To see the other types of publications on this topic, follow the link: Flow modeling.
Dissertations / Theses on the topic 'Flow modeling'
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 'Flow modeling.'
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
Cappiello, Alessandra 1972. "Modeling traffic flow emissions." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/84328.
Full text
2
Boulay, Fabienne. "Suspension-flow modeling : curvilinear flows and normal stress differences." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/11689.
Full text
3
Rycroft, Christopher Harley. "Multiscale modeling in granular flow." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41557.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 245-254).
Granular materials are common in everyday experience, but have long-resisted a complete theoretical description. Here, we consider the regime of slow, dense granular flow, for which there is no general model, representing a considerable hurdle to industry, where grains and powders must frequently be manipulated. Much of the complexity of modeling granular materials stems from the discreteness of the constituent particles, and a key theme of this work has been the connection of the microscopic particle motion to a bulk continuum description. This led to development of the "spot model", which provides a microscopic mechanism for particle rearrangement in dense granular flow, by breaking down the motion into correlated group displacements on a mesoscopic length scale. The spot model can be used as the basis of a multiscale simulation technique which can accurately reproduce the flow in a large-scale discrete element simulation of granular drainage, at a fraction of the computational cost. In addition, the simulation can also successfully track microscopic packing signatures, making it one of the first models of a flowing random packing. To extend to situations other than drainage ultimately requires a treatment of material properties, such as stress and strain-rate, but these quantities are difficult to define in a granular packing, due to strong heterogeneities at the level of a single particle. However, they can be successfully interpreted at the mesoscopic spot scale, and this information can be used to directly test some commonly-used hypotheses in modeling granular materials, providing insight into formulating a general theory.
by Christopher Harley Rycroft.
Ph.D.
4
El, Kheiashy Karim. "Flow-Transport Modeling and Quantification." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/548.
Full textAbstract:
Several research investigations have been conducted on the flow and sediment transport over bed forms in alluvial rivers (e.g. mean flow field, turbulence, shear partitioning, bed load transport and bed form geometry). Much of this work was either laboratory studies or small scale field investigations. Recently, advance in technology have improved the way data are collected and analyzed, e.g. flow data, velocity data and detailed bathymetric information that provide greater knowledge about the bed form geometry. Recent advances in computing power have also reduced the computational restrictions on using three dimensional numerical models in modeling flow applications to predict the temporal and spatial changes of flow and sediment environments. The work performed in this research quantified the periodic nature of bed forms types and geometries along the Lower Mississippi river. Correlations were performed relating the hydrodynamics of the river to the bed form types and geometries. The research work showed the inability of hydrostatic numerical modeling systems to accurately predict flow separation at the bed form crest but indicated that these models could reasonably predict the out of phase relationship between the bed form and the water surface profile. Furthermore the hydrostatic models predicted the total bed resistance as adequately as the non-hydrostatic models. It was found that non-hydrostatic models are required to properly simulate flow separation at bed form crests. Models such as MIKE 3 with constant z-level vertical discretization failed to capture the observed boundary layers unless very fine grids are used. A new procedure was developed as a part of this research, in which relations and dependencies between the hydrodynamic resistance and the bed form dimensions relative to the numerical model spatial scale were derived. This procedure can be used to aid in numerical riverine model calibration and to provide a better representation of flow resistance in hydrodynamic modeling codes.
5
Daniel, Michael M. "Multiresolution statistical modeling with application to modeling groundwater flow." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10749.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 205-211).
by Michael M. Daniel.
Ph.D.
6
Tao, Ye. "Optimal power flow via quadratic modeling." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45766.
Full textAbstract:
Optimal power flow (OPF) is the choice tool for determining the optimal operating status of the power system by managing controllable devices. The importance of the OPF approach has increased due to increasing energy prices and availability of more control devices. Existing OPF approaches exhibit shortcomings. Current OPF algorithms can be classified into (a) nonlinear programming, (b) intelligent search methods, and (c) sequential algorithms. Nonlinear programming algorithms focus on the solution of the Kuhn-Tucker conditions; they require a starting feasible solution and the model includes all constraints; these characteristics limit the robustness and efficiency of these methods. Intelligent search methods are first-order methods and are totally inefficient for large-scale systems. Traditional sequential algorithms require a starting feasible solution, a requirement that limits their robustness. Present implementations of sequential algorithms use traditional modeling that result in inefficient algorithms.
The research described in this thesis has overcome the shortcomings by developing a robust and highly efficient algorithm. Robustness is defined as the ability to provide a solution for any system; the proposed approach achieves robustness by operating on suboptimal points and moving toward feasible, it stops at a suboptimal solution if an optimum does not exist. Efficiency is achieved by (a) converting the nonlinear OPF problem to a quadratic problem (b) and limiting the size of the model; the quadratic model enables fast convergence and the algorithm that identifies the active constraints, limits the size of the model by only including the active constraints.
A concise description of the method is as follows: The proposed method starts from an arbitrary state which may be infeasible; model equations and system constraints are satisfied by introducing artificial mismatch variables at each bus. Mathematically this is an optimal but infeasible point. At each iteration, the artificial mismatches are reduced while the solution point maintains optimality. When mismatches reach zero, the solution becomes feasible and the optimum has been found; otherwise, the mismatch residuals are converted to load shedding and the algorithm provides a suboptimal but feasible solution. Therefore, the algorithm operates on infeasible but optimal points and moves towards feasibility.
The proposed algorithm maximizes efficiency with two innovations: (a) quadratization that converts the nonlinear model to quadratic with excellent convergence properties and (b) minimization of model size by identifying active constraints, which are the only constraints included in the model. Finally sparsity technique is utilized that provide the best computational efficiency for large systems.
This dissertation work demonstrates the proposed OPF algorithm using various systems up to three hundred buses and compares it with several well-known OPF software packages. The results show that the proposed algorithm converges fast and its runtime is competitive.
Furthermore, the proposed method is extended to a three-phase OPF (TOPF) algorithm for unbalanced networks using the quadratized three-phase power system model. An example application of the TOPF is presented. Specifically, TOPF is utilized to address the problem of fault induced delayed voltage recovery (FIDVR) phenomena, which lead to unwanted relay operations, stalling of motors and load disruptions. This thesis presents a methodology that will optimally enhance the distribution system to mitigate/eliminate the onset of FIDVR. The time domain simulation method has been integrated with a TOPF model and a dynamic programming optimization algorithm to provide the optimal reinforcing strategy for the circuits.
7
Sharma, Yugdutt. "Modeling transient two-phase slug flow /." Access abstract and link to full text, 1985. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/8605319.
Full text
8
Kouba, Gene E. "Horizontal slug flow modeling and metering /." Access abstract and link to full text, 1986. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/8700712.
Full text
9
Yu, Tungsheng. "Traffic flow modeling in highway networks." Master's thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12232009-020154/.
Full text
10
Gallant, Elisabeth. "Modeling and Assessing Lava Flow Hazards." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7792.
Full textAbstract:
Lava flow hazards are one of the few constant themes across the wide spectrum of volcanic research in the solar system. These dynamic hazards are controlled by the location of the eruption, the topography and material properties of the land upon which the flow spreads, and the properties of the lava (e.g., volume, temperature, and rheology). Understanding the influences on eruption location and how lava flows modify the landscape are important steps to accurately forecast volcanic hazards. Three studies are presented in this dissertation that address di˙erent aspects of modeling and assessing vent opening and lava flow hazards.
The first study uses hierarchical clustering to explore the distribution of activity at Craters of the Moon (COM) lava field on the eastern Snake River Plain (ESRP). Volcanism at COM is characterized by 53 mapped eruptive vents and 60+ lava flows over the last 15 ka. Temporal, spatial, and spatio-temporal clustering methods that examine different aspects of the distribution of volcanic vents are introduced. The sensitivity of temporal clustering to different criteria that capture the age range of magma generation and ascent is examined Spatial clustering is dictated by structures on the ESRP that attempt to capture the footprint of an emplacing dike. A combined spatio-temporal is the best approach to understanding the distribution of linked eruptive centers and can also provide insight into the evolution of volcanism for the region. Spatial density estimation is used to visualize the differences between these models. The goal of this work is to improve vent opening forecasting tools for use in assessing lava flow hazards.
The second study presents a new probabilistic lava flow hazard assessment for the U.S. Department of Energy’s Idaho National Laboratory (INL) nuclear facility that (1) explores the way eruptions are defined and modeled, (2) stochastically samples lava flow parameters from observed values for use in MOLASSES, a lava flow simulator, (3) calculates the likelihood of a new vent opening within the boundaries of INL, (4) determines probabilities of lava flow inundation for INL through Monte Carlo simulation, and (5) couples inundation probabilities with recurrence rates to determine the annual likelihood of lava flow inundation for INL. Results show a 30% probability of partial inundation of the INL given an e˙usive eruption on the ESRP, with an annual inundation probability of 8.4×10^−5 to 1.8×10^−4. An annual probability of 6.2×10^−5 to 1.2×10^−4 is estimated for the opening of a new eruptive center within INL boundaries.
The third study models thermo-mechanical erosion of a pyroclastic substrate by flow-ing lava on Volcán Momotombo, Nicaragua. It describes the unique morphology of a lava flow channel using TanDEM-X/TerraSAR-X and terrestrial radar digital elevation models. New methods for modeling paleotopography on steep-sided cones are introduced to mea-sure incision depths and document cross-channel profiles. The channel is incised ~35 m into the edifice at the summit and transitions into a constructional feature halfway down the ~1,300 m high cone. An eroded volume of ~4×10^5 m3 was calculated. It is likely that a lava flow eroded into the cone as it emplaced during an eruption in 1905. There is not suÿcient energy to thermally erode this volume, given the observed morphology of the flow. Models are tested that explore the relationship of shearing and material properties of the lava and substrate against measured erosion depths and find that thermo-mechanical erosion is the most likely mode of channel formation. Additionally, it is likely that all forms of erosion via lava flow are impacted by thermal conditions due to the relationship between temperature and substrate hardness. The evolution of these structures (their creation and subsequent infilling) plays an important role in the growth of young volcanoes and also controls future lava flows hazards, as seen by the routing of the 2015 flow into the 1905 channel.
11
Ocampo, Roel Maglente. "Understanding, modeling and using flow context." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445746/.
Full textAbstract:
This thesis presents a concept called flow context, defined as any information that can be used to characterize the situation of a sequence of protocol data units, called a flow, within a network. Flow context is designed to enable the realization of context-aware networks: networks that can sense, process, disseminate and use context information in order to enable or trigger services, or modify and optimize their operation. The thesis discusses a conceptualization for flow context, and describes its characteristics. A semantic model for flows and flow context in the form of an OWL-DL ontology is developed. The various components of the flow context life cycle, consisting of the stages of sensing, processing, dissemination and use, arc described. To account for its multi-faceted nature, a multi-dimensional approach to sensing flow con text is adopted. Novel implementations for three exemplar sensors, including sensors for intrinsic flow context, node and device characteristics, and for device location, are pre sented. Mechanisms for locating flow context sensors and propagating context event notifications using a distributed hash table (DHT) are described and evaluated. Simulation results suggest that DHTs can provide decentralized and scalable solutions for flow context location and dissemination. In addition, a novel mode of context distribution called path-coupled flow context dissemination is described. An evaluation of semantic flow context processing using the RacerPro reasoner is presented. Various platform-specific reasoning modes are tested, including the use of queries, ABox modification, and incomplete reasoning. Finally, several application scenarios illustrating the potential uses of flow context in areas such as mobility and moving networks, quality of service, intelligent flow classification, network management, and other applications, are presented. Many of these scenarios are demonstrated through proof-of-concept implementations, which may be further evaluated and developed into full, working, and useful applications.
12
Hansen, Douglas Dale. "Analytic modeling of leakage in confined aquifer systems /." Diss., ON-CAMPUS Access For University of Minnesota, Twin Cities Click on "Connect to Digital Dissertations", 2002. http://www.lib.umn.edu/articles/proquest.phtml.
Full text
13
Markowski, Michael J. "Modeling behavior in vehicular and pedestrian traffic flow." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 162 p, 2008. http://proquest.umi.com/pqdweb?did=1654493641&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
14
Løvgren, Alf Emil. "Reduced basis modeling of hierarchical flow systems." Doctoral thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-2170.
Full textAbstract:
In this thesis we consider the reduced basis element method for approximating the solution of parameter dependent problems described by partial differential equations. In particular we focus on fluid flow in pipes, bifurcations and hierarchical systems, where the flow is described by the steady Stokes equations, or the steady Navier-Stokes equations. The thesis consists of four papers and this introduction.
The reduced basis element method is different from traditional reduced basis methods in that it combines these methods with domain decomposition. A given geometry is decomposed into building blocks with the same topology as a few reference domains, e.g. a rectangle and a reference bifurcation. Relative to each reference domain we precompute and store basis functions found on a preselected set of deformations of the respective reference domains. A reduced basis solution is then found by mapping the basis functions from their respective reference domains to corresponding domains in the domain decomposition. A local approximation of the “true” solution on one domain is found using the basis functions belonging to that specific domain, and the global approximation is found by “gluing” the local approximations together with constraints across domain interfaces. Geometries where building blocks of the same topology are reused many times are attractive candidates for the reduced basis element method. When there is only one domain in the geometry, the reduced basis element method is seen as a traditional reduced basis method where the geometry of the domain is one of the independent parameters.
In the first part of the introduction we present the reduced basis method and the reduced basis element method. In the second part of the introduction we motivate the work done in the thesis, and give a summary of the papers.
15
Jupp, Laurence. "Dynamic modeling of complex fluids under flow." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288304.
Full text
16
Pelton, Robert John. "One-Dimensional Radial Flow Turbomachinery Performance Modeling." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2192.pdf.
Full text
17
Bradshaw, Sean D. (Sean Darien) 1978. "Physics-based, reduced-order combustor flow modeling." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/82215.
Full text
18
GANGWAR, ASHUTOSH. "Source Term Modeling of Rectangular Flow Cavities." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin991266184.
Full text
19
Myers, Lance Jonathan. "Mathematical modeling of foetal arterial blood flow." Doctoral thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5143.
Full textAbstract:
Bibliography: leaves 187-211.The aim of this thesis was to develop an accurate and comprehensive computer model of the foetal circulatory system and to use this model to investigate influences of various haemodynamic viriables on common Doppler blood flow velocity waveform indices. The foetal model consists of an number of vascular compartments, cascaded together using electrical transmission line analogies.
20
Vilhelmsson, Carl. "Compressible Flow Modeling with Combustion Engine Applications." Thesis, Linköpings universitet, Fordonssystem, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-138434.
Full textAbstract:
The high demands on low fuel consumption and low emissions on the combustion engines of both today, and the future, is highly dependent on advanced control systems in order to fulfill these demands. The control systems and strategies are based on models which describe the physical system. The more accuratly the models describe the real world system, the more accurate the control will be, leading to better fuel economy and lower emissions. This master's thesis investigates and improves the mass flow model used for a compressible restriction, such as over the throttle valve, EGR valve, or the wastegate valve, for example. The standard model is evaluated and an improvement is proposed which does not assume isentropic flow. This seems to explain the deviation from the isentropic Psi-function shown in earlier research such as (Andersson:2005). Furthermore a throttle valve is analyzed in ANSYS in order to show the generation of entropy. The presence of pressure pulsations in a combustion engine is also evaluated, especially how they effect the otherwise assumed steady flow model. It is tested if a mean value pressure is sufficient or if one needs to take the pulsations in to account, and the result shows that a mean pressure is sufficient, at least for the throttle when typical intake manifold pulsations is present. A dynamic flow model is also derived which can be useful for pressure ratios close to one. The dynamic flow model is based on the standard equation but with an extra dynamic term, however it is not implemented and tested due to complexity and time limitation. The proposed new non-isentropic flow model has proven promising and can hopefully lead to lower emissions and better fuel economy.
21
Hattangady, Nitin V. "Computer modeling of flow lines and flaw migration in bulk deformation prcesses." Ohio : Ohio University, 1987. http://www.ohiolink.edu/etd/view.cgi?ohiou1183045637.
Full text
22
Hattangady, Nitin V. "Computer modeling of flow lines and flaw migration in bulk deformation processes." Ohio University / OhioLINK, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1183045637.
Full text
23
Wong, Chun-kuen. "Dynamic macroscopic modeling of highway traffic flows /." Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25151538.
Full text
24
Grigoriev, Igor. "Turbulence modeling of compressible flows with large density variation." Doctoral thesis, KTH, Turbulens, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-183452.
Full textAbstract:
In this study we highlight the influence of mean dilatation and mean density gradient on the Reynolds stress modeling of compressible, heat-releasing and supercritical turbulent flows.Firstly, the modeling of the rapid pressure-strain correlation has been extended to self-consistently account for the influence of mean dilatation.Secondly, an algebraic model for the turbulent density flux has been developed and coupled to the tensor equationfor Reynolds stress anisotropy via a 'local mean acceleration',a generalization of the buoyancy force. We applied the resulting differential Reynolds stress model (DRSM) and the corresponding explicit algebraic Reynolds stress model (EARSM) to homogeneously sheared and compressed or expanded two-dimensional mean flows. Both formulations have shown that our model preserves the realizability of the turbulence, meaning that the Reynolds stresses do not attain unphysical values, unlike earlier approaches. Comparison with rapid distortion theory (RDT) demonstrated that the DRSM captures the essentials of the transient behaviour of the diagonal anisotropies and gives good predictions of the turbulence kinetic energy. A general three-dimensional solution to the coupled EARSM has been formulated. In the case of turbulent flow in de Laval nozzle we investigated the influence of compressibility effects and demonstrated that the different calibrations lead to different turbulence regimes but with retained realizability. We calibrated our EARSM against a DNS of combustion in a wall-jet flow. Correct predictions of turbulent density fluxes have been achieved and essential features of the anisotropy behaviour have been captured.The proposed calibration keeps the model free of singularities for the cases studied. In addition, we have applied the EARSM to the investigation of supercritical carbon dioxide flow in an annulus. The model correctly captured mean enthalpy, temperature and density as well as the turbulence shear stress. Hence, we consider the model as a useful tool for the analysis of a wide range of compressible flows with large density variation.QC 20160314
25
Oner, Erdinc. "A SIMULATION APPROACH TO MODELING TRAFFIC IN CONSTRUCTION ZONES." Ohio University / OhioLINK, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1108146637.
Full text
26
Kolb, Kelly Jean. "Modeling Bright Gully Deposits' Formation in Hale Crater, Mars: Implications for Recent Liquid Water." Thesis, The University of Arizona, 2008. http://hdl.handle.net/10150/193349.
Full textAbstract:
This study aims at uncovering the formation mechanism of the recent bright gully deposits observed on Mars in order to assess the viability of liquid water involvement. I use a high resolution topography model as input into a kinematic model to assess whether or not a dry granular flow could form the bright gully deposits seen in Hale Crater. I investigate a dry mechanism due to the difficulty of producing water on the martian surface under present-day pressure and temperature conditions. I examine a range of particle sizes, flow thicknesses, and upslope initiation points to examine how these parameters affect the run-out distances of flows. The results show that multiple combinations of parameters could produce flows that travel to within the observed deposits' boundaries. The results suggest that the recent bright gully deposits are not evidence of recent liquid water on the surface of Mars.
27
Sopko, James J. "Modeling fluid flow by exploring different flow geometries and effect of weak compressibility." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Jun%5FSopko.pdf.
Full text
28
Zhu, Jianxi. "Mathematical Modeling of Single Phase Flow and Particulate Flow Subjected to Microwave Heating." NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-12102006-235146/.
Full textAbstract:
The purpose of this research is to numerically investigate heat transfer in liquids and liquids with carried solid particles as they flow continuously in a duct that is subjected to microwave irradiation. During this process, liquid flows in an applicator tube. When flow passes through the microwave cavity, the liquid absorbs microwave power and its temperature quickly increases. The spatial variation of the electromagnetic energy and temperature fields in the liquid was obtained by solving coupled momentum, energy and Maxwell?s equations. A finite difference time domain method (FDTD) is used to solve Maxwell?s equations simulating the electromagnetic field. The effects of dielectric properties of the liquid, the applicator diameter and its location, as well as the geometry of the microwave cavity on the heating process are analyzed. For modeling particulate flow subjected to microwave heating, the hydrodynamic interaction between the solid particle and the carrier fluid is simulated by the force-coupling method (FCM). The Lagrangian approach is utilized for tracking particles. The electromagnetic power absorption, temperature distribution inside both the liquid and the particles are taken into account. The effects of dielectric properties and the inlet position of the particle on electromagnetic energy and temperature distributions inside the particle are studied. The effect of the particle on power absorption in the carrier liquid is analyzed. The effect of the time interval between consecutive injections of two groups of particles on power absorption in particles is analyzed as well.
29
Cai, Mingchao. "Modeling and numerical simulation for the coupling of surface flow with subsurface flow /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?MATH%202008%20CAI.
Full text
30
Botne, Kjetil Kandal. "Modeling wax thickness in single-phase turbulent flow." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for petroleumsteknologi og anvendt geofysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19307.
Full textAbstract:
Oil and gas transport is today a vital part of the industry. Oil cooled during transport in pipelines may precipitate paraffin wax. Precipitated wax may deposit on pipe walls and cause flow restrictions. Deposition models are used to understand and predict deposition of solids. A deposition model can help predict wax problems before a pipe line is set into operation. If the amount of deposited wax is predicted it can help operators to develop removal plans and strategies. A total of 21 wax deposition experiments performed by others were digitized and evaluated. The logarithmic deposition-release model showed a good match with 18 of the experiments. The experiments tested the effect of varying flow rate, temperature or both. Most experiments behaved as expected when flow rate and temperature were varied. The deposition-release model consists of two coefficients, k1 and k2. Both coefficients were evaluated against wall shear stress for the varying rate experiments. The coefficients in the varying temperature series were evaluated against the temperature driving force. Linear trends between most coefficients and physical parameters were found. These linear trends lead to the development of four models that predict wax deposition. The models use either wall shear stress, the temperature driving force or both as an input. All models produce similar results. Each model was based on an experimental series. A study of a real pipeline with wax deposition was also investigated. Temperature and viscosity calculations matched well with values used in the study. The study reported calculated wax thickness based on measurements of pressure drop. The pressure drop method was evaluated and explained. The method does not consider an altered pressure drop due to increased pipe roughness and non-evenly distribution of deposits. Both of these effects will increase the pressure drop. It was found that neglecting these will cause the calculated thickness to be overestimated. Because of the overestimation of thickness it was hard to get an accurate match with models.
31
Pedruelo, Xabier. "Modeling wind flow over complex terrain using OpenFoam." Thesis, University of Gävle, University of Gävle, Department of Technology and Built Environment, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-5005.
Full text
32
Rowley, Clarence W. Leonard Anthony. "Modeling, simulation, and control of cavity flow oscillations /." Diss., Pasadena, Calif. : California Institute of Technology, 2002. http://resolver.caltech.edu/CaltechETD:etd-12032004-075012.
Full text
33
HUERTAS, JACKELINE ROSEMERY C. "NUMERICAL MODELING OF 3D FLOW IN POROUS MEDIA." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9948@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORSimulações numéricas tendem a simplificar o comportamento de problemas reais, na maioria das vezes pela adoção de um modelo 2D para descrição da resposta hidráulico-mecânica de barragens de terra, escavações, fundações, etc., com base na maior facilidade da construção geométrica de malhas, rapidez de processamento, simplicidade na introdução das condições de contorno, menor dificuldade na obtenção dos parâmetros de engenharia, etc. Entretanto, para certos fenômenos como o fluxo através de barragem em vales estreitos ou no rebaixamento do lençol freático para execução de escavações para construção de fundações, os efeitos tridimensionais podem afetar consideravelmente os resultados obtidos com uma solução simplificada, seja em termos de vazão, cargas, gradientes hidráulicos ou fatores de segurança. Esta dissertação tem como objetivo principal analisar problemas de fluxo, na condição transiente e/ou permanente, considerando solos saturados e parcialmente saturados, em simulações 2D e 3D pelo método dos elementos finitos buscando destacar as principais diferenças entre as respostas obtidas, ressaltando as principais vantagens e dificuldades da realização de uma simulação 3D em relação a uma análise simplificada 2D. Os exemplos numéricos abordados neste trabalho se referem à barragem de terra Macusani, no Peru, à escavação realizada para construção das estruturas da Pequena Central Elétrica Canoa Quebrada - MT e ao rebaixamento do lençol freático para construção das fundações do shopping Brooklin na cidade de São Paulo - SP.
Numerical simulations tend to simplify the behavior of real problems, mainly through the choice of 2D models to describe the hydromechanical responses of earth dams, excavations, foundations, etc., partly because it is easier to construct geometrical meshes, it is simpler to impose the required boundary conditions, the computer calculations are done more rapidly and the estimation of the engineering parameters, either through field or laboratory tests, are less difficulty than it would be if the problem was treated as a complete 3D case. However, for certain phenomena such as the flow of water through dams situated in narrow valleys or the water drawdown in excavations for construction of building foundations, 3D effects can considerably affect the results when compared to a simplified 2D solution, either in terms of quantity of flow, hydraulic heads and gradients, security factors, etc. The main goal of this dissertation is the analysis of flow problems, both in transient and permanent conditions, considering fully saturated or partially saturated soils, employing 2D and 3D numerical models based on the finite element method in order to highlight the main differences between the computed answers, emphasizing the advantages and difficulties of both approaches. The numerical examples studied in this work are the earth dam Macusani, situated in Peru, the excavation carried out for the construction of the structures in the small hydroelectric plant Canoa Quebrada - MT, and groundwater drawdown for the execution of the foundations of the Brooklin shopping mall, in the city of São Paulo - SP.
34
Brunini, Victor Eric. "Modeling and design of semi-solid flow batteries." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/79549.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 111-116).
A three-dimensional dynamic model of the recently introduced semi-solid flow battery system is developed and applied to address issues with important design and operation implications. Because of the high viscosity of semi-solid flow battery suspensions, alternative modes of operation not typically used in conventional redox flow battery systems must be explored to reduce pumping energy losses. Modeling results are presented and compared to experimental observations to address important considerations for both stoichiometric and intermittent flow operation. The importance of active material selection, and its impact on efficient stoichiometric flow operation is discussed. Electrochemically active zone considerations relevant to intermittent flow operation of semi-solid flow batteries (or other potential electronically conductive flow battery systems) are addressed. Finally, the use of the model as a design tool for optimizing flow channel design to improve system level performance is demonstrated.
by Victor Eric Brunini.
Ph.D.
35
Hiltrop, Jonas. "Modeling neuroscience patient flow and inpatient bed management." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90769.
Full textAbstract:
Thesis: M.B.A., Massachusetts Institute of Technology, Sloan School of Management, 2014. In conjunction with the Leaders for Global Operations Program at MIT.Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014. In conjunction with the Leaders for Global Operations Program at MIT.
15
Cataloged from PDF version of thesis.
Includes bibliographical references (page 104).
Massachusetts General Hospital (MGH) experiences consistently high demand for its more than 900 inpatient beds. On an average weekday, the hospital admits about 220 patients, with the emergency department (ED) and the operating rooms (OR) being the main sources of admissions. Given MGH's high occupancy rates, a comparable number of discharges have to occur daily, and the intraday time distributions of admissions and discharges have to be aligned in order to avoid long wait times for beds. The situation is complicated by the specialization of beds and the medical needs of patients, which place constraints on the possible bed-patient assignments. The hospital currently manages these processes using fairly manual and static approaches, and without clear prioritization rules. The timing of discharges is not aligned with the timing of new admissions, with discharges generally occurring later in the day. For this reason MGH experiences consistent bed capacity constraints, which may cause long wait times for patients, throughput limitations, disruptions in the ED and in the perioperative environment, and adverse clinical outcomes. This project develops a detailed patient flow simulation based on historical data from MGH. The model is focused on the neuroscience clinical specialties as a microcosm of the larger hospital since the neuroscience units (22 ICU beds and 64 floor beds) are directly affected by the hospital's important capacity issues (e.g., patient overflows into other units, ICU-to-floor transfer delays). We use the model to test the effectiveness of the following three interventions: 1. Assigning available inpatient beds to newly admitted patients adaptively on a just-in-time basis; 2. Discharging patients earlier in the day; 3. Reserving beds at inpatient rehabilitation facilities, thereby reducing the MGH length of stay by one or more days for patients who need these services after discharge from the hospital. Intervention effectiveness is measured using several performance metrics, including patient wait times for beds, bed utilization, and delays unrelated to bed availability, which capture the efficiency of bed usage. We find that the simulation model captures the current state of the neuroscience services in terms of intraday wait times, and that all modeled interventions lead to significant wait time reductions for patients in the ED and in the perioperative environment. Just-in-time bed assignments reduce average wait times for patients transferring to the neuroscience floor and ICU beds by up to 35% and 48%, respectively, at current throughput levels. Discharges earlier in the day and multi-day length of stay reductions (i.e., interventions 2 and 3) lead to smaller wait time reductions. However, multi-day length of stay reductions decrease bed utilization by up to 4% under our assumptions, and create capacity for throughput increases. Considering the expected cost of implementing these interventions and the reductions in patient wait times, we recommend adopting just-in-time bed assignments to address some of the existing capacity issues. Our simulation shows that this intervention can be combined effectively with earlier discharges and multi-day length of stay reductions at a later point in order to reduce wait times even further.
by Jonas Hiltrop.
M.B.A.
S.M.
36
Zhang, Xin Ph D. Massachusetts Institute of Technology. "Modeling transient flow in intermittent water supply System." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111551.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 91-96).
Water distribution systems in cities throughout South Asia (and many other countries) only supply water on an intermittent basis (currently averaging less than 5hrs/day in most Indian cities). Intermittent Water Supply (IWS) creates inequities in water availability and carries public health risks associated with the ingress of contaminants from the surrounding ground through flaws in the aged piping systems. It is a major challenge to upgrade from intermittent to continuous water supply (CWS) as this involves an increase in the operating water pressures which promotes higher rates of leakage. There are currently no reliable computational models for characterizing the transient hydraulic behavior of IWS systems (including pipe filling and draining events) and hence, it is difficult to understand and control IWS systems. In a recent PhD thesis, Lieb (2015) developed an open-source code to solve the dynamics of IWS pipe networks through finite volume solution of the governing 1-D Saint Venant equations using the Preismann slot approximation. The current thesis extends and refines the algorithms proposed by Lieb to enable more robust simulations for pipe networks. Specific modification include algorithms for dry pipes and three-pipe junctions. The thesis proposes a new algorithm for representing the conservation of fluid mass, momentum and energy at a three-pipe junction which is validated by comparing computed loss coefficients with measured data reported in the literature. The research also validates predictions of mixed flow conditions (open-channel and pressured pipe flow conditions) with results from laboratory model tests. The proposed formulation has been applied to simulate a skeletonized pipe network (at a test site in Delhi), where simulations are compared with water pressures during intermittent water supply periods. The proposed analysis represents a first step towards comprehensive modeling of IWS that can be used to improve understanding and control of these systems and to manage the upgrading process for CWS operations.
by Xin Zhang.
S.M.
37
Monaghan, Rory F. D. (Rory Francis Desmond). "Dynamic reduced order modeling of entrained flow gasifiers." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/58191.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references.
Gasification-based energy systems coupled with carbon dioxide capture and storage technologies have the potential to reduce greenhouse gas emissions from continued use of abundant and secure fossil fuels. Dynamic reduced order models (ROMs) that predict the operation of entrained flow gasifiers (EFGs) within IGCC (integrated gasification combined cycle) or polygeneration plants are essential for understanding the fundamental processes of importance. Such knowledge can be used to improve gasifier reliability, availability and maintainability, leading to greater commercialization of gasification technology. A dynamic ROM, implemented in Aspen Custom Modeler, has been developed for a range of EFGs. The ROM incorporates multiple feedstocks, mixing and recirculation, particle properties, drying and devolatilization, chemical kinetics, fluid dynamics, heat transfer, pollutant formation, slag behavior and syngas cooling. The ROM employs a reactor network model (RNM) that approximates complex fluid mixing and recirculation using a series of idealized chemical reactors. The ROM was successfully validated for steady-state simulation of four experimental gasifiers. The throughputs of these gasifiers range from 0.1 to 1000 metric tonnes per day (3 kWth - 240 MWth). Sensitivity analysis was performed to identify the parameters most important to ROM accuracy. The most important parameters are found to be those that determine RNM geometry, particle physical and kinetic properties, and slagging. The ROM was used to simulate the steady-state and dynamic performance of a full-scale EFG system. In steady-state mode, the ROM was used to establish base case and fluxant requirements. The base case performance agreed with design specifications. Steady-state simulation was also used to determine important states for dynamic simulation. Six cases were examined in dynamic mode, including gasifier cold start. Dynamic results showed agreement with industrial experience for gasifier start-up times.
by Rory F. D. Monaghan.
Ph.D.
38
Terry, Aaron David. "Modeling Vocal Fold Intravascular Flow with Synthetic Replicas." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/8820.
Full textAbstract:
Communication by voice is foundational in our society and many rely on their voices for their occupations. Voice disorders affect a significant number of individuals each year, and diagnosis and treatment improvements are therefore sought via advancements in voice research. Contained in this thesis is a description of work intended to contribute to vocal fold research by using synthetic, self-oscillating vocal fold replicas to study the impact of replica vibration on perfusion fluid flow through the replica. Methods for manufacturing vocal fold replicas containing imbedded channels allowing for fluid perfusion are discussed. Experimental procedures developed for delivering perfusion fluid to the imbedded channel at a constant pressure during replica vibration are described. Methods for measuring perfusion parameters of perfusion fluid pressure, imbedded channel diameter, flow rate, and vibration parameters (subglottal pressure, frequency, amplitude, channel length, and glottal width) are detailed. Experiments performed using both stationary and vibrating vocal fold replicas are presented. Correlations between perfusion pressure and channel diameter are discussed. Vibration parameters were correlated to perfusion flow parameters and it is shown that perfusion flow rate through the channels decreased significantly with model vibration. Potential mechanisms for changes in perfusion flow resistance with vibration are discussed and analyzed. Output of a theoretical model, developed to incorporate some of the possible flow resistance mechanisms, was compared to vibrating replica experimental data.
39
Lopez, Diego. "Modeling reconfiguration strategies in plants submitted to flow." Palaiseau, Ecole polytechnique, 2012. http://pastel.archives-ouvertes.fr/docs/00/76/62/23/PDF/thesis_DLopez.pdf.
Full textAbstract:
La végétation terrestre et aquatique est soumise à une interaction forte avec l'écoulement du fluide environnant. Afin de surmonter les efforts fluides, les plantes se reconfigurent : l'écoulement provoque un changement de géométrie qui induit une réduction des efforts. Cette thèse présente un cadre théorique simple pour modéliser et comprendre les stratégies de reconfiguration par rupture et déformation. Il est montré dans ce travail que les arbres vont subir un élagage induit par le vent, ce qui constitue une stratégie de survie efficace face à des écoulements importants. Dans le cas général impliquant des déformations et de la rupture, on montre que la reconfiguration est un processus en deux temps, d'abord par reconfiguration élastique, puis par reconfiguration fragile. On obtient ainsi une caractérisation globale des stratégies de reconfiguration de plantes en fonction de leurs paramètres physiques. Un modèle homogénéisé est ensuite développé afin de généraliser le calcul de la reconfiguration de systèmes ramifiés sous écoulement. Avec ce modèle, un système ramifié est représenté par un ensemble de fibres. La formulation volumique du problème permet ainsi un couplage avec les équations du fluide, et ouvre des perspectives nouvelles pour l'étude des systèmes ramifiés en généralTerrestrial plants and aquatic vegetation are submitted to a strong interaction with the external fluid flow. In order to overcome the flow-induced loads, plants reconfigure: flow induces geometrical changes, thereby reducing the loads. This thesis presents a simple theoretical framework for modeling and understanding reconfiguration strategies, by deformation and breakage. It is shown that trees will undergo flow-induced pruning, which is an efficient survival strategy under important flow velocities. In the general case involving both deformation and breakage, reconfiguration is found to follow a two-step process, first elastic reconfiguration, and then brittle reconfiguration. We obtain therefore a general characterization of reconfiguration strategies in plants, depending on their physical parameters. A homogenized model is then developed in order to generalize the computation of reconfiguration of ramified systems under flow. According to this model, a branched system is represented by a bundle of fibers. The continuous formulation of this problem allows for coupling with the fluid equations, and provides new perspectives for the study of ramified systems in general
40
Jeyaraj, Jesudoss Asirvatham. "Numerical Modeling of Concrete Flow in Drilled Shaft." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7528.
Full textAbstract:
Drilled shafts are cylindrical, cast-in-place concrete deep foundation elements. Their construction involves drilled excavation of soil or rock using large diameter augers, and placement of the necessary reinforcing steel in the excavation followed by concreting. Where a high water table is encountered, drilling slurry is used to support the excavation walls and concreting is tremie-placed. Even though the history of drilled shaft construction goes back to the 1950s, the occurrence of anomalies persists in the form of soil inclusions, reduction in shaft cross-sectional area and exposure of reinforcement. One of the main reasons for the anomalies is attributed to the kinematics of concrete flowing radially from within the reinforcing cage to the surrounding annulus/concrete cover region. In view of this radial component of concrete flow and thus radially flowing interfaces between the concrete and slurry, the region outside the cage is more likely to contain veins of poorly cemented or high water-cement ratio material. These veins contain trapped slurry, which oftentimes consists of bentonite, jeapordizing the integrity of the shafts.
This research program focuses on the numerical evaluation of self-consolidating concrete (SCC) for drilled shaft application by taking into account realistic non-Newtonian concrete flow properties and the shaft structural blockages. For this objective, a 3-D computational fluid dynamics (CFD) model of the concrete flow in the shaft excavation is developed in ANSYS-Fluent. As a precursor to 3-D modeling, 2-D CFD modeling is carried out using COMSOL Multiphysics. In both 2-D and 3-D models, the Volume of Fluid method is used for computing the motion of the interface between the concrete and the drilling slurry. The models predict the flow patterns and volume fraction of concrete and slurry. The results are encouraging as the flow pattern from the simulation shows both horizontal and vertical creases in the concrete cover region. Moreover the flow pattern shows the concrete head differential developed between the inside and the outside the reinforcement cage. Further, the 3-D model is evaluated by studying the influence of the size of drilled shaft and arrangement of the bars and the results obtained are realistic.
With this 3-D model developed as a tool, the simulation of SCC and the normal standard concrete (NC) flow in drilled shaft concreting are studied in terms of creases and concrete head differential encountered in the flow. From the simulation, it is observed that in the flow pattern of SCC, the creases are very few compared to the one obtained from the flow pattern of NC. Moreover, the concrete head differential in the flow pattern of SCC is much less, than the head differential obtained from the flow pattern of NC flow. In the case of SCC, the head differential encountered about one inch. In the case of NC, the concrete head differential is 4-inch when the vertical rebars are spaced at 7-inch apart and 10-inch when the rebars are placed at 3.5-inch apart. Based on this numerical evaluation of SCC flow in the drilled shaft excavation, it is concluded that the performance of SCC is better than the performance of NC in filling the cover annular region of drilled shafts.
41
Ryu, Seungkyu. "Modeling Transportation Planning Applications via Path Flow Estimator." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4225.
Full textAbstract:
The Path Flow Estimator (PEE) concept was originally developed to estimate path flows (hence origin-destination flows) and link flows for a whole road network (given some counts at selected roads). It is now further developed as an alternative for modeling different transportation planning applications: (1) a bicycle network analysis tool for non-motorized transportation planning, (2) a multi-class traffic assignment model for freight planning, and (3) a simplified travel demand forecasting framework for small community planning.
The first application of the redeveloped PFE is to develop a two-stage bicycle traffic assignment model for estimating/predicting bicycle volumes on a transportation network. The first stage considers key criteria (e.g., distance related attributes, safety related attributes, air quality related attributes etc.) to generate a set of non-dominated (or efficient) paths, while the second stage adopts several traffic assignment methods to determine the flow allocations to the network. This two-stage approach can be used as a stand-alone bicycle traffic assignment to the transportation network given a bicycle origin-destination (O-D) matrix. The second application aims to enhance the realism of traffic assignment models for freight planning by incorporating different modeling considerations into the multi-class traffic assignment problem. These modeling considerations involve developing both model formulation and customized solution algorithm, which in turn involve asymmetric interactions among different vehicle types (i.e., cars versus trucks), a path-size logit (PSL) model (for accounting random perceptions of network conditions with explicit consideration of route overlapping), and various traffic restrictions imposed either individually or together to multiple vehicle types in a transportation network. In the third application, a simplified planning framework is developed to perform planning applications in small communities where limited planning resources hinder the development and application of a full four-step model. Two versions (i.e., base year and future year) of the PFE are proposed to address the specific transportation planning issues and needs of small communities.
These new PFE developments for planning applications are tested with different realistic transportation networks. The results suggest that the new PFE applications proposed in this dissertation provide an alternative to the traditional four-step travel demand forecasting model that can be used as a stand-alone application with better modeling capability and fewer resources.
42
Mylavarapu, Goutham. "Computational Flow Modeling of Human Upper Airway Breathing." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1377871159.
Full text
43
Pokhrel, Sajjan. "Computational Modeling of A Williams Cross Flow Turbine." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1515428122798392.
Full text
44
Hujihara, Masayuki. "MODELING FLOW AND WATER QUALITY IN AQUACULTURE GROUNDS." Kyoto University, 1997. http://hdl.handle.net/2433/202399.
Full textAbstract:
Kyoto University (京都大学)0048
新制・論文博士
博士(農学)
乙第9589号
論農博第2123号
新制||農||743(附属図書館)
学位論文||H9||N3047(農学部図書室)
16481
UT51-97-H426
(主査)教授 河地 利彦, 教授 坂本 亘, 教授 長谷川 高士
学位規則第4条第2項該当
45
Asadollahi, Shahbaboli Nora. "Numerical Modeling of Extreme Flow Impacts on Structures." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35208.
Full textAbstract:
Recent tsunami disasters caused devastating damages to well-engineered coastal infrastructures. In fact, the current design guidelines are not able to provide realistic estimations of tsunami loads in order to design structures to withstand tsunamis. Tsunami hydrodynamic forces are estimated using the drag coefficient. This coefficient is traditionally calculated based on a steady flow analogy. However, tsunami bores behave like unsteady flows. The present work aims at investigating the tsunami forces for different structure geometries to provide realistic guidelines to estimate drag coefficients considering unsteady flows. In the present paper, the dam-break approach is used to investigate the tsunami-like bore interaction with structures. A three-dimensional multiphase numerical model is implemented to study the tsunami induced forces on rectangular shape structures with various aspect ratios (width/depth) and orientations. The numerical model results are validated using measured forces and bore surface elevations of the physical experiments. A scaled-up domain is modeled in order to eliminate the effects of domain sidewalls in the simulation results. The drag coefficient relations with structure geometries and bore depths are provided. The obtained hydrodynamic forces and drag coefficients are compared with existing data in the literature and design codes.
For the second topic, a multi-phase three-dimensional numerical reproduction of a large scale laboratory experiment of tsunami-like bores interaction with a surface-piercing circular column is presented. The numerical simulation is conducted in OpenFOAM. The dam-break mechanism is implemented in order to generate tsunami-like bores. The numerical model is validated using the experimental results performed at Canadian Hydraulics Center of the National Research Council (NRC-CHC) in Ottawa. The unsteady Reynolds Averaged Navier-Stokes equations (RANS) are used in order to treat the turbulence effects. The Shear Stress Transport (SST) k-ω turbulence model showed high level of accuracy in replication of the bore-structure interaction. Further, a scaled-up domain is used to investigate the influence of the bed condition in terms of various downstream depths and roughness. Finally, a broad investigation on the bore propagation characteristics is performed. The resulting stream-wise forces exerted on the structural column as well as the bore velocity are compared and analyzed for smooth, rough, dry and wet beds with varying depths.
46
Wootton, David MacMullen. "Mechanistic modeling of occlusive arterial thrombosis." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17351.
Full text
47
McBrayer, Mickey Charles. "Calibration of groundwater flow models for modeling and teaching /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.
Full text
48
Wong, Chun-kuen, and 黃春權. "Dynamic macroscopic modeling of highway traffic flows." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31243757.
Full text
49
Preetham, Preetham. "Modeling the Response of Premixed Flames to Flow Disturbances." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19817.
Full textAbstract:
Modeling the Response of Premixed Flames to Flow Disturbances
Preetham
178 pages
Directed by Dr. Tim Lieuwen
Low emissions combustion systems for land based gas turbines rely on a premixed or partially premixed combustion process. These systems are exceptionally prone to combustion instabilities which are destructive to hardware and adversely affect performance and emissions. The success of dynamics prediction codes is critically dependent on the heat release model which couples the flame dynamics to the system acoustics. So the principal objective of the current research work is to predict the heat release response of premixed flames and to isolate the key non-dimensional parameters which characterize its linear and nonlinear dynamics.
Explicit analytical solutions of the G- equation are derived in the linear and weakly nonlinear regime using the Small Perturbation Method (SPM). For the fully nonlinear case, the flame-flow interaction effects are captured by developing an unsteady, compressible, coupled Euler-G-equation solver with a Ghost Fluid Method (GFM) module for applying the jump conditions across the flame.
The flame s nonlinear response is shown to exhibit two qualitatively different behaviors. Depending on the operating conditions and the disturbance field characteristics, it is shown that a combustor may exhibit supercritical bifurcations leading to a single stable limit cycle amplitude or exhibit sub-critical bifurcations wherein multiple stable solutions for the instability amplitude are possible. In addition, this study presents the first analytical model which captures the effects of unsteady flame stretch on the heat release response and thus extends the applicability of current models to high frequency instabilities, such as occurring during screech. It is shown that unsteady stretch effects, negligible at low frequencies (100 s of Hz) become significant at screeching frequencies (1000 s of Hz). Furthermore, the analysis also yields insight into the significant spatial dependence of the mean and perturbation velocity field induced by the coupling between the flame and the flow field. In order to meaningfully compare the heat release response across different flame configurations, this study has identified that the reference velocity (for defining the transfer function) should be based on the effective normal velocity perturbing the flame and the Strouhal number should be based on the effective residence time of the flame wrinkles.
50
Demirci, Turan. "Federated Simulation Of Network Performance Using Packet Flow Modeling." Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611704/index.pdf.
Full textAbstract:
Federated approach for the distributed simulation of a network, is an alternative method that aims to combine existing simulation models and software together using a Run Time Infrastructure (RTI), rather than building the whole simulation from scratch. In this study, an approach that significantly reduces the inter-federate communication load in federated simulation of communication networks is proposed. Rather than communicating packet-level information among federates, characteristics of packet flows in individual federates are dynamically identified and communicated. Flow characterization is done with the Gaussian Mixtures Algorithm (GMA) using a Self Organizing Mixture Network (SOMN) technique. In simulations of a network partitioned into eight federates in space parallel manner, it is shown that significant speedups are achieved with the proposed approach without unduly compromising accuracy.