frequency gravity waves alone. Under the assumption of equipartition of kinetic and potential energy for low frequency gravity waves, Eulerian measurements of velocities and pressure show significant energy due to non-divergent, rotational flow in both the perpendicular swell and longshore current case. A numerical model that can simulate horizontal flow with a directionally spread, random wave field incident on a plane beach was implemented. The model developed transient rip currents that are qualitatively very similar to those seen in the drifter trajectories from the field. The number and intensity of rip currents in the model depended on the beach slope and incident wave spectra. The energy content and cross-shore flux (and hence transport of material) of the rotational current flow component in the simulated flow fields is comparable to that due to low frequency gravity waves. The modelling also provided some evidence that there may be universal characteristics of the rotational currents. The field results and modelling show that variable rotational currents are ubiquitous in the field even when longshore currents and hence shear waves are not present. The term “infragravity turbulence” is suggested to describe the general class of nearshore hydrodynamics not directly associated with shear waves, which is largely disorganised, but contains well defined features such as transient rips currents and large scale horizontal vortices. The results have important implications in the understanding of the transport of material, including sediment, biological material, pollution, and sometimes bathers, in the nearshore zone.
28
Boegman, Leon. "The degeneration of internal waves in lakes with sloping topography." University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2005.0043.
Повний текст джерелаАнотація:
[Truncated abstract] Observations are presented from Lake Biwa (Japan) and Lake Kinneret (Israel) showing the ubiquitous and often periodic nature of high-frequency internal waves in large stratified lakes. In both lakes, high-frequency wave events were observed within two distinct categories: (1) Vertical mode one solitary waves with wavelength ˜100-500 m and frequency near 103 Hz and (2) sinusoidal vertical mode one waves with wavelength ˜5-30 m and frequency just below the local maximum buoyancy frequency near 102 Hz. The sinusoidal waves were associated with shear instability and were shown to dissipate their energy sporadically within the lake interior. Conversely, the solitary waves were found to be capable of propagating to the lake perimeter where they may break upon sloping topography, each releasing ˜1% of the total basin-scale internal wave energy to the benthic boundary layer.
29
Muthedath, Premkumar. "Numerical study of nonlinear free-surface flows." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-07212009-040300/.
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30
Oh, Il Geun. "A theoretical and experimental investigation into the nonlinear dynamics of floating bodies." Diss., Virginia Tech, 1992. http://hdl.handle.net/10919/40445.
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31
Glatthorn, Stephen. "VERIFICATION OF PILOT-SCALE IRON RELEASE MODELS." Master's thesis, University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/4003.
Повний текст джерелаАнотація:
A model for the prediction of color release from a pilot distribution system was created in 2003 by Imran. This model allows prediction of the release of color from aged cast iron and galvanized steel pipes as a function of water quality and hydraulic residence time. Color was used as a surrogate measurement for iron, which exhibited a strong linear correlation. An anomaly of this model was an absence of a term to account for pH, due to the influent water being well stabilized. A new study was completed to evaluate the effectiveness of corrosion inhibitors against traditional adjustment. Two control lines were supplied with nearly same water qualities, one at pH close to pHs and one at pH well above pHs. The resulting data showed that effluent iron values were typically greater in the line with lower pH. The non-linear color model by Imran shows good agreement when the LSI was largely positive, but underpredicted the color release from the lower LSI line. A modification to the Larson Ratio proposed by Imran was able to give a reasonable agreement to the data at lower LSI values. LSI showed no definite relation to iron release, although a visual trend of higher LSI mitigating iron release can be seen. An iron flux model was also developed on the same pilot system by Mutoti. This model was based on a steady state mass balance of iron in a pipe. The constants for the model were empirically derived from experiments at different hydraulic conditions with a constant water quality. Experiments were assumed to reach steady state at 3 pipe volumes due to the near constant effluent turbidity achieved at this point. The model proposes that the iron flux under laminar flow conditions is constant, while the iron flux is linearly related to the Reynolds Number under turbulent conditions. This model incorporates the color release models developed by Imran to calculate flux values from different water qualities. A limited number of experiments were performed in the current study using desalinated and ground water sources at Reynolds Numbers ranging from 50 to 200. The results of these limited experiments showed that the iron flux for cast iron pipe was approximately one-half of the predicted values from Mutoti. This discrepancy may be caused by the more extensive flushing of the pipes performed on the current experiments which allowed attainment of a true steady state. Model changes were proposed to distinguish between near stagnant flow and the upper laminar region, with the upper laminar region showing a slight linear increase. Predictions using the galvanized flux model were not accurate due to an inferior color release model that was developed for galvanized pipes. The model exhibits a high dependence on sulfate concentrations, but concentrations of sulfates in the current experiments were low. This led to low predicted flux values when the actual data showed otherwise. A new galvanized model was developed from a combination of data from the original and current experiments. The predicted flux values using the new model showed great improvement over the old model, but the new model database was limited and the resulting model was not able to be independently tested.M.S.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engr MSEnvE
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Petkova, Maya Atanasova. "Cloudy with a chance of starlight : coupling of smoothed particle hydrodynamics and Monte Carlo radiative transfer for the study of ionising stellar feedback." Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16557.
Повний текст джерелаАнотація:
Ionising radiation is present in a variety of astrophysical problems, and it is particularly important for shaping the process of star formation in molecular clouds, containing hot, high-mass stars. In order to account for the effects of ionising radiation within numerical models of star formation, we need to combine a hydrodynamics method with a radiative transfer method and obtain a radiation hydrodynamics scheme (RHD). In this thesis I achieve live radiation hydrodynamics by coupling the Smoothed Particle Hydrodynamics (SPH) code Phantom with the Monte Carlo Radiative Transfer (MCRT) code CMacIonize. Since SPH is particle-based and MCRT is grid-based, I construct an unstructured, Voronoi grid in order to establish a link between the two codes. In areas with large density gradients, a Voronoi grid based purely on the SPH particle positions achieves insufficient resolution, and therefore I propose a novel algorithm for inserting a small number of additional grid cells to improve the local resolution. Furthermore, the MCRT calculations require the knowledge of an average density for each Voronoi cell. To address this, I develop an analytic density mapping from SPH to a Voronoi grid, by deriving an expression for the integrals of a series of kernel functions over the volume of a random polyhedron. Finally, I demonstrate the validity of the live RHD through the benchmark test of D-type expansion of an H II region, where good agreement is shown with the existing literature. The RHD implementation is then used to perform a proof-of-concept simulation of a collapsing cloud, which produces high-mass stars and is subsequently partially ionised by them. The presented code is a valuable tool for future star formation studies, and it can be used for modelling a broad range of additional astronomical problems involving ionising radiation and hydrodynamics.
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Gokgoz, Kilic Sinem. "Dynamic fugacity modeling in environmental systems." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22557.
Повний текст джерелаАнотація:
Thesis (M. S.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.Committee Chair: Aral, Mustafa; Committee Member: Guan, Jiabao; Committee Member: Pavlostathis, Spyros; Committee Member: Uzer, Turgay; Committee Member: Yiacoumi, Sotira.
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Shimizu, Kenji. "Application of modal analysis to strongly stratified lakes." University of Western Australia. Faculty of Engineering, Computing and Mathematics, 2009. http://theses.library.uwa.edu.au/adt-WU2009.0079.
Повний текст джерелаАнотація:
Modal analysis for strongly stratified lakes was extended to obtain a better understanding of the dynamics of the basin-scale motions. By viewing the basin-scale motions as a superposition of modes, that have distinct periods and three-dimensional structures, the method provides a conceptual understanding for the excitation, evolution, and damping of the basin-scale motions. Once the motion has been decomposed into modes, their evolution and energetics may be extracted from hydrodynamic simulation results and field data. The method was applied to Lake Biwa, Japan, and Lake Kinneret, Israel, and used for a theoretical study. The real lake applications showed that winds excited basin-scale motions that had a surface layer velocity structure similar to the wind stress pattern. Three-dimensional hydrodynamics simulations of Lake Biwa indicated that most of the energy input from winds was partitioned into the internal waves that decayed within a few days. The gyres, on the other hand, received much less energy but dominated the dynamics during calm periods due to their slow damping. Analyses of field data from Lake Kinneret suggested that the internal waves, excited by the strong winds every afternoon, were damped over a few days primarily due to bottom friction. Theoretical investigations of damping mechanisms of internal waves revealed that bottom friction induced a velocity anomaly at the top of the boundary layer that drained energy from the nearly inviscid interior by a combination of internal wave cancelling and spin-down. These results indicate that gyres induce long-term horizontal transport near the surface and internal waves transfer energy from winds to near-bottom mixing. Modal structure of dominant basin-scale internal waves can induce large heterogeneity of nearbottom mass transfer processes. The method presented here provides a tool to determine how basin-scale motions impact on biogeochemical processes in stratified lakes.
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Al, Murib Muhanned. "Hydrodynamic and Water Quality Modeling of the Tigris River System in Iraq Using CE-QUAL-W2." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4230.
Повний текст джерелаАнотація:
The Tigris River is one of two primary rivers in Iraq and is, along with the Euphrates, the main source for drinking and irrigation water in the country. The Tigris River originates in the Taurus Mountains in Turkey, and is 1850 km long. The majority of the river lies within Iraq. The river passes through, and is the primary drinking water source for major cities such as Mosul, Baeji, Samarra, Baghdad (the capital), and Kut. The Tigris River joins the Euphrates River in Qurna city within Basra province to form the Shatt Al-Arab River which eventually discharges into the Persian Gulf.
As a result of fluctuations in flow rate along the Tigris River that cause both potential flooding and drought, Mosul Dam was built on the mainstem of the Tigris River upstream of the city of Mosul and was operated starting in July 1986 to control the river flow and to generate hydroelectricity. Some canals were also constructed to divert excess fresh water from the mainstem of the river at Samarra Barrage located 125 km north (upstream) of Baghdad to Tharthar Lake, an artificial lake located 100 km northwest Baghdad city. The Tigris-Tharthar canal, 75 km long, was constructed in 1956 to divert excess water from Samarra Barrage to Tharthar Lake and to prevent potential flooding in Baghdad. During dry seasons, high total dissolved solids (TDS) water is diverted from Tharthar Lake into the mainstem of the Tigris River through the 65 km long Tharthar-Tigris canal, which is located 25 km upstream Baghdad.
Due to rapid population growth and increasing industrial activates, the Tigris River is also facing many water quality challenges from inflows of contaminated wastewater from treatment plant stations. A water quality model that simulates the Tigris River system is therefore needed to study the effects of these discharges and how water quality of the Tigris River could be managed. To address this issue, CE-QUAL-W2 was used to develop a 2-D (longitudinal and vertical) hydrodynamic and water quality model of the mainstem Tigris River from Mosul Dam (Rkm 0) to Kut Barrage (Rkm 880). In addition, Tharthar Lake and its canals were modeled.
A full suite of hydrodynamic and water quality variables were simulated for the year 2009, including flowrates, water level, and water temperature. Additionally, water quality constituents such as total dissolved solids (TDS), phosphate (PO4), ammonium (NH4), nitrate (NO3), biochemical oxygen demand (BOD), chlorophyll-a (Chl-a), and dissolved oxygen (DO) were also simulated. Bathymetry of the Tigris River and field data such as flowrate, water level, TDS, NO3 were obtained from the Ministry of Water Resources in Iraq, while surface water temperatures of the Tigris River were estimated remotely using Landsat satellites. These satellites provided a continuous observation record of remote sites. Other water quality field data, such as PO4, NH4, BOD, and DO, were estimated from literature values.
Meteorological data, including, wind speed, wind direction, air and dew point temperatures, cloud cover, and solar radiation were obtained from the Iraqi Ministry of Transportation, the General Organization for Meteorology and Seismic Monitoring.
Model predictions of flow and water level were compared to field data at three stations along the mainstem of the Tigris River, including Baeji, downstream of Samarra Barrage, and Baghdad. The absolute mean error in the flow varied from 12.6 to 3.4 m3/s and the water level absolute mean error varied from 0.036 to 0.018 m. The percentage error of the overall flowrate at Baeji, downstream Samarra Barrage and Baghdad was 1.9%, 0.8%, and 0.8% respectively. Injecting a conservative tracer at Mosul Dam showed that a parcel of water reaches to Baeji, Samarra Barrage, Baghdad, and Kut Barrage after approximately 3 days, 5 days, 10 days, and 19 days, respectively.
Water temperature field data in Iraq are limited and there was no archive of existing field data. Therefore, I obtained estimates of surface water temperature on the Tigris River using the thermal band of the Landsat satellite, one of a series of satellites launched by the National Aeronautics and Space Administration (NASA). The calibration between satellite data and water temperature was validated using sparse field data from 2004, and the calibration then applied to 82 Landsat images from the year 2009. Landsat estimates showed a bias of -2°C compared to model results in winter months, possibly due to uncertainty in Landsat estimations. The absolute mean errors of the CE-QUAL-W2 model predictions of water temperature compared to Landsat estimated temperatures were 0.9 and 1.0°C at Baeji and Baghdad respectively. Temperature calibration in the Tigris River system was highly sensitive to meteorological input data. Landsat Images were also used to estimate longitudinal variation in surface water temperature of Tharthar Lake. It was found that surface water temperature in Tharthar Lake varied longitudinally along the North-South axis with warmer temperatures in the lower part compared with the upper part of the lake.
Total dissolved solids concentrations in the Tigris River significantly increased from Mosul Dam to Kut Barrage with peak concentrations of 900 mg/l and 1050 mg/l at Baghdad and Kut, respectively, due to high TDS water diverted from Tharthar Lake, irrigation return flow, urban runoff, and uncontrolled discharge of wastewater effluents. NO3 concentrations did not significantly increase between Samarra Barrage and Baghdad city. BOD concentrations within Baghdad were extremely high due to direct discharge of industrial wastewater into the mainstem of the Tigris River from outlets located within the city.
Management scenarios were simulated with the model of the Tigris River system and were compared with the base model. The main scenarios implemented on the Tigris River system were altering upstream hydrology, increasing air temperature due to the effect of climate change, disconnecting Tharthar Lake from the Tigris River system, and simulating long-term effects on Tharthar Lake. Increasing upstream inflows caused a decrease in TDS concentrations from 495 mg/l to 470 mg/l over all the mainstem of the river. In addition, CBOD concentrations decreased somewhat from 5.9 mg/l to 5.74 mg/l. On the other hand, decreasing upstream flows caused a significant increase in average TDS concentrations over the entire Tigris mainstem from 495 mg/l to 527 mg/l. Also, an increase in CBOD concentrations from 5.9 mg/l to 6.2 mg/l was predicted over all the mainstem of the river. Implementing the climate change scenario on the base model of the Tigris River system showed a 5% increase in annually averaged water temperature from 20.7°C to 21.68°C over the mainstem river. Climate change scenarios produced no significant impacts on TDS and CBOD concentrations in the mainstem, while DO concentrations decreased from 8.15 mg/l to 7.98 mg/l with a slight increase in Chl-a concentration from 1.97 µg/l to 2 µg/l in the mainstem. Disconnecting Tharthar Lake from the system showed a remarkable 25% decrease in TDS concentrations, with an average concentration changed from 495 mg/l to 397 mg/l in the mainstem due to an extra 36% increase in flow discharged downstream of Samarra Barrage. Also, Chl-a concentration significantly decreased by 40% with an average concentration changed from 2 µg/l to 1.2 µg/l.
Additionally, a 6-year model simulation of the Tigris River system was performed to evaluate the long-term effects on Tharthar Lake. No significant impact was observed in the average temperature of the lake. TDS concentrations in the lake decreased from 1239 mg/l to 1041 mg/l. PO4, NH4 and NO3 concentrations decreased by 2%, 66% and 26%, respectively. Chl-a concentration in Tharthar Lake decreased from 2.0 µg/l to 1.61 µg/l. After decreasing BOD concentrations of the Tigris River by 50%, BOD concentrations in the mainstem decreased by 24%, while DO concentrations increased by 2.8%. There were no significant impacts on Chl-a concentrations in the mainstem of the river. Finally, for a scenario where extremely low dissolved oxygen release from Mosul Dam in the summer, it was found that approximately 50 km below Mosul Dam was affected before DO concentrations reached an equilibrium concentration.
For further work on the Tigris River system, it is recommended to model the Tigris River from Kut Barrage to the confluence with the Euphrates River, about 400 km long, and connect it with the current model to have a complete model of the Tigris River system from Mosul Dam to the confluence with the Euphrates River. This is necessary to manage water the entire system of the Tigris River and also to provide enough water with good quality in Basra.
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Abdolmaleki, Kourosh. "Modelling of wave impact on offshore structures." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0055.
Повний текст джерелаАнотація:
[Truncated abstract] The hydrodynamics of wave impact on offshore structures is not well understood. Wave impacts often involve large deformations of water free-surface. Therefore, a wave impact problem is usually combined with a free-surface problem. The complexity is expanded when the body exposed to a wave impact is allowed to move. The nonlinear interactions between a moving body and fluid is a complicated process that has been a dilemma in the engineering design of offshore and coastal structures for a long time. This thesis used experimental and numerical means to develop further understanding of the wave impact problems as well as to create a numerical tool suitable for simulation of such problems. The study included the consideration of moving boundaries in order to include the coupled interactions of the body and fluid. The thesis is organized into two experimental and numerical parts. There is a lack of benchmarking experimental data for studying fluid-structure interactions with moving boundaries. In the experimental part of this research, novel experiments were, therefore, designed and performed that were useful for validation of the numerical developments. By considering a dynamical system with only one degree of freedom, the complexity of the experiments performed was minimal. The setup included a plate that was attached to the bottom of a flume via a hinge and tethered by two springs from the top one at each side. The experiments modelled fluid-structure interactions in three subsets. The first subset studied a highly nonlinear decay test, which resembled a harsh wave impact (or slam) incident. The second subset included waves overtopping on the vertically restrained plate. In the third subset, the plate was free to oscillate and was excited by the same waves. The wave overtopping the plate resembled the physics of the green water on fixed and moving structures. An analytical solution based on linear potential theory was provided for comparison with experimental results. ... In simulation of the nonlinear decay test, the SPH results captured the frequency variation in plate oscillations, which indicated that the radiation forces (added mass and damping forces) were calculated satisfactorily. In simulation of the nonlinear waves, the waves progressed in the flume similar to the physical experiments and the total energy of the system was conserved with an error of 0.025% of the total initial energy. The wave-plate interactions were successfully modelled by SPH. The simulations included wave run-up and shipping of water for fixed and oscillating plate cases. The effects of the plate oscillations on the flow regime are also discussed in detail. The combination of experimental and numerical investigation provided further understanding of wave impact problems. The novel design of the experiments extended the study to moving boundaries in small scale. The use of SPH eliminated the difficulties of dealing with free-surface problems so that the focus of study could be placed on the impact forces on fixed and moving bodies.
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Eusuff, M. Muzaffar. "Optimisation of an operating policy for variable speed pumps using genetic algorithms." Title page, contents and abstract only, 1995. http://web4.library.adelaide.edu.au/theses/09ENS/09ense91.pdf.
Повний текст джерелаАнотація:
Undertaken in conjunction with JUMP (Joint Universities Masters Programme in Hydrology and Water Resources). Bibliography: leaves 76-83. Establishes a methodology using genetic algorithms to find the optimum operating policy for variable speed pumps in a water supply network over a period of 24 hours.
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McGarvey, Brian Scott. "Coupling of Solid-State and Electromagnetic Equations for the Computationally Efficient Time-Domain Modeling and Design of Wireless Packaged Geometries with NonlinearActive Devices." Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14551.
Повний текст джерелаАнотація:
This document contains a proposal for the creation of a simulator that can accurately model the interaction of electromagnetic (EM) and semiconductor effects for modern wireless devices including nonlinear and/or active devices.
The proposed simulator couples the balanced semiconductor equations (charge, momentum, kinetic energy) with a FDTD full-wave Yee-based electromagnetic (EM) simulator. The resultant CAD tool is able to model the response of one semiconductor device to both small signal and DC bias based on the process parameters (material, charge distribution and doping) without any a-priori knowledge of the device performance characteristics, thus making it extremely useful in modeling and integrating novel devices in RF and Wireless topologies. As a proof of concept an n+--i--n+ diode will be simulated. In the future, more complicated structures, such as MODFETs, will be modeled as well.
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Huber, Anita. "Internal mixing in a mine lake." University of Western Australia. School of Environmental Systems Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0103.
Повний текст джерелаАнотація:
[Truncated abstract] Mine lakes are a water body created after an open-cut mine ceases operating. The lakes develop in the former mine-pit due to the combination of groundwater inflow, surface run-off and, in some cases, due to rapid filling from river diversion. While potentially valuable water resources, these lakes often have poor water quality and managing the water body is an important part of the overall process of mine site rehabilitation. As mine lakes form in man-made pits, they have a bathymetry that is typically quite distinct from natural lakes and this can, in turn, strongly influence the hydrodynamics and hence the water quality of the water body. Despite the potential importance of these water bodies, there have been very few studies on the hydrodynamics of mine lakes. This study describes a field investigation of the hydrodynamics of a former coal mine lake, Lake Kepwari, in south-western Western Australia. In particular, this study examines the hydrodynamic processes in both the surface mixing layers and the internal mixing in the density stratified lake. Wind sheltering in the surface mixing layer occurs due to the presence of the steep walls and lake embankments. A week long field experiment was conducted in December 2003 using a combination of moored thermistor chains with meteorological stations and the deployment of rapid vertical profiling turbulent microstructure instruments and CTD drops from two boats operating on the lake. ... Simulations indicated that inclusion of a site specific sheltering effect, based on the results of the field campaign, significantly improved the models‘ performance in capturing the surface mixed layer deepening associated with episodic strong wind events that occur on the lake. Considerable internal mixing was indicated by the high dissipation rates observed, particularly near the boundaries. Large basin-wide diffusivities were also calculated from the heat budget method over long periods, showed a consistency with time, and were slightly higher in summer than during the Autumn Winter period. Although light, there are persistent winds over the lake and yet little basin-scale internal wave activity or seiching. It is hypothesized that any seiching motion was rapidly damped by strong mixing over the hydraulically rough bathymetry bathymetry created by the remnant benches from the open cut mining operation itself. This boundary mixing, in turn, drives secondary relaxation currents that transport mixed fluid from the boundaries to the interior, resulting in high effective basin-wide diffusivities. A simple boundary mixing model is proposed to describe this process.
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ANGELO, GABRIEL. "Análise numérica da dinâmica do escoamento em circuitos de circulação natural." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10524.
Повний текст джерелаАнотація:
Made available in DSpace on 2014-10-09T12:41:29Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:03:20Z (GMT). No. of bitstreams: 0
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Castro, Marcelo Mendes de. "Modelação matemática de lagos e reservatórios: caso do Reservatório Billings." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/3/3147/tde-18082010-165433/.
Повний текст джерелаАнотація:
Modelos numéricos são importantes ferramentas para avaliação do comportamento de corpos hídricos, notadamente com relação ao decaimento e mistura de constituintes ao longo do tempo. Neste trabalho apresenta-se o método empregado para adaptação e aplicação de um modelo matemático hidrodinâmico 2DH para simulação de variáveis de qualidade das águas a reservatórios rasos ou polimíticos. A descrição do desenvolvimento do modelo empregado (IPH-ECO), do processo de análise das condições do reservatório, seleção de dado intervenientes, discretização espacial e temporal, definição das condições de contorno hidrológicas e de aporto de cargas poluentes, bem como a definição espacial dos pontos de controle para aferição e validação são discutidos. São apresentados os resultados da resposta do modelo aplicado ao Reservatório Billings, em São Paulo.Numerical models are strong tools to evaluate the fate of pollutants in lakes and reservoirs under transient conditions. This article brings the steps employed for preparation and implementation of a hydrodynamic 2DH model to simulate water quality variables in shallow or polymitc lakes. Description of the adaptation and implementation of IPH-ECO model process, compiling and setting of the hydrological and constituent loadings, spatial and temporal discretization and selection of control points are demonstrated and discussed. Some results of model calibration for Billings Reservoir, Sao Paulo, Brazil, are also presented.
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Geiger, Sam R. (Sam Rayburn) 1971. "Hydrodynamic modeling of towed buoyant submarine antenna's [sic] in multidirectional seas." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/29045.
Повний текст джерелаАнотація:
Thesis (S.M.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Ocean Engineering, and the and Woods Hole Oceanographic Institution), 2000.Includes bibliographical references (p. 100-101).
A finite difference computer model is developed to simulate the exposure statistics of a radio frequency buoyant antenna as it is towed in a three-dimensional random seaway. The model allows the user to prescribe antenna properties (length, diameter, density, etc.), sea conditions (significant wave height, development of sea), tow angle, and tow speed. The model then simulates the antenna-sea interaction for the desired duration to collect statistics relating to antenna performance. The model provides design engineers with a tool to predict antenna performance trends, and to conduct design tradeoff studies. The floating antenna envisioned is for use by a submarine operating at modest speed and depth.
by Sam R. Geiger.
S.M.
43
Watteaux, Romain. "Détection des grandes structures turbulentes dans les couches de mélange de type Rayleigh-Taylor en vue de la validation de modèles statistiques turbulents bi-structure." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2011. http://tel.archives-ouvertes.fr/tel-00669707.
Повний текст джерелаАнотація:
Cette thèse a pour objectif de détecter les structures turbulentes aux grandes échelles présentes dans une couche de mélange de type Rayleigh-Taylor incompressible à faible nombre d'Atwood. Diverses grandeurs statistiques conditionnées par la présence de ces structures ont été obtenues, et il est désormais possible de les comparer avec les résultats des modèles statistiques turbulents dits bi-structure, tel le modèle 2SFK développé au CEA. Afin de réaliser les simulations numériques directes du mélange turbulent, un code numérique tridimensionnel incompressible à densité variable a été développé. Ce code a été parallélisé dans les trois directions. Plusieurs méthodes de détection de structure ont été conçues et testées. Bien que toutes ces méthodes présentent différents intérêts, seule la plus efficace vis-à-vis de nos critères de détection a été gardée pour faire des simulations à forte résolution (plus d'un milliard de mailles, 1024^3). Un filtrage temporel de la vitesse verticale est utilisé dans cette méthode de détection afin de : 1) corriger les distorsions dues aux points d'arrêt et zones de recirculation dans l'écoulement, 2) minimiser l'effet de la turbulence aux petites échelles et mieux mettre en évidence les grandes échelles, 3) introduire un effet mémoire permettant de prolonger la bimodalité du champ de détection depuis les zones laminaires extérieures jusqu'au centre de la zone de mélange turbulent. Plusieurs simulations numériques directes 1024^3 ont été effectuées. Les résultats viennent conforter ceux obtenus avec le modèle bi-structure 2SFK et justifient une étude plus poussée des grandeurs statistiques en vue de sa validation.
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Kreider, Marc Alan. "A numerical investigation of the global stability of ship roll : invariant manifolds, Melnikov's method, and transient basins /." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-03142009-040740/.
Повний текст джерела
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Ou, Zhiliang. "Numerical simulation of flow around vertical cylinders." University of Western Australia. School of Civil and Resource Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0185.
Повний текст джерелаАнотація:
Local scour around bridge piers can cause serious damages and structural failure to the bridge. Correct prediction of the scour is an important criterion for the engineering design. Though the subject has been investigated for many decades, the theoretical developments have been very limited due to the complicated interaction of three-dimensional flow and the sediment transport. This thesis concerns the flow around a vertical bottom mounted cylinder exposed to currents and is considered as the initial phase of a study towards modeling local scour around vertical bottom-mounted structures. The aim of the present study is to obtain a better understanding of the complex three-dimensional flow and the mechanisms related to the scouring. The study started with the development of a three-dimensional numerical model to simulate flow around cylindrical structures. After validation of the model, the model was applied to investigate flow around an isolated rectangular cylinder. Unsteady flows around cylinders of a square cross section (A/D = 1) and a rectangular cross section (A/D = 2) were simulated to understand the flow properties around a cylinder other than a circular cross section. Three-dimensional flow patterns, pressure distribution, forces on the cylinder and vortex-shedding frequencies were discussed. It was found that the present numerical results generally agree well with the experimental data. Flow around a vertical cylinder mounted on a rigid bed was then investigated by the numerical model. A circular and a square cross sections were considered respectively. Flow structures of horseshoe vortex and the wake vortex which are the major mechanisms leading to the scouring around the base of the vertical cylinder were explored. The bed shear stress distributions that directly affect the scour processes were discussed. Finally the numerical model was applied to study the flow around a submerged square cylinder mounted on a bed, which has significant engineering relevance to the local scour around structures, such as bridge pier foundation itself, or a caisson placed underwater around the pier bottom for scour protection. The numerical calculations were carried out at different cylinder heights to investigate the effect of the cylinder height on the flow properties. It was found that for submerged cylinders with the height of less than one and a half of the cylinder side width the maximum bed shear stress amplification is about 60% of the value of an infinite long cylinder. The quantification of the shear stress reduction is important for scour protection design.
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Yang, Jie. "Spatial Coherence in a Shallow Water Waveguide." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14624.
Повний текст джерелаАнотація:
In shallow water environments, sound propagation experiences multiple interactions with the surface/bottom interfaces, with hydrodynamic disturbances such as internal waves, and with tides and fronts. It is thus very difficult to make satisfactory predictions of sound propagation in shallow water. Given that many of the ocean characteristics can be modeled as stochastic processes, the statistical measure, spatial coherence, is consequently an important quantity. Spatial coherence provides valuable information for array performance predictions. However, for the case of long-range, low frequency propagation, studies of spatial coherence influenced by various environmental parameters are limited insofar as having the appropriate environmental data with which to model and interpret the results.
The comprehensive Asian Seas International Experiment 2001 (ASIAEX01) examined acoustic propagation and scattering in shallow water. Environmental oceanographic data were taken simultaneously with the acoustic data. ASIAEX01 provided a unique data set which enabled separate study of the characteristics of the oceanographic features and their influence on long range sound propagation. In this thesis, the environmental descriptors considered include sediment sound speed and attenuation, background internal waves, episodic non-linear internal waves, and air-sea interface conditions. Using this environmental data, the acoustic data are analyzed to show the characteristics of spatial coherence in a shallow water waveguide. It is shown that spatial coherence can be used as an inversion parameter to extract geoacoustic information for the seabed. Environmental phenomena including internal waves and wind-generated surface waves are also studied. The spatial and temporal variations in the sound field induced by them are presented. In addition, a tank experiment is presented which simulates propagation in a shallow water waveguide over a short range. Based on the data model comparison results, the model proposed here is effective in addressing the major environmental effects on sound propagation in shallow water.
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Moulton, Melissa (Melissa Root). "Hydrodynamic and morphodynamic responses to surfzone seafloor perturbations." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104594.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2016.Cataloged from PDF version of thesis.
Includes bibliographical references.
Holes and channels were excavated in the surf zone on an ocean beach near Duck, NC, and observations of the subsequent evolution of waves, currents, and the modified seafloor were used to investigate nearshore dynamics. In one set of seafloor perturbation experiments, deep holes with steeply sloping sides were excavated in the inner surfzone seafloor. Observations of the infilling holes were used to make the first field estimates of the surfzone morphological diffusivity, which describes the rate of seafloor smoothing by downslope sediment transport. To improve the temporal resolution of bathymetric estimates, a mapping method was developed to combine infrequent, spatially dense watercraft surveys with continuous, spatially sparse in situ altimeter estimates of the seafloor location. In another set of seafloor perturbation experiments, channels were dredged across the surf zone with the propellers of a landing craft. Alongshore variations in wave breaking caused by the perturbed bathymetry resulted in strong rip currents in the channels under some conditions, whereas alongshore currents bypassed the channels under other conditions. The dynamics of the circulation response for changing wave forcing, bathymetry, and tidal elevation are investigated using the observations, a numerical model, and a parameter based on wave properties and bathymetry.
by Melissa Moulton.
Ph. D.
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Delaneze, Marcelo Elias [UNESP]. "Modelagem dinâmica espacial aplicada na avaliação das mudanças da cobertura da terra no entorno de dutos utilizando autômatos celulares: estudo de caso duto ORBEL." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/92738.
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delaneze_me_me_rcla.pdf: 1472015 bytes, checksum: 1596836f4441d15a50d94daf73c5a740 (MD5)Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP)
A obtenção de informação sobre as condições da rede dutoviária representa papel primordial na operação dos dutos, não só com o propósito de manter a eficiência operacional, mas também, para a minimização dos riscos associados a possíveis acidentes, tanto decorrentes dos processos naturais quanto de causas antrópicas relacionadas ao uso e cobertura da terra. Neste sentido, o emprego de modelos matemáticos em estudos ambientais gera importantes contribuições científicas ao planejamento ordenado de uma área, uma vez que ajudam a entender o impacto das mudanças no uso e cobertura da terra e a prever alterações futuras nos ecossistemas. A área de estudo compreende porções dos municípios de Duque de Caxias, Belford Roxo e Nova Iguaçu e tem por objetivo realizar experimentos de mudanças da cobertura da terra em médio prazo (10 anos) para a faixa de dutos ORBEL. A modelagem realizada neste trabalho foi desenvolvida no software Dinamica-EGO, utilizando como entrada mapas classificados de cobertura da terra, obtidos através de imagens do satélite Landsat 5/TM, e variáveis espaciais para explicar as mudanças ocorridas na cobertura da terra. Para a calibração do modelo, utilizou-se o método de pesos de evidência, disponível no Dinamica-EGO, primeiramente categorizando-se os mapas de variáveis contínuas e, posteriormente, calculando-se os pesos de evidência. Valores positivos favorecem determinada transição, enquanto valores negativos indicam baixa probabilidade de transição, e valores próximos a zero não exercem efeito. A validação do modelo se deu pelo método de similaridade fuzzy, com decaimento exponencial. Os resultados mostram que, para os dois períodos analisados (1987-1998 e 1998-2010), a taxa de mudança para a transição “vegetação arbórea para outros” é bem maior do que para...
Reliable information about conditions of pipeline network represents a major role in the operation of pipelines, not only in order to maintain operational efficiency, but also to minimize the risks associated with possible accidents such as rupture of the ducts due to landslides or mudslides mass block, causing damage to humans and the environment. The use of mathematical models in environmental studies allows significant scientific contributions to the physical planning of an area, since they help to understand the impact of changes in land use and land cover and predict future trends of changes in ecosystems. The study area includes portions of the municipalities of Duque de Caxias, Nova Iguaçu, and Belford Roxo and aims to carry out experiments in land-cover changes in the medium-term (10 years) within the catchment area of ORBEL pipelines. The modeling performed in this work was developed using the software Dinamica-EGO, using as input classified land cover maps obtained from Landsat 5/TM satellite images as well as spatial variables to explain the observed changes in land cover. For the model calibration, we used the method of weights of evidence that is available at Dinamica-EGO. Initially, the maps of continuous variables were categorized according to discrete ranges, which were then employed for the calculation of the respective positive weights of evidence. Positive values foster certain transitions, while negative values indicate low probability of transition, and values close to zero have no effect on changes. Model validation was executed by means of the fuzzy similarity method using exponential decay. The results show that for the two study periods (1987-1998 and 1998-2010) the rate of change for the transition 'others to woody vegetation' is much higher than for the other transitions observed in the same... (Complete abstract click electronic access below)
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Horko, Michael. "CFD optimisation of an oscillating water column wave energy converter." University of Western Australia. School of Mechanical Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0089.
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Although oscillating water column type wave energy devices are nearing the stage of commercial exploitation, there is still much to be learnt about many facets of their hydrodynamic performance. This research uses the commercially available FLUENT computational fluid dynamics flow solver to model a complete OWC system in a two dimensional numerical wave tank. A key feature of the numerical modelling is the focus on the influence of the front wall geometry and in particular the effect of the front wall aperture shape on the hydrodynamic conversion efficiency. In order to validate the numerical modelling, a 1:12.5 scale experimental model has been tested in a wave tank under regular wave conditions. The effects of the front lip shape on the hydrodynamic efficiency are investigated both numerically and experimentally and the results compared. The results obtained show that with careful consideration of key modelling parameters as well as ensuring sufficient data resolution, there is good agreement between the two methods. The results of the testing have also illustrated that simple changes to the front wall aperture shape can provide marked improvements in the efficiency of energy capture for OWC type devices.
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Van, Glubt Sarah. "Hydrodynamic and Water Quality Modeling of the Chehalis River Using CE-QUAL-W2." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3486.
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The Chehalis River Basin is located in the southwest region of Washington State, originating in the Olympic Mountains and flowing to Grays Harbor and the Pacific Ocean. The Chehalis River is over 125 miles, exists within five counties, and flows through agricultural, residential, industrial, and forest land areas. Four major rivers discharge to the Chehalis River, as well as many smaller creeks, five wastewater treatment plants, and groundwater flows.
Flooding is a major problem in the relatively flat areas surrounding the cities of Chehalis and Centralia, with severe consequences for property, safety and transportation. As a result, construction of a flood-control dam in the upper basin has been proposed. One major concern of constructing a dam is the potentially severe impacts to fish health and habitat. The Chehalis River has routinely violated water quality standards for primarily temperature and dissolved oxygen, and has had multiple water quality and Total Maximum Daily Load studies beginning in 1990.
CE-QUAL-W2, a two-dimensional (longitudinal and vertical) hydrodynamic and water quality model, was used to simulate the Chehalis River, including free flowing river stretches and stratified (in summer) lake-like stretches. The goals of this research were to assess the flood retention structure's impacts to water quality, as well as river responses to potential climate change scenarios.
In order to use the model to achieve these goals, calibration to field data for flow, temperature, and water quality constituents was performed. This involved developing meteorological data, riparian shading data, and flow, temperature, water quality records for all tributaries during the calibration period of January 1, 2013 to December 31, 2014. System cross-sectional geometry data were also required for the model grid. Because of the short travel time in the river, the model was sensitive to boundary condition data, wind speed, bathymetry, nutrient kinetics, and algae, epiphyton, and zooplankton kinetics.
Future conditions showed predictions of warmer water temperatures and slight changes to water quality conditions on the river. As fish in the area prefer cooler water temperatures, this could pose a threat to fish health and habitat. Flood retention structures also showed impacts to river temperature and water quality. Structures with the purpose of flood retention only (only operating during times of flooding) gave model predictions for daily maximum temperature higher than structures that employed flood retention and flow augmentation (operating during all times of the year). This suggested the management of flow passage or retention by the dam is important for water quality on the river.
As this research continues improvements will be made, particularly to temperature and water quality constituents. Additional data for the system would be beneficial to this process. Model predictions of temperature were sensitive to meteorological data, including cloud cover, which were largely estimated based on solar radiation. Additional meteorological data throughout the basin would be useful to temperature results. Temperature results were also sensitive to the model bathymetry, and additional investigations into segments widths and water depths may improve temperature predictions.
Water quality constituent data were largely lacking for the system. Many estimation techniques and approximations were used for input water quality constituents for the model upstream boundary and tributaries when little or no data were available, introducing uncertainty to the model. It was not possible to calibrate pH to field data because alkalinity data were essentially unavailable. However, other constituents had good agreement between model predictions and field data, including dissolved oxygen, nitrates, total phosphorus, and total suspended solids.